PLC Simulator
Pro
7 min

CCST 02 — Seal-In (Latching) Circuit

ccstladderseal-inmotorlatch
CCST 02 — Seal-In (Latching) Circuit scenario preview

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Briefing

Classic 3-wire motor control: momentary START_PB energises MOTOR_CONTACTOR, which seals in via its own contact. Momentary STOP_PB drops it.

Objectives

  • Latch MOTOR_CONTACTOR on momentary START_PB
  • Seal-in with MOTOR_CONTACTOR parallel branch
  • Drop on STOP_PB

Hints

  • Parallel the MOTOR_CONTACTOR contact with START_PB in the rung condition
  • Series the NC STOP_PB before the coil
  • MOTOR_CONTACTOR := (START_PB OR MOTOR_CONTACTOR) AND NOT STOP_PB

I/O Table

Inputs

START_PB

Start push-button (momentary)

BOOL · %I0.0

STOP_PB

Stop push-button (momentary)

BOOL · %I0.1

Outputs

MOTOR_CONTACTOR

Motor contactor coil

BOOL · %Q0.0

Your program will be tested against:

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

  1. #1Motor seals in on momentary start

    Motor seals in on momentary start

  2. #2Motor drops on stop

    Motor drops on stop

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