Dual Relay Driver Board Circuit


Posted on Feb 7, 2014

A simple and convenient way to interface 2 relays for switching application in your project. This relay driver boosts the input impedance with a regular BC547 NPN transistor (or equivalent). Very common driver. It can drive a variety of relays, including a reed-relay. Transistor Q1and Q2 are a simple common-emitter amplifier that increases the effective sensitivity of the 12 volt relay coil about a 100 times, or in other words, the current gain for this circuit is 100. Using this setup reduces the relay sensitivity to a few volts. R3 and R4 restricts the input current to Q1 and Q2 to a safe limit. Diodes D3 and D4 are EMF dampers and filter off any sparking when the relay de-energizes..


Dual Relay Driver Board Circuit
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