RADDS Power Stepper Driver with 1/128 Microstepping



  • THB6128 chip
  • Motor voltage 10 – 25V
  • Motor current 0 to 2.2 A adjustable via potentiometer (V-REF)
  • Motor decay adjustable via potentiometer (Decay)
  • Sleep and Boost Mode
  • Logic voltage is generated from the motor voltage
  • Up to 128 micro steps possible (recommended maximum of 32 micro steps for 8-bit electronics, such as Arduino Mega with RAMPS.)
  • Short Circuit Shutdown
  • Pre-installed heat sink
  • The size corresponds to the popular Pololu drivers and the pinout is compatible but not identical.
  • Max 1/128 micro stepping when used in combination with RADDS (or other 32-bits controllers that supports 1/128 micro stepping)
  • Can be used on RAMPS, rumba and other RepRap electronics, but 8-bit electronics usually are too slow for 1/64 and 1/128 micro stepping.

CAUTION: Inverted activation signal Enable = HIGH (at Pololu drivers enable = LOW, invert in firmware!)

Version tracker

V1 – This is the first RAPS128

V2 – C1 change from 10 µF to 0.1µF



Minimal pinout



Maximum pinout



Adjust V-REF


The arrows indicate the measurement points for the reference voltage. Use a voltmeter and measure the voltage between the ground terminal and the pot wiper on the driver’s v-ref potentiometer.
Recommended voltage range: 0.8 to 1.6 V. This corresponds to a theoretical peak engine power from 0.73 to 1.46 A


Adjust Decay


By turning the decay potentiometer, the way of voltage and current decay in the motor coils is changed. A medium setting has been proven to work with many Nema 17 motors.”