Current control out of arduino?

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dylan519510
 
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Current control out of arduino?

Post by dylan519510 »

Hello,

I am trying to use an arduino to control a stepper motor with a motor shield. That is all working perfectly fine, but for the purposes of the project I need to be able to vary the torque that the stepper motor supplies. Is this something that can be done within the arduino coding itself? I didn't have much luck surfing the web this morning (very possible I just don't know what im looking for). I know that the arduino has a 40ma max output and its recommended to keep it at 20ma for continuous operation. would I need to implement my current control at a point before I supply power to the board? maybe there is a way to use the board as feedback to control that input variance in a closed loop sense?

Thanks for any help in advance.

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adafruit_support_bill
 
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Re: Current control out of arduino?

Post by adafruit_support_bill »

The arduino pin current limits are not related to the current that can be supplied by the H-bridge circuits on the motor shield.

If you want to limit torque, you need to limit the current to each coil of the stepper independently. Limiting motor current to the board overall would not be effective, since that current is shared by both coils in various stages of the stepping sequence.

The best solution is to get a shield that supports current limiting. https://learn.adafruit.com/all-about-st ... he-stepper
The Synthetos g_shield is one such board.
http://www.adafruit.com/product/1750

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