PLC exercises with solutions
Practice problems of the kind used in PLC courses and job interviews, each solved from start to finish: the task, the inputs and outputs, how to think it through, the complete ladder program, common mistakes and a video. Every solution opens in the free online simulator, so you can run it, break it and change it.
Beginner · timers, set / resetPedestrian crossing: a chain of on-delay timersA push button, a three-colour car signal and a walk signal: the classic exercise for learning how a chain of on-delay timers turns one button press into a timed sequence. Fully solved, in four PLC families.Beginner · set / reset, edges, interlockDrawbridge control with one button on each sideA drawbridge over a river and only two push buttons, one on each bank. The press on your side closes the bridge, the press on the far side opens it again, and it must work in both directions. The trick is to make the PLC remember who is crossing.Intermediate · one-shot, toggle bit, seal-inAlternating pump control (duty / standby)Two pumps empty a tank, and each time the high level switch triggers they take turns: A, B, A, B. A short exercise that teaches three building blocks at once: the one-shot, the toggle bit and the seal-in.Fault finding · edge logic, short-cycling, alarmsFault finding: the stuck Lead floatA duplex sump has Stop, Lead and Lag floats. The Lead float arm gets stuck in the closed position. What does edge-triggered alternating logic do on the next fill cycle? Predict it, prove it in the simulator, and fix it.
How to use these exercises
- Read the task and the I/O list, then stop and try it yourself in the Playground. Load the blank example to start with just a power supply and a PLC.
- Compare with the worked solution: the reasoning matters more than the exact rungs. There is usually more than one correct program.
- Open the finished solution in the simulator, press RUN, and try the variations at the end of each exercise.
New to ladder logic? Start with ladder logic basics and the free guided course, then come back here.