How to control 12vdc relay with microcontroller!

[lockoutseniorproject]

Microcontroller - arduino uno http://www.sparkfun.com/products/10356

Relay - simple 12vdc spdt relay

I was wondering if the microcontroller outputs enough voltage to control this relay, and how i would go about making these components work together - thank you!

 

[(*steve*)]

No, you will need to use the arduino's output to drive a transistor and use that to switch the relay current. You will also need a diode across the relay contacts to protect the transistor.

This lays it out really well.

 

[lockoutseniorproject]

where would we attach the external power supply in your diagram? also would a 3906 transistor suffice.

 

[GreenGiant]

where would we attach the external power supply in your diagram? also would a 3906 transistor suffice.

The external power would connect to Relay Power V+

That transistor would work, but be cautious it is only rated for up to 300mA so without a current limiting resistor you run the risk of burning it out