Motor jumping around when on 12v, but smooth when running off of 5v

[Karl Rees]

My stepper motor is running smoothly when running off of 5v, but when I apply 12v, it jumps around almost randomly. It wasn't much of a problem (actually, for a while I thought it was a pleasant surprise that would minimize cables), until I added my DSLR to the mix and suddenly it couldn't lift the focuser up. I'm assuming the 5v doesn't provide enough power to lift the focuser. But with 12v, the motor shaft just bounces around even if nothing is attached.

Anyway, I'm wondering if anyone has suggestions. My configuration:

Arduino Uno (v294 firmware)
LP293D shield
17HS4401 Nema17 motor
Crayford style focuser (motor connected via flexible coupler)

I've tried both running the 12v through the arduino to the shield and removing the jumper and applying the 12v directly to the shield.

Thanks,
Karl

[brownrb]

1. The pdf clearly states, many times, not to use a steper motor whch has a coil current grater than about 600mA. Yours is 1.6A. It is a wonder you have not blown things up.
2. What is a LP293D shield? Not sure that is supported., or is it a typo?
3. 12V power must be wired direct to the stepper driver board
4. jumping around is caused by wiring or code sequence issues. If it is a supported board, then it is a wiring issue. Either the coil pairs are wired to the wrong connections on the driver board or there is a broken connection.

https://www.dropbox.com/s/ks3cwabbg2cxcou/Stepper%20Motor%20Issues-01.mp4?dl=0