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I am trying to drive 4 Nema17 stepper motors using 4 DM542 drivers, controlling them using a teensy4.1. The step and direction signal is level shifted to 5V, the DM542 are powered using a separate 48V supply. In general this setup works great, however sometimes randomly one of the steppers refuses to turn. The corresponding driver is powered, since the motor is applying a holding torque. This issue shows up randomly and fixes itself randomly too. This is not a satisfying answer however, so I am looking for clues on what the underlying issue might be. What have I tried so far:

  1. Wiring issue: I have checked whether one the the leads wiggles itself loose or something and was not able to find any issues in the wiring.
  2. Broken stepper or driver: I have changed the drivers and steppers around and was not able to detect any pattern. However lets say, if the issue occurs with stepper 1 connected to driver 1. Now connecting a different stepper 2 to driver 1 will cause stepper 2 to stall. Switching the teensy pins connected to driver 1 to driver 2, will cause the motor connected to driver 2 to stall. This suggests that the problem is on the teensy side of things. But:
  3. Check for a software issue: I am quite sure that this is not a software issue on the teensy side because like I said, generally this setup is working great. Of course there is a chance of a random software bug, however if this issue occurs, resetting the teensy does not fix it. Rather waiting for a few minutes does.
  4. Checking the signals with an oscilloscope: Interestingly I was not able to check the signals to a stalling driver because 1. the issue does not occur that frequently and 2. the one time I was actually ready with a scope on hand, the issue fixed itself immediately as soon as I placed the scope probes on the signal pins.

I have to admit that I am out of my depth right now, so any hints on what might cause this problem or what steps I can take for a proper diagnosis are appreciated.

Edit Reacting to comments made by Tony Stewart EE75: The level shifter being used is a BSS138 (https://www.sparkfun.com/products/12009). The DM542 is setup to provide a max peak current of 2.37A (RMS of 1.69). Microsteps are set to 25600. I struggle to provide a max accleration of the steppers, or comment on the Friction on the shafts. The application is a build similar to https://github.com/T-Kuhn/HighPrecisionStepperJuggler .

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  • \$\begingroup\$ Also make sure the 48V wiring is routed well-away from the 5V control pulses; better yet, use shielded cabling and ground only one end of the shield. Seen one where all wiring (non-shielded) was ran together, and spikes on the 48V lines caused random interference in random control lines. \$\endgroup\$
    – rdtsc
    Commented May 23, 2022 at 18:49
  • \$\begingroup\$ Check if power cycling the Teensy by removing the supply, rather than using the reset button solves the problem. \$\endgroup\$ Commented May 23, 2022 at 19:29
  • \$\begingroup\$ The wires for power and control are wired in different directions. And yes since using the reset button from the teensy is putting it into program mode, I was cycling their power supply during resets. \$\endgroup\$
    – AndGL
    Commented May 23, 2022 at 19:35

1 Answer 1

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With this high voltage, I think it is a driver thermal problem with OTP protection.

The driver must use current limiting to use this high voltage and may need a fan to keep cool 35 mm type or more.

Otherwise , you have to reduce supply voltage. Acceleration parameter is also critical for slipping. Since a=F/m this is also proportionally to current and heat rise with your present thermal resistance.

So you either adjust current limit, reduce V+ or add force air cooling or reduce max acceleration in steps/second motion or examine friction loss and improve all/any until it has enough margin to NEVER fail under ALL environmental and load conditions.

OTP inside switching or linear regulators is thermally sensed and self resetting, normally.

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  • \$\begingroup\$ According to the DM542 spec sheet the drivers can handle up to a 50V power input. The motors feel hot to the touch after some time, the drivers not really. I was thinking along those line too, but it doesnt seem to be caused by the components heating up as the issue sometimes occurs after a longer power down. \$\endgroup\$
    – AndGL
    Commented May 23, 2022 at 19:37
  • \$\begingroup\$ Watt about acceleration and friction? And watt are all your settings ? Add to question ;) \$\endgroup\$ Commented May 23, 2022 at 21:35

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