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Author Topic: Overheating.  (Read 8850 times)

garethr

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Overheating.
« on: April 24, 2015, 17:50:23 »
Anyone able to help with an issue I'm having.  I have just done the motor upgrade to the nema14 motor on my eq5 mount but seem to have problems with motors and astroeq box over heating.  I have lowered the current as much as possible so the motors are just turning nicely but everything gets very hot and when I try to issue a slew command they seem to run at half speed.  Worried that I have damaged the control box :(
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TCWORLD

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Re: Overheating.
« Reply #1 on: April 24, 2015, 19:46:26 »
Which part of the PCB is overheating?
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Tom Carpenter (AstroEQ)

garethr

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Re: Overheating.
« Reply #2 on: April 24, 2015, 20:15:24 »
Tom

It seems to be the 2 motor chips for a better word and the small component next to the mini usb.  I have wired up in the following way black and yellow from astroeq to A &C and red and green to B&D.
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garethr

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Re: Overheating.
« Reply #3 on: April 24, 2015, 20:20:19 »
Tom
Looking at your diagram I think I have RA 1A and RA1B to A&C and the other to B&D is that the problem. Concerned that I have fried your board
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garethr

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Re: Overheating.
« Reply #4 on: April 24, 2015, 20:37:12 »
Tom.

Just taken the cover off and it's the 1cm square black chip by the power supply fed from c12 if that helps. It smells like its burn out if so whats the cost for a replacement board please or a new unit. My fault a little knowledge is dangerous :)
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TCWORLD

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Re: Overheating.
« Reply #5 on: April 24, 2015, 20:41:13 »
Do you have a multimeter?

If so, could you measure the reference voltage on the motor drivers (don't connect the motors so the board doesn't overheat). There is a via (small hole) between the motor driver chips and the current limit potentiometers. If you measure the voltage from there to ground.
The test points are marked with yellow circles on the attached image.
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Tom Carpenter (AstroEQ)

garethr

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Re: Overheating.
« Reply #6 on: April 24, 2015, 21:17:55 »
Tom.

I'm getting 2.5V on DEC and 0.5V on RA.

Would you rather speak over a PM?
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TCWORLD

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Re: Overheating.
« Reply #7 on: April 25, 2015, 07:03:52 »
Sounds like the DEC motor board is dead, or you have the potentiometer turned far too high. The 0.5V seems about right - the motor current is essentially twice that voltage (so 0.5V => 1A), but the 2.5V basically means the driver basically isn't limiting the current at all, hence it will get very hot (as will the reverse protection diode on the input).

Do you get the same voltage if you turn the DEC potentiometer all the way anti-clockwise?
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Tom Carpenter (AstroEQ)

garethr

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Re: Overheating.
« Reply #8 on: April 26, 2015, 19:55:39 »
Tom.

Now have both readings on DEC & RA @ 0.5 V approx and both motors run ok
Warm but not hot which is great thanks.
A bit of a concern is the hissing noise from the motors what's causing this do you think.
Fix one problem and along comes another.  :)
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TCWORLD

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Re: Overheating.
« Reply #9 on: April 26, 2015, 20:31:23 »
The hissing is normal, don't worry about it. Actually it is a good sign as it means the current limit is actively working - it's based on PWM so what you are hearing is the sound of the motor coil being pulsed at a high frequency.
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Tom Carpenter (AstroEQ)

garethr

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Re: Overheating.
« Reply #10 on: April 26, 2015, 20:51:20 »
Tom

That's good to know thanks.  Last question when slewing motors individually it's fine for speed but when I ask for goto it seems very slow any ideas using cartes du ceil to slew to targets.  Sorry to keep asking but feel I'm so close.
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TCWORLD

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Re: Overheating.
« Reply #11 on: April 26, 2015, 22:51:31 »
Did you set your go-to speed in the configuration utility when you programmed it? There is a box at the bottom of the config screen for each motor (labelled Goto Speed). Test with EQMOD to see what the highest reliable speed you can slew at, and put that value in the goto speed box. e.g. if in EQMOD you can do 200x nicely, put 200 in the goto box.
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Tom Carpenter (AstroEQ)

garethr

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Re: Overheating.
« Reply #12 on: April 27, 2015, 08:11:46 »
Tom,

That's the puppy,  All working as it should now brilliant.
Testimony as to how good your kit is after all the pain I out it through it still works even though there was smoke coming out at one point :-[
Thanks for your patience and help. :)

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