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I am using the DRV8825 stepper motor driver. The NEMA 17 is rated for 1.2 A and the NEMA 23 I'm using says it's rated for 2A. I have two NEMA 23s and they both soon choke out (stop moving).

When I was using the carrier board from Pololu, the lower current worked for any motor (adjusted by the current limiting potentiometer). But it didn't have enough torque. So I made a PCB, put on the DVR8825 and attached a beefy heat sink (chunk of aluminum) and thermal paste between the two.

The issue could be a heating issue. But the new heat sink dissipates heat pretty well. I mean, it could be going into automatic shutoff. But then, that doesn't explain how the NEMA 17 always works and the NEMA 23s stop working at higher current after a 3-4 seconds.

I will try to experiment with my resistor decade boxes for a slightly lower current. This will lower the torque, but it might work out. Is there something else that might be going awry? I can go into further detail of the PCB design, but I believe the design in relation to heat dissipation is not the issue.

Edit

More information and testing...

The MCU is an ESP32. It is powered by a VX07805-1000 DC regulator: The https://www.digikey.com/en/products/detail/cui-inc/VXO7805-1000/7350297

When the ESP32 is powered via micro-USB, it seemingly runs indefinitely. When it's just the voltage regulator, it runs for about eight seconds. Then the NEMA23 stops.

I switched out a fresh VX07805-1000s. The same thing happens. After eight seconds, the NEMA23 just stops. Even if the ESP32 is plugged in (running indefinitely), and the micro-USB is taken out, it still stops after about eight seconds.

The heat sink is cool to the touch. After running it for a few minutes it gets warm. Either way, I think it's clear it's not a heat diffusion issue (related to thermal shutdown).

The voltage regulator's max output current is 1 A:

enter image description here


The ESP32...

enter image description here

https://www.espressif.com/sites/default/files/documentation/esp32_datasheet_en.pdf#page=42

...seems to allow that?

OH WAIT!

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  • \$\begingroup\$ What is your supply voltage for the driver? \$\endgroup\$ Feb 15 at 17:44
  • \$\begingroup\$ EPP200-24 volt (8.4A) meanwell.com/productPdf.aspx?i=713 \$\endgroup\$
    – adamaero
    Feb 15 at 18:02
  • \$\begingroup\$ Does the bigger (higher inertia) one keep going if you reduce the speed? \$\endgroup\$ Feb 15 at 18:53
  • \$\begingroup\$ Weird thing is, one NEMA 23 works alone (indefinitely). But when combined with another or with the NEMA 17, it stops after 1-8 seconds. That is for the 24 V power supply. The bigger motor, from previous tests, I believe acted the same way at slower speed. \$\endgroup\$
    – adamaero
    Feb 15 at 20:35

3 Answers 3

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the NEMA 23 I'm using says it's rated for 2A. I have two NEMA 23s and they both soon choke out (stop moving).

The Pololu page says this: -

It operates from 8.2 V to 45 V and can deliver up to approximately 1.5 A per phase without a heat sink or forced air flow (rated for up to 2.2 A per coil with sufficient additional cooling).

I'd be looking at this as the likely cause of your problem. You are sailing a bit close to the wind for my liking and, we only have your word that the current is not greater than 2.2 amps for each stepper. Link the data sheets is my advice.

I would also look into the power supply you are using to make sure it is capable of supply over 4 amps into the two motors.

Is there something else that might be going awry?

It sounds like you have the thermal management under control so I'd look into the over-current problem mentioned above.

I am using the DRV8825 stepper motor driver.

Then you need to show your schematic and your PCB layout. I can make some estimations using Pololu's design but, it's much more difficult when you have rolled your own circuit.

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  • \$\begingroup\$ What would explain a stepper motor just stopping though? I think what you suspect is that it has to do with the motor's current rating. But what explains the behavior of just dying abruptly? \$\endgroup\$
    – adamaero
    Feb 15 at 18:15
  • \$\begingroup\$ Are you saying that you get device failure? \$\endgroup\$
    – Andy aka
    Feb 15 at 18:17
  • \$\begingroup\$ I'm not sure what that means. All motors work at lower current. The NEMA 23s aren't destroyed. I just intuitively think they would not stop abruptly if they could not handle the current, and that it would be maybe a slow decline? Well, then again these are stepper motors. \$\endgroup\$
    – adamaero
    Feb 15 at 18:20
  • \$\begingroup\$ You used the term "dying" ad that usually means a fatal destruction of a device. The DRV8825 has an over-protection facility and that will immediately take action based on what I've read in the data sheet. \$\endgroup\$
    – Andy aka
    Feb 15 at 19:05
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I can not provide much technical help but I have pushed 8825s to their limit as well, even driving two NEMA 17 motors with one driver and have seen great results on performance when using a big heatsink and thermal paste but with active cooling. It may help if you have not already done this, they can get quite hot.

Edit: I can't recall off the top of my head but I am running them past 1.2A

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  • \$\begingroup\$ It might take some days, but I'll try a fan. Thanks \$\endgroup\$
    – adamaero
    Feb 15 at 22:43
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The operating voltage of ESP32 ranges from 2.3 V to 3.6 V. When using a single-power supply, the recommended voltage of the power supply is 3.3 V, and its recommended output current is 500 mA or more.

https://www.espressif.com/sites/default/files/documentation/esp32_datasheet_en.pdf#page=19

The voltage regulator output is 5V. Maybe that's the issue?

Reviews/questions answered say it can handle 5V:

Yes, the device itself is 3.3v. Vin will take 5v no problem but wouldn’t recommend any higher voltages.

https://www.amazon.com/DORHEA-Development-Unassembled-NodeMCU-32S-Microcontroller/dp/B08DQQ8CBP/

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