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Author Topic: Stepper motors do not operate - locked and get hot  (Read 1969 times)

jtc125

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Stepper motors do not operate - locked and get hot
« on: April 27, 2018, 16:46:32 »

I recently finished my DIY AstroEQ, with the PCB and Pre-Programmed IC’s from Tom and with components as listed on AstroEQ.  I went through the Configuring and Programming / update utility, connecting the AstroEQ as indicated regarding sequence of connection.  Power LED is on.  After connecting the USB cable from the AstroEQ to my computer the USB light starts flashing.  During the configuring process, the Status LED comes on and flashes at different times until complete.  The only issue that I had was a Com port issue but managed to resolve that.  I have NEMA 14 bipolar stepper motors Nema 14 Bipolar 1.8deg 18Ncm (25.5oz.in) 0.8A 5.74V.
 I have a Meade LX70 system and from previous discussions it appears this is comparable to an EQ5 mount.   After setting the Motor Step Angle to 1.8 deg and gear ratios and other recommended settings, the update utility finishes. 
I wanted to briefly test operation of the stepper motors and ran Cartes du Ciel to slew the mount.  However, the stepper motors did not move.   The status LED did not come on.  After trying to determine what might be the matter for a few minutes I happened to pick up the AstroEQ and it was getting warm, probably from the motor drivers.  I attempted to rotate the stepper motors by hand and both were locked.  They were also very hot.  I disconnected the power to let everything cool down.   As soon as I disconnected the power to the AstroEQ, the motors unlocked and rotated freely by hand.  I did verify the RJ11 / coil connections on the Stepper Motors per the illustrations (RJ11 2345 and Motor CDBA connection sequence)  in the forum from Feb. 19, 2016 as being correct.  I am using a RJ11 6P6C termination jack at each motor with 4 wire flat cable to AstroEQ Dec and RA.  The termination wire points are tinned in solder and “punch” connected to the jacks for 2345 identified connections.
Has anyone experienced this problem or might know why the stepper motors locked and get hot while AstroEQ is supposed to be slewing.
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doramason

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Re: Stepper motors do not operate - locked and get hot
« Reply #1 on: April 27, 2018, 23:19:59 »

probably the drivers are set to a much higher current than they should. You should adjust the voltage on the drivers to 0.4V maximum if they are DRV8825.

« Last Edit: April 27, 2018, 23:21:44 by doramason »
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jtc125

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Re: Stepper motors do not operate - locked and get hot
« Reply #2 on: April 28, 2018, 03:09:03 »

You were correct.  One was at 1.7 volts and the other a little less.  I initially was thinking that they would probably at least turn and I could check the voltage and adjust from there.  I was able to run the motors in the EQMOD test mode but didn't get them to track from the tracking software even though it indicated they were.  So, some more homework for me.  Thanks for the quick reply.
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