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Time-Delay Electromechanical Relays
19 questions By Tony R. Kuphaldt
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Question 19 of 19
When the pushbutton is pressed, the relay immediately energizes and sends power to the electric horn. When the pushbutton is released, the horn remains on for a few moments before turning off, due to the capacitor’s stored charge continuing to power the relay coil. So, the capacitor and relay form a time-delay control circuit for the horn:
Suppose this circuit has functioned as designed for quite some time, then one day develops a problem. The horn sounds immediately when the pushbutton is pressed (as it should), bit it immediately silences instead of continuing to sound for a few more moments when the pushbutton is released. Based on this information, identify these things:
- Two components or wires in the circuit that you know must be in good working condition.
- Two components or wires in the circuit that could possibly be bad (and thus cause the off-delay action to fail).
Reveal answerObviously the horn, relay, switch, and battery are all working normally. The capacitor could be bad (failed open), as well as the wiring/connections between the capacitor and the coil.
Notes:The purpose of this troubleshooting question is to get students to think in terms of fault elimination: deciding what things cannot be bad in order to better isolate what might be bad.
