# Motor driver selection

I am building a 2 wheel robot to carry 7KG of load. I used this link to get the torque required for each motor which is 11Kg-cm. So I choose 2 of these motor which has 36Kg-cm(2x more) torque. I noticed that the stall current is 14A.

Can I use Adafruit Motor Shield for Arduino which is rated 3A peak current capability?

If not what current rating driver should look into?

Thanks!!

• possible duplicate of H-bridges and stall current – Ian Jul 17 '13 at 15:39
• I dunno Ian -- I think this one stands on its own, although they are similar. – TimWescott Jul 17 '13 at 20:35
• Kg-cm is not a measure of torque, because while a centimeter is a measure of distance, a kg is a measure of mass, not force. Presumably you mean kg-g-cm, or 110N-cm (roughly) for the motor. – TimWescott Jul 17 '13 at 20:37
• Similar, but not a duplicate: propose to leave open for now – Andrew Jul 22 '13 at 10:56

The Adafruit Motor Shield for Arduino should work, if two conditions are satisfied:

1. the Adafruit Motor Shield for Arduino can limit its own current, or there's enough data available so that you can.
2. the motor you want to use can generate sufficient torque on 3 amps

The answer to (1) should come from the data for the Adafruit Motor Shield for Arduino. The answer to (2) should come from the motor data (look for the motor torque constant. It should be in (torque units)/(amp). Given what the motor uses for torque units, it'll probably be in kg-cm/amp, however improper those units may be as a measure of torque. Multiply that torque constant by 3A, and you have your answer for the motor.

• Ok checked out adafruit website, the new motor shield has flyback diodes, thermal shutdown protection and 3 Amp peak current. Also decided to change motors as I relised I didnt need that much torque. So current torque is 0.45Nm so decide to use this motor. – user1850666 Jul 18 '13 at 15:20

You could use it, but that would mean you will have to limit your power supply a lot. When your robot starts up, it will need a serious amount of power for the time it takes to accelerate, if you have a power supply of 12V, you will probably immediately burn out the motor driver you mentioned.

A motor driver that would work (from Sparkfun, I couldn't find a high power motor driver at Adafruit) is this shield.

That said, you could use these motors, with the shield you mentioned, but you will have to limit your power supply, and that is going to cost you: speed, acceleration, torque and a big headache. You are way better off getting a higher power shield.

I am in no way affiliated with Sparkfun, I just knew they had a shield that will suit your needs.