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Does the Adafruit v2 motor shield regulate current and volta
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Does the Adafruit v2 motor shield regulate current and volta

by leokswang on Fri May 20, 2022 10:54 pm

Does the Adafruit v2 motor shield regulate current and voltage?

If my wall adapter supplies 4 amps and 12V to the motor shield which is connected to 2 stepper motors that have a rated current of 1.68A and rated voltage of 3.27V each. Will the Adafruit Motor Shield V2 lower the voltage and the current to that level?

Thank you!

leokswang
 
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Re: Does the Adafruit v2 motor shield regulate current and v

by tepalia02 on Fri May 20, 2022 11:36 pm

https://learn.adafruit.com/adafruit-mot ... ing-motors
This document says that The motor driver chips that come with the kit are designed to provide up to 1.2 A per motor. Looks like it is less than the current required by your motors.

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Re: Does the Adafruit v2 motor shield regulate current and v

by adafruit_support_bill on Sat May 21, 2022 6:53 am

The driver chips on the motor shield are not current limiting 'chopper' type drivers.

The motor driver chips that come with the kit are designed to provide up to 1.2 A per motor.

That is not the way to interpret the spec. 1.2A continuous is the maximum the chip is rated to handle. It does not actively limit the current to that level.
The current delivered to each phase of the motor will be a function of the supply voltage and the phase resistance and will follow Ohm's Law: I = V/R. If that current level exceeds the 1.2A rating of the driver chip, you will likely burn out the driver chip.
https://learn.adafruit.com/all-about-st ... he-stepper

a rated current of 1.68A and rated voltage of 3.27V

Working backwards using Ohm's Law, they implies that the motor has a phase resistance of R = V/I = 3.27V/1.68A = 1.95 Ohms per phase.

If you were to power that with 12v via the shield, the motor would attempt to draw 12v/1.95 Ohms = 6.1A/phase. of 12.2A total. That would simultaneously overload the power supply, the motor and the shield.

We do have the DRV8833 which is a current limiting stepper driver. https://www.adafruit.com/product/3297
You could also use a pair of DRV8871's: https://learn.adafruit.com/current-limi ... th-drv8871
Check http://www.pololu.com for a wider selection of stepper drivers - including many with current limiting.

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