Did I toast my EasyDriver?

So, yesterday I tired to run a stepper motor taken from an old CD drive using an Arduino Nano and an EasyDriver v4.4.
I took the following pinout using a 12V/1.25A AC Adapter connected to the Drivers M+ and GND pins. I read using 12V will not harm the driver, and apart from a very hot IC and stepper it worked like a a charm. I did not leave the Driver more than a few minutes powered.

However, today the stepper seems to stall whatever step frequency I am using. Is the Driver toasted or is it an other problem and how can I fix it?

It somehow works now, don't ask my why

Do you know the difference between voltage and current flow?
I suspect you didn't care about to adjust the current limit, or did you?

That's explaining the hot driver and - if you wait a little bit longer running it (a few minutes is already a very very long time for all candidates involved), it will kill at least your stepper motor.
The driver has a built-in protection mechanism which will recover from being overheated (I don't know how often you can overheat, but I would immediately do something about it), but your poor stepper motor hasn't got such a protection.

Once it's burnt, it's burnt forever.

I guess, that the CD stepper motor would come with max. 150 - 200mA; if you can identify the type exactly, you could search for the data sheet and see what the max current is.

Then you have to follow the procedure how to limit the current of the Easy Driver.
If nothing was destroyed before - that will do the trick.

Addit:
Current adjustment seems not that easy with an Easy Driver, as you won't find a special Vref point on the breakout board other than at the main chip itself. See Q9 of that link.

As on top you can't be sure that even the silk screen instructions are correct (min/max seems sometimes been mixed up) I would do the following:

  1. look carefully where the potentiometer stands now - is it turned to the right of left outmost position and what does this position say (max or min) ?
  2. if it is one of the extreme positions, turn it half way into the other position and watch what happens to your motor and feel how hot/warm the driver gets
  3. If the motor still turns and the driver doesn't get that hot, go ahead and turn it full way in the sense you did in 2.
  4. Now you should be in the min position of the driver and it should still deliver it's 150mA to the motor, which still mightbe ok for turning it

Alternative1:

  • if the potentiometer stands in between the extreme positions - CAREFULLY turn it into either direction and watch, if the driver still gets hot or even hotter (than immediately turn it off, let it cool down and turn it to the opposite direction to its extreme position which then should be the min position).

Alternative2:

  • if you have a multimeter and a very fine probe and a "cool", not shaky hand (and some electronics experience), you could identify the Vref pin of the main chip which is Pin1 (first pin, closest to the potentiometer, if I could read the datasheet clearly enough - which was a little tricky). Here you should measure the voltage (multimeter black wire to GND, voltage range to 20V, later to 2V, red wire (+) with small probe at pin1). By turning the potentiometer lower the voltage to its smallest value which will be 1V, which will result in the minimum current = 150mA).

Thanks for your answer.

I regulated the current on the motor currunt following this information until the current was just high enough for the needed torque (1.7V measuring by your suggestion).
The stepper motor is way cooler now (I can touch it for a long time), I think the IC is as well (still only touchable for 1 sec.). Following the datasheet, high temperatures as >130°C are not a problem.

Thanks for your help. Is there anything else I should do?

Congrats!

As I don’t have the Easy Driver (I only work with drv8825, TMC21xy or bigger ones) I didn’t see that they apparently had a Vref probe location on the board. Great that you found it out.

The only thing that might still be an issue - try to find out what motor you have, even 141mA (if the 1,7V formula of your link is correct) may damage your motor on the long run, if the max motor current would be 100mA. But that’s something which I can’t say from here - that’s why the datasheet is so important.

until the current was just high enough for the needed torque

How did you determine that the torque was ok - do you have load on the motor or does it just turn?

Nevertheless, if the motor stays cool, it might work without lowering the current.
I guess that you just want to play around with it, to learn about Arduino, drivers and motors?

So, if you go for a project where you need a motor run for hours then that’s the case where you actually have to deal with the proper adjustments.

Following the datasheet, high temperatures as >130°C are not a problem

I would not count on that. If the surface of the chip gets so hot at its outer side, the heat has already traveled from the inner dye through the plastic so that the electronic inside would be even hotter. On the long run this will damage the chip.

My suggestion: use a cooling unit, either passive or active.

rpt007:
[...] even 141mA (if the 1,7V formula of your link is correct) may damage your motor on the long run, if the max motor current would be 100mA. But that's something which I can't say from here - that's why the datasheet is so important.

This is the datasheet of an CD drive stepper motor. It should be very similar to the one I have, I don't think there are major differences between models.
Using U=R*I, the current would be 170 mA at 1.7V - how do I know what current my driver supplies and if that will work? I somehow fail at these simple electronics ::slight_smile:

rpt007:
How did you determine that the torque was ok - do you have load on the motor or does it just turn?

I took the whole laser positioning system out of a CD drive - minimum torque means the motor can move the carriage. It stays cool even after minutes of load.

I am just playing a bit with these electronics, nothing serious. Perhaps I will use the stepper in a DIY CNC or printer, but not now :slightly_smiling_face:

If it is just for test reasons and themotor and driver behave like you described, I think you are ok with that.
So you can study and play a little bit with stepper drivers and motors.

Have fun :slight_smile:

Great. Thanks for your help! :slight_smile: