An easy to build and very low cost electronic device protector circuit diagram

This is an easy to build and very low cost circuit designed to protect your electronic devices/devices such as PCs, TVs, recording equipment, refrigerators and other appliances during sudden trips and restoration of household power supply. Due to this condition, appliances such as refrigerators and air conditioners are more susceptible to damage.

This electronic equipment protection circuit switches off the main power supply to the load in the event of a power trip. Power can only be restored through manual intervention. Therefore, switch on the power supply only after it has stabilized.

The circuit consists of a step-down transformer followed by a full-wave rectifier and smoothing capacitor C1 as the power supply for relay RL1. Initially, when the circuit is switched on, the supply path to the step-down transformer X1 and therefore the load is incomplete because the relay is de-energized. To energize the relay, briefly press switch S1. This completes the path of power to transformer X1 and the load through the closed contact of switch S1. At the same time, power to the relay becomes available and energized, providing a parallel path for power to the transformer and load.

If there is any interruption in the power supply, no power is supplied to the transformer and the relay de-energizes. So even if the power is interrupted for a short time, the relay will de-energize and you will need to press switch S1 almost immediately (when power continues) to make it available to the load.

Very short duration (e.g., 1 to 5 milliseconds) disturbances or changes do not affect the circuit because of the presence of bulk capacitors that must be discharged through the relay coil. Therefore, this circuit provides appropriate safety against unstable power supply conditions.