05 - E3D Hemera Current Adjustments (VREF)

The standard Hemera motor has a rated motor current of 1.33A.

This value is likely to be different from the motor you may have been previously using with your printer.

In order to provide the Hemera motor with the correct amount of current, so as to have it's ideal torque level, and not over heat, it is required to make some adjustments to the VREF on your stepper drivers.

This guide will provide the information needed for the 3 most common stepper driver types. A4988, DRV8825 and the TMC drivers.

VREF = Rated Motor Current x 8 x Rsense

VREF = 1.33 x 8 x 0.05

VREF = 0.532

0.532 - 0.0532 = 0.4788

VREF = Rated Motor Current / 2

VREF = 1.33/2

VREF = 0.665

0.665 - 0.0665 = 0.5985

LV 8729 calculation:

VREF = Max current / 2

VREF = 1.33 / 2

VREF = 0.665

0.665 - 0.0665 = 0.5985

Duet settings,

In typical use cases the current setting should be 60% - 90% the rated current of the stepper motor.

In the case of Hemera that would mean setting the current to between 0.798 A - 1.197 A.

for more information please see: https://duet3d.dozuki.com/Wiki/Setting_m...

The TMC driver series uses a root mean square (RMS) value for the calculations.

RMS = Max rated current / 1.41

RMS = 1.33 / 1.41

RMS = 0.94

TMC 2100 calculation:

VREF= (RMS current x 2.5) / 1.77

VREF = (0.94 x 2.5) / 1.77

VREF = 2.35 / 1.77

VREF = 1.33

1.33 - 0.133 = 1.197

VREF = 1.197

For more specific information regarding setting current with TMC drivers please refer to the datasheet for your specific step stick/ driver being used.