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Electrician Red Seal · Question

A technician is troubleshooting a PLC-controlled conveyor system. The conveyor stop button is wired as a normally closed (NC) contact to a digital input module. When the button is pressed, the input status LED on the PLC module remains ON, and the conveyor continues to operate. What is the most likely cause of this issue?

If the stop button is NC and the LED remains ON when pressed, it indicates the circuit never opened. A broken wire would prevent the circuit from opening, keepi

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Question: A technician is troubleshooting a PLC-controlled conveyor system. The conveyor stop button is wired as a normally closed (NC) contact to a digital input module. When the button is pressed, the input status LED on the PLC module remains ON, and the conveyor continues to operate. What is the most likely cause of this issue?

Answer options: ✅ A broken wire in the stop button circuit, preventing the circuit from opening.

  • The PLC input module is faulty and not detecting the state change.
  • The stop button is wired as normally open (NO) instead of normally closed (NC).
  • A programming error in the PLC ladder logic is ignoring the stop input.

Correct answer: A broken wire in the stop button circuit, preventing the circuit from opening.

Explanation: If the stop button is NC and the LED remains ON when pressed, it indicates the circuit never opened. A broken wire would prevent the circuit from opening, keeping the input energized. A faulty input module or programming error might be present, but the symptom of the LED remaining ON points primarily to the input circuit itself.

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