Overvoltage protection circuit diagram

As shown in the figure is an overvoltage protection circuit . When the external voltage E does not exceed the set voltage Vs, the negative resistance light-emitting diode VD1 is cut off, VT ​​is also cut off because there is no base current, the relay J does not pull in, and its normally closed contact J1-1 is closed to supply power to the load RL. When the external voltage E exceeds the set voltage Vs, VD1 changes from off to on, and VD1 lights up to indicate overvoltage. The current flowing through VD1 provides VT base current, VT is turned on, J is closed, and the normally closed contact J1-1 is disconnected, cutting off the power supply to the load, and playing a protective role. When the external voltage E returns to below Vs, press the reset button AN to cut off VDl and VT, release J, and resume power supply to the load. Capacitor C1 in parallel with VD1 is anti-electromagnetic interference and can be selected in the range of 0.01μF ~ 0.1μF.

ck="window.open(this.src)" alt="Click to see larger image" />