Unusually high failure rate for stepper motor / driver breakout boards

Robotics
1

Hi there!

I have a project that needs 12 stepper motors and driver boards. I bought 15 of each to have some headroom, and I’m noticing only 9 are working. I could use some help identifying what’s wrong with the 3 installed motor+driver pairs that are not spinning as this failure rate seems unusually high.

Here is the setup:

  1. Stepper motor (heatsinks added on by me, but not really needed since the VREF is set very low for the payload I need to spin)
  2. Driver breakout board
  3. Arduino Nano Every controlling the breakout board

IMG_6179
IMG_61791920×1440 764 KB

Here is what is identical on all 12 setups (9 working and 3 not):

  1. Arduino running SerialStep example
  2. Connection is the same as the example:
    ARDUINO → PRODRIVER
    D8 → STBY
    D7 → EN
    D6 → MODE0
    D5 → MODE1
    D4 → MODE2
    D3 → MODE3
    D2 → ERR
  3. VREF pot is set to 0.34V to 0.36V
  4. Motor A+ is connected to the red wire, A- to green, B+ to yellow, B- to blue
  5. Resistance between red/green pairs is 34-36 Ω
  6. Resistance between blue/yellow pairs is 34-36 Ω
  7. Resistance between other pairs is infinite/disconnected (e.g., red/blue, red/yellow, green/blue, green/yellow)
  8. If I connect the motor to the breakout board with board and Arduino power disconnected, then turn the shaft by hand, the PWR LED flickers on the breakout board so I think this shows the motor is not burnt out
  9. I am driving the 12 motors with 2x 60W @ 12VDC AD/DC adapters, 6 motors each, so I think I have plenty of current to go around

However, on the 3 failing setups:

  1. The motor makes stepping/clicking sounds, but the shaft does not spin
  2. If I measure VM → GND, I get 12.1N to 12.3V
  3. If I swap the motor for a known working one, the same driver+Arduino combo works fine

It seems like the failure rate on these motors is just very high. I can’t think of anything I’ve done that would break them - I’m a fallible human but am generally experienced (computer engineering major 15 years out of school now).

Curious if anyone has any troubleshooting tips? Hopefully I am just missing something and these parts can be resurrected. Otherwise I may just need to buy another batch and do a big RMA at the end, which doesn’t seem right. I’d rather get to the bottom of what’s actually going wrong here.

Thanks,

Zach

2

Id agree that this failure rate is pretty high here.

It sounds like the motors are trying to step and move the shaft but are being prevented from doing so.

With a problem motor disconnected can you freely move the shaft?

If the coils are mixed up via wiring this can happen but I am confident that is not the cause here since you have had much success with numerous other setups.

It is possible that the motors suffered some trauma during shipping. If a motor was say dropped on the shaft or smashed into something with the shaft I can see this kind of mechanical issue happening.

How was the shipping box? Was the packing material sufficient? Is there any obvious damage to the exterior of any problem motors?

3
  1. I can turn the shaft on a motor that’s not working but there is some physical resistance, it feels the same as one that works
  2. I have double checked the wiring, and even cut and stripped the motor lead lines to rule out a connection issue
  3. The shipping box didn’t seem damaged, but I suppose it’s hard to tell for sure what happened in transit
4

Hi Zach (@zachrattner ),

Please check you are not trying to accelerate the motor too quickly. Stepper motors need to be accelerated up to the desired speed. How fast you can ramp the speed depends on the size of motor and the load. If the speed change is too rapid - e.g. a, ‘instant’ step from zero to full speed - the motor will stall, buzz and just get hot. (I’ve done it many times…!)

I don’t know enough about the TC78H670FTG library to know if it supports speed ramping. I suggest experimenting with changeStepResolution and / or the stepSerial clockDelay parameter. You may find that by lowering the speed, all 12 motors start to behave as expected.

I hope this helps,
Paul

5

Thanks but I’m trying to do 100 steps (half a rotation) over the course of 2000ms, and most of the motors can do it ok. So I think speed is not the problem?