My goal is to implement a stepper motor drive system for my home made telescope mount. I ordered Pololu A4983 stepper motor driver with voltage regulator and Pololu 3.9V, 600mA stepper motor for the purpose. Links to the products:
I have done read the instructions and data sheets for the driver and stepper and I’m quite sure I have connected everything correctly. Motor turns smoothly and with constant velocity. I use Arduino Duemilanove to control the driver board.
The only problem is that the torque the motor provides in 1/16 step mode is extremely low. In full step mode the torque is only slightly better. I can easily stop the turning of the motor shaft by simply touching it lightly. I know that the torque goes down with micro stepping, but I was surprised that the torque is practically almost zero.
Do you have an idea what I’ve done wrong? I have set the current limiting to 600 mA by measuring the voltage on VREF pin. According to A4983 data sheet the current limit is calculated by I = U / (8*R), where U is the measured voltage from VREF pin and R is the resistance of current sense resistors (0.05 Ohms according to Pololu website). Hence, I set the voltage to 240 mV. I use 12 1A power supply for the driver board. The motor is heating up quite a bit, but I can still quite comfortably touch it.