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Old non-Goto CG-5 hand controller died

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#1 TrackballJerry

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Posted 04 February 2011 - 03:13 AM

My hand controller for my 7-year-old Celestron CG-5 mount just died. This is the non-GoTo mount, with plain old stepper motors for the R.A. and Dec. axes. (The motor kit was Celestron part #93523.) I can't find anything obviously wrong with the controller, but other than the power light coming on, it's dead as a brick. Nary a hint of power to either the R.A. or Dec. motors.

I've tried different power supplies, cleaning the switches, removing and re-seating the single enormous ROM chip, and checking the cables for continuity. No joy.

Does anybody know what usually dies in these things? (And how to fix it?)

Does anybody have one laying around that they're not using anymore?

Thanks,

Jerry

#2 orlyandico

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Posted 04 February 2011 - 03:42 AM

Probably the stepper motor driver chip, or stepper MOSFETs/transistors. These are the usual culprits. If it's using a stepper chip, that chip would most likely be a ULN2003 or MC1489 which are discontinued already.

I cracked open my Orion single-axis drive and it has a ton of little transistors for the stepper motor driver circuit. A pain in the a** to replace and quite time-consuming.

Unless 3-4 hours of your time is worth < $80, just buy another dual axis drive, "oddog2" on ebay has a few for $80.

#3 Ian Robinson

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Posted 04 February 2011 - 06:11 AM

You can still get the 93523 G5 modules. Try Scope City
Donald E. Pensack
General Manager
Scope City, Inc.
730 E. Easy St.
Simi Valley, CA

I got a complete set of new stepper motors and G5 module from them in April.

They are hard to find and believe me I hunted everywhere by the internet.

Also the Skywatcher EQ5 stepper motor version dual axis drives uses a virtually identical dual axis drive handpaddle. They are interchangeable.

#4 Trev

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Posted 04 February 2011 - 09:46 AM

Mine just did the same thing and as far as I can tell right now it seems that the on/ off switch (N/off/S) is the culprit.

#5 TrackballJerry

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Posted 04 February 2011 - 04:34 PM

Thanks for the leads!

Alas, the trouble seems deeper than the on/off switch on mine.

Orlyandico, can you provide a link to those drive units that "oddog2" has on Ebay? I spent a half hour searching and couldn't find them. (My Google-fu and Ebay-fu must have died along with my controller.)

Good to know that Scope City still has a few if I have to buy a new set at full retail, but that'll be a last resort.

I actually don't mind spending a few hours replacing parts if I knew which parts to replace. Mine has a thicket of transistors, too (16 of 'em), but since both drive axes are dead I'm guessing the problem is farther back, maybe in the ICs. I see two chips on the board: an 8-pin HA17393 and a 40-pin GMS97L51.

Another idle thought: how hard would it be to build a circuit from scratch to drive the R.A. motor? I only use it for tracking so I wouldn't need slew speed or reverse, and I never use the Dec motor anyway, so I could just keep that for a spare R.A. motor if that ever burns out.

Jerry

#6 mcoren

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Posted 04 February 2011 - 09:21 PM

You could try to make your own. See this link.

#7 orlyandico

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Posted 05 February 2011 - 04:11 AM

oddog2 is out of the $80 controllers, most of them are $110.

here's a DK-3 for much less, not sure if your steppers take the 8-wire DIN plug. it looks like a clone of my Vixen DD-1:

http://cgi.ebay.com/...17#ht_500wt_922


From your description... your controller is very similar to my Orion EQ-1M drive. The GMS97L51 is an Intel 80C51 clone. And the thicket of transistors is the power driver (they were too cheap to get an L293 or ULN2003 stepper driver chip).

If the 80C51 is blown.. you are SOL. That is the processor and contains a program for the stepper driver, so if you buy a new one it will not have the program burned-in.

Alternatively instead of making your own RA drive, scrounge an EQ-1M or equivalent single-axis drive, this one is a measly $15 (+ $10 S/H)

http://cgi.ebay.com/...c#ht_583wt_1139

I am 100% sure that this drive is the same as the EQ-1M. The problem is that it's for a 100-tooth gear, you would need to replace the 3.58MHz crystal on the board with a 5.12MHz one to match the 144-tooth CG-5 gear.

#8 TrackballJerry

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Posted 06 February 2011 - 10:54 PM

>I am 100% sure that this drive is the same as the EQ-1M. The problem is that it's for a 100-tooth gear,
>you would need to replace the 3.58MHz crystal on the board with a 5.12MHz one to match the 144-tooth CG-5 gear.

That sounds relatively straightforward. How would I recognize the crystal, and do you know what part number I need to replace it with?

Thanks,
Jerry

#9 orlyandico

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Posted 07 February 2011 - 01:03 AM

The crystal looks like this:
http://www.ladyada.n...s/HC-49US_t.jpg

You'll have to go to Jameco and ask them for a 5.120 MHz crystal, it will probably not be an HC49, but will look like this:
http://www.scantool....Mhz_crystal.jpg

doesn't matter, will still fit, you'll just have to fold it down. There's no polarity or anything, it's an almost idiot-proof operation. :-)

here's how i did it to an EQ-1M
http://orlygoingthir...nt-hacking.html

BTW 5.120 MHz crystals are kinda exotic (took me several days to find one). Jameco certainly carries it, but they have a minimum order amount. Since the crystal costs $0.50 you will have some problem. :mad:

p.s. Only realized now that you're the famous trackball telescope guy. Big fan. :jump:

#10 orlyandico

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Posted 07 February 2011 - 01:24 AM

btw I just checked your part numbers online now.. the GMS97L51 is indeed a 12MHz Hynix 80C51 processor, while the HA17393 is a comparator. I'm willing to bet the HA17393 is used as a switch debouncer. On my EQ-1M this function is done by a 74LS05..

#11 TrackballJerry

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Posted 07 February 2011 - 01:50 AM

Many thanks! I may do this if I can't find a cheap replacement for the original controller.

>Only realized now that you're the famous trackball telescope guy. Big fan.

Cool! I'm kind of fond of that design myself. After the death of this EQ mount controller, I'm even happier with the trackball than before.

I've got to ask: What do you do that makes you so familiar with these electronic parts? My electronics education peaks out at the transistor and diode level, so I'm always in awe of people who can tinker with ICs.

Jerry

#12 orlyandico

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Posted 07 February 2011 - 01:51 AM

hi jerry, i'm an electrical engineer. i'm also famously cheap. :grin:

one "fun" idea i'm having... stepper-based drives are cheap (like the $80 / $110 oddog2 one). If you take an existing stepper drive, throw away the hand controller, and fabricate a stepper driver that connects to a PC parallel port.. then you can use Mel Bartels' scope.exe and you got GoTo!

the nice thing is, no need for messy mechanical fabrications (which I'm notably poor at..) because the dual-axis drive bolts up to the GP / CG-5 / SVP without hassles.

Of course the GoTo will be very slow due to the very large gear reduction on these cheap stepper motors (it will be like the original Vixen SkySensor... try your patience at 64X sidereal slew rate).

of course you also need a computer but you can get a Pentium-1 laptop for $50 these days..

#13 TrackballJerry

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Posted 07 February 2011 - 02:34 AM

EE! Okay, now I don't feel like such a shmoe for not knowing this stuff.

I had a look at your website detailing your hack for the EQ-1M. Man, that controller looks a lot like mine! Same mother and daughter board configuration, same square buttons you have to pop off before you open the case, same switch positions. Clearly made by the same people, or one was copied from the other.

Now that I know what a crystal looks like, I found the one in my controller. It's labeled CQ 3.579545. I assume that means it's a 3.58 MHz crystal, so alas, I can't rob that for the EQ-1M if I go that route.

Fortunately I do have an electronics store in town (Eugene, Oregon) that can probably order me a 5.12 MHz crystal.

Hey, the email notice I got when you posted your next-to-last post had a truncated line about trying an acrylic lighting globe for a trackball, but it was too soft. I had the same problem with a polycarbonate globe that I'm using for a scaled-up Astroscan (see http://www.cloudynig...wflat.php/Cat/1,2,3,4,5,8/Number/3706832/Main/3705922 ), but I was able to use it after putting a coat of fiberglass inside the ball. Just one layer of fiberglass stiffened it up like you wouldn't believe! So don't give up on that sphere.

Jerry

#14 orlyandico

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Posted 07 February 2011 - 02:36 AM

hi jerry.. i gave up on the sphere and sold off my 10" dobsonian parts. i did try to reinforce the acrylic sphere with a layer of fiberglass tape and epoxy inside.. but it was only a 16" sphere (could not get any bigger ones) and i was putting a 10" mirror inside. so it needed a massive 25lb of weights in the bottom to get it to balance.. so you can imagine the eye-popping weight of that ball. :mad:

(and the slides dented the ball anyway in spite of the reinforcement due to the massive weight of the thing)

my problem now is finding a mount beefy enough for my closet queen C9.25 :p which in retrospect doesn't really replace the 10" f5 dob because of its teeny weeny FOV.

#15 TrackballJerry

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Posted 07 February 2011 - 02:42 AM

Forgot to mention: I live about 20 miles from Mel Bartels, so I could probably get him to help me retrofit my scope for his scope.exe GoTo program. :-)

But I'm not a GoTo sort of guy. I'm not a snob about it (at least I don't think I am), but half the fun for me is the star-hopping to find an object.

Jerry

#16 orlyandico

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Posted 07 February 2011 - 02:52 AM

Singapore has a miserable limiting magnitude of 3 most of the time. :(

making GoTo almost mandatory.

re: Mel Bartels.. the guy has an asteroid named after him!

#17 TrackballJerry

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Posted 07 February 2011 - 03:17 AM

re: Mel Bartels.. the guy has an asteroid named after him!



Yeah, he's a phenomenon, that's for sure. He and another guy named David Davis taught me how to grind mirrors, and I'm constantly amazed at how quickly they can zero in on the problem (and the solution) when you're doing the final figuring.

Mel and I tried to teach a grinding class together a couple years ago. That was a hoot! Our styles don't match at all, so we were giving the students all sorts of contradictory advice. I thought he was going to bean me with a blank before we were done, but he took it all in stride.

Jerry

#18 TrackballJerry

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Posted 11 February 2011 - 02:19 AM

Hi, Ian,

I noticed that you'd started a topic a year or so ago asking if anyone had ever successfully swapped an Orion TrueTrack D/Axis controller (part no 7832) for EQ5 for their old Celestron CG5 D/Axis controller (part no 93523). I saw no responses to your question, but in this topic you recommended the Skywatcher EQ5 controller or buying a remaining Celestron drive kit from Scope City. Does that mean the Orion TrueTrack drive *doesn't* interchange, or did you just not go that route?

Thanks,
Jerry

#19 Starhawk

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Posted 11 February 2011 - 11:51 AM

My problem came up with a Vixen Polaris I wanted to put drives on. The mount only has RA axis support for a drive. So, I got a CG-4 drive thinking this would work. The problem ended up being not making a bracket to mount the Dec motor, but rather the Polaris has 144 tooth gears and the CG 4 has 130 teeth. So, I needed to speed up the drive. Since I am a mechanical engineer, I did it by getting a set of gears with an 11:10 ratio. This matched the RA rate, and interestingly, caused the drive to be much quieter Than the solid thumping it made when the motor was hard mounted to the worm shaft.

Thanks for the link on the PIC controller. It has been a dream if mine to make my own mount, and that would be a perfect way to drive it.

-Rich

#20 TrackballJerry

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Posted 14 February 2011 - 05:50 PM

I ordered a couple of 5.12 MHz crystals from DigiKey today, and two of the $15 Galileo hand controllers off Ebay. (I figured since shipping cost almost as much as the drives and more than the crystals, I might as well buy two and have a spare in case I ever blow another controller.)

So with a little soldering I should be able to get my mount running again. I'll let you know how it goes once the parts arrive.

Jerry

#21 Ian Robinson

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Posted 14 February 2011 - 07:23 PM

Hi, Ian,

I noticed that you'd started a topic a year or so ago asking if anyone had ever successfully swapped an Orion TrueTrack D/Axis controller (part no 7832) for EQ5 for their old Celestron CG5 D/Axis controller (part no 93523). I saw no responses to your question, but in this topic you recommended the Skywatcher EQ5 controller or buying a remaining Celestron drive kit from Scope City. Does that mean the Orion TrueTrack drive *doesn't* interchange, or did you just not go that route?

Thanks,
Jerry


I just went down that route, since it came with a set of new motors and a spare set of motors is always handy to have JIC.
It worked out cheaper to go original too by about 100AUD even including airparcel post from the USA. I think ScopeCity was keen to off-load these old units that have been sitting around in boxes collecting dust (and costing them money too).

The local dealers here all told the same thing, that the EQ5 dual axis drive kit is interchangeable with the old style CG5.

I did get a CG4 dual axis drive paddle from the local Celestron distributor gratis, he told me the paddle was compatible but it didn't track right and DEC only gave one rate (1x) so was not much good. I'm keeping it as spare parts - the hand pushbutton board and some other components might be handy to have one day.

Looking inside the G4 unit the circuitry is different to the G5 unit.

I wound up eventually repairing getting the old G5 paddle so I now have the new one, that I use, and the old one as a spare.

I've also done the Shoestring autoguider conversion to them and have yet to test that mod. Weather here has been lousey for astronomy since about November.

#22 orlyandico

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Posted 14 February 2011 - 08:01 PM

FWIW doing the shoestring mod is laughably easy (about as easy as replacing a crystal). i spent more time cutting a slot in my Vixen DD-1's casing (for the cable).

#23 TrackballJerry

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Posted 14 February 2011 - 10:25 PM

I think ScopeCity was keen to off-load these old units that have been sitting around in boxes collecting dust (and costing them money too).


I must have sounded either gullible or desperate, because they asked me for $199 for one. That's $53 more than Orion sells their current model for.

For $45 I've got two single-axis controllers and the parts to modify them for my mount's 144-tooth gears. Since I never use the Dec motor anyway, this is a better solution by far.

Jerry

#24 orlyandico

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Posted 14 February 2011 - 11:26 PM

jerry, you might also want to add RA guiding to that :-)

i suspect it's really easy to mod the single-axis drive so that a GPUSB can talk to it.

unless of course your needs are purely visual.

#25 Ian Robinson

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Posted 15 February 2011 - 04:48 AM

I think ScopeCity was keen to off-load these old units that have been sitting around in boxes collecting dust (and costing them money too).


I must have sounded either gullible or desperate, because they asked me for $199 for one. That's $53 more than Orion sells their current model for.

For $45 I've got two single-axis controllers and the parts to modify them for my mount's 144-tooth gears. Since I never use the Dec motor anyway, this is a better solution by far.

Jerry


Prices for the EQ5 dual axis kit were way more than that here in Australia at the time.
Would probably be a different story now that the AUD > USD.






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