# How to calculate Current for pancake stepper motor - To change in Pronterface

DISCLAIMER: New to electrical engineering topics. I'm a 3d-printing hobbyist. I don't know all the Jargon being used but trying my best to keep up.

PROBLEM

Recently bought a Nema 17 stepper pancake motor to replace the Ender 3 extrusion stepper. It's only used for direct extrusion with a BMG 3/1 gear ratio, which leads me to believe it doesn't need a lot of juice to have it work optimally.

*Got this from TriangleLab:*


https://www.aliexpress.com/item/32768043304.html?spm=a2g0s.9042311.0.0.27424c4d4HQcug

This thin stepper is running very hot. Via pronterface and/or octoprint, I adjusted the "current" from the default ender 3 E850 to E50, using command M906 and saving with M500.

It is still running hot and TriangleLab hasn't been very forthcoming.


NOTE: i'm not sure what "current" is being referred to, amps or voltage. I just followed this youtuber's advice for the adjustment...

Used this guy's method: https://youtu.be/GHUr1a3nXDU

Question

How do I know if the stepper is running TOO hot? (not sure what the consequences of a hot stepper might be, other than the thing burning out and becoming a fire hazard.)

Is there a calculation that is better than just eyeballing the situation and doing random tweaks?

Any info would be much appreciated. Thanks in advance.

**Triangle Lab's Stepper specifications**

NEMA 17

- 1.8° Step Angle
- 200 Steps Per Revolution
- 1.0 Amp
- per phase 5.1 Ω 5.9mH
- 21 N/cm Holding Torque
- 23mm Body
- 20mm Output Shaft(5mm diameter)(17mm D-Shaped)


......

Current is amps. The set of specifications you gave states

1.0 Amp

so as long as your current is <= 1.0 Amp then it doesn't really matter how hot it's getting because the motor is rated for that current.

• Thank you. I came across this and will check later to adjust the potentiometer screw on the motherboard instead of meddling through the command prompt in Octo. Ref: youtube.com/watch?v=hC4J29rxPlQ Oct 28, 2020 at 1:06
• * Assuming there are no external heat sources further warming the motor.
– Ben
Nov 5, 2020 at 16:40

Ender 3's stock mainboard does not allow you to set driver currents in firmware, as it requires a TMC driver in UART mode and creality 1.x and 4.2.x mainboards run the stepper drivers in standalone mode. There's a little screw pot by each driver for setting the reference voltage.