Trouble getting smooth movement out of Adafruit Motor/Stepper/Servo Shield with NEMA 17 motors

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silvermanphoto
 
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Trouble getting smooth movement out of Adafruit Motor/Stepper/Servo Shield with NEMA 17 motors

Post by silvermanphoto »

Hi! I’m having trouble creating a smooth and evenly accelerating two-axis drawing robot (gripping a tiny laser diode with no weight) controlled by a Grand Central M4 Express and the Adafruit Motor/Stepper/Servo Shield for Arduino v2. I’m driving two NEMA 17 stepper motors from the shield with motor power wired into the shield (not powering it from the Grand Central). I’m using a 12 Volt 6 Amp supply, so I don’t think lack of power is the problem. These motors are supposed to have good torque, but they will only work in “double” stepper mode, not single and not microstep mode, so they are jerky and noisy instead of smooth and quiet. I’m using the Adafruit Motor Shield V2 library and Accelstepper. Can anyone give a little guidance? I need this to draw slowly and as super smoothly and quietly as possible.

Thanks!
Joel
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Re: Trouble getting smooth movement out of Adafruit Motor/Stepper/Servo Shield with NEMA 17 motors

Post by adafruit_support_bill »

I’m driving two NEMA 17 stepper motors
We need some information about the electrical specifications of the motors you are using.

"NEMA 17" is a frame-size designation only. It tells us where the mounting holes on the faceplate are. It does not tell us anything about the electrical characteristics.

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silvermanphoto
 
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Re: Trouble getting smooth movement out of Adafruit Motor/Stepper/Servo Shield with NEMA 17 motors

Post by silvermanphoto »

They are:
Bipolar 42 Stepper MotorStep Angle: 1.8 deg.
Rated Current/phase: 1.5A
Holding Torque:13Ncm(18.4oz.in)

https://www.amazon.com/gp/product/B07TG ... UTF8&psc=1

Thanks for your help on this!

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Re: Trouble getting smooth movement out of Adafruit Motor/Stepper/Servo Shield with NEMA 17 motors

Post by adafruit_support_bill »

The motor specs published there are woefully incomplete. They do not even mention phase resistance which is the single most important detail for determining compatibility with simple H-Bridge drivers such as the ones used on the shield.
https://learn.adafruit.com/all-about-st ... he-stepper

Searching the web I found several motors with the same model number (17HS4023). Most list the phase resistance as either 3.5 or 4.0 Ohms.

A low phase resistance like that makes it a marginal case for compatibility with the shield. Assuming 3.5 Ohms, you would need to keep the supply voltage to no more than 4.2V to avoid overloading the driver chips. And that is right at the low-voltage threshold of the chips.

With a 12v supply, the motor will tend to overload the driver chips. The erratic behavior you are seeing is likely due to the drivers shutting down.

The motor is most likely intended for use with a current limiting "chopper" type driver. We have the DRV8833, but that is limited to a 10v supply voltage. We also carry the Synthetos gShield which could handle those motors. And www.Pololu.com carries a wide variety of current limiting drivers for small to medium size steppers.

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Re: Trouble getting smooth movement out of Adafruit Motor/Stepper/Servo Shield with NEMA 17 motors

Post by silvermanphoto »

OK! Is the Synthetos GShield stackable on top of the Grand Central, so I could control three sets of two of these motors using two GShields stacked on top of the Grand Central?

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Re: Trouble getting smooth movement out of Adafruit Motor/Stepper/Servo Shield with NEMA 17 motors

Post by silvermanphoto »

Actually a better question since I have three Adafruit motor shields to use, can you please help guide me towards the specs of NEMA 17 sized motors I could swap out on my robotic arm that will microstep? I don't need a lot of torque, I just need to move around this tiny laser diode I got from you: https://www.adafruit.com/product/1054

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Re: Trouble getting smooth movement out of Adafruit Motor/Stepper/Servo Shield with NEMA 17 motors

Post by adafruit_support_bill »

I don't think the G-shields are stackable - since they use a lot of digital pins that I don't believe are configurable.

The #324 motors in the store are a good match for the shield. They have a 35 Ohm phase resistance, so you can drive them with 12v with no danger to the shield. https://www.adafruit.com/product/324

We are currently out of stock on these. But some of our larger distributors like Mouser or DigiKey may still have some on the shelves. SparkFun also carries one with similar specs.

The other question is speed. The shields use the i2c bus for stepper commands. This makes it easy to stack multiple shields to control many motors. The down-side is that the i2c bus can become a bottleneck. If you are trying to move 6 motors at the same time, the speed will be limited.

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