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Solid State Circuit Breaker (20V 650mA)


Schematic for Solid State 20V 650mA Circuit Breaker from 5 NPN Transistors

How it Works

Grounding the On or Off Buttons will turn the Toggle Switch on or off.

When the Toggle Switch is on, it turns on the Output Relay and RLoad is powered.

If the voltage across R8 exceeds 0.65 volts (I=0.65/R8), it trips the Current Limit Sensor which generates an OFF signal.

The OFF Signal is hooked up to the Off Button of the Toggle Switch.

Bread Board Circuit in Operation

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Transistor Specifications

Transistor Specifications

LED Resistor Values

LED Resistor Values


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