Stepper motor missing steps with DRV8825

[Franck M]

Hi,
Testing DRV8825 and Easydriver before deciding with which to go on. With DRV8825, the stepper motor (nema 17, 42-34) the motor is jupping every where missing lots of step. With Easydriver the motor rotation is much more smooth but the Easydriver is getting very hot. Don't know how to have the DRV8825 working properly with my stepper motor (using last firmware HW203 for both)
Any idea ? What am i doing wrong with the DRV8825?
Regards
Franck

[brownrb]

https://www.youtube.com/watch?v=3TIrv_IkQuY
I am assuming you set the motor current correctly as per video.

Is there a problem with all speeds F/M/S or is just a problem with Fast?

[Franck M]

Hi Robert,
thanks for replying. Yes I set the DVR8825 to 0v, ask the driver to move for 5000 steps and started to increase the voltage. I'm arround 0,4v on vref

I made tests with PRO and PRO 2, F/M/S. I also changed the step siez full/half/... etc the motor is
still jiggling and vibrating while turning. I also tryed with 3 different drv with the same result. More than that even it started not to answer to Halt - now when I plug the power on the drv, the motor start to turn.

I would say the motor has an issue if I did not manage to have it turning smoothly with the Easydriver.

Anyway, I going to get another motor to test.

Regards
Franck

[brownrb]

The FAQ does cover some of this and givs some tips.
In general stuttering comes down to
1. stepper coils wired incorrectly
2. stepper current incorrect
3. Occassionaly a blown drv8825
4. possible firmware changes the user has made

The FAQ covers 1 and 2 adequately
3. You cannot disconnect OR connect a stepper when there is 12V applied to the focuser. The DRV chip will blow. Adequate warnings in the PDF, not inserted for fun
4. As stated elsewhere the timings values are critical and even small changes can have dramatic effects

In general, these values work for the DRV8825

#define FAST1DELAY          2800          // delay times - values are based on BOTH step mode and motor speed settings
#define FAST2DELAY          1200
#define FAST4DELAY          600
#define FAST8DELAY          300
#define FAST16DELAY         100
#define MED1DELAY           3500
#define MED2DELAY           1800
#define MED4DELAY           1000
#define MED8DELAY           400
#define MED16DELAY          200
#define SLOW1DELAY          6000
#define SLOW2DELAY          3600
#define SLOW4DELAY          2000
#define SLOW8DELAY          800
#define SLOW16DELAY         400

#define MOTORPULSETIME      5             // drv8825 requires minimum 2uS pulse to step

I would suggest that you copy these values into your firmware, then reprogram the controller.
Set the step mode to FULL and the motor speed to fast
Back the current right off till the motor is not moving at all when a move 500 command is issued,
Then adjust the current manually until the motor starts to move when a move command is sent, and rotate just a little fraction more. Retest the move 500 and get the motor moving smoothly

Then try slow and medium speeds - theses should work fine

Reset tp half steps and fast speed
Check that the motor moves. If it doesnt quite move, rotate pot just a fraction more till stepper moves smoothly. Then check half steps with slow and medium speeds.

That should then be it.

If you cannot get the motor to move smoothly at all with the DRV then its either stepper coil wiring or a blown DRV

BTW, what stepper motor did you get? A link please?

Regards
Robert

[Franck M]

Hi Robert, thanks for support. Eventually, I got a new stepper motor (https://www.ebay.fr/itm/162792645698?_trksid=p2380057.m570.l6004&_trkparms=gh1g%3DI162792645698.N41.S1.R1.TR1) and manage to do some new tests with both the DRV8825 and the EasyDriver.
With the easydriver, the motor works smoothlywith or without coil power (the A3967 is getting quite hot). With the DRV8825 and coil power the motor is jumping. With no coil the motor turn but lose steps (more in one direction than the other). So I think I'll go the the EasyDriver.

[brownrb]

Hi Franck
I cannot see any wiring diagram for that stepper so I assume you have tested and identified the coil pairs. For the easydriver, I take it that you have set the vref or current correctly?
The easydrivers I have found tend to run quite hot, even with coil power off.

I think there is some interrupt driven code versions posted on the yahoo group that is pretty good at moving.

As part of myFocuserProE project I have been experimenting with new ways of doing things and there will probably be some code transfer back into the myFocuserPro2 as a number of things have changed for the better, including stepping/moving.

Regards