Stepper motor not holding

I am trying to use a a4988 regulated driver board (#1183) to drive a nema 17 stepper. The application pushes a small trolley up an incline on rails in 10 to 50 step increments. About every second or third movement, the stepper does not brake/hold and the trolley slides back down. I’ve tried a few different steppers but all with the same result. I am not turning the driver off or disconnecting anything in any way, so I don’t understand why it won’t hold.

Any suggestions would be greatly appreciated.

Charlie

You haven’t given enough information for anyone to decide, but there are several possibilities.

  1. The stepper does not have the necessary holding torque
  2. The current limit is set too high, so the driver is overheating and shutting down
  3. The power supply is not capable of providing the necessary voltage and current
  4. Some combination of the above

[quote=“Jim Remington”]You haven’t given enough information for anyone to decide, but there are several possibilities.

  1. The stepper does not have the necessary holding torque
  2. The current limit is set too high, so the driver is overheating and shutting down
  3. The power supply is not capable of providing the necessary voltage and current
  4. Some combination of the above[/quote]

I’m sorry. I’m not exactly sure what other info I should providing I am pulsing the a4988 with 5 to 20 steps from an Arduino Nano. The stepper motor is a run-of-the-mill Nema 17 bought from Ultimachine (although I tried several others with similar results). The EN (pin 7), and DIR (pin 13) are tied low. The reset and sleep pins are tied together and all the MS pins ( 8, 9 & 10) are low. the 5V (pin 2) and VDD (pin 3) are tied together and the Arduino Nano is powered from the 5v (pin 16). The only pin I am manipulating at all is the step pin. (pin 14)

I tried adjusting the current limiter trimmer and did not seem to help (although admittedly, I am not 100% sure I did it as it should be done).

The power supply is a 11.1v 3S lipo battery, fully charged. I would think that would be more than enough for the stepper.

If you will give me an idea of what sort of info I should be providing, I will gladly do so. I could really use he help.

Charlie

At the minimum you need to provide enough information to address the above issues. NEMA 17 just specifies the dimensions of the mounting plate of the motor, and there are thousands of different motors with that plate.

  1. The required holding torque or force for your mechanical setup. If you don’t know how to evaluate your mechanical setup, this blog post should be helpful pololu.com/blog/10/force-and-torque

  2. The holding torque, current rating and resistance of the motor winding, or a link to the product page

  3. The current limit to which you set the A4988. It sounds like you don’t know how to do that, so carefully follow the instructions on the Pololu A4988 product page (watch the video).

  4. The current draw limit of the battery, or a link to the product page. There are many battery sizes and some have overcurrent protection built in!

ahhh…home work.

Great. You’ve given me enough info to try and understand what I am doing better. Thank you. I will follow up with what you have suggested. Your right…I don’t know what I am doing with setting the current. Also you are right in that I don’t understand what I should about the steppers.

I will soon, though.

Thanks very much
Charlie