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Help please with DC and Stepper Motor HAT for Raspberry Pi a
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Please be positive and constructive with your questions and comments.

Help please with DC and Stepper Motor HAT for Raspberry Pi a

by andreinadejde on Wed Dec 30, 2020 8:38 pm

Hi,

I'm looking for some pointers on what I might be doing wrong in my hobby project. I've recently purchased a DC and Stepper Motor HAT for Raspberry Pi and following this guide: https://learn.adafruit.com/adafruit-dc- ... i/overview

I've soldered and powered everything up using a 12V 2A power supply and all the test code runs successfully.

I am now trying to drive a bipolar stepper motor like this one: https://ooznest.co.uk/product/nema14-stepper-motors/ I have the smallest one and the technical sheet says its a 1Amps/Phase at 12-24V.

From my limited understanding that should work with the hats 1.2A per channel 12V output and my power source should be enough to drive one of these motors. However the moment I plug the motor in the power led on the hat starts blinking once a second and while the motor does spin when I run commands it runs intermittently. Eg: I run it 1000 steps on a loop and it spins 4-5 times
with breaks in between.

Am I just not running enough power for this motor or is it something else. Should I try a 12V 5A power supply or would that damage the HAT?

Thank you very much for your help!

andreinadejde
 
Posts: 3
Joined: Wed Dec 30, 2020 8:23 pm

Re: Help please with DC and Stepper Motor HAT for Raspberry

by andreinadejde on Wed Dec 30, 2020 8:48 pm

I just double checked my motor and its actually a nema17 model like this one: https://ooznest.co.uk/product/nema17-stepper-motors/

Its a 1.4 Amps/phase so I guess it's a power issue then.

The question is would I be able to drive the motor through the HAT even with a larger power supply (the 5 Amps for example) or would it be just to much for the chip?

Thank you!

andreinadejde
 
Posts: 3
Joined: Wed Dec 30, 2020 8:23 pm

Re: Help please with DC and Stepper Motor HAT for Raspberry

by adafruit_support_bill on Wed Dec 30, 2020 8:55 pm

Do not use a larger power supply. You are already overloading the HAT.

he technical sheet says its a 1Amps/Phase at 12-24V.

That is the maximum that the motor is rated to handle. The actual current draw depends on the supply voltage and the driver.

The motors you are using have a low phase resistance (2.7 Ohms) indicating that they were designed for use with a current limiting 'chopper' type driver like the DRV8833: https://www.adafruit.com/product/3297

With a simple (non current limiting) H-bridge drivers such as the TB6612 chips on the HAT, the maximum current draw per phase will be determined by Ohm's Law: I = V/R. So the peak current draw will be 12v / 2.7 Ohms = 4.44A. In other words, these motors are not compatible with the HAT.

https://learn.adafruit.com/all-about-st ... he-stepper

adafruit_support_bill
 
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Re: Help please with DC and Stepper Motor HAT for Raspberry

by andreinadejde on Wed Dec 30, 2020 9:21 pm

Thank you! I'll stop using it with the HAT.

I'll read the article you shared so thank you for that.

I also have some of these https://learn.adafruit.com/adafruit-tb6 ... r-breakout but I think they'll have the same power problem.

Is it possible to run a separate higher power circuit for the motor and drive it thought the HAT with some transistor setup or am I better off looking for a compatible driver?

Thanks again for your help!

andreinadejde
 
Posts: 3
Joined: Wed Dec 30, 2020 8:23 pm

Re: Help please with DC and Stepper Motor HAT for Raspberry

by adafruit_support_bill on Wed Dec 30, 2020 9:37 pm

The TB6612 breakout uses the same drivers as on the HAT. It is possible to use the motor outputs of the HAT to drive current limiting drivers such as the DRV8833 or DRV8871.

adafruit_support_bill
 
Posts: 80988
Joined: Sat Feb 07, 2009 10:11 am

Please be positive and constructive with your questions and comments.