Over Voltage Protector

Over Voltage Protector Circuit Using SCR

PARTS LIST
VR1	2.5kΩ
SCR1	1A 50V SCR
S1	N.O. Switch
RL1	12V Relay

A silicon-controlled rectifier is installed in parallel with 12v line and connected to a normally-closed 12v relay, RL1. The SCR’s gate circuit is used to sample the applied voltage. As long as the applied voltage stays below a given value, SCR1 remains off and RL1’s contacts remain closed, thereby supplying power to the load. When the source voltage rises above 12V, sufficient current is applied to the gate of SCR1 to trigger it into conduction. The trigger point of SCR1 is dependent on the setting of R1. Once SCR1 is triggered (activating the relay), RL1’s contacts open, halting current flow to the load.

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