Arduino & 2X 12VDC Motors

Can anyone tell me how to connect 2X 12VDC Drill motors to my arduino. I have 2 TIP121's and 2 5vdc SPDT relays.
I have heard that a 5v /240Vrated DPDT relay can be used alone to be able to drive a 12V dc motor, is this true.
I am looking for the easiest way to control the 2X 12VDC Drill motors forward and backwards with the click of a c# app button.
Pleas guys, there must be some of you experienced electronics engeneers that got some easy circuit for me, and and some source code with 4 arrows to control the 2 motors.
Press forward, and both motors go forward
Press backwards and both motors move backwards
press right and only right motor spins
Press left & only the left motor spins.
I have got Firmata, but I need buttons to do the PWM, and not a slider, so if someone out there are brave enough to tackle this, I would really appreciate it a lot.

Thank you so much.

Another question would be whether these are permanent magnet motors, shunt wound, or series wound? I've never actually taken apart a rechargeable drill; I would assume PM simply because it would be cheapest for the manufacturer to build, but IIRC, you sometimes see the other two used as well because of their speed vs torque curves. Series wound tend to have high torque at low speed (useful in a drill), but they can suffer from "runaway" without a load applied.

Whatever you do, since these motors are likely gear motors, don't attempt to hold the shaft with your fingers (even if they aren't attached to the gearbox, which would actually be the best way to test them). Instead, clamp the shaft with a pair of vice grips and clamp the motor to a bench or something. Hook up your multimeter in-line (really you should do this across a small power resistor or shunt, but inline will work), and use the largest amperage input on the meter (meters usually have two inputs for the positive lead; one that is for regular voltage/amperage/resistance readings, and a second for higher-amperage readings - use the second one), set it to amperage measurement, and briefly apply power using a power supply.

What you are trying to avoid is burning the motor out (and/or the meter); you also want everything clamped down to keep things from "going everywhere" and potentially causing harm. Something to keep in mind is that you might find the stall-current of the motor may be greater than your meter (in which case you might blow the meter if it is cheap, or the fuse if it is better); I am not sure what a drill motor might run at, but I would guess a stall current of potentially 5A, if not greater.

:slight_smile: