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Homebrew Celestron-compatible GPS

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#176 Sakcyb

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Posted 04 November 2020 - 09:02 AM

This is the photo of the AUX port in #50

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Edited by Sakcyb, 04 November 2020 - 09:03 AM.


#177 mlord

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Posted 04 November 2020 - 09:11 AM

I can see why:  that photo uses a mirror image version of the colours.  In Lord Beowulf's and my own versions the blue wire is "no connect", rather than the white wire.  Very very tricky for something so simple!

That photo is actually "correct" to the wikipedia pin numbering, so Lord Beowulf and I have apparently been using the mirror image colours all along.  Nice and consistently confusing, for sure.

 

I'm going to switch over to the standardized colour order (pin-1 white is "no connect", pin-3 is 12V) from here-on, but that would require me to re-crimp all of my RJ12 plugs and also resolder the other ends too.  Not worth going back to working projects, but going forward..


Edited by mlord, 04 November 2020 - 09:12 AM.


#178 Sakcyb

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Posted 04 November 2020 - 09:17 AM

On a related note, that caution also applies equally strongly to any homebrew splitters one might construct or purchase -- the need to ensure the wires end up in the correct order from end-to-end is critical.

 

For my soon-to-arrive Celestron Nexstar 6e, which has only a single AUX port, I have acquired one of these boards from Amazon:

 

https://www.amazon.c.../dp/B017B69D3U/

 

These are very easy to use, and very useful for projects like this.  One can just plug them into the AUX port on the mount using a pre-wired 6P6C RJ12 cable, so long as both ends of the cable are wired identically (both ends match my earlier RJ12 photo, or both ends match the mirror image of that photo, but no mixing between the two!). Using the breakout board in that fashion uses one port to connect to the mount, leaving three for the hand-controller and other accessories (eg. GPS, Wifi).

 

Or you can do what I have done here, which gives me four available ports:

 

attachicon.gif6p6c_4way.jpg

Because flat telephone cable has such teensy conductors, I soldered them directly to the board rather than trying to get them to grab inside the screw terminals.  I will probably wire this into me upcoming all-in-one project, using the screw terminals to connect the Arduino to the expanded AUX bus.  Nice and tidy.

 

I will be adding hot-melt glue blobs over the wires to mechanically strengthen them.

This is the plan I made to split the AUX port. Also works well just be sure to have your orientation of the two RJ12 plugs right on the little straight though extension. The splitter one can get off shelf here.  

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Edited by Sakcyb, 04 November 2020 - 09:28 AM.


#179 mlord

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Posted 04 November 2020 - 09:23 AM

I have a very similar 2-way splitter here that I have been using.  Except mine requires that the short patch cable have the connector tabs ON THE SAME SIDE OF THE CABLE.  Yours appears flipped.  Best to verify with an ohm-meter that things come out correctly before plugging anything into that!

 

2way_splitter.jpg


Edited by mlord, 04 November 2020 - 09:24 AM.

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#180 Sakcyb

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Posted 04 November 2020 - 09:33 AM

My little extension initially was exactly like yours but it did not work right. I checked the splitter with the WiFi module it did not power up. Thankfully I did not blow anything up So I then did multimeter it out and had to cut the one RJ12 plug off and redo it flipped round and now it works right. Don't ask me why all I can think is our splitters are probably differently wired inside. So one just have to make 100% sure about this then. It has to be a exact straight through split. This is where this photo is very important to take note of.

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Edited by Sakcyb, 04 November 2020 - 09:58 AM.


#181 mlord

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Posted 02 December 2020 - 02:40 PM

My own GPS module is currently working on a lowly Celestron 114LCM from the recent Amazon Prime Day sale (CAD$277).    After using it for a few nights, I now want to get a 9.25" EVO.  Except those aren't available at the moment, so instead a 6se is on the way to me (Costco).  smile.gif

 

I will move the GPS accessory over to the 6se along with the AUX port splitter I made, and report back here on how that works (should be fine).

A small update.  The GPS module and four-way splitter work fine on the 6se, and also on the new EVO-8 that arrived here the other day.  I'm a bit surprised at how good the Wifi and Android SkyPortal app work with the EVO-8, and I suspect my GPS+splitter box will soon end up in the classified, after the 6se gets returned to Costco.

 

GPS_splitter.jpg

 

I also built a prototype hand-controller for the Celestron Focus Motor, but in the end decided to return the motor, so that project is also now at a dead-end here.  Code and photo were posted in another thread.


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#182 mlord

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Posted 02 December 2020 - 09:04 PM

.. I suspect my GPS+splitter box will soon end up in the classified

Scratch that thought!  It's a keeper!

 

Clear sky tonight, lots of stuff visible despite the rather bright Moon.  So I got to try out the EVO-8 for the first time.  Optics seem okay, but I saw this weird horseshoe distortion when trying to collimate it.  Was worried about that until I noticed the horseshoe shaped formation of frozen dew on the corrector glass.  shocked.gif

 

So I gave up on finer collimation for now (no dew shield yet, gotta make one I guess) and tried out the SkyPortal app.  The app itself is wonderful for viewing the sky and identifying stars.  I went through the 3-star alignment using it over Wifi Direct to the EVO-8, and it claimed success!  And then it promptly lost communication with the scope and refused to re-establish it.  Crap app in that respect, as so many others here have also reported.  Or maybe it's the Wifi in the EVO?  Dunno, but I'll likely build a homebrew Wifi to compare it with.

 

So.. turned off the EVO, plugged in my trusty home-brew GPS module, powered it back up and.. life is good again!  I used the SkyPortal app standalone to identify a rather bright star (Vega) and did a 1-star alignment on the hand-controller.  The mount performed amazingly well after that.

 

The point?  I'm keeping the GPS module for use with the EVO after all.  I'll probably velcro it to the top of the OTA.
 


Edited by mlord, 02 December 2020 - 09:05 PM.

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#183 mlord

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Posted 05 December 2020 - 08:42 AM

Why not jump in and use something newer with more capabilities? The Espressif ESP32 platform ricks a 32 bit processor and Wifi/BT onboard, and it is cheap - $10 is a heck of a price:

 

https://www.amazon.c.../dp/B0718T232Z/

3.3V.   and way more stuff than is useful.

Okay, now that I have an interest in wireless connectivity with my new EVO, this is beginning to be worth the extra effort to interface with.  The built-in Wifi of the EVO seems to be poorly implemented (big surprise, not!) -- if the connection with my smartphone ever lapses, the mount requires a power-cycle before it ever works again.  That's just poor programming in the mount electronics, a lack of basic fault tolerance considerations.

 

Although I didn't buy the EVO for its Wifi, now that I've tasted it I want more!  laugh.gif

 

So.. solution is to roll one's own, more reliable wireless option(s).  The ESP32 with both bluetooth and Wifi built-in is a good starting point.  A belated thank-you to CltFlyboy for the original suggestion there!

 

Some effort will be needed to figure out the protocols -- as near as I can tell, no-one else has documented interfacing Wifi or Bluetooth directly to the AUX bus -- they tend to use the serial port on one of the older generation hand controllers instead.

 

A discrete 74LV136 chip should be sufficient to buffer/tristate the bus lines and also to do the 5V <--> 3.3V level conversions.  Once there is some useful progress, I'll start up a new thread here to document things and to help others here play along if they choose.

 

Cheers


Edited by mlord, 05 December 2020 - 08:44 AM.


#184 mlord

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Posted 06 December 2020 - 04:30 PM

Okay, now that I have an interest in wireless connectivity with my new EVO, this is beginning to be worth the extra effort to interface with.  The built-in Wifi of the EVO seems to be poorly implemented (big surprise, not!) -- if the connection with my smartphone ever lapses, the mount requires a power-cycle before it ever works again.  That's just poor programming in the mount electronics, a lack of basic fault tolerance considerations.

I have discovered a workable "fix" for the Evolution-8's built-in wifi.  See here for more info:

https://www.cloudyni...box/?p=10707686



#185 mlord

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Posted 11 December 2020 - 12:26 AM

ESP32 based home-brew GPS:

 

esp32_gps.jpg

 

It works.  grin.gif

 

Now back to the Wifi/BT thread to continue with adding wifi-adapter functionality to this exact setup.


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#186 Sakcyb

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Posted 11 December 2020 - 01:51 AM

Following this one keenly Vostok 1 it looks GOODwaytogo.gif Do share your circuit and code when you are donebow.gif


Edited by Sakcyb, 11 December 2020 - 01:53 AM.


#187 mlord

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Posted 11 December 2020 - 08:11 AM

These ESP32 boards are both better and more difficult to work with than their ESP8266 predecessors and old-school arduino boards.

 

The small arduino boards (eg. Pro Mini) easily fit within the confines of a prototyping breadboard.  As do _some_ of the ESP8266 boards (wifi, but no bluetooth).

 

But virtually all of the ESP32 boards are too wide for comfortable breadboard use, which is why the one I'm using here has only one side plugged into the breadboard, with the other side overhanging in space.  There are one or two narrower versions, but those lack the pin names on the board, and there are just SO MANY pins that the names turn out to be much more necessary than I expected!

 

When shopping for an ESP32 board, I have decided to go for the larger/longer 38-pin versions, with the highest number of I/O ports available.  Within this category, I look specifically for boards that have the AMS1117 3.3V regulator physically next to the pin labelled VIN, 5V or sometimes V5.

 

That pin is the raw power input, and I connect it directly to the 12V from the AUX bus on the telescope mount.  The AMS1117 itself is okay up to about 15V input, so all is well when the AMS1117 is connected directly to the VIN input pin.  But some boards locate the regulator further from that pin, indicating that they likely have other circuitry involved, which probably won't be happy with 12V there -- I fried one such board already!

 

So when shopping.. look for boards with a layout like the one pictured here.  The AMS1117 regulator is the large 3-pin chip with a top tab, just down and right from the VIN+GND pins (at top left).

 

DOIT-DEVIT_V1_ESP32.jpg

 

The EPS32 has three "hardware" serial UARTs, which can be assigned at programming time to any of the GPIO pins, not just those labelled as such.  Cool.  I'm using UART2 for the AUX bus, and UART1 for the GPS.  The other UART0 is connected to the onboard USB serial converter, so I'm avoiding that one, though it does get used for printing debug messages and for programming the board.  I imagine it too could be reassigned to different pins at run time, thereby avoiding conflict with the USB port.  But I haven't had need to try that yet.

 

IMPORTANT tip:  Any time the USB port is connected to a PC, the 12V power from the AUX bus must be disconnected from the VIN pin.  Otherwise you may fry the connected PC.  The board will then be powered from USB, and everything still works, including communications with the telescope mount.  There is a diode onboard for safety, to prevent frying the connected PC, but I'm not yet willing to rely on it!

 

Cheers


Edited by mlord, 11 December 2020 - 09:08 AM.

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#188 mlord

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Posted 11 December 2020 - 11:25 AM

IMPORTANT tip:  Any time the USB port is connected to a PC, the 12V power from the AUX bus must be disconnected from the VIN pin.  Otherwise you may fry the connected PC.  The board will then be powered from USB, and everything still works, including communications with the telescope mount.  There is a diode onboard for safety, to prevent frying the connected PC, but I'm not yet willing to rely on it!

I can now withdraw that precaution, at least with the board I am using here.  The diode does indeed prevent the 12V power from back-feeding over USB to fry an attached computer.

 

So, safe with this board at least.



#189 mlord

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Posted 11 December 2020 - 12:30 PM

An update on the GPS stuff:  I think it is better to not clone the Celestron Hardware/Firmware version numbers in the home-brew code, so as to avoid confusion with the Celestron Firmware Manager (CFM).

 

I have now tested things with "made up" version numbers and the telescopes still detect/use the GPS just fine, so I'll be using the new/different version values from hence forth.



#190 mlord

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Posted 15 December 2020 - 11:49 AM

I have made one important change to the GPS wiring from this topic:  added 330ohm resistors in series with each of the TX/RX/RTS signals between the AUX bus and the Arduino.  This limits damage potential in case of a "collision" on the AUX bus.  These are also used in my new project, even though it more correctly tri-states those pins instead of ever driving them HIGH.

 

My own home-brew GPS is now part of the (working!) GPS+WiFi+BT project:

https://www.cloudyni...ry-for-aux-bus/


Edited by mlord, 15 December 2020 - 11:51 AM.


#191 mlord

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Posted 21 December 2020 - 10:58 AM

Hi everyone.

 

I suspect there are quite a few lurkers on the forum here who would love to build their own GPS module, if only they could.

 

Well, it is a lot easier than it may first appear from reading through this rather long topic thread!

 

I am going to make another, simple homebrew GPS module, and if you like, then please follow along.  I'll be posting simple step-by-step instructions (there are very FEW actual steps!).

 

Tools required:

A) You'll need to be capable of soldering a few wires to some small small metal pins.  Any soldering iron with a reasonably slender tip will do the job. Along with this you'll need some very skinny rosin-core solder for electronics use, and well as separate flux (liquid or paste).  Yes, one can sometimes solder without extra flux, but it is MUCH more difficult than with extra flux.

 

B) You should also own or acquire a "multimeter" for verifying the wiring after construction, before attaching anything to the telescope mount. If you don't already have a "multimeter", they are cheap and easy to find.  Many dollar stores sell them, as does Amazon:

https://www.amazon.ca/s?k=multimeter

All you need from it is DC voltage measurement, and resistance (ohms) measurement.  They all have those two basic functions, so no need to pay more than perhaps CAD$16 for one.  I have a bunch here that I purchased years ago for about CAD$8/each.

 

C) Wire cutters/strippers for very small diameter (22g to 30g) wires.  Eg, this thing:

https://www.amazon.ca/x/dp/B07D25N45F/

 

D) Optional:  A hot-melt glue gun.  Very handy thing to have in general.  We can use it in this project to help strengthen wire connections after soldering, as well as to join things together.

 

The parts I will be ordering from Amazon for this include:

 

(1) Arduino Pro Mini 5V moduleNot the 3.3V version. The name "Pro Mini" is important here.  I am getting this specific one:

https://www.amazon.c.../dp/B019SX75HU/

If you want to reduce the amount of soldering required, you could hunt for an identical module but with pre-soldered header pins.  The linked one above comes with the "header pins" separate from the board, so some of those will need to be soldered on later.  You may find a version for sale that already has the pins soldered in place, which is fine as well.

 

(2) You will need a USB-to-serial 5V TTL cable, for one-time loading of the GPS programming into the Arduino.  I already have several of those here, but you could order this one:

https://www.amazon.c.../dp/B07JN8YLPV/

The important thing is that it has the individual wires separated out at the end, with those black socket thingies that will plug directly onto the "header pins" of the Arduino board.  It should also have an RTS line, though one can get by without that if necessary.

 

(3) The GPS module.  I now recommend this small/cheap BN-180 module:

https://www.amazon.c...uct/B086ZKWYP5/

Pretty much any GPS module will do though, so long as it has a 5V-compatible serial interface and includes the jumper wires with the same black socket thingies that the serial cable also has.  The BN-180 is the smallest, cheapest one here, but the BN-220, or BN-880 will also work exactly the same (just pricier and slightly bulkier).

 

(4) A 6-wire "telephone" cable, commonly called a 6p6c cable (6-pole, 6-conductor).  Eg. this one:

https://www.amazon.c.../dp/B0002J1SUU/

It should be at least 2' long or so, and anything beyond that will be wasted here.

 

(5) Optional:  three resistors, 330ohm each, give or take 50ohms.  1/8watt rating or better.

These are not really needed, but they do add a bit of security in case of a wiring or programming error.  In practice, the programming is already done and working, so no worries there.  And we will use the multimeter to triple-check the wiring before plugging anything into the telescope mount.  I will use them because I have them "in stock" at my workbench.  But you don't need them.

 

(6) Optional: a small cardboard or plastic box, large enough to house the Arduino board and the GPS module.  Which is not large at all -- probably a small matchbox would do!  You can worry about this part after wiring up the project, when you'll have a better idea of what is needed.  I plan to just wrap mine in poster-board cut-outs from a cereal box (better than it first sounds!).

 

So, that's it.  If you want to play along, get yourself the 5V (not 3.3V) Arduino module, USB-serial cable for it, plus a GPS module, and a 6p6c telephone cable.

 

To be continued once my own parts arrive here in a day or two.


Edited by mlord, 21 December 2020 - 04:28 PM.

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#192 mlord

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Posted 22 December 2020 - 11:32 PM

Okay, my GPS module and Arduino Mini Pro both arrived today.

 

gps_and_arduino_pro_mini.jpg

 

I have assembled these into a working Celestron compatible GPS module:

 

connected.jpg

 

Now.. what to do about the instructions?  I can do it blow-by-blow here in this thread, or I can just link to a slightly clunky web page I made for it:   http://rtr.ca/homebrew_gps/  At least with the latter I'll be able to edit/update it over time based on feedback from people who follow along with it.

 

 

 


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#193 Sakcyb

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Posted 23 December 2020 - 11:11 AM

Okay, my GPS module and Arduino Mini Pro both arrived today.

 

attachicon.gifgps_and_arduino_pro_mini.jpg

 

I have assembled these into a working Celestron compatible GPS module:

 

attachicon.gifconnected.jpg

 

Now.. what to do about the instructions?  I can do it blow-by-blow here in this thread, or I can just link to a slightly clunky web page I made for it:   http://rtr.ca/homebrew_gps/  At least with the latter I'll be able to edit/update it over time based on feedback from people who follow along with it.

You have gone though a lot of trouble making this guide, Thank you!



#194 mlord

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Posted 23 December 2020 - 01:06 PM

Thanks.  I think I'll stick to the slightly clunky web page.  laugh.gif

And I will be updating it off and on with simple additions.

 

Eg. I'm going to add support for a WiFi on/off switch for the Evolution mount, so that one can easily turn off the internal WiFi when using the hand-controller with GPS.  That is really easy to do, so worthwhile and optional.



#195 mlord

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Posted 23 December 2020 - 04:51 PM

I have updated the project page http://rtr.ca/homebrew_gps/ with more photos and stuff.

The optional WiFi kill switch is now there, with updated Arduino code to support it.

I also splurged and used a small black box to encase the project, with generous use of black hot-melt glue. Telescope.gif

 

project_installed.jpg


Edited by mlord, 23 December 2020 - 04:51 PM.


#196 Speo

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Posted 24 December 2020 - 11:24 PM

Hi everyone.

 

I suspect there are quite a few lurkers on the forum here who would love to build their own GPS module, if only they could.

 

Well, it is a lot easier than it may first appear from reading through this rather long topic thread!

 

I am going to make another, simple homebrew GPS module, and if you like, then please follow along.  I'll be posting simple step-by-step instructions (there are very FEW actual steps!).

 

Tools required:

A) You'll need to be capable of soldering a few wires to some small small metal pins.  Any soldering iron with a reasonably slender tip will do the job. Along with this you'll need some very skinny rosin-core solder for electronics use, and well as separate flux (liquid or paste).  Yes, one can sometimes solder without extra flux, but it is MUCH more difficult than with extra flux.

 

B) You should also own or acquire a "multimeter" for verifying the wiring after construction, before attaching anything to the telescope mount. If you don't already have a "multimeter", they are cheap and easy to find.  Many dollar stores sell them, as does Amazon:

https://www.amazon.ca/s?k=multimeter

All you need from it is DC voltage measurement, and resistance (ohms) measurement.  They all have those two basic functions, so no need to pay more than perhaps CAD$16 for one.  I have a bunch here that I purchased years ago for about CAD$8/each.

 

C) Wire cutters/strippers for very small diameter (22g to 30g) wires.  Eg, this thing:

https://www.amazon.ca/x/dp/B07D25N45F/

 

D) Optional:  A hot-melt glue gun.  Very handy thing to have in general.  We can use it in this project to help strengthen wire connections after soldering, as well as to join things together.

 

The parts I will be ordering from Amazon for this include:

 

(1) Arduino Pro Mini 5V moduleNot the 3.3V version. The name "Pro Mini" is important here.  I am getting this specific one:

https://www.amazon.c.../dp/B019SX75HU/

If you want to reduce the amount of soldering required, you could hunt for an identical module but with pre-soldered header pins.  The linked one above comes with the "header pins" separate from the board, so some of those will need to be soldered on later.  You may find a version for sale that already has the pins soldered in place, which is fine as well.

 

(2) You will need a USB-to-serial 5V TTL cable, for one-time loading of the GPS programming into the Arduino.  I already have several of those here, but you could order this one:

https://www.amazon.c.../dp/B07JN8YLPV/

The important thing is that it has the individual wires separated out at the end, with those black socket thingies that will plug directly onto the "header pins" of the Arduino board.  It should also have an RTS line, though one can get by without that if necessary.

 

(3) The GPS module.  I now recommend this small/cheap BN-180 module:

https://www.amazon.c...uct/B086ZKWYP5/

Pretty much any GPS module will do though, so long as it has a 5V-compatible serial interface and includes the jumper wires with the same black socket thingies that the serial cable also has.  The BN-180 is the smallest, cheapest one here, but the BN-220, or BN-880 will also work exactly the same (just pricier and slightly bulkier).

 

(4) A 6-wire "telephone" cable, commonly called a 6p6c cable (6-pole, 6-conductor).  Eg. this one:

https://www.amazon.c.../dp/B0002J1SUU/

It should be at least 2' long or so, and anything beyond that will be wasted here.

 

(5) Optional:  three resistors, 330ohm each, give or take 50ohms.  1/8watt rating or better.

These are not really needed, but they do add a bit of security in case of a wiring or programming error.  In practice, the programming is already done and working, so no worries there.  And we will use the multimeter to triple-check the wiring before plugging anything into the telescope mount.  I will use them because I have them "in stock" at my workbench.  But you don't need them.

 

(6) Optional: a small cardboard or plastic box, large enough to house the Arduino board and the GPS module.  Which is not large at all -- probably a small matchbox would do!  You can worry about this part after wiring up the project, when you'll have a better idea of what is needed.  I plan to just wrap mine in poster-board cut-outs from a cereal box (better than it first sounds!).

 

So, that's it.  If you want to play along, get yourself the 5V (not 3.3V) Arduino module, USB-serial cable for it, plus a GPS module, and a 6p6c telephone cable.

 

To be continued once my own parts arrive here in a day or two.

Thanks for sharing this cool project. I will build one, I have all the parts, but I am not sure which sketch to use. Could you please point me to the location of the latest version of the code?



#197 mikenoname

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Posted 25 December 2020 - 01:23 AM

You have gone though a lot of trouble making this guide, Thank you!

+1



#198 mlord

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Posted 25 December 2020 - 10:42 AM

Thanks for sharing this cool project. I will build one, I have all the parts, but I am not sure which sketch to use. Could you please point me to the location of the latest version of the code?

There's a download link for my current sketch (aka. "Arduino program") from the matching step of the web guide, here:

http://rtr.ca/homebr...al_cable_wiring


Edited by mlord, 25 December 2020 - 10:47 AM.

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#199 mlord

mlord

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Posted 25 December 2020 - 11:42 AM

If anyone here has the slightest bit of doubt about which wire goes where, then send me a photo of your 6p6c (RJ12) connector (gold pins up), along with a photo or list of which colour wires you have connected to which pins, and I will endeavour to verify the wiring for you!


Edited by mlord, 25 December 2020 - 11:43 AM.


#200 Speo

Speo

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Posted 25 December 2020 - 09:17 PM

There's a download link for my current sketch (aka. "Arduino program") from the matching step of the web guide, here:

http://rtr.ca/homebr...al_cable_wiring

Works like a charm with my Nexstar 8SE. Thank you.

 

I used a NEO 6M GPS that I had laying around for few years. This actually works much better than the original Celestron SkySync GPS. The original SkySync does not work inside my house and sometimes it takes a while until it gets a position. This NEO 6M is a lot faster and works even inside the house. I am quite happy.

 

Thanks again!!!   

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Edited by Speo, 25 December 2020 - 09:17 PM.

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