Transistor Circuit Issue

I'm attempting to drive a 12V motor using the Arduino to supply a logic signal to switch it on and off.

I've got a TIP120, +12V conected to Collector, Diode from emitter to collector, one of the motor leads on the emitter, the other to ground.

When I put a logic signal from the arduino through a 1K resistor to the Base, I get a +5V signal out to the emitter...

Shouldn't this be 12V? what am I doing wrong?

You've built an Emitter Follower, which has current gain but no voltage gain. Put the load (motor) in the collector circuit and wire the emitter directly to Ground. The base resistor may need to be a little lower, but start off with 1k Ohms. Connect the diode in parallel with the motor, non-conducting.

The emitter voltage can't go above the the base voltage. You want to connect the emitter to ground, the collector to one of the leads of the motor, and the other motor lead to the +12V. Keep the diode. then it should work.

Thanks! Got it working. I knew this, I just seem to have forgotten in the haze of time....