I bought a dozen types of stepper motors with rated voltages ranging from 4v to 12v and currents from 2A to 0.3A. I am unable to get anywhere near the rated torque on all motors except those with rated voltages 10v and higher.
My setup:
Power supply: Agilent E3610A set to output 12V (current limited to 2A)
MCU: Teensy 3.1
Stepper Driver: Pololu A4988 (Cant provide link due to low reputation)
Now, for steppers like this one with rated voltage of 4.2v and current 2A – no matter what I do with current limiting pot on the surface of the driver – I simply cant get the motors draw more than a fraction of their rated currents. Its a single turn pot – so I fall off the adjustment space before current (measured at power source AND motor coil) reaches any appreciable amount (usually it maxes out around 0.1-0.2A). Torque too is very low, naturally. I tried voltages 8-17V (the range limited by the driver board and my power supply) – but still, cant get the motors produce more torque.
All 4 wire steppres are in bi-polar config.
Interestingly, it is not a problem with steppers rated 10-12v, for instance CanaKit stepper (cant provide link due to low reputation) rated at 0.33A and 12v – I can get them draw more current, although even in that case – there is a huge mismatch between the current they ought to draw based on VREF pin reading, and what the actually draw. For instance, measuring the VREF (~1v)and applying the formula – I should have gotten 2.5A (or slightly less due to 70% energization) – but I really measure only 0.29A on the coils.
Everywhere I read, it looks like I should not have this problem. I.e. read the threads on SE (cant provide links due to low reputation)
What am I missing? All is wired up together on a breadboard. Wiring is solid, but could this be a problem? Should I consider a different driver?
Appreciate any tips!
Best Answer
Some high current steppers should have much greater power, some as many as 30 to 80 volts. The best you can start with (without no datasheet) is to measure coil resistance and calculate.
Something here you might use.
You'r drive A4988