Relay Driver Circuit

The following circuit will allow you to drive a 12V relay using logic voltage (an input of 4V or greater will trip the relay). The circuit has its own 12V power supply making it self contained but the power supply portion can be left out if an external supply will be used. The circuit shows an output from the power supply that can be used to power other devices but it should be noted that the supply is unregulated and not particulary powerful with the parts stated. The 12V DC output is suitable for powering a few LEDs or low voltage lights but should not be used to power other electronic boards or motors.

Part Name Jameco Part # Quantity
12V 500ma Power Transformer292251
1N4002 Diode769612
2 pin Terminal Block1523462
2.2K Resistor (1/4W)303141
2N3904 NPN Transistor383591
3 pin Terminal Block1523541
3A Fuse 694381
4.7K Resistor (1/4W)310261
2A 50V Bridge Rectifier1781831
SPDT Relay (12V)129349CH1

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