Author Topic: ArduMoto for DC motors  (Read 1777 times)

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Offline anu_2k6Topic starter

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ArduMoto for DC motors
« on: November 17, 2013, 08:00:37 AM »
I bought an Ardumoto Driver shield which can drive up to 2Amps per channel.
I also bought a pololu 29:1 metal gearmotor with encoders.
The gearmotor has a stall currrent of 5Amps at 12V.

I only noticed this once I bought both items.
My question is, how do I connect the motors to the ardumotor which only drives 2Amps ?

Offline jwatte

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Re: ArduMoto for DC motors
« Reply #1 on: November 17, 2013, 05:18:32 PM »
If you don't pull any load on the motors (don't stall them) then the driver will make the motors spin.
Once the load becomes enough to draw more than 2A, one of two things will happen:
1) The Ardumotor will overheat and destroy itself.
2) The Ardumotor will detect and prevent over-current, and the motors won't run.

You really want to match the motors to your controller; if the controller is too weak, you will never be happy with the result.

Offline anu_2k6Topic starter

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Re: ArduMoto for DC motors
« Reply #2 on: November 18, 2013, 07:21:00 PM »

 So is the only solution buying an appropriate controller?
I thought there might be a way to work around the problem? :/

Offline bdeuell

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Re: ArduMoto for DC motors
« Reply #3 on: November 18, 2013, 08:08:14 PM »
The datasheet claims outputs can be used in parallel to increase current rating, but assuming you have two motors you would then need two boards.

The chip does have a current sense output but they appear to have tied it to ground in the circuit diagram. If you have access to these outputs you could use them to monitor the current draw of the motors and adjust the control accordingly. As was stated before performance will not be satisfactory if you really need a higher current controller.

What current you should expect to need to handle will depend on many factors such as the environment, type of drivetrain and control type. the easiest way to determine the current draw is with some testing. If you find that you are drawing less than 2 amps with a safety margin and that the current is fairly predictable then your controller will probably be fine. A good controller design would have a overcurrent protection tho to prevent failure.

The safest bet is always to use a controller that can handle the stall current of your motors. I have seen underrated controllers blow up or overheat too many times!!! I'm sure there are plenty of controllers out there that can handle the 5 amps and don't cost too much.


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