Arduino Drives a relay

You can easily drive a relay 5 ,12 or 24 volts easily, giving a very small signal and driving a transistor . As known, out from microcontroller is just a few milamps, so is not enough to drive straight a relay that drains around 30 mA.

In the circuit below, transistor base current is 304μA and Ic  is 25 mA. Relay is 12v. Signal is 5v .

schematic

 

 

I made this small circuit on my expansion boards. I try to make it exactly as the schematic for better understanding

drive relay from signal

back

 

 

 

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