I recently bought some chinese replica a4988 driver boards from:
Those boards are of the same shape as your a4988 boards.
In addition, I have some NEMA 17 stepper motors with a holding torque of 4.5 kg*cm for 2.2V, 2A and 1.1 Ohm.
Unlike your boards there is no clear relation about the current limit as a function of the VREF coming out of the potentiometer. I tried playing with the potentiometer and found out that when I crank it to the maximum the drivers get hot (a bit uncomfortable to touch but will not burn you) and the motors get only slightly warm if at all at 12V. Despite that, the motors seem to give a reasonable amount of torque. According to your product page setting the potentiometer to maximum should cause the drivers to quickly enter overheating/overcurrent protection and may also damage the motors but it seems to be far from that.
Therefore I want to ask:
- Is there a way to find out the relation between VREF and the current limit? I only have a simple multimeter so I can’t perform any advanced analysis such as reading signals with an oscilloscope. I think it may be that the potentiometer doesn’t yield the full range of current limiting the a4988 is capable of giving.
- If the above is not the issue, what can cause such a situation?