A4988 stepper driver temperature too LOW?

Hi everyone,

this is my first post, have learned a lot from this forum.

In the past I was using some smaller stepper motors (12 V, 0.33 A, 0.23 Nm, datasheet) and experienced the usual fiddling around: I had to dial the potentiometer to about 1/3 to 1/2 on the driver board to get good performance without skipping steps or overheating the driver. Both the A4988 and the stepper would get warm, but you could still touch them without pain.

Now my question/problem: After switching to some other steppers (2.55 V, 1.7 A, 0.40 Nm, datasheet) and setting the trimpot to full output (highest current measured at power supply output) I was expecting to overheat the A4988. But to the contrary: Both driver and stepper are quite lukewarm even after hours of operation, performing better than the previous steppers.

I can imagine how the stepper is not getting hot (not enough current from the driver), but why is the driver not getting hot on full output?

I am using a A4988 based Pololu clone. Supply Voltage (tried 12 to 30 V) does not affect temperature but higher voltages give better rpm.

So what am I missing? This driver/stepper combination should not be that uncommon - how are your results?

Thanks,
Thomas

Interesting. It doesn't seem likely that higher drive current would result in lower driver temps. Is this driver a step-stick clone limited to 1A? If so then even at "full" current it's running at half the chip capacity. Which would also explain why the motors are cool. Do you have heat sinks on them?

I don't know if it is limited to 1A. Would that explain the hotness using the other steppers? How can I tell if those drivers limit at 1 A?

Maybe there is something to the resistance/voltage rating of the stepper motors.

No, there are no heatsinks on the drivers.