Motor Start/Stop & Fault Monitoring

Briefing

Build the command and diagnostic logic for a three-wire motor starter. A momentary START must latch the run command; STOP, E-stop status, and thermal-overload status must drop it. Fault indications stay latched until the cause is clear and the operator acknowledges with STOP. A 500 ms command/feedback mismatch check detects an auxiliary contact that remains on after the contactor command turns off. This is a training simulation of standard PLC logic, not a design for a safety-rated emergency-stop circuit.

Objectives

• Start button pulse energises the contactor and the motor seals in
• Stop button drops the contactor
• E-stop drops the contactor and latches a fault until reset
• Thermal overload drops the contactor and latches a fault until reset
• Auxiliary feedback remaining on while the contactor command is off latches a fault after 500 ms
• A reset acknowledges a cleared fault but never restarts the motor by itself

I/O Table

Your program will be tested against:

All test cases run automatically when you submit. Assertions are hidden until you pass.

1. #1Start energises contactor, stop drops it

   Press start -> contactor on; press stop -> contactor off

2. #2Start pulse seals in via latch

   Momentary start-pulse — contactor stays on after button release

3. #3E-stop latches fault, clears only via stop-pb

   E-stop drops contactor + raises fault; releasing E-stop does not clear; stop-pb clears

4. #4Thermal overload latches fault, needs reset + stop-pb to clear

   Thermal trip drops contactor + fault; clears only after thermal resets AND stop-pb pressed

5. #5Stuck auxiliary feedback latches fault

   MOTOR_AUX asserted while MOTOR_CONTACTOR is off for >500ms -> fault