PLC Trainer

How to use this

Read a lesson, then open the Lab and load the matching example. Every lesson has a What, a Why and a How. When a lesson clicks, try its Challenge: the trainer runs your program against a test and tells you exactly where it went wrong.

// declarations (field devices)
input Start pushbutton        // momentary, normally open
input Stop pushbutton nc      // normally closed: reads 1 until pressed
input Auto switch             // stays where you put it
analog Battery 0 100 75 %     // slider: min max start unit

// rungs:  condition -> action[, action]
(Start | Motor) & Stop -> Motor     // | is OR (parallel), & is AND (series)
!Auto -> ManualLamp                 // ! is a normally-closed contact (XIO)
Battery < 50 -> SET Charger          // compare: < <= > >= == !=
Battery >= 90 -> RST Charger         // SET/RST = latch / unlatch
Start -> TON T1 3s                  // on-delay timer: T1.DN, T1.TT, T1.ACC
Run -> TOF T2 500ms                 // off-delay timer
Box -> CTU C1 5                     // counter: C1.DN, C1.ACC
Reset -> RES C1                     // reset a timer or counter
true -> AlwaysOn

Ladder view (green = power flowing, live while running)

Challenges

Pick one, read the job, edit the program, then press Check my program. You can also Open in Lab to play with it by hand.

Ohm's law and 4–20 mA

4–20 mA signal

UART frame

Type a character to see how it's sent on the wire (8N1: start bit, 8 data bits least-significant first, stop bit).

Modbus RTU request builder

Builds the exact bytes a client sends, including the CRC-16 checksum.

Modbus register decoder

Turn raw register values (as a driver or gateway shows them) into the real number, trying each data type and word order.

Quiz

Pick an answer to see why. Your best score is remembered on this computer.

Glossary