Hello everyone,


I am an electrical/automation student, and I am currently learning PLC programming and HMI design. I have some experience with small school projects, such as controlling motors, sensors, basic automation sequences, alarms, and simple HMI screens.


However, I realize that school projects are quite different from real industrial systems. I want to improve my practical thinking and understand how PLC programs are designed in real factories.


So I would like to ask the engineers here:


Could you share some real industrial PLC/HMI problems or project scenarios that you have worked on?


For example:

• Machine control sequences
• Conveyor systems
• Pump or motor control systems
• Alarm handling
• Interlocks and safety logic
• Auto/manual operation
• HMI screen structure
• Troubleshooting cases
• Communication between PLC, HMI, VFD, sensors, or other devices

I am not asking for confidential company programs or private documents. I just want to learn from realistic examples and practice solving problems like an automation engineer.


Any advice, sample requirements, or real-world scenarios would be very helpful for me.


Thank you very much.

 

Here's a practical problem for you! Nothing too crazy, but it's a PLC program you will likely write a million times lol

Application: "Lift Station Monitoring and Control"

A lift station has two pumps, a radar level sensor, and two backup floats.

When the level in the wet well reaches 8 feet, a pump needs to turn on to drain the well to 4 feet.

Each time a pump is called to run, they alternate which comes on. The first time, Pump A is called. The second time, Pump B is called....

However, neither pump is allowed to run for more than 2 hours at a time, and if the level of the wet well exceeds 9 feet, both pumps must run to avoid flooding.

Lastly, if the radar level transmitter goes out or stops working, this control scheme MUST still operate as normal.

....

Write a PLC program for this application. Typically called "Lead Lag", "Pump Alternation", or "Duplex Pump Control".


EXTRA CREDIT:

Add a third pump (triplex pump control)

 

Hello everyone,


I am an electrical/automation student, and I am currently learning PLC programming and HMI design. I have some experience with small school projects, such as controlling motors, sensors, basic automation sequences, alarms, and simple HMI screens.


However, I realize that school projects are quite different from real industrial systems. I want to improve my practical thinking and understand how PLC programs are designed in real factories.


So I would like to ask the engineers here:


Could you share some real industrial PLC/HMI problems or project scenarios that you have worked on?


For example:

• Machine control sequences
• Conveyor systems
• Pump or motor control systems
• Alarm handling
• Interlocks and safety logic
• Auto/manual operation
• HMI screen structure
• Troubleshooting cases
• Communication between PLC, HMI, VFD, sensors, or other devices

I am not asking for confidential company programs or private documents. I just want to learn from realistic examples and practice solving problems like an automation engineer.


Any advice, sample requirements, or real-world scenarios would be very helpful for me.


Thank you very much.

A good practice project is a conveyor line with multiple sensors, barcode verification, and reject stations. Include start up sequencing, emergency stop recovery, alarm history, manual and auto modes, and VFD communication. Then intentionally create sensor failures or communication timeouts and practice troubleshooting systematically instead of only making the system run.


Moderators note : removed inserted link in quote

 

See this description for operation of float switches:

https://tripledpump.com/the-difference-between-normally-open-and-normally-closed-float-switches/

 

I think you can implement a Automatic conveyor sorting system https://www.researchgate.net/public...NTATION_OF_PLC_BASED_AUTOMATIC_SORTING_SYSTEM

 

Hey namdinh541,

It’s awesome to see a student proactive enough to look beyond textbook code. School projects usually assume everything works 100% of the time, but real-world industrial automation is mostly about handling what happens when things go wrong.

Since The Instrument Guy gave you a solid duplex pump challenge, here is a real-world conveyor/packaging line scenario that covers the exact Auto/Manual, Interlock, and Fault logic you’ll run into every day on the factory floor:

Project Scenario: 3-Stage Conveyor Line with Bottle Jam Detection
1. Operational Requirements:

• Conveyor Sequence: You have 3 conveyors in series (C1 -> C2 -> C3). To prevent product pile-ups, they must start in reverse order (C3 first, then C2, then C1) with a 3-second delay between each. They must stop in forward order (C1 first, then C2, then C3) so the belts clear themselves out.
• Auto / Manual Control:
  • In Auto Mode, the sequence runs automatically via START/STOP buttons on the HMI.
  • In Manual Mode, an operator can jog each conveyor individually, but only if safety interlocks are clear.
• Bottle Jam Fault (Timer Logic): A photo-eye sensor (PE1) sits over Conveyor 2. If bottles are moving normally, PE1 toggles ON and OFF continuously. If PE1 stays ON for more than 4 seconds continuously, it means there's a bottle jam.
  • Action: Instantly stop C1 and C2, raise a "CONVEYOR 2 JAM" alarm on the HMI, and sound a horn. C3 keeps running for 5 seconds to clear remaining bottles down the line.
• VFD Speed Matching & Modbus/EtherNetIP Monitoring:
  • Conveyors run on VFDs. If Conveyor 2 speed drops below 80% of target setpoint (read via communication status word), fault the line and lock out Auto mode.

What to Build on Your HMI:

1. Main Status Screen: Live status (Green = Running, Red = Faulted, Yellow = Manual) for each conveyor, line speed indicator, and mode selector switch.
2. Alarm Summary Screen: Active alarms with ACK (Acknowledge) and RESET functionality. Require the operator to press ACK first, fix the jam, and then press RESET before the line can restart.
3. Manual Control Screen: Jog buttons with explicit visual warnings that safety interlocks are active.

A Few Golden Rules for Practice:

• Never use latches (SET/RESET) for physical outputs if you can avoid it. Use seal-in logic so if power or communication drops, outputs fail safe (OFF).
• Separate your logic: Keep your Physical Inputs/Outputs mapped to internal tags first, put your Interlocks/Faults in another routine, and write your Main Sequence separately.

Give this a shot in your simulator or CAD software! Once you get the jam detection and start/stop delays working cleanly, try breaking a sensor signal in forced mode and see if your logic catches it safely.