Wiring Schematic Diagram

A 12VDC overvoltage protector circuit is shown in the schematic diagram below. This circuit will work to disconnect the protected device from the power supply when an overvoltage occurs at the supply. This circuit uses a silicon-controlled rectifier (SCR) and normally-closed 12-V relay, K1. The silicon-controlled rectifier is connected in parallel to 12-V line to monitor for the overvoltage condition. This applied signal is sensed by the SCR’s gate.

Until the voltage drops below the set value, the K1′s contacts remain closed and SCR1 remains off. The SCR1 will be triggered causing K1′s contacts open and halt current flow to the loas when overvoltage occurs. You can use R1 to set the trigger point of SCR1