Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

CPC battery charging 2004 unit

  • Please log in to reply
7 replies to this topic

#1 carolinaskies

carolinaskies

    Apollo

  • *****
  • topic starter
  • Posts: 1395
  • Joined: 12 Dec 2014
  • Loc: Greenville SC

Posted 21 March 2019 - 08:15 PM

So I finally got a chance to get my CPC1100 out this week. C2004 I believe based on initial date displayed on setup... more on this later. 

Been working on it since purchase last year. Upgraded to newest USB controller (old one apparently crapped out), swapped out power port and toggle switch which were bad.  Back when I was diagnosing things I had unplugged the GPS and replugged it in and powered everything up with side panel off.  The light on the top of the GPS antenna was blinking... does anyone know if that means it's charging or what?  

I buttoned up the fork arm (can we line up the engineers who put two bolts behind the OTA and threaten to break some fingers?) and powered the scope up. 

Powered on no problem.  Mount slews no issue.  

The problem is that GPS deal.  The scope powers up showing 2/18/04... hence I think it is likely a 2004 CPC unit.  Reports 'GPS Linking' but even after 5-10 minutes it never appears to synch to GPS satellites.  As I said above, before I buttoned the fork arm up where the GPS antenna & board are located the light on the antenna was blinking... does this light indicate GPS is working?  

I read on an old post that the button battery is 'rechargeable' so I am doing as suggested on that page and have unplugged the hand control and am leaving the mount in the ON position for 40 hours to charge that battery (this is so the mount will not track, but simply sit and charge).   There are two different GPS modules that were used apparently, one a Motorola and another later in-house Celestron.  The former needs 40hrs to charge while the latter only 24hrs.   

Anyone with a CPC GPS issue resolved like this want to chime in on experiences?   I know I don't need the GPS and can hand input everything.  BTW that brings to question why it seems location/time/date information is lost.. is it stored somehow in that GPS module?   

 



#2 Michael_Swanson

Michael_Swanson

    Surveyor 1

  • *****
  • Posts: 1967
  • Joined: 23 Apr 2003

Posted 22 March 2019 - 12:18 AM

Hi Paul,

 

The version 4 and NexStar+ hand control will start off displaying the date/time when it was last used up until the GPS links.  So the 2/18/04 is almost certainly not coming from the GPS module.  But, you are correct that at least the hand control is from 2004 or earlier.  It is possible the mount is newer and the HC was from another mount and sitting in a drawer since 2004.  The HC will also store the location from it's last use.  Those date/time/location entries are not stored until the end of the alignment routine as I recall.  Or if you specifically set them in the menu using Setup Time-Site.

 

The GPS module will keep date and time as long as the module's battery/super capacitor has sufficient charge.  

 

I haven't seen that specific GPS modules with the covers off but since it is an off-the-shelf GPS receiver, the common behavior of the LED is to blink in one pattern when it is still linking and then blink in another pattern once it has linked.  And most of them have an error blink pattern as well.  

 

A Celestron GPS module with a completely discharged battery/super capacitor can take 30 minutes to link.  Be sure you have the mount outside in an unobstructed area.  Unlike your smartphone, Celestron's GPS receivers almost never work inside a building.

 

Final note, on this page of my website:

https://www.nexstars...OddsEndsCPC.htm

Be sure to read the article "Problems Obtaining GPS Link".  The link to David Craig's article on that page and then also this article:

https://www.nexstars...es/GPSBoard.htm

may help as well.

 

Best regards,
Mike Swanson
Author of "The NexStar Users Guide II"
Author of "The NexStar Users Guide"
Author of "NexStar Observer List"
https://www.nexstarsite.com



#3 carolinaskies

carolinaskies

    Apollo

  • *****
  • topic starter
  • Posts: 1395
  • Joined: 12 Dec 2014
  • Loc: Greenville SC

Posted 22 March 2019 - 08:30 AM

Thanks for the links Michael. 

For reference here is the mount arm exposed... looks similar to ones from your page except being the CPC design. 

20190318_183341_result.jpg


The 2004 must be from the PCB board or GPS because the hand control is the latest micro-USB Nextstar+.  

Going to attempt the charging of GPS to see if it makes any difference, then the reset of the capacitor discharge if necessary, per the links found through your page. 
  

Looking at the ridiculous cost of the Celestron GPS replacement I'm curious if anyone has attempted to use one of the DIY GPS units available for less than $20?  

Seeing as the fork arm contains both the control and the GPS receiver it seems logical that something like the following might be a simple replacement to a more modern GPS unit. 

https://www.amazon.c...ctronics&sr=1-3

 

 

 



#4 mclewis1

mclewis1

    Thread Killer

  • *****
  • Posts: 18444
  • Joined: 25 Feb 2006
  • Loc: New Brunswick, Canada

Posted 22 March 2019 - 10:11 AM

The NexStar architecture (hand controller, motor controllers, and optional stuff like WiFi, focuser, etc.) will talk to a Celestron GPS unit (either internal or external) but won't talk to a simple commercial GPS unit unless there's some other intelligence in between.

 

A few folks have worked with inexpensive Arduino or Pi modules to get a GPS module to talk to the scope. There is also a software product from Celestron called NexGPS that will allow a Windows PC running NexRemote (which is an older hand controller) to also take GPS data from a commercial GPS unit attached to the PC and load NexRemote with the data.

 

Generally however most find it's just not worth the effort to get a 3rd party GPS unit to work with a Celestron mount.



#5 carolinaskies

carolinaskies

    Apollo

  • *****
  • topic starter
  • Posts: 1395
  • Joined: 12 Dec 2014
  • Loc: Greenville SC

Posted 22 March 2019 - 11:07 AM

The NexStar architecture (hand controller, motor controllers, and optional stuff like WiFi, focuser, etc.) will talk to a Celestron GPS unit (either internal or external) but won't talk to a simple commercial GPS unit unless there's some other intelligence in between.

 

 

When I look around I see the GPS unit such as the one I linked above which essentially connect a receiver to a interface board which powers the receiver and transfers the signal into the downstream device.   From certain threads on CN it's clear the GPS receiver unit isn't an exotic interface... as I recall it uses TTL for communication.  No where have a read where someone simply tried to connect one of the inexpensive receivers to the Celestron interface board to see if it will work.  I did read where someone had identified an OEM GPS Receiver available in minimum quantity of 5 @ $30/unit but did not pass along a part number-description.  

Now if we add into this the past history of after-market GPS units, including handheld being linked to older Celestron non-onboard GPS mounts it's clear the signal the main control board receives from the GPS must be just a basic package returned by most handheld GPS units.   Unlike the programming for drive systems, external location data must logically be gathered in a basic format.  This leads to a possible conclusion that identifying aftermarket GPS units which return a particular sequence of information should yield candidates for swap out.   

Much like the RS232 interface pinouts for computer control is different between Meade, Celestron, and other mounts, I think it likely determining the proper connections between the receiver and the Celestron interface board should yield correct data.   
 

Perhaps I'm thinking about this too simply, yet as I say, I haven't read where anyone attempted an actual swap out of the receiver alone with commesurate results. 

The DIY projects I have read about creating a new GPS module seem to rather trod the path of recreating the external GPS input to the RS232 port of the mount rather than attempt to ascertain if an actual swap of individual components is possible.  

 



#6 Michael_Swanson

Michael_Swanson

    Surveyor 1

  • *****
  • Posts: 1967
  • Joined: 23 Apr 2003

Posted 23 March 2019 - 02:20 AM

Hi Paul,

 

You are correct in your assessment that the GPS receiver is pretty much generic and the interface board makes it work with a Celestron scope.  If the receiver itself is bad, it is certainly possible you can find one that will replace it.  It would be trial and error though.  There have been a couple of discussions about this here on Cloudy Nights, but as I recall no one ever followed through to purchase and replace the receiver.

 

As Mark notes, a complete replacement using something that plugs into the AUX port is the only certain way to do this.  I would recommend PixSoft's StarNX-GPS if you go that route:

https://www.nexstars.../StarGPS-NX.htm

 

It is tiny and could be mounted inside the fork arm.  You would need to disconnect the existing interface board from the rest of the electronics so that it wouldn't also be replying to queries from the hand control.

 

Best regards,
Mike Swanson
Author of "The NexStar User's Guide II"
Author of "The NexStar User's Guide"
Author of "NexStar Observer List"
https://www.NexStarSite.com



#7 carolinaskies

carolinaskies

    Apollo

  • *****
  • topic starter
  • Posts: 1395
  • Joined: 12 Dec 2014
  • Loc: Greenville SC

Posted 23 March 2019 - 06:51 PM

Hi Paul,

 

You are correct in your assessment that the GPS receiver is pretty much generic and the interface board makes it work with a Celestron scope.  If the receiver itself is bad, it is certainly possible you can find one that will replace it.  It would be trial and error though.  There have been a couple of discussions about this here on Cloudy Nights, but as I recall no one ever followed through to purchase and replace the receiver.

 

As Mark notes, a complete replacement using something that plugs into the AUX port is the only certain way to do this.  I would recommend PixSoft's StarNX-GPS if you go that route:

https://www.nexstars.../StarGPS-NX.htm

 

It is tiny and could be mounted inside the fork arm.  You would need to disconnect the existing interface board from the rest of the electronics so that it wouldn't also be replying to queries from the hand control.

 

Best regards,
Mike Swanson
Author of "The NexStar User's Guide II"
Author of "The NexStar User's Guide"
Author of "NexStar Observer List"
https://www.NexStarSite.com

I saw that StarGPS, personally I think it's still well overpriced recognizing the actual cost of components is minimal. And it isn't as simple replacement of the onboard GPS as some modding will have to be done to run the cable.  I would likely simply externally attach the unit.   It is cheaper than the Celestron receiver, so if I HAD to do it well it could be done.  

I've unplugged the CPC1100 from charging and plan to set it out in the yard and attempt to see if the GPS works.   I may also reflash the firmware as I think when I did that before I had the GPS unplugged so it may be possible the system isn't identifying it.  



#8 Michael_Swanson

Michael_Swanson

    Surveyor 1

  • *****
  • Posts: 1967
  • Joined: 23 Apr 2003

Posted 24 March 2019 - 06:04 PM

Hi Paul,

 

The GPS receiver is cheap, but PixSoft had to design a processor unit, create firmware and manufacture in fairly small quantities a protocol adapter between the the GPS receiver and the Celestron comm bus (the AUX bus).  The little "GPS-Celestron" cable actually has a microprocessor in it.  It is providing the function of the Raspberry Pi or Arduino in do-it-yourself projects we've seen others develop.  In addition to being just a bit cheaper than the Celestron SkySync, it is smaller and as I mentioned, could be mounted inside the fork arm.

 

One more suggestion with your existing GPS, I've heard from another individual who has been hacking his NexStar 11 GPS that he believes it is possible on some of Celestron's earlier GPS units that if the battery/super capacitor on the GPS board is bad, it could possibly prevent the GPS from ever linking.  Try removing the battery altogether and see if it will link.

 

Best regards,
Mike Swanson
Author of "The NexStar Users Guide II"
Author of "The NexStar Users Guide"
Author of "NexStar Observer List"
https://www.nexstarsite.com




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics