
S109 driver is based on the Toshiba TB67S109 stepper motor driver chip design. It employs four layers of thick copper precipitation PCB with automatic patch processing. This driver uses indexer (DIR / STEP) control interface. Its maximum driver current can reach 4A. It can drive the 57 stepper motor, compatible with the Pololu pin definition.It can be used as a substitute for the A4988 module.

Current limits can be adjusted by measuring the VREF and the adjustable resistance (pls check wiring diagram). Connect the voltmeter + to VREF, [-] to the GND and read the value.
S109 uses 0.10ohm current sense resistor, so the current limits can be calculated as follows:
[Current Limit = VREF x 2]
Please do not exceed the current rating of the motor current, or motor and motor driver will be over-heated, or even damage.
The following table shows the microsteps setting for the S109A module
L = Jumper disconnected (without jumper cap) H = Jumper closed (plugged in jumper cap)
| Microsteps | Standby mode | 1 | 1/2(A) | 1/4 | 1/2(B) | 1/8 | 1/16 | 1/32 |
|---|---|---|---|---|---|---|---|---|
| MS1 | L | L | L | L | H | H | H | H |
| MS2 | L | L | H | H | L | L | H | H |
| MS3 | L | H | L | H | L | H | L | H |
Please be sure to install the heatsink and air cooling. Do not run it without cooling for long time use.
Please submit any technical issue into our forum