<p>If the motors are in parallel, then setting it at 0.4V means each motor will only get <em>a quarter of</em> the current a single motor would get at 0.8V. If you set it to 0.8V each motor will get half. I think 0.8V (same as for the other motors) would be an appropriate setting. Stepper drivers are constant-current, not constant-voltage.</p>

<p>Are the steps/mm for your Z-axis correct? Perhaps it's just trying to move too quickly.</p>

CC BY-SA 3.0
2016-10-24T06:48:45.490Z
Thank you Tom. Happens when you are focusing on a problem on your own that the big picture is invisible. The issue was in the acceleration, I reduced it from the default 3000 to 1000 and the same also for the feed rate from 5 to 3 and it is now working fine. The stepper voltage is at 0,8 as per the others.
FeliceM
CC BY-SA 3.0
2016-10-23T14:19:18.797Z
2016-10-23T14:19:18.797Z
Tom van der Zanden
<p>I am rebuilding my printer, a hold Prusa/Mendel that has been boxed for years. I have changed the board ( I am using a Rumba) and the drivers (I am using <a href="https://www.pololu.com/product/2133" rel="noreferrer">Pololu 8225</a>) with heatsinks and 1/16 microsteps.</p>

<p>5 motors type <a href="https://www.openimpulse.com/blog/products-page/product-category/42byghw811-stepper-motor-2-5-4-8-kg%E2%8B%85cm/" rel="noreferrer">42BYGHW811</a>, rated: 2,5 A, R 1,25 Ohm.
I have set the stepper voltage at 0,8 V for XYE which gives a current of 0,64 A and they seems to work without problems.</p>

<p>To get the same current on Z, where I have 2 motors in parallel, I should set it at 0,4 V but the motors do not turn at such low voltage. They just make noise, no turn. I have M8 rods nicely lubricated on such axis and I can turn them easily by fingers. If I go up to 1 V the motors turns but then the driver gets very hot and I loose steps. May be I should play with the acceleration too?</p>

<p>I am not sure if the above settings are correct. Your hints from your actual settings and experiences will be appreciated.</p>

<stepper><stepper-driver>
How should I power these stepper motors
FeliceM
# How should I power these stepper motors

(Asked by: username_0 on 2016-10-23)

I am rebuilding my printer, a hold Prusa/Mendel that has been boxed for years. I have changed the board ( I am using a Rumba) and the drivers (I am using [Pololu 8225](https://www.pololu.com/product/2133)) with heatsinks and 1/16 microsteps.

5 motors type [42BYGHW811](https://www.openimpulse.com/blog/products-page/product-category/42byghw811-stepper-motor-2-5-4-8-kg%E2%8B%85cm/), rated: 2,5 A, R 1,25 Ohm.
I have set the stepper voltage at 0,8 V for XYE which gives a current of 0,64 A and they seems to work without problems.

To get the same current on Z, where I have 2 motors in parallel, I should set it at 0,4 V but the motors do not turn at such low voltage. They just make noise, no turn. I have M8 rods nicely lubricated on such axis and I can turn them easily by fingers. If I go up to 1 V the motors turns but then the driver gets very hot and I loose steps. May be I should play with the acceleration too?

I am not sure if the above settings are correct. Your hints from your actual settings and experiences will be appreciated.

**Tags:** stepper, stepper-driver

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## 1 answers

### Answer by username_1 on 2016-10-23. Score: 3 | Accepted answer

If the motors are in parallel, then setting it at 0.4V means each motor will only get *a quarter of* the current a single motor would get at 0.8V. If you set it to 0.8V each motor will get half. I think 0.8V (same as for the other motors) would be an appropriate setting. Stepper drivers are constant-current, not constant-voltage.

Are the steps/mm for your Z-axis correct? Perhaps it's just trying to move too quickly.

> **Comments:**
> **username_0**: Thank you Tom. Happens when you are focusing on a problem on your own that the big picture is invisible. The issue was in the acceleration, I reduced it from the default 3000 to 1000 and the same also for the feed rate from 5 to 3 and it is now working fine. The stepper voltage is at 0,8 as per the others.  

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