Please help on Relay

Thread Starter


Joined Nov 22, 2006
Hi ..

I have a 5v line at 10ma that I would like to use turn on a 5v relay
that would turn on a 9.6v motor.

Someone suggested I use a 2N3904 transistor to do this .. but I have no idea how to hook it up -- I'm new in electronics.

If somebody could help me and draw me a small diagram I would sure appreciate it.

I need this for a magic trick I am working on.

Thank you!

- Steve


Joined Jan 22, 2004
let's try to clarify things out first.
1. what is the power source of your relay that must be triggered by the transistor.
2. what is the coil resistance of your relay coil
3. do you intend to use your 5v/10ma source to power your relay?



Joined Nov 1, 2006
I'm afraid 10ma. won't be enough to drive a 5V relay coil. I'd use a PN2222 or NTE123A transistor to drive the the relay from the 5V source since it can handle a little more current & power than a 2N3904. Both have the same pinouts. Put the relay coil between the transistor collector & the + side of your 9.6V supply. Also, be sure to connect a freewheeling [reverse biased] diode such as a 1N4001 across the relay coil to protect the transistor from voltage "spikes' generated when the relay de-energizes.