STB Cool Stepper Driver

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Revision as of 06:22, 28 May 2014 by STB (talk | contribs) (Heat Consideration)
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Release status: experimental

STB Cool DRV8825 V11.jpg
Stepper driver for RAMPS, Sanguinololu, Gen7, RUMBA, Easy Electronics...
GPL 2.0
CAD Models
External Link


Currently this is work in progress. Some samples are available for testing.

Board Revisions

STB Cool Stepper Driver V1.10 (8+8 pins):

  • Selectable current limit 1.8A/2.5A with solder jumper
  • If the current is too high for the heat sinking, the motors will stop and the powersupply of the printer must be cycled.

STB Cool Stepper Driver V1.00 (8+8 pins):

  • Initial release


Tuning motor current

From the TI DRV8825 datasheet [[1]], the calculation for the maximum trip current is:

 I_CHOP= Vref/(5*Risense) 

The sensing resistors are Rs=0.1 ohm, so a Vref of 1.25V should produce a maximum current of 2.5A. By default the STB Cool Stepper Driver is limited to 1.8A which is enough for most applications and no special heatsink is necessary. For the full 2.5A range SJ1 on the backside of the driver has to be shorted. The reference voltage can be measured direct on the center tab of the potentiometer R4.

Current settings

0.5A 0,25V
0.75A 0,38V
1.00A 0.5V
1.25A 0,63V
1.50A 0.75V
1.75A 0.88V

Connections (top view)

Heat Consideration

Best cooling results are given if the heatsink is mounted on the area on the backside of the PCB where the soldermask ist cut out.

See also


Contact STB