Creating a Robust Current-Triggered Relay Protection Circuit > 자유게시판

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Engineering a current-sensitive relay shutdown system involves designing an automatic cutoff that interrupts power when current exceeds safe limits. The centerpiece of this circuit is a current-sensing unit, a threshold comparator, and a relay as the final disconnect switch.

Start by selecting a current sensing method. A standard approach is to place a low-ohm current-sensing resistor directly in the load circuit. The resistor should be rated to handle the maximum expected current without overheating. When current flows through the shunt, a small voltage drop develops across it proportional to the current level.

Then, feed the sensed voltage into a differential amplifier.

The circuit compares the feedback voltage with a calibrated setpoint indicating the maximum allowable current. You can create the reference with a precision voltage reference IC. The output of the comparator will be a binary state indicating trip or normal conditions.

This output must activate the relay via an isolation stage such as a BJT like the 2N2222 or an IRF540 MOSFET, to protect the comparator from the relay’s inductive load.

Use a relay rated for your control voltage with contacts rated above your maximum operating current and voltage. The switch contacts should be wired in series with the load and the power supply so that the power is fully interrupted upon activation.

To eliminate unwanted relay flutter at borderline levels, introduce a small amount of regenerative feedback to establish a deadband. This ensures the circuit turns off at one level and only turns back on after the current drops significantly below the threshold.

Enhance safety by placing a fuse or breaker before the relay circuit. Also, install a push-button reset mechanism so the system can only be restarted after the fault condition has been cleared.

Calibrate using an adjustable supply and resistive load to confirm accuracy and delay. Confirm every part meets or exceeds the system’s electrical demands, and انواع رله follow proper electrical safety practices when working with mains powered systems.

Relay-based overcurrent circuits deliver a durable, transparent, and field-serviceable safety mechanism.