Stepper motor stopped working.

Ask questions about DIY board assembly issues, fault finding and testing. (Covers all Megasquirt versions and board.)

Moderators: jsmcortina, muythaibxr

Post Reply
Dougal
Helpful MS/Extra'er
Posts: 36
Joined: Wed Feb 15, 2017 1:16 am

Stepper motor stopped working.

Post by Dougal »

MS2 V3.0 plus relay board.
I've been using a Nema 17 3d printer motor acting on a quadrant to control the throttle spindle on bike throttle bodies for idle air control.
It's been working great for a month or so but now fails to move the mechanism. The motor moves when running free. I replaced the motor but same result.
I have just tested for voltage across SP1/SP2 and SP3/SP4 expecting to see a transient 12v as the motor moved. I actually got a reading of .001v dc. The min/max reading showed -.002/.001v dc.
Is my test method correct?
And if so and I am now effectively getting no voltage at the stepper outputs what can I check for the cause. Driver chip or something round about it?
Thanks.
Dougal.
billr
Super MS/Extra'er
Posts: 6828
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Stepper motor stopped working.

Post by billr »

What is the coil resistance of that motor?
racingmini_mtl
Super MS/Extra'er
Posts: 9128
Joined: Sun May 02, 2004 6:51 am
Location: Quebec, Canada
Contact:

Re: Stepper motor stopped working.

Post by racingmini_mtl »

That type of motor will fry the stepper driver chip. They will draw over 2A while the chip can only safely handle 0.75A.

Jean
jbperf.com Main site . . . . . . . . . . . . . . . . . . . . . . jbperf.com Forum
Image
Dougal
Helpful MS/Extra'er
Posts: 36
Joined: Wed Feb 15, 2017 1:16 am

Re: Stepper motor stopped working.

Post by Dougal »

I thought I'd probably fried the chip.
While it was working, it was just used for cranking and warm up, set for power whilst moving only, so I probably just got away with that! It was whilst having a play with closed loop idle that it failed - more work for it to do.
That motor was 1 amp per phase with a phase resistance of 3.5 ohms. I now have a motor that would do the job with a phase current of .4 amps and a phase resistance of 30 ohms, does that sound better?.
Can the stepper chip be replaced DIY? And if so where can I get it? Otherwise where can the board be repaired? I'm in the UK.
Thanks for your help.
Dougal.
billr
Super MS/Extra'er
Posts: 6828
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Stepper motor stopped working.

Post by billr »

The stepper driver IC can be a DIY job if you are a skillful solderer; it's SMD with fairly fine-pitch leads. The IC can be had from any electronics vendor, Digi-Key is where I would go to in the USA. In the UK, James Murray would be the obvious choice for repairing it for you. Yes, the 30 ohm motor should be OK.

Note that the motor with 3.5 ohm coils was rated for 1A per coil, but was trying to draw over 3A when driven from the simple 12V "on-off" driver in the MS. It's no wonder the driver IC was stressed until it failed.
Dougal
Helpful MS/Extra'er
Posts: 36
Joined: Wed Feb 15, 2017 1:16 am

Re: Stepper motor stopped working.

Post by Dougal »

Many thanks for the comprehensive reply.
Post Reply