Motor Start/Stop

Briefing

Classic 3-wire motor start-stop with seal-in, emergency stop, and thermal overload protection. The contactor must latch on a momentary start-button press, drop out on stop, and latch a fault on E-stop or thermal trip. Faults may only be cleared by an explicit stop-button press once the underlying condition has gone away. You also need to detect a welded contactor via the auxiliary feedback contact.

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 stuck-on while the contactor is de-energised latches a fault

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