Protection Circuit For Electrical Appliances From Power Supply Variations PCB

Posted on Feb 5, 2014

Here is a very low-cost protection circuit to save your electrically operated home appliances, such as TV, DVD player, refrigerator, and other instruments during sudden tripping and resumption of mains supply. Appliances like refrigerators and air conditioners are more sensitive to damages due to such mains supply variations. Thus the circuit prov

Protection Circuit For Electrical Appliances From Power Supply Variations PCB
Click here to download the full size of the above Circuit.

ides suitable safety against erratic power supply conditions. The simple circuit given here switches off the mains supply to the load as soon as the power trips. The supply can be resumed only by manual intervention. Whenever the supply is found to be stabilized, then it switch on. The circuit consist of a step down transformer followed by a full wave rectifier. The capacitor C1 act as a filter or smoothing capacitor which act as a power supply source for relay RL1. Initially, when the circuit is switched on, the power supply path to the step-down transformer X1 as well as the load is incomplete, as the relay is in de-energised state. The relay can be energised by the switch S1 for a short period of time. This completes the path for the supply to transformer X1 as also the load via closed contacts of switch S1. Meanwhile, the supply to relay becomes available and it gets energised to provide a parallel path for the supply to the transformer as well as the load. If there is any interruption in the power supply, the relay activates Thus, once the supply is interrupted even for a short period, the relay is de-energized and you have to press switch S1 momentarily (when the supply resumes) to make supply available to the load.

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