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Author Topic: RA Motor hot even when not slewing  (Read 1031 times)

pterodyne

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RA Motor hot even when not slewing
« on: August 19, 2018, 19:46:26 »

I have my losmandy titan astroEQ running ok. Unfortunately I am back home in south Baja California and I remembered something I forgot to fix.  I noted that my RA motor gets somewhat hot just sitting there, not tracking or slewing.

I have VREF set to 1, and very large heat sinks (NEMA 23).  The DEC motor doesn't get hot slewing or not.  I also have made the fast decay hack by shorting thew two appropriate pins on the RA axis only.  In another thread Tom suggested replacing the DRV8825 for a similar problem.  Unfortunately I am over 3000KM from the observatory now, and my remote hands person probably couldn't replace the DRV 8825.  It seems to be operating fine however as far as tracking and slewing. 

SO the real question is, should I try to address?  Is the motor in any danger (fairly expensive stepperonline motor)? driver (who cares).  Id say I probably need to remove the diode too as it is always really hot.

I can touch both the motor and the heatsink ok without burning but I don't have a ir thermometer.

Thanks.
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TCWORLD

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Re: RA Motor hot even when not slewing
« Reply #1 on: August 19, 2018, 22:27:27 »

Steppers do get hot. The coils are always energised regardless of whether or not they are moving (otherwise they lose all torque and can move at the faintest nudge).

If the RA is hotter than Dec, it is probably just the current limit for the RA will be set higher allowing more current through the motor.

If neither driver nor motor are too hot to touch, it is probably not worth worrying about, you shouldn't do any damage. But adjusting the current limit would help the motor run cooler.

Kind Regards,
Tom.
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Tom Carpenter (AstroEQ)

pterodyne

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Re: RA Motor hot even when not slewing
« Reply #2 on: August 19, 2018, 23:24:11 »

Thanks...  Ill just leave it for now..
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