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Running a 3.5V Stepper with Adafruit MotorShield V2.3
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Please be positive and constructive with your questions and comments.

Running a 3.5V Stepper with Adafruit MotorShield V2.3

by chris_m_1986 on Fri Aug 07, 2020 3:14 am

Hello,

for my Project I am running a Nema 17 (17HS08-1004S) with the motorshield. First, I thought the stepper would use 12V so I supplied power through the DC-jack of the arduino. This led to the stepper running extremely hot and after reading the specs again i figured it only using 3.5V. My problem now is that my project can only run with 3.5V from the DC-jack of the arduino (with jumper) and the additional power of the usb-input since i have two KY-040 and a I2C-Display attached to the 5V. Is there any way to get everything running with just one power source maybe over some sort of power regulator? Otherwise I would have to find a stepper that takes at least 5V...problem with that is that I need a 20mm stepper and those small steppers usually just take 3.5V.

Maybe on a different note: I tried to software-debounce those darn KY-040...it's basically impossible. Although the pullup resistors for the CLK and DT help a lot, those encoders are flunky as s***. Also I have one of them call an interrup. Therefore any debouncing via timing is not possible. Online I just found standard procedures and none work very well for that KY-040.

This is my first project using Microprocessors (Usually I develop code on a MAC) and I'm quite impressed, what one can do and how easy to use the development environment is. I just wonder what the intention was to access the motor object via pointers in the library version 2. I understand that has been changed from version 1. In a practical application it does not make a big difference..I'm just curious about this choice.

However, I'm very happy with your products and would be thankfull for a response especially towards my voltage issue.

Christian

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Re: Running a 3.5V Stepper with Adafruit MotorShield V2.3

by adafruit_support_bill on Fri Aug 07, 2020 5:57 am

I am running a Nema 17 . . .

NEMA 17 is a frame size specification. It tells us the location of the bolt holes on the faceplate. But nothing about the electrical characteristics of the motor.
after reading the specs again i figured it only using 3.5V.

Unfortunately, the rated voltage is probably one of the least useful and most misunderstood specs on a motor datasheet. I suspect that the manufacturer never intended that motor to be run with a 3.5v supply. The voltage rating typically refers to the maximum continuous DC voltage. But stepper motors only see DC voltage when they are not moving, so that number doesn't mean much. Motors with low voltage ratings are often high-torque designs intended to run with higher voltage power supplies in combination with current limiting drivers.

I located a full datasheet here: https://www.oyostepper.com/images/uploa ... -1004S.pdf
And sure enough, this motor has a similarly low phase resistance (3.5 ohms) - indicating a high-torque motor design intended for use with a current limiting 'chopper' type driver. Unfortunately, the TB6612 drivers used in the shield do not have current limiting, so they are not a good match for high-torque motors.
https://learn.adafruit.com/all-about-st ... he-stepper

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Re: Running a 3.5V Stepper with Adafruit MotorShield V2.3

by chris_m_1986 on Fri Aug 07, 2020 6:25 am

The 3.5V was already infered from the 1A and 3.5Ohm of the datasheet. The datasheet also specified 12V which I carelessly just interpreted as the required supply (Almost burned my wooden table).
Interestingly enough, giving it the 3.5V via the DC-input it does run. Just that I simultaneously need to supply the other stuff via the USB-port. It does work that way...just a little inconvenient with all the cables.

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Re: Running a 3.5V Stepper with Adafruit MotorShield V2.3

by chris_m_1986 on Fri Aug 07, 2020 6:38 am

Also which stepper motor would you recommend for this motor shield? What would be suitable specs?

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Re: Running a 3.5V Stepper with Adafruit MotorShield V2.3

by adafruit_support_bill on Fri Aug 07, 2020 6:54 am

Interestingly enough, giving it the 3.5V via the DC-input it does run.

Typically, they will run at the rated voltage. They just won't achieve anywhere near the rated torque or speed. But it may be good enough for some applications.

Just that I simultaneously need to supply the other stuff via the USB-port. It does work that way

If you have a good stiff 3.5v supply and that is sufficient for your motors, you could use a boost converter to get the 5v for the rest of the electronics. https://www.adafruit.com/product/1903

Also which stepper motor would you recommend for this motor shield? What would be suitable specs?

Assuming you want to use your 12v supply, you will want a motor with a phase resistance of 10 ohms or more to keep the current per phase at or below the 1.2A continuous rating of the drivers on the shield.

We have these motors that work well with the shield: https://www.adafruit.com/product/324

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Re: Running a 3.5V Stepper with Adafruit MotorShield V2.3

by chris_m_1986 on Fri Aug 07, 2020 8:57 am

Thank you very much! The boost converter looks like a viable option.

I intend to control a manual focuser on a telescope with the motor. Given the focuser knob is very sensitive and the ratio of the pulleys I'm using, torque is basically not an issue. The one single requirement is precision. I used a stepper in order to have a full consistent discrete mapping of the focusers range.

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Please be positive and constructive with your questions and comments.