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Author Topic: RA rotates same direction/autoreverses  (Read 179 times)

khobar

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RA rotates same direction/autoreverses
« on: August 03, 2019, 00:02:23 »

My final gears arrived today and I'm bench-testing the mount (LX70) inside. At first it was working as expected - very smooth, very quiet. But after 10 minutes or so I noticed the RA motor turning in the same direction no matter what I commanded in EQMOD. This followed a DEC motor "stall".

Any ideas why my RA motor would suddenly start rotating same direction/autoreverse?


Thanks.
« Last Edit: August 03, 2019, 00:44:12 by khobar »
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khobar

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Re: RA rotates same direction/autoreverses
« Reply #1 on: August 06, 2019, 02:55:41 »

Upon closer inspection of the driver boards on the AstroEQ, I found what appeared to be a cold solder joint. I touched up that and any suspect pins and, so far, the problem seems resolved. Fingers crossed.

 
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TCWORLD

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Re: RA rotates same direction/autoreverses
« Reply #2 on: August 06, 2019, 20:42:18 »

Glad you've sorted it.

Kind Regards,
Tom.
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Tom Carpenter (AstroEQ)

khobar

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Re: RA rotates same direction/autoreverses
« Reply #3 on: August 07, 2019, 03:13:55 »

I'm getting there!

I am now stumped, however. I'm taking advantage of our monsoon season by bench testing indoors, and while it seemed like everything was slewing nice and smooth, there's something amiss.

I have the LX70 (CG5) mount pointed north. Input all the correct information regarding location, time, date, etc. I tell Stellarium or Cartes du Ciel to slew to Saturn and while the program(s) think the scope is doing its thing, the scope actually overshoots by a huge margin.

My config is 1.8, 2.666666667, 144, 550 for RA, and 1.8, 2.666666667, 144, 550 for DEC. 16uSteps, Enabled. Click "Update" and the RA and DEC fields are the same (see attached). I can set RA to 800 (824) fine, but DEC doesn't seem to like to go that high. 550 works fine.

I have tried disabling ustepping, and changing the value, and it just seems to affect the speed at which things go wrong.

Any thoughts?

Cheers!
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TCWORLD

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Re: RA rotates same direction/autoreverses
« Reply #4 on: August 07, 2019, 08:59:30 »

Does it track at sidereal rate correctly? If you time one revolution of the 15T gear, it should take 86164.0905 / 144 ~= 598 seconds.
When tracking also, does the mount rotate in the correct direction?
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Tom Carpenter (AstroEQ)

khobar

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Re: RA rotates same direction/autoreverses
« Reply #5 on: August 07, 2019, 15:13:34 »

Thanks Tom.

Even eyeballing RA before coffee this morning, I can tell it's tracking fast, and a rough measurement confirms - it makes one revolution in about 222 seconds. That's not right, or is it?  :o

From jslight in another thread: "The EQ5 mount has a 144:1 worm gear ratio for both axes.  360 / 144 = 2.5, the angle of mount movement with one revolution of the shaft.  If you are using the 40 and 15 tooth pulleys from the FAQ (with the 40 tooth pulley on the mount shaft), then 2.5 / 2.6666667 = ~0.9375, the angle of mount movement with one revolution of the stepper.

Sidereal rate ≈ 1 / 4min.  So it should take about 3 minutes and 45 seconds for a full stepper revolution at sidereal rate."


I have manually counted the teeth both on the 15T and 40T gears.

The motors are: STEPPERONLINE Nema 14 Bipolar Motor Stepper 7.5V 0.5A 32.6oz.in/23Ncm 4 Leads 1.8 deg

As for direction, at the moment I have the mount pointed North, and while tracking, RA rotates West. This is consistent with the direction buttons in EQMOD, and with slewing within CdC and Stellarium. I *think* that's right.
« Last Edit: August 07, 2019, 15:29:58 by khobar »
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khobar

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Re: RA rotates same direction/autoreverses
« Reply #6 on: August 07, 2019, 15:48:30 »

Some additional info:

Physically slewing DEC 90 degrees only shows about 45 degrees in EQMOD.

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TCWORLD

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Re: RA rotates same direction/autoreverses
« Reply #7 on: August 07, 2019, 18:24:51 »

Suggests that there is an issue with the microstepping mode in the hardware.

This could be due to a cold solder joint on one of the MSx pins.

Alternatively it could be that you haven't soldered the driver board type jumpers - there are two jumpers between the MCU and the drivers that need to be bridged (e.g. by a piece of wire) depending on which driver type you are using as noted on the silkscreen.

Have you selected the correct driver board in the config utility?
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Tom Carpenter (AstroEQ)

khobar

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Re: RA rotates same direction/autoreverses
« Reply #8 on: August 07, 2019, 20:26:11 »

Pins 2&4 on M1 (DEC) driver board were shorted. Unfortunately, I don't know what I did to clear the short. Maybe it's gone for good, maybe not. But it's gone for now. ;)

As a result, I was able to slew both axes at full speed (800) simultaneously. That's a big difference already.

DEC was reversed.

Mount now slews in general direction of Saturn in Cartes du Ciel! I'm sure it will do likewise in Stellarium. That makes me very happy indeed!

Thanks very much, Tom. I am so looking forward to clear skies to give it a go outside.



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khobar

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Re: RA rotates same direction/autoreverses
« Reply #9 on: August 08, 2019, 00:10:04 »

Small update.

It seems my joy is short-lived. Electrically, the mount moves smoothly and quite quickly, but pointing doesn't seem to be working as I had thought. After having left the mount powered up in park for about an hour, I tried to slew to Saturn again and it pointed roughly WSW.

I'll keep at it. I must be overlooking something.

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khobar

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Re: RA rotates same direction/autoreverses
« Reply #10 on: August 08, 2019, 14:34:52 »

Yesterday evening, I ran Stellarium in "real time" and pointed the mount at perhaps six targets including Saturn, Jupiter, and the moon. The mount slewed to them fine (as verified from our patio).


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