Firing 12V Relay with arduino? (With external power supply)

I have a 12VDC electromagnet that I would like to "turn off" with a push button on an arduino Uno. I've done a bit of research and it seems like a transistor might be the best way to go but I'm at a the end of my knowledge here. Any ideas? Currently to turn off the magnet we're disconnecting one of the power leads from the power supply, which works, but for seemingly obvious reasons we'd like to use the arduino.

Thanks in advance!



Low Rds, Logic level, N-channel MOSFET transistor.

How much current are you switching?

The power supply delivers 1.2A, I believe the magnet is pulling about 1.1-1.2 amp (14 watt)

MOSFET like AOI-514 between negative lead of electromagnet and Gnd then.
Can be controlled by Arduino directly.

Will run nice & cool for you: Power dissipated = 1.2A1.2A.0119ohm = 17mW

Thank you!

Just wondering, is there any way to do it with things we already have laying around the lab (It's a state funded lab so ordering things is a bit of a pain)

The relay we have is High DC Inrush Current Relay Standard, SPST-NO, 5 Terminals, 12V DC Control (McMaster-Carr).

We have a ton of resistors of most all ranges, capacitors too (not sure how those could come into play but worth mentioning i guess) and a bunch of 500mA positive voltage regulator, 5V.

Thanks again!


I didn't want to bump the thread but I ended up using a BCE transistor with some luck. It needs a good bit of tweaking but I think we can make it work. Thank you again for you help