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 sensor, a decision circuit, and a relay serving as the power interrupter.

Start by selecting a current sensing method. A common approach is to install a precision shunt resistor in series with the current path. 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 generate the reference voltage using a simple voltage divider and a zener diode. The comparator signal will be a digital signal high or low depending on whether the current exceeds the threshold.

The comparator’s signal needs to be amplified by a switching transistor such as an N-channel MOSFET or a general-purpose NPN transistor, to decouple the sensitive electronics from the relay’s demanding coil current.

Choose a relay with a coil voltage compatible with your control circuit and contact ratings that exceed the maximum load current and voltage. The relay contacts should be wired in series with the load and the power supply so that when the relay is de-energized, the circuit is broken.

To prevent rapid cycling or انواع رله chatter when the current is near the threshold, add hysteresis to the comparator using positive feedback. This ensures the circuit switches off at a higher point and resets only after the load current falls well below the setpoint.

For added reliability, include a fuse or circuit breaker upstream as a secondary protection layer. Also, install a push-button reset mechanism so the system can operate only after intentional human intervention following a trip.

Validate performance with programmable current source and simulated load conditions. Confirm every part meets or exceeds the system’s electrical demands, and follow proper electrical safety practices when working with mains powered systems.

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