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Providing Maximum Torque to Stepper Motor with v2 shield
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Providing Maximum Torque to Stepper Motor with v2 shield

by mangojelly on Sun Mar 14, 2021 2:12 pm

I'm looking at driving a ACME leadscrew with a stepper motor and 2:1 gear reduction using the v2 motor shield and Arduino UNO. Similar to an electromechanical linear actuator like this: https://cdn.shopify.com/s/files/1/0615/2193/articles/linear_actuator_exploded_view_e9e7f578-d69e-40df-b16f-972e323171d8_520x500-min.png?v=1612895817

I have issues with the stepper slipping under minimal load and I'm wanting to make sure I’m applying max torque to determine if the motor is just undersized or if it’s the way I’m powering /controlling it that could fix my issue.

Arduino Uno is connected via USB to computer and VIN jumper installed. The shield is powering 2 stepper motors (but they only run one at a time while the other motor is not released since I need holding torque).

1. Is USB enough to supply max current to the motors or do I need to use a power supply and remove the VIN jumper? What is the benefit of powering the UNO via USB and motors with a 12v power supply?
2. What’s the best way to drive the stepper for max torque? I believe it is using step type DOUBLE and at low RPM? Even at 10 rpm and DOUBLE it starts to skip.
3. Would a stepper motor be suitable for this application or can DC motors provide much higher torque? I like the inherent positioning that a stepper motor provides over DC motors.
4. I also notice about every few rotations it vibrates a lot/emits higher frequency noise for about a half rotation. Since it’s not every single rotation I didn’t think it’s a mechanical alignment issue and wasn’t sure what might cause that also.

NEMA-17 motor: https://www.adafruit.com/product/324

mangojelly
 
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Re: Providing Maximum Torque to Stepper Motor with v2 shield

by adafruit_support_bill on Sun Mar 14, 2021 3:00 pm

The #324 NEMA-17 motors will achieve maximum torque when powered with 12v using DOUBLE step mode. At 12v they will pull a maximum of 350mA per phase - or 700mA total.

USB is only 5v. At 5v they will provide only about 40% of the torque compared to running at 12v.

The shield is powering 2 stepper motors (but they only run one at a time while the other motor is not released since I need holding torque).

Unlike DC motors, stepper motors pull more current the slower they go. They will be pulling max current when stationary with holding current applied.

A 12v/5A supply like this should provide plenty of power for your 2 motors.

adafruit_support_bill
 
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Re: Providing Maximum Torque to Stepper Motor with v2 shield

by mangojelly on Mon Mar 15, 2021 10:05 pm

Thank you for the fast reply. I will try using it with a 12V power supply and see what kind of improvements I see and report back.

That is very good to know about the current draw with stepper motors as well.

mangojelly
 
Posts: 2
Joined: Sun Mar 14, 2021 10:52 am

Please be positive and constructive with your questions and comments.