STB Cool Stepper Driver

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STB Cool Stepper Driver

Release status: working

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


Version 1.10 is the final and tested version. It is available now.

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

Microstepping Settings

Low means pin is connected to GND, high means connected to 3.3..5V.

Microstepping settings

M0 M1 M2 Microstep Resolution
Low Low Low Full step
High Low Low Half step
Low High Low 1/4 step
High High Low 1/8 step
Low Low High 1/16 step
High Low High 1/32 step
Low High High 1/32 step
High High High 1/32 step

Connections (top view)

STB DRV8825 Connections.png


STB DRV8825 Schematics.png


TOP Layer BOT Layer
STB DRV8825 TOP.png STB DRV8825 BOT.png

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. Glueing the heatsink to the top of IC1 gives only limited improvements.

See also