@▷ Power Guard | Diagram for Schematic

Power Guard

Power Guard Under and Over Voltage Protector


Under and Over Voltage Protector

A few circuits on under/over voltage protection have appeared recently in EFY. But this circuit is simple, very easy to construct and inexpensive. It can be added to existing stabilisers, in which case DC power supply can be taken from the original stabiliser circuit and only a few additional components, including one relay, are required to make the circuit.

Power Guard Under and Over Voltage Protector circuit

PARTS LIST R1 1KΩ R2 820Ω R3 10KΩ 1/2W C1 1000µF 25V C2 250µF 25V VR1 4.7KΩ VR2 4.7KΩ T1 HL 100 T2 HL 100 RL 12V 450Ω Z1 Bz 148 Z2 Bz 148 D1 BY 126 × 4 T 12V 500mA

When supply voltage is within limit. T2 conducting and T1 is in a non-conducting state. At low voltage, zener Z2 will not breakdown and T2 will not conduct, which results in de-energising the relay. This adjustment is done by adjusting VR2.

At high voltage, zener Z1 will breakdown and T1 will go in conducting state and the relay will de-energise. This adjustment is done by adjusting VR1. Normally-open contact of the relay is used in control circuit. Red LED gives high low voltage cut-off  indication.

"Power Guard Search Tags"
power supply, Power Guard
Advertiser