In addition to the standard languages, some PLCs, e.g. the GE Fanuc Series 90, enable the use of C code/applications to program non-standard actions.

Thank you for this neatly explained article.

Please let me know if my understanding below is correct as the Modbus slave is a server side endpoint:
1. All Modbus Slaves must be installed with a valid SSL certificate.
2. Customer has to buy ssl certificates for all the IP addresses of the slave devices (wildcard will help minimizing the cost).
3. Current age Modbus Slaves need to be replaced with the slaves that are capable of allowing installation of SSL certificates.
4. Securing the Private Keys of each device’s certificate.

Can I download this?

Looking forward to Nokia 5G!

mtpattie664,
It is somewhat misleading advertisement because they want you to stay on their website and read it. But I was able to download this way. First click the pop out icon near top right hand side to open it in a new window. Then click on the open original icon on top right on the PDF window. Now the download icon becomes enabled. If it did not then try to print PDF and then save it as PDF.

I can not view the document right now.

Thank you Bijan Ghofranian

As a business owner from 1998 to 2014 and now as the engineering manager of an OEM that makes high throughput assembly machinery, the workforce gap has been an issue since the late 90’s.  Trying to find talent during this time has been somewhat difficult and about 4 years ago I started looking around at regional and then national colleges and universities that had a 4 year program, teaching the specific aspects of a control systems engineer.  I found all the typical EE and CompSci programs that maybe had a class or two for PLC programming, but no real comprehensive program that taught many of the aspects covered by a skills matrix I had for my Control Systems Engineers at my place of work.  The problem with hiring an EE or a CompSci major out of college is that one knew the coding methods and the other, some of the hardware design aspects.  But hiring either one meant a long period of OJT where I would lose efficiency of a tenured person to work with the new hire.  As a small business owner, I couldn’t afford that and even at my current place, we are so busy, I need to keep a very high level of efficiency and competency and my new hires need to hit the ground running.  That usually means that we need to hire control systems engineers from other positions at other companies and that comes at a premium as all the good engineers are gainfully employed.  So, I went back to my alma mater, The University of Hartford, two years ago armed with data, statistics, pay information and showed them that this line of work is not going away, in fact it is growing, and the skills gap and workforce shortage is growing.  I also came in with a skills matrix and a proposed curriculum of what I expect a Control Systems Engineer to have as a base knowledge.  The welcomed me with open arms and this past September, an Automation minor and an Automation concentration to the existing Electo-Mechanical Engineering program was rolled out.  There are two students that recently declared the minor and will be graduating this coming May!  To help out with this new program, UHart asked me to be an adjunct professor.  So now after nearly 40 years in the process and automation controls industry, starting as a junior in high school, I feel like I am giving back to help teach the next generation of control systems engineers!

Simple and clear

I’m learning PLC

Most of equations in table and some text are not rendering correctly in any browser.

I have heard about Solid State Relays but never understood the concept until i read this article. It is by far the best read i have had when it comes to understanding the concept and also the advantages of large load devices using solid-state relays instead of traditional mechanical relays. Thank you, Mr. David for this informative blog.

pressure relief valve,pressure safety valve

Is special 2-wire cable required?

The reason I ask is that there are many industrial I/O systems that have extensive 2-wire cables feeding a variety of RS-485 (Modbus/RTU) and 4-20mA instruments… I’m wondering whether the existing 2-wire cables can sometimes be re-purposed to implement Ethernet-based I/O instrument replacement?

Another potential application is where many in-building analog intercom systems are based on 3-wire cables.  Replacing with an Ethernet-based intercom system would be desirable, but replacing cables behind drywall would be prohibitive.

If the distances are short, perhaps the cable characteristics are somewhat forgiving?  I could see many neat applications for this—especially in retrofit applications, if existing cabling could be re-purposed.

The ultimate user guide to Ethernet-APL (Advanced Physical Layer) / Single Pair Ethernet (SPE):
-Justification
-Technical description
-Design & installation
-Integration & architectures
-Application protocols, interoperability, interchangeability
-Commissioning & management
-Control & safety
-Cybersecurity
-Innovation
-Migration

Here:
https://www.linkedin.com/pulse/future-device-io-apl-single-pair-ethernet-jonas-berge/

CAN WE UPGRADE GE 90-30 PLC TO ARDUINO PLC .  (300 IO)
ANY HELP

A lot in this article about what is AC. I would increase its value by adding more about ‘How Do You Measure AC Voltage’. For example instead of just informing to place COM lead on the reference point, I would explain the difference between using ground and neutral as your reference point, and voltage drop. Etc.

pl add below Tags in Exemples
ZSO - Position Switch Close
ZSC - position Switch Open

This is a long well-written article you have written. Proxy sensors most sensor manufacturers bread and butter. Here at Balluff, we offer a huge range of these on there own.

I hope you do not mind me sharing this video but it shows sensors being used for object detection well. https://youtu.be/gM3JrM-2024

An interesting new product they have produced there.

How does ground side (neutral) motor control circuit switching square with NFPA NEC 430.74?  Consider a typical control circuit wherein the Hot conductor leaves the controller enclosure, runs to a remote start station, and returns to the enclosure either to the starter coil then OL device or to the OL device then starter coil.  In this circuit a grounded conductor either trips the short circuit / overcurrent device instantly or when the start circuit is enabled, depending on which conductor is grounded.  In either case the motor does not start.  The value of not preventing an orderly shutdown, alarm signaling, etc. is clear.  However, 430.74 would seem to allow ground side switching only if there are no remote stations.  I am, of course, referring to US installations only.

Industrial IOT is always best for industrial automation

The integrator gain is not unitless.  It has units of output/(error*time)

The diagram shows a PID with all the gains acting on the error.  This introduces zeros into the closed loop transfer function which will result in overshoot.  Some controllers have an option for the derivative gain to act only on the changes in the PV or feedback.  I call this a PI-D.  If the proportional gain also acts on the feed back there will be no zeros.  I call this I-PD.  Bandwidth is reduced but there are not zeros that cause overshoot.  Another advantage is that since all three gains are integrating.  The integrator is integrating errors.  The proportional term is integrating changes in the PV and the derivative gain is integrating changes in the rate of change in PV.

You have provided very good information about AC Motor Braking, but you have not given much information about Dynamic Braking Resistors. I would like to leave a source link on this subject. https://aktif.net/en/product-and-services/motor-control-and-braking-resistors/dynamic-braking-resistors

Processing power isn’t much of an issue these days.
It takes a little skill do to a proper system identification to get an accurate model.
Something that wasn’t mention is that the longer the dead time, the further one most calculate into the future.  This increases the need for CPU power.  CPU power can be reduced by updating at intervals that are twice as long if the application doesn’t require high frequency changes in the set point or target trajectory.

very informative

In the case of the RMC controllers the feed forwards gains are determined by the inverse of the open loop transfer function.  The motion trajectory and the feed forward outputs must be computed on-the-fly because often commands are issued while the actuator is still in motion.  I have NEVER been provided a model ahead of time.  The feed forwards gains can be estimated but usually they are found empirically by trial and error or by using an auto tuning program

Feed forwards can be used for temperature systems too.  The control gain usually has units of degrees/% control output.  So if you want to estimate the output for changing the set point to 50 degrees above ambient you would multiply the 50 degrees by the inverse of the the controller gain which will have unit units of % control output per degree.

The big advantage of using feed forwards is that it will estimate what the integrator term will eventually reach quickly instead of letting the integrator term wind up over time , over shoot then unwind.

Modbus TCP and ProfiNet are two very different protocols.  What they have in common is that they use the same hardware but after that they differ.
The Modbus TCP stack is very small and simple and is only good for transferring basic PLC types.  The byte and word order is a problem for 32 bit values because it isn’t really defined in the specification.  Manufacturers of equipment that Modbus TCP do what they please and sometimes this results in incompatibilities or 32 bit data must be re-arranged after receiving to be in the desired format..  We have seen this way too often.  We checked our code by testing it with a Modicon PLC to make sure we could send and received 32 bit DINTs and REALs in the right order without having to shuffle bytes or words afterwards.  Another problem with Modbus TCP is the TCP part.  You want to use TCP to send data such as parameters that must be right.  However, when sending basic I/O back and forth,  TCP is a problem because if there is an error then TCP will force the re transmitting of old data.  It would be best if there was a standard Modbus UDP because UDP wouldn’t force the re-tranmission of old I/O data.

ProfiNet is a big beast.  The stack size is huge.  The ProfiNet stack size is bigger than the Ethernet I/O,  Omron Fins,  Mitsubishi’s protocol and Modbus TCP combined.  ProfiNet has a lof of code that is run early on that will make define connections or packets.  ProfiNet allows for the I/O data to be transferred back and forth very efficiently.  It is just too bad that the start up code is so big.  It is good thing that memory is cheap.  ProfiNet is a HUGE improvement over Siemens’ previous Ethernet protocols.

ProfiNet devices must be certified to claim ProfiNet compatibility.  This is a big deal for the customer and the vendor.  Obviously the cost of the testing is eventually past on to the end user but it also means there are no problems with the byte ordering that occurs with Modbus TCP.

We have implemented many Industrial Ethernet protocols on our product so we are quite aware of the development time,  the amount of resources, difficulty to implement and support that each protocol requires.

perfect

Modbus/TCP was the 1st industrial Ethernet protocol, its basically Modbus on Ethernet.  PROFINET is at least two generations of functionality improvement over Modbus; 1st generation being PROFIBUS.  The 1st question that was asked in creating PROFIBUS was “how do we make this better than Modbus”, vastly that is diagnostics.  Diagnostics to reduce downtime thus improving productivity.

The Autonomous mobile robots is applied to express industry.

Thanks for the article, it was interesting.
However, I have a query about the photo which is supposed to depict a “linear power supply”.
Looking at the number of chokes, and what appears to be a high frequency transformer instead of an iron cored mains transformer, I suspect that this is a switchmode power supply of some sort.
Kind regards, Roger Valmadre.

that’s a good article, thanks

We are using several level sensor for our industries for a long time and they still working well.

The author didn’t say “Why bother?”
SFC are good for machine control.  SFC make it easy to organize ladder or structured text in steps or states.

SFC also makes the program more efficient because only the active step or state gets scanned instead of scanning the whole ladder.

hello there;
if i have continous real signal (4-20 ma) from pressure smart sensor, so to get high precision should i choose input module with high resolution? then i should use instruction ladder to make scaling of signal but. so what i do to this signal to make my pc to read this signal by modbud tcp/ip with saving of real signal in high precision.
regards

This site is the best for me

A metering pump passes a specific volume of liquid in a defined time period providing an actual volumetric flow rate. Delivery of fluids in specific adjustable flow rates is sometimes called metering.

Ladder logic is a poor tool for implementing state machines.  Obviously it can be done but SFC or sequential function charts are much better.  In each step one can use ladder ( LD ) or structured text ( ST ).  I prefer structured text.  On top of that, a good SFC implementation will high light the current active steps.  Better yet is to log the transitions from one step to another.

Excellent article. I also program a lot of state machines in Pro-face HMI/SCADA touchpanels. The big benefit of these Japanese touchpanels is that they also contain a ladder logic soft PLC. Even the small GP4116 ones also. When the customer makes a new machine and is not 100% sure how things should work, you should use this way of implementation. It makes sure that your program is servicable in the future and it can be modified very easily when the customer comes with changes lateron.
It looks like a lot of work for a simple solution, but when more and more changes come this way of implementation actually saves a lot of time and money at the end. And what is most important: everything works like it should, and no strange things happen (if you didn’t make a mistake).
I shared the article on my LinkedIn page.

Enjoyed your article…I try to promote state machine plc programming in my plc classes…i have found that using asm charts seems to be helpful . I try to show that a state machine properly documented by a graphical method or chart can then be implemented in whatever you prefer . Ladder, SFC, Structured Txt, or we even do a ardunio implementation at times.

I had 2 questions:
1) Why is turndown ratio is often defined as ratio of maximum to minimum of process unit? The explanation above doesn’t match with the definition
2) In the first example (calibration range 0 to 300 and turndown ratio 20:1), the minimum span value is 14. So can we range the intrument for 15-30 or 30 to 75?
It would be really a helpful if you could clear these doubts

Regards,
Harsh Suvarna

thanks

Do not use master-slave if the controller is controlling the master.  The snych out from the master in the diagram above is the actual position which is not perfect.  There is always a little following error or at least quantizing ( feed back resolution ) error, sample jitter and or phase delay from reading the master’s actual position.  In the example above the controller is controlling all three actuators so the three actuators should be follow the target position generated by the controller.  The target position is usually an almost perfect position because it is a floating point value with very fine resolution, no sample jitter, or phase delay between the three actuators.  On top of that the controller usually generates a target velocity and acceleration too which are handy for generating feed forwards.

If the controller is not controlling the master as in example 3 then electronic gearing should be used.  A good example is a flying shear similar to example #3 above.  Now the trick is to try to generate a perfect target position, velocity and acceleration from the encoder feedback.  It is best to use a high resolution encoder that is sampled at consistent intervals so the encoder velocity and acceleration can be determined accurately.  Mechanical conveyors are never perfect.  There is usually some surging that occurs.  Chain conveyors generate jitter as the chain goes over the sprockets.  This jitter makes it difficult to computer accurate target velocities and accelerations for the slaves to follow. 

Below is an example of electronic gearing.  There is a feed chain that is moving the wood through a scanner that determines how best to cut the wood for maximum yield.  The wood is not cut straight but in general the cuts follow the grain and the wood is dried out straight later.  There are 3 sets of chipper heads that follow the cubic-spline/cam generated by the optimizing computer.  Notice that each set of top and bottom chipper heads are delayed by a number of encoder counts before executing their cubic-spline.  Unlike the video above, the three sets of chipper heads are not doing the same thing at the same time.  On top of that each piece of wood is different so the the 6 cubic-splines are down loaded to the controller for the next piece of wood while the current piece of woods is being chipped.  Yes, the is from 2004 somewhere in Canada.
https://deltamotion.com/peter/Videos/JAN-04%20VSS_0001.mp4

thank you

It will be very useful if you show the formulas or how you got the answers. Thank you

Excellent explanation

Whoever wrote this calculus tutor is brilliant!!!  Thank you

This article is clear and helpful to me as a novice. Thank you.https://okmarts.com/transmitter/yamatake/yamatake-azbil-transmitter-ry7910d1001.html

This so called white paper was an offensive waste of time.  You haven’t even tried.  It contains no useful information at all.  Welcome to my SPAM folder.

A lot you mention here is very good for instructors. I been teaching over 35 plus year in the Oil and Gas Industry. I didn’t realize I was doing it right all along. Especially the comment: it is better to teach a few things well than to teach many things poorly! I always said that. Put a lot of institutions press to teach to much in the time given. We are not all build the same, we all have different pace to accomplish goals. Simply, Just get it done.

Hi,  There is a great trend toward use of CFD in analysing fire and explosion outcome (Heat radiation, Explosion shock blast )and toxic/ flammable gas dispersion in oil & gas industry specially for offshore installation where flow and heat and pressure shock flow is obstructed by congestion of equipment and modules. there are few commercial CFD software developed by GEXCOM Company (FLACS), DNV Kameleaon and few others.
Masoud Sadra, Process Safety & Risk Principal Engineer

Well written! Many folks (myself included) don’t know or can’t remember basic calculations and the engineering field can be an intimidating place to admit unsurety. There is no loss of pride in learning basic principles.

Hi Jeff, This article is amazing, it gives a clear understanding of how important is the safety of the workers by using the wearables (IIoT). It’s true that you mentioned wearables will be able to reduce injuries and work fatigue. It’s correct that mental well-being as well productivity of the workers are the main aspects which have to be understood with the help of IIoT.

Hi, this is an informative article regarding the challenges and techniques for manufacturing wearables. Like you mentioned it’s true that producing a wearable that is accurate, efficient, and comfortable to wear is the most important challenge. In the coming years, I believe IIoT will expand more in the manufacturing and construction industries. Good work.

Nice article, thanks!

As for Ethernet/IP: “EtherNet/IP protocol is a universal interoperable standard that has seen years of successful applications in an industrial environment.”
Well, this is only partly true. In fact, the most important vendor (Rockwell) uses proprietary extensions to Ethernet/IP (having in the past change the interface).
More details, references (and speculations why 😊 ) can be read in “The theory versus practice” chapter of my blog:
https://d2000.ipesoft.com/blog/meet-the-most-widespread-communication-protocol-in-us

As for Modbus: though being one of the most widely used protocols (due to its simplicity), it lacks a lot of features and provides a lot of space for making errors. Therefore there is a lot of problems with various “mutations” of this protocol, resulting in a lot of complications. More details can be read in my blog: https://d2000.ipesoft.com/blog/communication-modbus-protocol

From the point of design, openness, and interoperability, BACnet protocol (used for building automation) is superior to both Modbus and Ethernet/IP. Using ASN.1 syntax and encoding, arbitrary values (even complicated structures) can be exchanged between both parties.
https://d2000.ipesoft.com/blog/communication-bacnet
https://d2000.ipesoft.com/blog/communication-bacnet-part-2
https://d2000.ipesoft.com/blog/communication-bacnet-part-3

Of course, it’s an older standard, so it lacks encryption and universality of OPC UA, which is a relatively new standard with an ambition to replace a lot of private protocols (we work with Simatic S7-1200/1500, B&R PLCs, and others, which already implement it - whether as a pair option [Simatic] or by default [B&R]).

very well explained. googol . keep it up

Thank you for a fantastic read.
I absolutely agree with your viewpoint. The use of cloud computing has the ability to change the architectures of industrial automation systems that have historically been on-site systems that required capital investment to incorporate functions. The cloud computing model, on the other hand, offers on-demand storage, computing, and application software, with engineers only paying for what they use.
Thanks again.

Very helpful article but one comment. “You cannot express how much power is used in during a day a month . . .” Beg to differ, but every electrical utility bill uses the term “Kilowatt Hour”, often expressed as “kW/hr”. One kW/hr is the consumption of 1000 watts of electricity for a period of one hour.
Respectfully Submitted Dave Ogden 618.789.4163

Thank you so much by this article very well writed.
Edemilso Farias Ilha
Brazil

I am a Python user but the article is biased.  When I program in Python I must import numpy, scipy and matplotlib as a minimum.
I often must import even more like tkinter, functools, hmi_widgets jsonfile and menubar.

While I do agree Python is a great tool I think the article must be honest.
What I think is great is jupyter lab and jupyter hub.  These interfaces make Python usable for the average person.
There are a few good forums where one can get answers for Python, Jupyter Lab and Jupyter hub.
A good site to watch is
https://www.youtube.com/channel/UC2GuY-AxnNxIJFAVfEW0QFA
http://apmonitor.com/
I am not affiliated with apmonitor.  I just think they do great work in the area of optimization and simulation.

You could maybe add a section on Node-Red and Bacnet ..

https://flows.nodered.org/flow/62cc521cb1f6498281800f007e80b014

>There are several ways to overcome the problems presented by the lead wires.
Yes, one can “loop calibrate” to compensate for lead wire resistance, but it’s better to never even use a 2 wire RTD whose measurement circuit includes the lead wire resistance.  It is far easier to use 3 wire RTD’s, which are the de factor standard in the process industries, because a 3-wire RTD input circuit uses the 3rd wire to compensate for the lead wire resistance.  99% of all RTD analog inputs are designed as 3-wire RTD inputs.  One has to hunt for the device that is a 2-wire only RTD input, for example, a 1/32 DIN temperature controller without terminal block screws for a 3rd wire.

👍

Thank you for sharing this article. In ISO 9001:2015, the requirement is called “Measurement Traceability” and calibration is a component of this requirement.

When I clicked on this article I was expecting to read about a differential pressure sensor.  Differential pressure measurements using two pressure sensors can be problematic because most pressure transmitters are in fact differential with the surrounding atmosphere being the what the pressure is measured against for both transmitters.  So errors can be introduced by sensor location and flow in an out of a tank.  The error range of the measurement is also the sum of the two transmitters error, or at least twice the that of the lowest accuracy sensor.  I am aware of 2 port differential sensors with a single sensing element which are very useful but the the ones I have used did not prove to be dependable.

Hello, what standard are you following for the eletrical symbols above?Is it IEEE?

Good

Hi.
Is it allowed to reuse this article or part of it?
Regards, Matjaž.

Excellent blog
Machine-to-machine communication, or M2M, is exactly as it sounds: two machines “communicating,” or exchanging data, without human interfacing or interaction. This includes serial connection, powerline connection (PLC), or wireless communications in the industrial Internet of Things (IoT). Switching over to wireless has made M2M communication much easier and enabled more applications to be connected.

Thanks Ethan, I’m looking forward to the third part!

Hi

Thank you, For technologies and academic projects visit our website Takeoff Edu Group.
https://takeoffprojects.com/android-based-projects

Fuzzy logic is a joke, a fad that died years ago.  It is an attempt to control something without understanding it.  There are many better algorithms that will produce much better results.  I have downloaded many papers on fuzzy logic where they claim they can control something better than a simple PID.  The fuzzy logic papers make fuzzy logic look better than a PID by making the PID control look bad.  This only shows the authors have lost all credibility because they don’t understand the control basics.  Some of the papers were presentations at engineering seminars.  This also shows that those that reviewed the paper know little.  So here is my rebuttal.
https://studio.youtube.com/video/5389Mh6Xibo/edit
I will take on all challengers.  Be prepared. 
If you want to optimize the control for something more than a simple SISO system then there is LQC or MPC.

Seriously,  do you really expect people to adjust input curves using hit or miss when everything can be calculated?
System identification can determine a model and then the controller gains can be optimized to put the closed loop poles in the desired location.
I have an answer for those that mention non-linear systems too.

My YouTube channel gets deep fast.  Most don’t understand the mathematics and bail after 3 minutes.  However look at the comments of those that stick around and understand what I am saying.
If you don’t like my YouTube channel then look at the apmonitor channel on YouTube.

Hello,
Is the sensor fail if 24V is applied directly to the loop power sensor terminals?

“Fuzzy logic control systems are generally cheaper to develop compared to more traditional approaches, and tend to be more efficient, robust, and reliable.”
This is false.  Fuzzy logic takes far more CPU power,  memory and program to implement than a simple PID.
How can you say fuzzy logic is more reliable when you don’t know where the closed loop poles are or how they can drift as the plant changes?

” A fitness function is also required since you must provide the means for one program to be measured against another in the sense that one is better at solving a given problem.”
This doesn’t make sense.  If you need to compare against another reference program that works then why not use the reference program?

How is this done in an industrial environment?  Trial and error can be costly.

Test

test 2

Dear Anish, during the regular control of INDUSTRY 5.0 development I was delivered your article. My name is Michael Rada, I am the FOunder of INDUSTRY 5.0 and since 2013 already implement its principles in a real business environment. It is a pity that you have not found any of more than 1000 articles published on the topic, keynotes, presentations, and interviews. Let me share with you the latest of my keynotes delivered at the CII conference at the end of August. Here is the original recording done by the organizer - https://www.youtube.com/watch?v=kuXqCHVcoXw

If you want to know more feel free to connect with me or any of the assigned 75 INDUSTRY 5.0 AMBASSADORS that already represent the INDUSTRY 5.0 principles all around the globe.

So!  Where would you use this?
If you want to approximate functions then using something like Levenberg-Marquardt,  gradient descent, or BFGS would be more efficient for finding coefficients.  One could try a simple polynomial or one with a numerator and denominator to find the best fit over a range.

There are 6 ways to wire the 3 wires from a 3-wire RTD to the 3 terminals on an analog input.  2 out of the 6 combinations will work, the other four will not.  It’s amazing how many people wire those 3 conductors so the analog input does not work and report a temperature reading.

Welcome to the 1980’s.  Lumber sorters are smart.

Being somewhat proficient in Autocad Inventor and Solidworks, this “SOLIDWORKS vs. AutoCAD for Mechatronics” article was at least misleading.  it would behoove the author to at least become familiar with like software packages to compare before drafting something akin to comparing and apple to an orange.

Even normal HV circuit breaker makes loud bank when closing. The capacitor bank explosion would have quite loud and concerning for anybody unfortunate to be near by and witness it.

Thank you so much :D

Thanks to you, I now have a proper understanding of the basic mechanism of RF transmission !

That’s a pretty important thing for a newly licensed ham.

James - KI5SMN 73!

I installed a data acquisition (DAQ) system on thermal oxidizers in 2018 for a customer.  The field devices communicated to the historian via the corporate intranet over Ethernet.  Everything ran flawlessly until the company did a ‘network upgrade’ about a month ago.  Only one of the 7 field devices continued to report to the historian and that stopped after a power cycle and cold restart.  I suspected that the upgrade included managed switches which were not programmed for this specific traffic, but that was not the case.  The field device DAQ vendor had a firmware update what were ‘exposed ports’ that apparently were detected by software monitoring in the newly upgraded network.  The monitoring software disabled communications with ‘bad boy’ field devices with exposed ports.  The firmware updates fixed the field devices (now with non-exposed ports) which now communicate with the historian.  There were other security upgrades in the firmware that have not been publicized.  Good to know that there is increased cyber security vigilance.

Have a look at the secure process automation using BDATA’s lightweight BIoT blockchain network

This article presented a good overview of the PFD/ PID development process. Thank you.

What are the negative effects of grounding a DC power supply? Could noise from other devices play a role? For example a panel containing Variable Speed Drives?

HMI’s ( and SCADA - PC based interface) often required to mimic a plant or process. HMI development software came with library of objects and tools that were used to create the mimic. But for a perfectionist, the mimic never looked close to the real life item. Modern HMIs allowed the developer to import pictures and bit map images to create the mimic. This allowed the end user to see their plant or process in much realistic way. The PC based GUI’s are getting a facelift often (from multiple developers) but HMIs were lagging a bit.  Now HMIs and SCADA are much more capable than the initial days.

Incredible design and execution!

I prefer Ladder Logic for simple digital controls; as you mention it’s easier to debug when the software animates the on/off states.
For data manipulation: if I can achieve this simply in ladder logic using just one or two function blocks, then I’d choose that option, but for more complex data manipulation I’d prefer ST.

This is great…

I used to prefer ladder because that’s what was available when I first started programming over 25 years ago. When ST became available, I only programmed complex data manipulations and calculations in ST - I once had to write my own steam table calculations about 15 years ago which required summing a bunch of products created by looping through arrays of constant coefficients that multiplied measurements - ST was perfect for that! Now that I program for the same types of equipment (switchgear) but have to use a wide variety of PLC platforms per customer direction, I prefer ST for its portability. Sometimes the syntax is slightly different between platforms, but find and replace operations in a text file makes syntax changes pretty easy. Porting between platforms is almost impossible in the diagram-based languages of LD, FB, or SFT because it requires reprogramming each diagram.

LD is great for those who learned logic with relays and switches/contacts like electricians/technicians, but as the next generation comes up behind me and college-educated EEs seem to be doing more of the programming, they seem to prefer ST because many of them haven’t been exposed to relay ladder logic, but they’ve had to program a lot in text languages. Some of the younger electricians/techs I work with who have grown up with more programming in their lives don’t seem to mind programming in ST either.

Recently, I’ve ended up designing a couple of fairly complex controller algorithms using MATLAB and then used Simulink Coder to port my algorithms to ST for use in a PLC. That’s a pretty cool thing.

I use ST in about 75% of my programs.
The SELECT CASE statement is very powerful and makes programming a machine sequence very straight forward. 
It does take a different mindset to program in ST vs Ladder. 
One of the biggest differences being that when programming in ST a bit acts like a latched bit in Ladder.  Once set it remains set until is is turn off.
this can cause some issues if you do not keep it in mind but in general I find it much faster to develop in ST, easier to debug and alter sequences esp when using the Select Case statements and almost portable between different platforms. 
If I have developed a handy function on a Omron and want to use it on a AB then mostly only a little tweaking in notepad is all that is required. 
I do my Mapping to I/O in Ladder because it is easier to see , as mentioned the “logic flow” is presented visually.

One note , the two code snippets are almost functionally the same but is bot start and stop buttons are both on in the ladder code the motor will be off but in the ST code shown the motor would be On
easlier changed by using this

IF pbStop THEN
MotorON := 0;
ELSIF pbStStart THEN
      MotorON := 1;
END_IF;

OR

if pbStart then MotorOn:=1;end_if;
if pbStop then MotorOn:=0;end_if

ST is preferred by younger software programmers, as it is akin to other languages like Python, Java etc. It is much more easier for purely software trained individuals to program using ST. But once commissioned the trouble shooting and maintenance is handled by electrical team, who may not have software code development experience. All electricians are aware of electrical drawings and can appreciate the similarities with ladder logic. This is what drives the ladder logic preference. I came to know that some organisations pay individuals to convert code developed using ST to Ladder for use by maintenance team. Like Siemens, Omron allows ST to be used along with Ladder (embedded within Ladder). If a certain add-on instruction (which is proven and never need to be looked at) is a function and used repeatedly, within ladder environment then if it is ST, this will not bother the maintenance team, hopefully.

I see now sum of errors.  When dealing with rates. like flow, there needs to be an integrator.
I have seen this problem in Fig 2 before.  It can be solved with two Pi controllers.  LQC can also be used but turns out to be essentially to PI controllers with the gains computed by the LQC function that minimize the ‘cost” function.  Where is the FLC,s cost function.  Also, fig 5 looks linear.  Using linear gains is simpler.

Figure 2 needs an else clause.

One big difference is debugging and online manipulation. Ladder logic makes it possible to view runtime status of logic and often allows individual rungs to be locked and forced with predictable results. Most structured text implementations don’t allow this type of interaction (and with loops and conditions, it would be difficult to implement).

You forgot sample jitter.  Sampling and uneven intervals will result in errors especially if the samples are to be digitally differentiated.

Such a fine description and explanation. Love it!

Written in an unusually clear manner. Chapeau!

So what is new?  In the wood industry they have been scanning log and boards and using computers to determine how best to cut them for 40+ years.
In the late 1980s and early 1990s we made press monitors that would measure the forces on each die of a press that made beer and soda can tops ( ends ).  We could tell when a bearing was going out by monitoring the standard deviation of the forces.  All of the die monitor machines were connected by BNC Ethernet cables to send data back to a collection computer that could graph the data.

Looks to be good, can it be used in steam application of 67 ata pressure and 485 Deg C temp.?

I’d wondered why there were two sets of numbers on relay contacts. Super informative article! This will save me having to always look for relay schematics.

“This means more precise motions are possible with electric actuators than with other systems. “
I would like to see an electric actuator do this.
https://deltamotion.com/peter/pdf/articles/Multi-Axis%20Motion%20Controller%20Accelerates%20Gear%20Testing%20_%20Quality%20Magazine.pdf
Precision is a function of feed back ,  mechanics, and controller.
Hydraulic actuators have resolution as fine as 100 microns.

This is an excellent article, bringing out the talent of these powerful women! Congrats.

Author here: Thank you for your feedback!  The gear testing article is neat- I’ll be reading it in detail later this evening.

You can definitely get fine resolution with other systems, and it is very dependent on the controller and feedback mechanism.  Even the most precise actuator is only as good as the control and the sensor.

It’s not uncommon to get sub-micron resolution from electric actuators, particularly in the semiconductor industry. https://www.pi-usa.us/en/products/linear-actuators-motorized-precision/l-220-high-resolution-linear-actuator-1201906/#specification for example.

Once again, thank you for the feedback, because I love hearing from people who read my articles!

-Seth Price

David seems to imply that analogue instrument impedance varies depending on the voltage being measured.

Quote: ‘Most analog meters have an internal resistance that varies according to the voltage applied. It is usually displayed as a number of ohms per volt. A common value might be somewhere in the 20,000 ohms per volt range (ref Simpson 260 series).’

That is not quite right. The ohms-per-volt description is per scale range. For example, if the 250V range is selected (using the Simpson 20,000 o.p.v example) then the resistance of the instrument will be 20,000 x 250 = 5,000,000 Ohms, or 5 Megohms. As long as the meter is kept on that 250V range its resistance will be constant at 5 Meg, regardless of the voltage being measured.
Best way to prove this is to find a circuit diagram of a simple analogue meter. There is a different resistor for each voltage range.
Another good use for an analogue meter is proving a circuit is dead. A lot of the older DMMs had such a high input impedance that they would pick up all kinds of stray voltages, making the electrician reluctant to touch a dead cable. Fluke and others have overcome this by having a lo-res range, but many cheaper DMMs are susceptible to this problem. Most analogue meters don’t need a battery (exception the Micronta above, which is electronic) so they are always ready for use. (Always check your instrument on a known voltage source to confirm it is working, both before and after using it to prove a power circuit dead).
Sorry to be a nerd but someone has to do it.

Educative, Thank you

One simple debounce method is to use both the NO and NC contacts of a switch, using NO to set a latch and NC to reset it. This method is not generally used due to needing a dual throw switch and an extra wire but it may be of great help to someone who’s starting out in digital logic or moving from relays as it “just works”. A minimal implementation needs one non-inverting logic gate (and a resistor).

Two important snags to watch for:
1: adding a flyback diode to a relay increases “id10t errors” as it is now possible to wire the relay backwards and burn out the driver.
2: adding a flyback diode to a contactor coil may increase the time it takes to open and potentially reduce its ability to break high currents, increasing contact wear on the contactor.
Bidirectional TVS devices are available, these restrict the flyback voltage instead of eliminating it. This is often a better solution, though the TVS gets hot in operation so it must be sized for the application. The DC contactor coils I’ve seen had TVS devices factory-fitted by default.

He missed the biggest use for dc motors, fractional HP variable.  Where can you find a 1/4 HP, 120 V, 3 phase motor?

It is about time. most businesses are relying too much if china for their supply chain.

We note you refer to Laser Measurement in the first link of ‘Related Content’.

However it is worth mentioning ‘Draw Wire Position Sensing’. This is basically a multiturn potentiometer [possibly geared down] pulling a draw wire out of the housing, not disssimilar to pulling the metal tape out of a measuring tape. The difference is the draw wire pulls back in automatically.

Obviously used where the effort to pull is negligable compared to the equipment size; it can be used in harsh and in particular water environments where measured device goes under, such as sluice gates.

An obvious disadvantage is that foreign material can enter the transducer with the drawire, although can be negated by orientation. Only once have I seen mould growth enter, on the wire itself which had been immersed in dam water for several months.

https://www.micro-epsilon.co.uk/displacement-position-sensors/draw-wire-sensor/?
https://www.seatools.com/subsea-components/wire-length-measurement-sensor/

How do I or can I get a pdf version of this article for training purposes? 
TECHNICAL ARTICLE
What is the BACnet Protocol?

The content is very good. But I would also like to teach these materials on YouTube.

ST is fine for handling strings and moving data, but the ladder is really useful for everyday logic.
I mean, when they wake you up at 3am to fix some problem, in that situation you can appreciate that the ladder is easier to understand than ST.

Great article. Growing up on a farm and now in manufacturing controls hard to believe the progress in ag.

I can think of lots of applications but how force is delivered is basically as mentioned above.  Now controlling force precisely is not covered.  Different applications need different types of feedback.  In lab environments a load cell iat the end effector is best as long as the amplifier is fast.  In a mill a load cell normally as a half life of a few seconds.  In this case NetForce=PressureA*AreaA-PressureB*AreaB.  Of course this ignores seal friction but seal friction is usually small compared to normal operating forces.

Is TIA software or hardware?

The problem with “timers” is that they really aren’t “timers”.  They are delays.  This is indicated many times above.  If you put a 10 ms time preset in a PLC program and count how long it takes for the timer to time out 1000 times,  The time will be over 10 seconds.  Timed interrupts are better for better timing because 1000 timed interrupts will take verly close to 10 seconds but any error will not accumulate over time.  Timed interrupts are still prevented from triggering at exactly the time interval because sometimes the PLC goes into an “overhead” phase where interrupts are turned off.

Thank you for the invite!

Thanks, @Damond Goodwin for sharing this info. Yes, I totally agree with your point robot will bring a great revolution to the warehouse process. On the other hand, many e-commerce giants already accept robots as a service because they help to cater to the need of modern customers and increase work efficiency. Visit GreyOrane to know more about the automation industry and how they will impact your warehouse positively - https://www.greyorange.com/

There are much better ways to tune a system
Z-N is an attempt to tune the system without really understanding it. ( having a model ).
Also,  Z-N doesn’t work on every kind of system.  Some systems are integrating systems like level control or position control.  Some systems are non-integrating like speed control and temperature control.  Some systems have one real pole.  Other have two.  Some have two complex poles.
Repeating the same old stuff doesn’t really help advance control theory.

Might want to check your claim on your tongue being 30 milliohm resistance.  I’ll bet money the voltage drop at the battery terminals when you lick it is negligible, all that resistance that make it not dangerous is primarily your tongue, not the battery.  I’d say you’d probably have a current of a few milliamps, so you do the math on that and you’ll end up with a power dissipation of MICROWATTS, which the batter can supply for a very long time

Could you suggest some sensor supplier for transmitters?

Nice article. You skipped over some other Logic Controller families in the AB history. The first attempt at a micro was the Modular Automation Controller (MAC) that was released in “the PLC2 days”. It was followed by the PLC4, which added some serial networking capabilities. It as so “rock solid” that some of my former customers forgot that some were installed in their plant because none had ever failed. The SLC5/05 actually wasn’t the first of their PLC processors with ethernet capability, as the 1772 LWP PLC2 product had an AUI port that allowed mounting a ethernet transceiver to the front of the processor. The microPLC I found most helpful in training new users in Ladder Logic programming was the SLC100, which had a user manual with a very detailed description on use of their hand held programmer and ladder logic relay programming concepts (including the straightforward presentation of time and event driven drum sequencers). Just an ole dinosaur’s recollection of the progression of the product line.

Hi Jon, may I ask you a question.

I am finishing my FDP (Final Degree Project) which is about programming the automatic control of an industry line.
At some point, I needed to compare if two REAL variables were equal (it was about a SetPoint of a machine and the current Position values) so I used the EQ operator, setting as sources both variables. When I ran the simulation that part of code did not work as expected.
I was lucky because those variables had only one decimal number so what I did was to create auxiliary variables converting to INTEGRER those values multiplied by 10 and then use those variables instead of the main ones in the EQ operator. This way the process worked fine.
My question is if that issue might have happened because the way REALS are saved in memory is different from the rest of numbers or if it might have been another reason because from what you explain in the article it should be possible to compare those two numbers correctly.

Thanks for the article and sorry if there’s something not well explained in my comment. I’m not native English speaker.
Carlos.

Quite insightful,.., thank you

Thanks, nice.

Good book

Great article by a great guy!!! We will use this as better basic training in our QC and metrology lab.

In the section “Series Contacts with an Output Coil”, GreenButton is being read twice. Shouldn’t it be:
if (digitalRead(GreenButton)==HIGH && digitalRead(RedButton)==HIGH ) {

And in the next section “Parallel Contacts with an Output Coil”, again the GreenButton is being read twice. Shouldn’t it be:
if (digitalRead(GreenButton)==HIGH || digitalRead(RedButton)==HIGH ) {

Enjoyed your article
FYI Often is spelled wrong in this sentence, “Ofen, it is recommended to connect the DC - output to a bonded ground in order to reduce or eliminate this common-mode noise.”

Thanks for sharing your thoughts on this subject. I had similar problems in the past. When you see it the first time: you switch the IO signal off and the relay stays on….you think that some weird black-magic is going on…..

Add a Pull Down / or pull up resitor to take care of that probelm
you measured 2.2 volts with the output off but that occured with a meter with 10 megohm impedence.  Adding a 2.2K resistor connected to 0v will pull the voltage down low enough turn off your opto coupler.

Also “The downside to using a relay output module is the limited switching speed. If using inductive DC loads, a relay module may also experience premature failure if you do not protect the load coils with diodes from the flyback voltage.”
The coil of the relay module is controlled by the PLC and will not fail because of load current.
The contacts of the output module may arc but they are a lot more tolerant of inductive loads than typical PNP or NPN outputs on a PLC
The real downside to relay output modules is the cost.  They cost more per output, they do not have the densisty of transistor outputs which uses more panel space.  Switching speed esp. with an inducitve load is not usually an issue.  Depending on the card layout they are good when different voltages or sources of voltages need to be used.  They also typically have higher current ratings than transistor outputs.

A relay and optocoupler module seems a bit redundant, though it might find use where you want to operate a relay from a microcontroller. In that case you might want to keep the relay coil’s DC supply away from the microcontroller. Optocouplers also give you the freedom to wire for active high or active low.

There is a need for readily available adaptor circuits to go from 12/24V to a 3.3v GPIO. I could sketch out several but I couldn’t point to a nice convenient assembled module that you could just hook up and use.

A simple guideline I’d give is that the primary side should follow the *grounding rules of the upstream supply*, and a transformer earth terminal should connect to the protective earth of the supply.  The secondary side ground strategy can be chosen to suit the specific installation. TN-S is probably a good default, with a “earth” point specific to the control cabinet.

I wouldn’t normally consider the split configuration for a control circuit but it has one potential fringe benefit, the earth leakage currents of mains filters will cancel which may be useful if a significant number of switch mode power supplies are supplied from the control transformer.

I’ve found that when I’ve done Ladder Logic, it is easier for non-programmers to understand because of the graphical nature and relay-type logic.  Plus, software lockup is more difficult because a ladder is typically scanned top-bottom first time, every time.
(Of course, data handling and such can be a real pain with ladder logic and function blocks.)

My high school students are currently learning to code Arduino robots with the intention to teach a unit on learning a little ladder logic in a few months.  This article is exceptionally helpful.  You have made it so that transition will be easy.  Thank you.

> being PC-based control, you also have access to C++

What makes it PC based? AR Embedded is VxWorks based, like a majority of other brands (including AB Logix). B&R’s hardware architecture varies, but includes traditional DIN mount boxes, not just Industrial PC. The DIN mount varieties do C and C++ too.

They do have ARwin runtime options that run along side Windows (not unlike CompactLogix 5480). Would you call Allen-Bradley “PC Based”?

I see “PC Based”, “SoftPLC”, and “Soft Real-Time” used to take subtle jabs at tech forward brands like B&R and Beckhoff, like they aren’t “real” PLCs. What I rarely see are technical definitions of the terms and/or justification as to why they apply to some product lines or brands and not others.

Good article thank you.  I use OSP (one shot pulse) with Distributed Control System configuration.  Your article has given me insight into the functioning of this command.

Several other reasons for the wide spread use of 4-20mA as a process signal:

1.  ‘Smart’ transmitters can, in many cases, signal a fault condition with 4-20mA; typically a high value at 21.5mA or a low value at 3.6mA

2.  4-20mA being essentially DC signal, can operate with a superimposed, higher audio frequency signal, HART, for digital communications.  HART is primarily used for configuration and troubleshooting, but can be used for low throughput data communications.

3.  4-20mA can be designed and approved as Intrinsically Safe

4.  The mentioned 1 km distance can be extended to several kilometers with either a larger conductor size or higher loop DC voltage power supply. 

5.  An accidental or deliberate electrical short on the output of a 4-20mA analog output does not damage the 4-20mA circuit because 4-20mA is a regulated output.

6.  Even a cheap $10 DVM can be used to troubleshoot a 4-20mA circuit. 

7.  As a current signal, it offers a wide choice of dropping or shunt resistors on analog inputs for conversion to a voltage signal.  Although 250 Ohms is common, values from 1 Ohm to 500 Ohms are encountered.

8.  Depending on ground potentials, 4-20mA can drive two devices’ analog inputs in series, as long as the total resistance load can be driven by the available loop voltage.

9.  4-20mA analog output offers enough ‘power’ to drive many models of analog or smart valve positioners.

Industry 4.0 and all the terms are marketing garbage.  You get what you need to do the job.  It doesn’t make much difference what you call it.
BTW,  what happened to industry 3.0, 2.0 and 1.0.  I must have missed those.

Nice article. As an “old analog guy” I started in the process control industry in the 1960s. I worked for Taylor Instruments (no longer in business under that name) and remember 1-5mA, 4-20mA and 10-50mA (I think the latter was European - not sure). We offered all three as options. In those days, half our instruments were pneumatic, 3-15 psi, amazing precision from that mechanical stuff.  I didn’t design those - only electronics. 1mA would be too small for loop-powered instruments. I wasn’t aware of the safety concerns over 30mA - learned that from your article.
A senior engineer I worked under told me once worked on a project to design their first transistorized milllivolt transmitter. They did have products using chopper-stabilized vacuum tube amplifiers. He said he met the performance and cost goals but, in a management-level review, was told, “No - too many transistors!”

Back in the dark ages I used a 16 bit micro controller and a 256 element look up table that represent the angles from 0 to 90 degrees.  I used the upper 8 bits to index into this table and the lower 8 bits to interpolate between two entries.  My angles went from 0 to 1 or 1 to 0 depending whether I needed a sin() or cosin() function.

Looks like a fantastic product, would like to see the time current curves, what product series name has Siemens given to this product? Is it suitable for classified locations?

More than 20 years ago, I worked on a project where we had to use a resolver to measure position. That position had to be used by a PLC, which had no trigonometric functions on board. Since a PLC with sine/cosine functions was $300 more expensive and I had to use 40 PLC’s, I chose the same approach as mentioned in the article. Linear interpolation in 4 or 5 sections. I ended up having the same 1…2% error, which was acceptable.

Where can I access your next article on program logic conversion from APACS to Controllogix?

Remembering Field Sensing Devices
NPN = More “N’s”, Negative Switching (INput module should be PNP)
PNP = More “P’s”, Positive Swithching (INput module should be NPN)

Nice and great idea !
Would be glad to check out what is inside these textbooks

Cheers
James

The PDF Version links to the new chapters only go to the full text of Version 2.32 (Released 4 January 2019) Tony Kuphaldt’s excellent book, Lessons in Industrial Instrumentation. The links under Education > Textbook lead to the same 3311 page book.
How can one access the Control Automation version?

Fuzzy Logic is a farce.  Closed loop control is all about using the controller to move the open loop poles to new closed loop pole locations that will provide the desired response.  I have down loaded many FL documents that compare FL to PID.  They are a joke.  The show the FL controlling better than the PID but it only shows their ignorance of control.  They don’t know how to tune a system using a PID.
https://youtu.be/5389Mh6Xibo
I am not saying that PID is the ultimate control method but when augmented with feed forwards and a Smith Predictor to compensate for dead time, a PID is hard to beat.

There are other methods of control like Neural Nets and Model Predictive control.  NNs still need a way to compensate for the dead time.  MPC is computationally intensive and requires a good model.  My company uses something like NNs to ID food products.  It takes a lot of training to train a NN.
MPC requires an accurate model.  I have videos about how to compute the models.

FL is on par with Ziegler-Nichols where one tries to control what he doesn’t understand.

One of my favorite quotes.
[quote=Lord Kelvin]
I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind.

rI am muhammad Ishtiaq Khan form FBL Industrial Services,  please share safety valve brochure,

Three major limitations of MPC requires all sorts of tricks (approximations) which might question the optimality of solutions. Works well if problems are linear, deterministic and with NO inequality constraints but unfortunately many problems violate all of these limitations!

Very well explained. Couple of things I would like to add. When the input supply is single phase, the recreated 3 phase at the motor still has the same supply voltage as single phase. In my experience VFDs do not increase the supply voltage (for example single phase 230V input supply produces, 3 phase 230 V). This is an aspect electricians needs to be aware - this is not equivalent to normally available 3 phase (which could be 400v 3 phase). Modern VFDs have come a long way from earlier VFDs, now the VFD can almost do a mini- PLC’s work, including ethernet communication, PID control (without the needs of external controller or PLC), because of ethernet communication, it can also report back many parameters live which could be useful for monitoring/fault finding. Many modern human interface devices have the capability to store parameters, which could be useful to copy to other similar VFDs. Number of parameters are quite high, often in 100s. Finally though the VFDs have become almost essential in speed/torque/position control applications, the harmonic disturbance that they are introducing is becoming a problem, affecting mains supply’s sinusoidal form, which adds to problems of additional neutral current, pulsating torque disturbance in motors etc. Many manufacturers are suggesting adding dynamic harmonic correction equipment (which is often difficult to justify for investment), I feel in future, the VFD manufacturer should introduce counter measures within the VFD to reduce harmonics disturbance in the supply lines.

I think it is worth considering the prevalance of “XXX over Ethernet” implementations specifically.

Ethernet, specifically 10baseT and 100baseTX, has many attractive features for an industrial network such as inexpensive cable, relatively good noise immunity, well standardised connectors, built in isolation, an option to supply power over the connection and support for many-to-many networking.

” Imagine trying to sort an array that is 60 elements long with rung logic! “
That is what ST is for.

This article was awesome and acts for me as sunlight on a confusing night. your “thought experiments” was very useful for understanding
I very much appreciate that

I’d like to see those “thought experiments” you used in the Luft detector. Although I understand the Luft detector part, I’m not so sure about GFC!

how combining two deep learning models

how combining two deep learning models in matlab

Of course they are featureing virtual PLC’s , since they have seemed to have given up on shipping real ones.

Nice one

I love Instrumentation and everything in Control Automation
I already Feel great coming across this platform.

Good article, I normally put 150 ohm resistor at all points of a RS485 loop and seems to work OK.
I did not know about just doing the furthest 2 points from each other, I will try it some day to see if everything still works.

I actually have an open source project on GitHub to test the communications if anyone needs it, you can change the code to suit yourself its all there.
https://github.com/PhilipMur/Serial-Comm-Tester
I also have some CRC and checksum calculators there, handy for verifying things.

I‘m from Kassow Robots. We still have a lot to do this year.

https://www.kassowrobots.com/

We have something new this year 2023 - wait Till the Automatica this year

https://www.kassowrobots.com/

I still have nightmares 15 years after having worked with RSlogix… The software itself is alright, but the versioning system was horrible, and getting it to talk to RSlinx, an dalso using RSLogix500 was just horrible, if you updated any part of one, you had to update everything, and this was true with minor version changes.  I did do some cool stuff with it though

Well done on this, David. Gives a great start with such a complicated program. I also have the same thoughts as Rx7man since it is a chore and ordeal to link to any Rockwell PLC for me with this key status and revisions. Nightmarish!

in fig.2,3,4,5 the contact for the “thermal OL” should be NC ...?

Correction: Cables with fewer conductors—> smaller overall diameter—> REDUCED minimum bend radius, not increased.  Otherwise an interesting article on SPE.

Baud rate is not ‘simply’ bit rate. https://techdifferences.com/difference-between-bit-rate-and-baud-rate.html

There are sooo many issues with this that I just don’t know where to start?!!!
Why would any industrial installation want to replace 4 pairs of 100m cable with 1 pair that only runs 40m??  To save what?  A few square mm?!
What about backwards compatibility?  No 10 or 100 Mbps devices allowed on new networks because they can’t use the cabling?!
I have been in industrial automation for 25 years now, and I’ve seen less than 10 gigabit installations - and none of them are using the full bandwidth!!
What about the PLCs (and network switches and PCs/terminals for that matter) - are whoever came up with this idea expecting the entire industry to redesign and support a new connector, new firmware and probably new protocols for using less wires?!
Sorry, but I find this absolutely ridiculous :D

What are applications of capacitors?
Capacitors are used in many places.

1. Power Supply Filtering: Capacitors are used in power supplies to filter out any noise or ripples from the main incoming AC supply.

2. DC-DC Converter Output Filtering: Capacitors are used to filter out the high frequency switching noise generated in DC-DC converters.

3. Coupling: Capacitors are used to couple two circuits together, allowing AC signals to pass while blocking DC signals.

4. DC Blocking: Capacitors are used in circuits to block any DC signals from passing, while allowing AC signals to pass.

5. Timing: Capacitors are used in timing circuits to control the rate at which current flows.

6. Audio Equipment: Capacitors are used in audio equipment to filter out unwanted noise and smooth out the signal.

7. Motor Start and Run Capacitors: Capacitors are used in electric motors to help start them up and then keep them running smoothly.

For more electronic components products, please go to QUARKTWIN official website.

What are applications of capacitors?
Capacitors are used in many places.

1. Power Supply Filtering: Capacitors are used in power supplies to filter out any noise or ripples from the main incoming AC supply.

2. DC-DC Converter Output Filtering: Capacitors are used to filter out the high frequency switching noise generated in DC-DC converters.

3. Coupling: Capacitors are used to couple two circuits together, allowing AC signals to pass while blocking DC signals.

4. DC Blocking: Capacitors are used in circuits to block any DC signals from passing, while allowing AC signals to pass.

5. Timing: Capacitors are used in timing circuits to control the rate at which current flows.

6. Audio Equipment: Capacitors are used in audio equipment to filter out unwanted noise and smooth out the signal.

7. Motor Start and Run Capacitors: Capacitors are used in electric motors to help start them up and then keep them running smoothly.

For more electronic components products, please go to QUARKTWIN official website.

Cool

So good

The definition of Beta in this article is incorrect.  Beta is the ratio of the orifice plate bore diameter, d, to the inside diameter of the pipe, D.  Hence Beta = d/D.

The article provides an overview of the common reliability techniques used in the Industry. It serves its purpose.

I agree with most of this article and glad to see that someone actually posted some of the work to do everyday in CS. They actually also get reports daily about Control System Vulnerabilities from several security agencies monitoring and testing your like said systems. I can’t reveal those Specialist due to the nature of their work. NES, CIPS are great assets to have with very knowledgeable people helping in the background.
Probably the biggest challenge IS/IT have is having the Plant personnel buy in to restrictions you have to put on their Control systems to keep infiltration out. OP’s still wanted to make logs and load them on Flash drives. They wanted an alarm monitor to be a Television in the PM hours, They didn’t like signing in every Shift on all Control Monitors. All of the changes and data was logged on the DCS and recorded on raid drives stored daily on a Terrabyte Station.
I did it for about 7 years before I retired 2 years ago.
You Guys are doing Good work and thank all of you working behind the Scenes to Keep the Bad Guys out..
BobM Central Florida 36 years I/C Controls and System Administration.

Correction:  The IEEE-488 connector on the right in Figure 4 was developed specifically for parallel communications (GPIB), not serial communications.  The DB-25 connector was widely used in telephony era of internet communications with Bell 202 modems.

Very interesting this question about safety at industry.
Edemilso Ilha from Brazil

This is a very good case of the product aligning process in the food industry. If you wanna look into more cost-effective solution, please contact us as well .(JavaScript must be enabled to view this email address)

pip install paho-mqtt gives an error:
At line:1 char:1
+ pip install paho-mqtt
+ ~~~
  + CategoryInfo       : ObjectNotFound: (pip:String) [], CommandNotFoundException
  + FullyQualifiedErrorId : CommandNotFoundException
How do I fix this please? .(JavaScript must be enabled to view this email address)

Antonio Armenta obviously has never used Modbus TCP before. His statement is woefully incorrect. There is no code needed just configuration. For example, configuring the Modbus I/O table I put in the IP address of for example a TeSyS T Ethernet Motor Controller. Then I put the address that the control word comes from and the number of words that need to go to the TeSyS T. Then continuing on to read the items that are available from the TeSys T, You list the address of the table in the TeSyS T and then the address of where it is going. The communication portion is completed for this MCC bucket. You will still need code to turn on the required bits to make the motor run and to gather the desired data from the TeSys.

Motor inrush is a function of motor design not load.  A motor is a transformer and at start-up it is a transformer with a shorted secondary.  In other words, a short circuit; hence high inrush.  The inrush is the same whether the motor is loaded or unloaded, although the duration may be different.  As the inductor sees current flow it magnetizes the stator and becomes a “choke” which limits the current.

Do you connect a device in Modbus with RS485 o TCP only with PLC IDE ? A device like client and a device like master.

nice

Interesting test, thanks for writing this up.  I’m glad this version is not there yet.
This will sound a little tinfoil hat….
First I propose that the commercially available AI products are not the most advanced that exist, especially if people were deliberately training a model for control systems (CISA?)
Second, it is a given that control systems have been attacked as a war like action.
AI is/will be a tool of war, and infinitely more difficult to defend against than the human version of cyber war.

Maybe I missed something obvious here but ChatGPT got EVERYTHING wrong. Code wrong. Explanations are word salad. Yet your conclusion is it’s a great tool for learning??? If you don’t know any better and everything you are taught is wrong, how can that be a great resource?

Note to editor: do your job. This should not have been published with that conclusion,

The reason this occurs is more fundamental. Consider LON. It is a much more modern protocol but not very commonly used. Ethernet and UART (serial) chips are produced very inexpensively in the millions. In contrast LON has vastly less market share so fewer chips and the chips are much more expensive, pricing it out of the market.

Second is one huge gap in industrial protocols are device profiles. When you plug most devices into a PC, the device announced “I’m a keyboard” and thus the PC can set up everything to handle keyboards. Part of this is necessity. Do we need device profiles for a single bit from a push button or for a pilot light? A huge amount of PLC communications is single bit or single analog devices, and that hasn’t changed since PLCs have existed. I would argue though that if we could define that push button in the software and pass that device profile on all the time we spend tagging and commenting would be passed on. Rockwell tried to do this in PlantPAX but you spend a lot of time entering stuff that doesn’t get used. And the issues with HART device profiles are infamous.

So like if or not we end up passing around tables of either bits or analogs, something that gets little if any benefit from device profiles.

Here’s a simple way of looking at it on a DC motor.
Electrically at low frequencies where stray inductance doesn’t count the motor behaves like a capacitor.
It stores energy as angular momentum, not charge but the principle holds. Current accelerates the motor, adding to its momentum.
The motor’s back emf is a function of its rotation speed.
When you first apply voltage you need to “charge up” the motor’s momentum, which takes significant energy.

Great article!

Low level standardization tends to enforce lock in. Truly useful standardization would be brand and platform independent. For example a state machine can be implemented on almost any controller. The differences between brands and tools make standardization a tall order. In a standardized world, conversion to another brand wouldn’t be a major rewrite project. I won’t hold my breath.

I’ve been holding my breath on this topic too long. That’s why I decided to do something about it by publishing the PLC Code & Standard, a field guide for PLC programmers and those who work with them later this year. There are way more benefits to applying a standard than just saving time on your next project and making servicing easier: A standard should lead you to think about how things are done in you controllers and why. For instance the I/O mapping that was talked about should do more than just copying the raw module tag to a named UDT. I/O conditioning involves decisions on treating all I/Os of a given type the same. What signal conditioning is applied, what diagnostics are applied, what alarming. How is the programming done in the best way to make access quicker, depending on what is driving the access - the tag name or the drawing/documentation reference. What sort of standardization do you apply to the tag name itself, and then the descriptor. And all of it needs to be responsive to your plant, your project. Well, if you work in this field you know its needed, but nobody wants to put in the work just to show the competition how it needs to be done, or see it ripped off just like current engineering standards are. I guess that why I had to wait to get near retirement before I put all my notes from the past fourty years of working in this field together in a formal way. If you are interested you should go to plc-control.com and express your interest.

I mean was these concepts utilized by siemens and RA few decades back. I still remember the softlogix RA had achieved this on windows platform with controlnet PCI cards running on industrial PC. Similarly Siemens also had WinAC RTX that ran on windows. Those days Virtualization was catching up. But this is not a new concept and also OEM’s like Honeywell had these few years before in the market in DCS like virtual UOC with full fledged redundancy and all. Seems like vendors need to catch up!

valuable informations, thank you.

“and you may be wondering why we even have different types of sensors and transistors.”
Price was one of the main reasons.  30+ years ago NPN transistors where more common and less expensive.  NPN is grandfathered in. 
It is a PIA trying to explain it to some of the panel builders and still catches me out occasionally.  As humans I think we are hardwired to understand PnP.  It makes a lot more sense to a tech to ground a meter on a 0V terminal and check to see if 24V is present than the other way around,

That’s an impressive increase in readership! 
Very interesting distribution of top topics.  It never ceases to amaze me how much confusion there is over ‘wet’ vs ‘dry’ contacts.

Why complicate a simple subject with rising this or leading that?  An “ on-delay” timer starts the timing function immediately upon energization and then the contacts change state.”Off-delay” contacts change state immediately a stay changed until power is removed and the timing function is complete.  “Off-dela” is seldom used.

“Great article! Troubleshooting and testing single-phase AC motors can be a complex task, but your explanation of the common failure modes and symptoms is really helpful. It’s interesting to learn about the different parts of a single-phase motor and how they work together. Your insights on broken windings, insulation failure, motor overload, and capacitor failure provide valuable information for diagnosing motor issues. Thanks for sharing your expertise!”

Nice book. How can I get the e-copy?

Registered just to say that it was a pleasure to read. Thanks!

I’d like to add two practical details that may be missed by someone like me who’s only occasionally had to deal with pneumatics:

1: The photograph depicts a valve with two actuators, meaning it has a neutral position and two directions. The symbol depicts a valve with one actuator meaning it defaults to an active position. This means that a driven cylinder will actively move to its “base” position if power is lost. Occasionally this may be desirable behaviour in order to drive a system to a safe state if control is lost, but more often it risks causing unexpected motion. It also means that in the event of a pipe break there may be no way to isolate the cylinder unless there is an upstream valve.

When driving anything of significant size it is sensible to assume the need for a two actuator valve, it can be swapped for a sincle actuator type if power-loss behaviour later turns out to be desirable.

2: Many multi-way solenoid operated valves use a smaller solenoid operated valve to drive a cylinder that moves the main valve. I believe this is called “pilot-operated” but Google invariably leads me to Three Mile Island so I struggle to find relevant search results. In pneumatic valves the feeds to the other valves are often hidden, built into the valve body or the manifold, but where a valve is used in an unusual way it may be nessecery to break out these feeds and supply them separately, for example if the system pressure is unsuitable or if a medium other than compressed air is being routed.

In the initial preloaded example the leds would flash, and off USB only, I cannot get the relay or leds to flash with this. But I see in the watch the variables changing what am I doing wrong

Thanks for this wonderful handbook!

Very interesting article!

Delta motor low voltage wiring diagram

Figure 4. Lead connections for low-voltage Delta wiring In this case, can I use a VFD to run this 380 volt motor?

Speed of material as it passes through the planer is astounding.

Solenoids are NOT AC only. DC only solenoids may include a diode to shunt the current generated during field collapse. AC solenoids will not have such a diode built in.

I wish they’d photographed someone using it and included it.  It isn’t clear how it fits your hand or how it works.  The big circle is the pull-ring once the cable is squeezed by the black parts?

“Cutting-blade depth, adjustable in 3 mm increments” ?
That is just under .125”  .01” would make a lot more sense, I think a decimal point is missing.

I’ve been using Raspberry Pis for all sorts of projects with 100% success, some of which have been operating for 3-4 years without my needing to touch them.  At work we have used a couple of Raspberries to solve problems that otherwise would have required a Windows PC.  In a manufacturing process, the last thing you want is a centrally-administered Windows PC which can be rendered useless in the middle of a shift because the Ivory Tower pushes an update (that often breaks something).  Since there is now a dotNet clone for Linux, we don’t need a Windows PC for EVERYTHING anymore.

I enjoyed this article and found it to be very informative and insightful on the different types and application techniques of Ethernet ports, especially the part about the top-down, bottom-up approaches.

Entertaining and give me new insight, thank you

There is no complexity difference between FBD and Ladder. They are both boolean logic.  The only difference is the editor. Schneider Electric is a much better editor as you just double click on the pin and the program Control Expert brings up the list of filtered tags. Double click on the tag and it is assigned. No adding a tag with a connection to the black as in Rockwell’s Control Studio. I figure I can program 80% faster with Schneider’s product than with Rockwell’s.

Great intro.  I look forward to the next in the series.  Thank you.

thank a lot! so clear so easy you did a wonderful works!
hard topics with easiest way

I am getting the decimal value for Figure 2 as 48524. Can you explain the steps you took to get 12733? Thank you

Event-based programming is probably a new term for Programming by Using Interrupts!

It is Colombia, not Columbia… Lost interest as soon as I read how unprofessional the writer was by not getting the name of the country right

I assume the input side is loop powered and that the output side is not an active 4-20mA output and the output needs a loop power supply as well.  Correct?

very informing

Thats the reason, In analog signal cable (4-20 mA) stranded wire is preferred over solid or single strand

very good article

You have put together a very nice series here. I hope you are going to finish this out.  The database is pretty important for me, we are doing a Smart Town with manufacturing and a hybrid power source Hydrogen/Solar so I have to be able to mine the data, to track inefficiencies, usage stats as well as automated manufacturing systems for the project. It’s really friggen cool actually.

I am very impressed with the capabilities of the In-Sight SnAPP Vision Sensors. I believe that these sensors have the potential to be a game-changer for many industries.

For example, I can see how these sensors could be used to improve the safety and efficiency of manufacturing processes. They could also be used to improve the accuracy of medical diagnosis and treatment. Additionally, I believe that these sensors could be used to develop new and innovative products and services.

I am excited to see how the In-Sight SnAPP Vision Sensors are used in the future. I believe that they have the potential to make a positive impact on the world.

This sensor as crucial component medical imaging device project, it will help visualize the human body systems and also helps in diagnosis.

I don’t know how I missed this article until today (day after Halloween).  Super ideas!  My barely runner-up costume this year was a regulatory auditor using a conventional Count Dracula costume. 

I managed to do the “Giant Spark” thing yesterday on a “let’s see if it works on the bench” episode with an electric actuator.  My screwdriver slipped and hit the paper clip on the L1 line terminal screw (powered by the super-safe line cord with a couple alligator clips) and the actuator’s grounded steel housing.  Interesting that an ordinary nickel plated steel paper clip melted, acting as a ‘fuse’, while the 15A circuit breaker feeding the power did not trip.  Learn something every day is my motto.  With a little work I can probably come with an arcing/sparking costume next year, maybe with one of those high capacity lithium car starter batteries.

We renovated an oil rig with a lot of new hydraulic pipes. In one area someone did some grinding work on a steel frame near by without covering up the pipes. This created dozens of tiny holes in the stainless steel pipes.

I enjoyed reading this article and thank you for taking your time to writing. I lack knowledge in this topic but shouldn’t the transfer come before full wave rectifier in switch mode power supply?

Short and precise…great.

Hey

It certainly can get confusing with similar terms but reversed meanings.
On my shop air system I have a solenoid valve that is normally closed until I turn on the shop lights Come in the door, turn on the lights and at the same time OPEN the air valve. At the end of the day I turn off the lights and “CLOSE” the air system valve..
On the shop furnace I have a limit switch that OPENS the thermostat circuit when the overhead door is open thus shutting off the furnace.

Good article. One minor thing I’d point out is that there are many types of transistor that would be capable of producing a fully analog drive waveform. However, the major appeal of switching semiconductors fully on or fully off is that the voltage dropped across the devices is at minimum during conduction and the current through them is negligible when they’re turned off. In both states, therefore, they dissipate the least possible power. In an analog drive mode, there would be a significant combination of voltage across and current through the devices for most of the cycle. Consequently they would be absorbing significant power.

A theoretical analog VFD could produce lovely low-distortion sine output with none of the nasties associated with switchmode operation - but efficiency would be absolutely horrendous.

A constant volts/hertz ratio is crucial to the motor when operating at less than ful speed.  Ergo, the voltage MUST change along with frequency.  The buss voltage remains constant but the apparent voltage changes.

Honestly, I’d rather use Studio 5000 and avoid this platform altogether.

CCW is an absolute disaster.

I will never design another machine using the Micro800 and I will actively persuade my customers to avoid the platform.

The user experience is flat out terrible.

The advantage of placing the transformer after the rectifier/filter is that the resulting DC can be converted to pulsed AC to feed the transformer at a significantly higher frequency than the incoming line voltage. The advantage is that a given amount of power can be magnetically transfered through a much smaller transformer if the operating frequency is increased significantly. That means lower cost, size and weight at a given power level. It seems overly complex to convert AC to DC, then to high-frequency AC, then back to DC, but to put it simply, iron and copper (i.e. the transfomer components) are more expensive than the required electronics.

The micro 850 and 870 are becoming a usefull plc for self contained equipment. They have added remote IO capability with the 850e and 870e. You can develop using the logix format with a changeable option at the top. You can copy paste from and to control logix with the Mico 800 series. While some bugs do still exist in CCW, Rockwell is making improvements. The major weak point is the panelview 800. They should add grouping and pop-up capabilities.

Still a long way to go making CCW a nice program to use, but good to hear they are making updates. Besides fixing the many strange bugs, it would be nice to have some features added like resettable timers (I had to make my own because they were necessary), in/out parameters on UDFBs, the ability to use variables within UDTs in Modbus mapping, etc. Also, as TheSirOwl mentioned, the PanelView portion of CCW could use a large amount of changes and additions.

Hm, interesting timing. I’m just about to release a white paper on PLC tag-naming. Mine is a bit more opinionated and prescriptive - likely due to my advanced age (or different experiences).

Great!!!

Hello eng.munir
I appreciate your support and proficient experince with abb scada system where i have a problem after make switching over between udw1 and udw2 there is error appeared on event control alarms “ udw error in in the inserter “ that cause only the event list table not updated since two weeks “ only event list table” while the other table updated like measurements and accumulator, i appreciated your support to solve this problem .
for contact
My email : .(JavaScript must be enabled to view this email address)

Regards

Nice write-up, Informative

Close but no cigar.  Motors are perfectly happy with the inrush current but the load may not like the acceleration.  Water hammer truly only occurs when the pump is stopped but can be mitigated with the proper soft start.  Most electrical soft starts employ a bypass contactor to allow smaller rated SCRs and reduce cost.  That’s enough for now.

Excellent coverage of using a DVM to test a SSR, with the caveats needed to understand the limitations of a meter’s diode test circuit when dealing with the SSR’s input and output circuits.

Valuable information of FF design, thank you.

Journals on Machine control using AI (machine learning, vision techniques) to do selections of materials and other machine functions

Hello, i have a reed relay, it says the name is in datasheet
SIP-1A05, is the code, Pang Chang the brand. It is installed in a remote control for crane, and aparently, it is excited bay a magnet, which works as a safety key, instead of using the coil (which exists), to close the contact. Have you heard of such a use for a relay? Or have you heard of that reed relay?

It would be better to state that the absolute pressure is equal to the gauge pressure + atmospheric pressure at the site.
There are many industrial plants in eleveted site
There are many industrial facilities at locations elevated above sea level where the atmospheric pressure is significantly less than 101.325 kPaa. The error in all types of calculations involving gases can be serious.

I much prefer the standard method of displaying via ladder style diagrams as shown in NFPA79 etc, rather than overly artistic versions used in the articles.

This article was very present to read and goes into details keeping it very simple for readers to understand.  Finding the correct words when teaching others makes the world of a difference.  Thank you for this amazing article. 
Is there a way to fire a 120V Contactor from Safety Outputs?  Putting 2 Relays in (using 2 contactors) to switch the power for the 120V Contactor doesn’t seem right.  I’ve looked for solutions and would love any feedback!  Thank you! 

Lead much here
Very interesting course

Sorry the word is “learn”

Hi, good write.
I have transducer from electrical panel connected to A0 and not reading any decimals. Must I divide by 5850 too for Opta Finder board?

Great article! Your detailed guide on designing a custom machine alarm system from PLC to HMI is incredibly informative and well-explained. It’s an invaluable resource for engineers looking to enhance their automation systems.

Some important issues which must be signed out:
1. Absolute encoder is doesn’t need Homing procedure.
2. Using Index encoder pulse allows increase Zero point repeatability especially from Too-to-Tool case.
3. Over temperature Alarm is one of maun safety operation one.

Thank you for the explanation. It is very insightful.

Thank you david

It is not uncommon to see 3 way solenoid operated valves, however there are two solenoids one at each end. When driving a cylinder this helps prevent sudden unexpected movement if power is lost, since the valve drops to its neutral position not to an active “return” position. An example of this was an access port on a vacuum chamber. It didn’t need to stop half way, so a two way valve seemed adequate until we considered the possibility of it flying open with vacuum on one side and atmosphere on the other OR flying shut with a manipulator arm passing through.

Also this type of valve is frequently piloted, the solonoids operate smaller pilot valves which then operate the cylinders that move the spool. This is important as the most common configuration I’ve encountered in pneumatics takes the air supply for the pilot valves from the centre port of the spool, which is great for systems switching clean compressed air in a textbook pneumatic cylinder drive configuration but in other usages it is nessecery to route an auxiliary air supply to the pilot valves.
Even in a simple pneumatic application it may be worth separating the pilot air supply and passing it through an extra layer of air preparation.

Thanks!
Very useful Information.

I love this Qa
Thanks to the developers

I would like to know details about the Digital Multimeter.

Here we go!!!

The best explanation ever!

Good article!

Good one!

Fig.-2 has an error with OUT2

Many meters today have a function named LOW-Z voltage. it presents a very low impedance to the circuit and the output will read very near “0” Volts when output is off..

Light weight

Very informative and visionary for future technology

The section under the Fieldbus I/O Mapping heading seems to be cut off. What does the rest of the section say?

This was an excellent article. I particularly appreciate the reminder of backing up your PLC‘s, etc. And I would add to your list replacing back lights on your HMI displays. They slowly get dim and the operators don’t see the images as well as they should.

Interesting article, thank you.

The subscription model works well in my opinion, especially in the current, quickly changing software environment. Nowadays this does not only include the operating system(s) the software was designed for, but also Open Source and other dependencies that are likely part of many software products. Vulnerabilities found in dependencies need to be integrated into the product and pushed out to customers periodically. And given that legislation is on the way (i.e., EU’s cyber security act) that imposes an additional burden on software vendors regarding software development processes and maintenance (rightly so), then offering subscriptions is a sustainable option for the vendor. If the price is fair, then the subscription model is probably the best scenario for customer, vendor, and the longevity of the software product.

Very helpful to understand the safety light curtains, especially the explanation for the restarting interlock, muting and blank functions of the safety light .curtain

Thanks its really great well done

From my point of view,  using latching software commands versus seal-in ladder logic in PLC programming is a broader, logical issue, not just specific to PLCs. This is a common challenge across various applications and industries.

When considering latching and sealing-in, it’s important to focus on the specific requirements of the application. Latching commands set a variable to true when a condition is met and keep it true until another condition resets it. This is similar to assigning a value to a variable. For example, in alarm systems, an alarm needs to stay on until a reset button is pressed. Similarly, in sequential processes on production lines, each step needs to be confirmed before moving to the next. In these cases, latching provides a clear and maintainable way to handle state changes.

Seal-in logic, on the other hand, involves maintaining an output state by branching around input conditions. This is particularly useful for initializing processes, such as turning on motors with a momentary start button and stopping them with a momentary stop button. For instance, motor starters use this method to turn on a motor with a start button and off with a stop button. Safety systems also benefit from seal-in logic to ensure processes stop immediately when a safety condition is violated.

Another approach to consider is the use of masking, which involves using bits to enable or disable certain conditions in the logic. This helps manage complex conditions without altering the core logic. For example, in a safety system, masking can ensure that an emergency stop condition overrides all other commands, maintaining safety irrespective of the machine’s current state.

Understanding the difference between states and events is crucial. States refer to the current condition of a system that persists over time, such as a motor being on or off. Events are changes in the state of the system, such as a liquid in a tank going from a level below a certain threshold to above that threshold. This distinction helps design logic that correctly responds to momentary changes in the condition of a process (events) and the continued condition (state) of the process over time.

In conclusion, the choice between latching and seal-in logic is application-specific. Both methods have their advantages, and the key is to apply them judiciously based on the context and desired behavior of the system. This ensures robust and reliable control logic, addressing the logical challenges inherent in any control system, not just those specific to PLCs.

awesome!

I wasn’t familiar with the term seal-in, though having read a description I understand the concept.

Seal-in suits heavily asymetric conditions, especially those where there are many overriding conditions. The classic case is starting a motor where there are several conditions that indicate the motor must not start, then if none of those apply there might be a start button with a hold contact. While there is a machine state here it is secondary to the purpose of the logic, since the logic could be converted from the latching “press to start” to “hold to run” simply by deleting the hold contact.

Latches suit symetrical situations where the primary purpose of the ladder is to hold state, and the latch is a shorthand to indicate to anyone reading the code that the latch can be in either state during operation. This can be implemented as seal-in logic but doing it as seal-in may hide the fact that a state is being stored, which could complicate code maintenance.

The significant difference is in initialization. During PLC mode transition from stopped to running the “seal in” logic output will be set to the “off” or “de-energized state” at initialization. The “latch/reset” logic version the output will remain in what ever state it was in when the controller was taken out of run mode. This can be very significant from a facility operations perspective! This can be dealt with by programming an initialization routine to take controlled variable to a known state at the transition from stopped to run.

An important distinction between the 2 methods in regards to potential safety problems:  Most PLC Latch/Unlatch (Set/Reset) instructions are retentive, meaning if an output was energized when a power failure occurs, then when power is restored, the PLC will put that output back in an energized state.  The seal-in method will not.  It all depends if you want the operation to resume after a power cycle with no human interaction.

When testing SSR outputs, I always try to use a voltage test in circuit. The SSRs I need to test are typically in a machine already and triggering the input side is usually easy enough to do. Besides avoiding misleading results with a diode or resistance test, the voltage can tell you if too much voltage is getting through the contacts when they are supposed to be turned off, causing leaking voltage problems.

This article starts out by listing the 5 languages in IEC 61131-3, but it only uses one: LD (ladder diagram). There is no ST (structured text) used. There is use of an Arduino extension and C++, but that’s not ST as defined by the IEC standard.

Hello All, In foundation filedbus setup, how to resolve F809 Plus’s Segment Monitor’s DITB Block device need maintenance soon error. Any advice is greatly appreciated.

This article would make an excellent ‘Part 2’ of a series, but as it stands, it does not teach How To Read Ladder Logic. It does a good job of pointing out some of the pitfalls that could be encountered and some of the techniques that can be used to handle them.

Please do a part 2 of this. This was very informative.

That article addresses my interest to see the implementation issue in RTD sensors thank you,

This article is very valuable. In addition to the robot, the controller also has batteries that need to be replaced I remember “inheriting” a lab of four Fanuc LR and M robots.  Two years of no maintenance the 1.5v x 4 C batteries at the base of the robot and the 3.6v battery (in the controller that keeps the SRAM) all dead.  Had to remaster everything.  Fun times.

Slightly surprised I didn’t see any mention of using ferrules as an (industry standard) alternative to tinning stranded wire for use in spring and screw terminal applications.

Moving away from ladder logic is a big mistake. Keeping machine downtime to a minimum is a facility’s number one priority behind safety. Troubleshooting a system outage is done more easily (and much quicker), using ladder logic. Think hard, before you discount my words.

The manufacturing machines we are designing are using Beckhoff’s xPlanar technologies. No belts or rollers, very cool!

Had this experience recently with a single phase motor + external starting capacitor setup.  Ended up using a Single Phase -> Single Phase VFD and swapping U and V (swapping run and start windings).

hımmm, thanks

Very interesting.  I was asked (at a job interview) “What is the voltage across an open switch?” My answer was that it was impossible to answer that question.  Seeing the puzzled look of the interview panel (or wanting to disqualify me immediately) I explained without knowing the voltage “source” one cannot indicate the voltage across an open switch.  If the circuit was North American domestic light it would be approximately 110V.  And that I can easily answer the question of what is the voltage across a closed switch ...nearly zero volts.  Another time, I disqualified myself from a research proposal when the author indicated the voltage at a certain point (e.g. A) , omitting a reference.  As this article emphasizes, voltage is always across two points.

  Really interesting article

will be fine if you embedded the article by GIF or even small tutorial video

For figure 2a (left), aside from the lower output box also labelled out1, when it should be out2, it is necessary to explain why the ladder diagram rung2 requires both out1 and in2 to both be active in order to activate out2. It is necessary to indicate whether or not this is standard SFC behaviour, because there are questions about whether or not out2 depends only on in2 being active.

Also, based on the form of rung2 of Figure 2b (right), why does ‘END’ lie on the line by itself? Why doesn’t if follow the same form of rung2, with dependence on out1 and in3?

Also, based on the form of rung2 of Figure 2b (right), why does ‘END’ lie on the line by itself? Why doesn’t it follow the same form of rung2, with dependence on out1 and in3?

[Correction] - Also, based on the form of rung2 of Figure 2b (right), why does ‘END’ lie on the line by itself? Why doesn’t it follow the same form of rung2, with dependence on out2 and in3?

Best have pdf

Nice text book

Thanks for the great info, great article.

Valuable information

Thank you for all the time and effort of article’s you have written sir they are great in explaining the subject and help newbies like me. I love reading your articles.

The air piloted configuration appears relatively common, and it isn’t unusual to see directional control valves with built in piloting using air from the central input port.
Also when choosing between a single or double solenoid valve to control a pneumatic cylinder remember that in the event of loss of power the double solenoid valve will drop to a “neutral” position, whereas a single solenoid valve will dump the remaining air supply into the cylinder causing it to retract immediately.

I clearly understand now the evolution of digital technology and its impact on automating and communicating different process variables.

Thanks a lot for such an informative article!

Great introductory article for this topic, though I think the equation is missing a set of parenthesis:

Availability = MTBF / (MTBF + MTTR)

I haven’t really looked at any of this stuff before, and the equation threw me for a second.

Thanks,

Donnie

As a student programmer fascinated by warehouse technologies, I found this article very insightful. The explanation of WMS functions like inbound delivery, storage optimization, and inventory control highlights how crucial these systems are for modern logistics. It’s amazing how much efficiency and accuracy they bring to operations.

As a student programmer fascinated by warehouse technologies, I found this article very insightful. The explanation of WMS functions like inbound delivery, storage optimization, and inventory control highlights how crucial these systems are for modern logistics. It’s amazing how much efficiency and accuracy they bring to operations.

really good graphics, great explanations.  Great graphic on the multiple metals used to connect a thermocouple to an electronic amplifier through a series of dissimilar-material junctions.

Very good information

I like the illustrations with conducting components marked in red color. Makes it easy to comprehend. It would be nice to continue this with typical examples of application of the various breaking concepts.

Your post is interested. It is good for education and training

Great, BTW arduino opta more capable

great

𝕯𝖗. 𝖂𝖎𝖑𝖈𝖍𝖊𝖗’𝖘 𝖆𝖗𝖙𝖎𝖈𝖑𝖊 𝖔𝖋𝖋𝖊𝖗𝖘 𝖆 𝖈𝖑𝖊𝖆𝖗 𝖆𝖓𝖉 𝖎𝖓𝖋𝖔𝖗𝖒𝖆𝖙𝖎𝖛𝖊 𝖌𝖚𝖎𝖉𝖊 on using the Arduino Opta with OpenPLC for DC motor control. The step-by-step instructions and wiring diagrams make it easy to follow. Definitely a great way to explore the capabilities of the Opta!

Your short summaries mix conventional and electron flow and are wrong.

A sourcing module has + connected to its common and supplies conventional current from the I/O terminals out to the field devices.

A sinking module has - connected to its common and receives conventional current from the field devices back to the I/O terminals.

To avoid confusion I find it best to stick exclusively to conventional current flow.

Very helpful article…

In many Hydraulic installations, where shock loading and unloading occur, the surges in pressure can be absorbed by the installation of a bladder accumulator. This device simply absorbs the shock spikes and prevents all the damage as stated in the article. Another point of interest is where there are fluctuating pressures in the system, the pressure gauges downside of the tank should be fitted with “Snubbers” , devices that prevent the gauge from oscillating by provision of an orifice to limit surges . Just a thought.

For any system designer/implementer, it would be very shortsighted to install ANY equipment that does not provide full redundancy in communications . Cables in the field are often damaged and normal, well designed systems keep the plant running.

Very well written article, thank you.

VERY POWERFUL $ KNOWLEDGEABLE

Im working in a hydro power plant and am interested in these motor circuit diagrams. How do i download them please if you can assist. Patrick Yogaro

Helpful info. Thanks alot

You didn’t mention an integration into the overall system. I can imagine, that with Arduino this would be practically impossible, whether PLC would offer wide range of communication connections without hassling with precise timing issues.

I used Arduino type boards with grbl software and off the shelf stepper controllers for a very cost effective door frame drilling setup. You can program it in standard G code which many people know and can handle curves, interpolation, etc.
By the way, I’m still here.

I am glad I discovered this site!

This looks like a huge step forward for manufacturing. Real-time insights and easy integration sound like exactly what’s needed to cut down on downtime and improve efficiency. Excited to see how Smart Factory solutions like this change the industry!

Great overview! Machine vision is becoming more and more essential for improving production efficiency and quality control. Thanks for sharing this guide!

The AI Startup Challenge 2024 winners, T-Robotics and Mbodi, have been selected for their innovative AI-based solutions in industrial robotics. With a focus on simplifying operations and enhancing performance, they will receive $30,000 in funding and access to ABB’s startup accelerator, SynerLeap. The winning solutions are expected to leverage generative AI to improve industrial processes, enabling robots to adapt more flexibly to real-world environments.

buen documento

It must be noted that each H-bridge switch has a freewheeling diode for the possibility of current flow when the switch is off.

There is an error in Figure 1. The VPN Server should be between the Internet Provider and the Target device, otherwise the Target device would be transmitting unencrypted data across the Internet.

If you actually have a remote VPN Server (not a great idea) you should have another VPN Client in front of the Target device.

This is the kind of article that is very useful.
Screen shots are very helpful.
Examples in setting up the safety communication could be helpful as well.
Personally I always seem to have a bit of a fight getting it to work.  Some devices have very specific settings that need to be followed with Safety I/O
I do not do a lot of Fanuc but am saving this incase it comes up.
More like this please.

I now clearly understand the evolution of digital technology and its impact on data transfers and resolving communication bottleneck easing devices communications .

Manufacturing Execution System (MES) software plays a vital role in modern manufacturing by bridging the gap between enterprise resource planning (ERP) and the production floor. Popular MES platforms like Siemens Opcenter, GE Digital’s Proficy, and Rockwell Automation’s FactoryTalk offer real-time monitoring, production scheduling, quality management, and performance analysis. These tools help manufacturers streamline operations, reduce downtime, and improve product quality. By integrating data from machines, operators, and systems, MES software enhances visibility and decision-making across the production cycle.
For businesses seeking scalable and efficient MES solutions, INS3 offers innovative tools tailored to the dynamic needs of the manufacturing industry.

I think there’s no 100mm air gap for this kind of product, must be 10mm

Thank you, that helped me a lot

This section is interesting because of the option of tubing for certain applications. Of course, if pressure is not too high you could use a simple push to connect option rather the presented nuts and ferrule option.

Thanks. This is an insteresting set of questions.

Looking forward to it.

This is educative

Interested in references for the revision of my process control textbook.

I am interested in references for the revision of my process control textbook.

Fascinating glimpse into the roots of industrial automation! The invention of the Modicon 084 PLC in the late 1960s truly revolutionized manufacturing by replacing banks of relays with programmable digital logic—thanks to pioneers like Dick Morley and Odo Struger. It’s inspiring how passion and innovation continue to drive systems integrators like INS3 today.

No download Link.

Great breakdown of where PACs and PLCs each make sense. I’ve noticed in some projects the lines are getting blurred, especially when controllers are expected to handle IoT connectivity along with classic control tasks. For example, platforms like norvi.lk show how compact controllers can combine PLC-style reliability with modern IoT features, which makes the PAC vs. PLC decision even more interesting in practice.

Does it need a calibration after an emergency stop button is pressed or a power loss?

The first sentence in your article is inaccurate:
“Two main differences will drive the focus of this article. In both rotary and linear motion, hydraulics uses valves instead of waveforms to spin motors.”
For linear motion almost all hydraulic systems use hydraulic cylinders. These have no motor in them. The system has a motor that provides hydraulic pressure/flow, but the actuators themselves do not have an internal motor unlike electric actuators.

Its important to review basic once after some years while this reminded me of my collage days when all this information weighed on us like we will never understand.

can you provide the plc software

all companys

GoPay menghubungi WhatsApp, 0853.5353.1650 resmi,untuk Batanun gopay promosi dan informasi

Nice!

wow, this seems to be very interesting. Let’s see how well or bad this evolve and how it is “received” in the field.

thanks for your help

I am an electrical engineer I have more than 15 years experience and skills.I need to see apartical plc

One thing I want to add although it is off the topic but still related to controls systems which utilities AC power sources.
DON’T CONNECT TOGETHER THE COMMONS OF DIFFERENT SOURCES.
WHY?

Fun write up!! To ground, or Not to ground is the question.
I have worked in a multitude of jobs across multiple industries.
My Answer: Single point ground to earth! Other grounds never should go to other grounds

The circuit in figure 1 will never work. There must be a common reference potential.

The right choice really depends on your system layout. Could you share more details about your setup?

There are optical sensors like the T-Sense from VAF.

+++!

Good content and much information.thanks for good content posting

Excellent… “data without context is virtually worthless”

Based on my assessment, Banner’s wireless vibration sensors do not seem suitable for GT Compartment Bearing-2 monitoring. The compartment temperature is very high, and the sensor’s battery is not designed to handle continuous heat exposure. This can lead to fast battery degradation, incorrect vibration readings, or complete sensor failure.

Could you please confirm the maximum operating temperature for this Banner wireless vibration sensor model? This will help determine whether it can safely function inside the GT compartment.

Any update on when this worksheet will be available for download ?

Informative article

Terminology evolves, and HMI has become common in industrial and academic circles—but in day-to-day product work, we’re still designing GUIs. The label matters far less than execution.

In embedded systems, success comes down to clarity, usability, and performance under real constraints. A well-designed interface—whether you call it GUI or HMI—is what enables operators, engineers, and users to work efficiently and safely. Strong design thinking outweighs terminology every time.

What measurement principle is it based on? What is the wavelength of the laser?

Thanks for sharing this! I tried the Weidmuller Configurator recently — it really helped finalize my bill of materials faster than manual selection.

Very helpful topics for everybody .

I have been using AD PLC’s to control facilities on my ranch now since 2018. I started using them in 1981 when I worked with Modicon 484’s and 584’s at Southwire and then worked with them at paper mills for a few more years and passing the PE before switching to embedded controller board and firmware design and spent the next 35 yrs working on that at companies like AMD, IBM, ARM, and Dell. Semi-retired now, I have gone back to using PLC’s as I don’t want RPi’s and custom boards that no else will be able to work on.
Compared to the old Modicons, they are so much nicer to work on. But understanding old Modicons is like understanding the primal DNA of all PLC’s. After all Modicon invented Modbus.
One of my flagship designs uses an Ethernet Analog PLC (and because of that I standardized on that higher end model so I would only have to keep one spare. it is for my septic system controller which also uses one of AD’s GH1 VFD’s to control operation of the 3ph pump. A 3 ph pump is much more reliable that a single phase and the built in soft start/stop adds to the mechanical life by removing water hammer. It uses an analog level rod instead of float switches so you can always see what the level is right from this very PC I’m typing on this very moment at my desk. This is wonderful for mitigating problems in the middle of the night or when we get a polar vortex from Canada that drops the temp tp 18F (I’m in S Texas so that’s horrible cold to us 😉 )

“When signal routing is thoughtful, the entire cell feels predictable. When it’s not, the cabinet becomes a scavenger hunt every time something goes wrong.” Over forty years in the field, and this very true. cj

I need notes on this instrument.

The standard gantry has two axes only, which are defined as Master and Slave .

Excellent Book . Very clear explaination of Voltage , Current , and Resistance and Ohms Law.

Excellent Presentation of Voltage , Current , Resistance and Ohms Law

We want to implement cybersecurity in IoT

Cara mendapatkan akes nya

Cara minta Keringanan Pembayaran SPinjam Shopee: Hal Pertama bisa menghubungi Tim Shopee Langsung Via Chat 085624222474. Atau 08567629772. Proses pengajuan pendaftaran memerlukan kesulitan keuangan yang nyata, seperti hutang berbunga tinggi atau penurunan pendapatan. hingga satu bulan berikutnya tanpa terkena pinalti tambahan.

The PDF link is broken

Hello,
The link you posted to “ABB’s capacitor reforming instructions.”
https://library.e.abb.com/public/1c0f84b7c70f4bd78d86a7c0e2ef2b8e/Capacitor_reforming_instructions.pdf

When trying to access the resource, you get an xml page which reads, in part:
“<Error>
NoSuchKey
<Message>The specified key does not exist.</Message>...”

I know keeping up with bad links is a Sisyphean task, but it’s only been four days since you posted, so I think it was wrong from the beginning.

Please consider fixing this,
Thanks!

Good illustration

This is a fascinating topic. Having worked as both a PLC programmer, a JavaScript programmer, and a DevOps engineer, I’ve seen firsthand how slowly industrial automation evolves compared to the breakneck speed of the software and IT world.

However,  we can solve the ‘single point of failure’ issue common in traditional hardware. By containerizing vPLCs and deploying them across a Kubernetes (K8s) cluster, we can achieve true High Availability (HA) at the edge.

In this architecture, if one physical node fails, the orchestrator automatically redistributes the workload. This moves us away from expensive, proprietary redundancy modules and toward a more flexible, software-defined industrial stack.

Nice article. I would add that that’s why many contactors comply with the mirror contact function, when both NO-NC contacts are open, is (certified) sign that at least one contact is likely welded. Very usefull to chenck in evry opening and trigger safety if isolation is at risk.

I share the same general idea, but I would emphasize one additional point:
the HMI should not only serve as an interface between the human operator and the PLC,
but also as a controlled interface for an external “software operator”.

The traditional rule that the PLC must keep the process running safely without relying on the HMI is absolutely correct.
The HMI should be limited to parameter input, visualization, operator interaction, and status indication.
The PLC should remain deterministic, simple enough to verify, and responsible for all basic real-time and safety-related control functions.

However, in complex production systems, the effective control loop is often not just PLC + HMI,
but PLC + HMI + operator. The operator observes the process, reacts to deviations, compensates for process uncertainty,
and adjusts parameters based on experience. In many cases, this improves product quality,
but it also introduces human error, fatigue, and unpredictable reaction times.

Some of these operator functions can be partially automated by an external software module.
This module may use a process model, optimization algorithms, statistical analysis, machine learning,
or other methods that are difficult or impractical to implement directly in the PLC.
It should not replace the PLC or become part of the critical real-time control layer.
Instead, it should interact with the machine through a clearly defined HMI/API layer.

In this architecture, the HMI becomes not only a visualization and command interface,
but also an arbitration layer between the human operator, the PLC, and the external “software operator”.
It should clearly show who is currently controlling the process, which mode is active,
and whether the external algorithm is only providing recommendations or actively applying corrections.

The most important requirement is safe and transparent handover.
The operator must be able to take control back at any time,
and switching between manual, automatic,
and software-assisted modes should not cause sudden jumps in process parameters or unexpected machine behavior.

This approach keeps the PLC reliable and deterministic, keeps the HMI stable and understandable,
and allows advanced operator-assistance algorithms to evolve faster without compromising the basic safety and reliability of the machine.

In other words, the HMI should not be treated only as a screen for the PLC.
It should also provide a controlled and transparent interface for software modules
that take over part of the operator’s role in complex but non-hard-real-time tasks.
This is especially useful where a simple PID loop is not sufficient, while implementing the whole logic directly in the PLC would make development,
testing, and future improvements unnecessarily slow and difficult.

I need wastup number thanks

Cant find the pdf.

I believe this solution would be particularly valuable when evaluating units or equipment for replacement and modernization projects. AspenTech Inmation Data Platform can help consolidate historical and real-time data, providing comprehensive reports on the condition and performance of a unit before making investment decisions.
However, I have one question: how can the Temperature Monitor be installed on steam lines, especially when the pipes are insulated, such as those found in steam boilers or industrial furnaces?
I think this technology would be especially effective for testing heat exchangers or monitoring temperatures during the different stages of air compression in large centrifugal air compressors, where continuous temperature monitoring can provide valuable insights into equipment performance and reliability.

Servo systems are one of those technologies that seem simple on the surface—just a motor with feedback—but that feedback fundamentally changes what the system can do. The ability to continuously compare commanded motion with actual motion is what enables the precision, repeatability, and dynamic performance required in robotics, CNC machinery, and advanced automation. Without feedback, you’re essentially hoping the motor reached its target; with a servo, you know whether it did and can correct errors in real time.
_____________
Alexandra
RDC Control