PLC vs. Microcontrollers

B

Basharat Ahmad

PLCs are (already designed hardware) more robust, adopted by the industries on large scale internationally, therefore PLC,s are mainly used for the logic control and process automation.

microcontroller circuits require extra hardware, like transistors and relays to be soldered with, to convert it into the fully working PLC as I have done with one 8 bit microcontroller.
 
Hi,

> PLCs are (already designed hardware) more robust, adopted by the industries on large scale internationally,
> therefore PLC,s are mainly used for the logic control and process automation.

> microcontroller circuits require extra hardware, like transistors and relays to be soldered with, to convert it into the
> fully working PLC as I have done with one 8 bit microcontroller.

I have a FYP on smart road traffic light and i am confused whether i use PIC or PLC in my hardware could i have an advice from you.

thanx
 
V

Vladimir E. Zyubin

> I have a FYP on smart road traffic light and i am confused whether i use
> PIC or PLC in my hardware could i have an advice from you.

It seems to me your solution name is "Arduino"... -40 +80 C, friendly C-like programming environment, convenient hardware interface to integrate, and very cheap -- about $10-15.

Best,
Vladimir
 
It really comes down to where you want to spend money. If you're experienced with PIC programming and can design and build the I/O interface without too much trouble, that will likely be the cheaper route. If you're in a hurry, have the money, and know how to work with them, a PLC will be faster to develop and implement, and may be easier to market if you're trying to go that direction.
 
K

Ken Emmons Jr.

I second that motion... Arduino's are the hot ticket right now. The cool thing about the Arduino is that you buy one for cheap money and hook up a USB cable, install the programming package, and you are starting to program in C/C++ like environment with already written libraries for IO and commonly used devices.

I wish there were a 32 bit ARM microcontroller platform that was as easy to use as the arduino, but so far there haven't been any that have emerged that seem very strong (Please correct me if I'm wrong, I'd love to know of such a thing!). That with an RTOS, industrial 24V IO, and optional LCD would be a very, very cool little device for simple to intermediate control needs.

Ken
 
W

William Sturm

Ken Emmons Jr. said  >  (I wish there were a 32 bit ARM microcontroller platform that was as easy to use as the arduino, but so far there haven't been
> any that have emerged that seem very strong (Please correct me if I'm wrong, I'd love to know of such a thing!).)

Have you seen either of these?

http://www.digilentinc.com/Products/Catalog.cfm?NavPath=2,892&Cat=18
or
http://leaflabs.com/

I haven't used either one yet, but for the price it wouldn't be too difficult to give one a try...

I think the Arduino folks are working on a 32 bit design also...

 Bill Sturm
 
Hi Bill,

These both look interesting. I'll have to bookmark these and check them out when I get out of work. I noticed at least one with an Ethernet offering which was interesting. If they have a TCP/IP driver stack that would enable a lot of applications.

Thanks,
Ken
 
V

Vladimir E. Zyubin

> I wish there were a 32 bit ARM microcontroller platform that was as
> easy to use as the arduino

Google "Maple". Or "Iteadmaple". Cortex M3 based Arduino-like platform. A bit problematic programming tools comparing to "pure" Arduino on ATmega, but 70 MHz and the ARM architecture with the same price...
 
V

Vladimir E. Zyubin

> If they have a TCP/IP driver stack that would enable a lot of applications.

There are Arduino-compatible mezzanines with TCP/IP for Ethernet and WiFi.
 
but microcontroller have such speed that those top to bottom line execution doesn't matter and there is option of interrupt, so can this advantage override plc?
 
C

Curt Wuollet

It might, but you have to remember that a PLC _is_ a microcontroller, with an executive and hardware that deals with many of the imperfections of the real world, like contact bounce, horrendous lead dress, noise and general cruft. This makes it much more stable, easier to apply and bulletproof. It also has a simple and well known programming paradigm, protection against ESD and modest electrical overstress and carelessness. One of my few accomplishments has been to design circuits to add these to microcontroller and PC card I/O. To make use of speeds greater than kHz requires _much_ greater care in wiring, even to the point of using transmission line techniques, differential signaling, impedance matching, etc. The heavy filtering and controlled rise and fall times that make PLC slower serve the purpose of working with long wires and high noise levels. But, provided you have a much more controlled environment and you attend to the details, a microcontroller can go way beyond what you can do with a PLC. In a big box with a couple VFDs, a motor starter or two, many feet of square dressed wiring and very questionable grounding, you would probably wish you had used the PLC.

Regards
cww
 
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