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Old Oct 03, 2010, 07:29 PM
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Fred.'s Avatar
Azores
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DIY UHF GPS tracker / beacon

Hi,
I am new here but have 2000+ posts on a FPV forum in Spain, where i have posted some electronic DIY projects, like a cheap UHF LRS , small simple projects and this is the last one, a simple GPS tracker/ beacon that will transmit its position via UHF on 433mhz with a range of at least 1.5km
The beacon transmits NMEA form the GPS each 20seconds for 2seconds aprox. at 4800bds (works with 9600 with amodified hex on the RX) , and this is displayed by a simple decoder based on the pic 16f84, wich is NOT my project.
I have recently lost my FPV plane fully equipped, with its HD camera, and if i had this device on board (that i was already projecting) i could have found it.
If this project can help you to avoid this, i will be happy.
Obviously I fly in zones where there is no GSM coverage, or else a commercial tracker would be fine.
If you donīt want to use the GPS you can always omit it and use it only as a simple beacon.

So here it is :
The transmitter:

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Shematic:
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Not showed on the schematic (but present on the PCB) are the led with its resistor, and a 1nF in parallel with 100nF for PS decoupling.


The receiver:
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The GPS Display project:

http://www.qsl.net/iw2bc/disp_gps.html

And here, the hex for 6Mhz and 10Mhz crystals:
http://www.aeromodelismovirtual.com/...?t=3786&page=5

A RX2-433-5V Radiometrix module is directly connected to the input.

Range with 5v, directly connected to the RX output with a Y cable for example, is 1.5km, and if connected at 12Vwould be much more. (In that case donīt forget the 78L08 regulator for the GPS supply, as showed on the shematic.)

This beacon has been built by others and tested at 7km with a simple antena.

The PCB layouts:I uses Sprint Layout, from Abacom, they have a demo version that allows to print:
http://www.abacom-online.de/uk/

Components list:
comps list


gps tracker UHF SMD
GPS Display
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Last edited by Fred.; Mar 01, 2011 at 08:53 PM.
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Old Oct 03, 2010, 07:36 PM
What arbre?? oh tree!
Puffer Ghoti's Avatar
Canada, QC
Joined Apr 2006
255 Posts
Looks interesting, I have an 433mhz FMKit beacon. This seems to offer a different dimension. You refer to a simple decoder to go with this, tell us more...
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Old Oct 03, 2010, 07:56 PM
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Looks like that would be a fun build! I would be very interested in seeing your build log if you make one.

Hopefully you did not lose your plane with the GoPro on it Looking forward to more of you videos
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Old Oct 03, 2010, 08:24 PM
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Fred.'s Avatar
Azores
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Quote:
Originally Posted by Williwaw View Post
Looks like that would be a fun build! I would be very interested in seeing your build log if you make one.

Hopefully you did not lose your plane with the GoPro on it Looking forward to more of you videos
Updated with the components list.
Thanks, but fortunately (...) the camera was the Pencam HD... a good camera, i have been looking for the plane for days, but as it had an autopilot it can have fallen to the sea. Video just went off suddenly, together with OSD data

You can find several more videos made with it on my youtube canal, (i rarely use vimeo )
http://www.youtube.com/user/FredMicro
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Old Oct 04, 2010, 12:00 AM
Just clumsy. Oh, forgetful too
MikeTheCrash's Avatar
undefined
Joined Jun 2008
3,374 Posts
very interesting. I lost a plane too and have been thinking of a solution like this but i have no electronics knowledge. My DOSD+ offers gps pass-through so it is very relevant

Can it have a time delay so it won't interfere with long range RC systems while flying?

Does it store gps data in case of disconnection in a crash landing?

Could I build one? I can solder but that's it

How much does it cost to make?

Thanks

Mike
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Old Oct 04, 2010, 03:19 AM
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this looks indeed very interesting! Problem is that i dont have the tools to make my own pcb.
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Old Oct 04, 2010, 06:23 AM
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Fred.'s Avatar
Azores
Joined Dec 2008
223 Posts
Hi,
The PCB in single sided and quite simple to make.
The beacon only transmits in the lack of the PPM signal, so no problem with the Long range system.( i also use a UHF LRs that is have designed and both transmitting at the same time was not an option)
The most expensive parts are the radiometrix modules, but you can find them on ebay sometimes and even new they are much much cheaper than a fully equipped plane
The system by itself doesnīt store the position, but the GPS (normally) continues to send its last received position so no problem here.The gps is always powered, only the RF is switched when PPM is missing.If you donīt want to use PPM you can use some RSSI signal, it just transmits when voltage on its input gets low.
The problem in sharing another GPS (beside the lack of redundancy useful for such a system ) is speed, the receiver is made to work @4800bds, and i have a hex for 9600 somewhere.

Also, instead of building the independent receiver, you could input the NMEA frames to a laptop or PDA or something to read it, but i have not tried that.
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Old Oct 04, 2010, 07:02 AM
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Romania, Dolj, Craiova
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Please, can you consider an alteration of this project as follows:
- can get data from GPS at 9600 and 38400, as most 5Hz GPS used in modern OSDes are using
- do some compression, like a Manchester encoding, or else,
- issue this data as an audio stream, will download it using the existing FPV equipment
- build the ground decoder as software, a laptop application, able to rebuild NMEA string and push it into a virtual COM port - here I can contribute myself

This way the plane flight can be recorded in real time as a map track, and know the last place before it stops transmitting.
Other can use the decoded data to drive tracking antennas.
Much of these functions are present in Dakar OSD, but the resulting hardware is much complicate than yours, and use video for data download, I want audio instead, to be able to record flights as audio tracks.

Thank you
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Old Oct 04, 2010, 10:05 AM
Just clumsy. Oh, forgetful too
MikeTheCrash's Avatar
undefined
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Quote:
Originally Posted by Fred. View Post
Hi,
The PCB in single sided and quite simple to make.
The beacon only transmits in the lack of the PPM signal, so no problem with the Long range system.( i also use a UHF LRs that is have designed and both transmitting at the same time was not an option)
The most expensive parts are the radiometrix modules, but you can find them on ebay sometimes and even new they are much much cheaper than a fully equipped plane
The system by itself doesnīt store the position, but the GPS (normally) continues to send its last received position so no problem here.The gps is always powered, only the RF is switched when PPM is missing.If you donīt want to use PPM you can use some RSSI signal, it just transmits when voltage on its input gets low.
The problem in sharing another GPS (beside the lack of redundancy useful for such a system ) is speed, the receiver is made to work @4800bds, and i have a hex for 9600 somewhere.

Also, instead of building the independent receiver, you could input the NMEA frames to a laptop or PDA or something to read it, but i have not tried that.


thanks for your answer, it makes me realise that it's probably too DIY for me!
PM me when you start to produce them
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Old Oct 04, 2010, 11:24 AM
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Originally Posted by MikeTheCrash View Post
thanks for your answer, it makes me realise that it's probably too DIY for me!
PM me when you start to produce them
Thanks for the answer on the PM Fred.

Ah, you can do it Mike! I'll send you a PCB for free...It's also not very expensive if you mess it up.

Anyway, I'm ordering the parts tomorrow...this looks like fun.
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Old Oct 04, 2010, 11:25 AM
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Originally Posted by MikeTheCrash View Post
thanks for your answer, it makes me realise that it's probably too DIY for me!
I am sure it is not...
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Old Oct 04, 2010, 11:28 AM
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Originally Posted by RENATOA View Post
Please, can you consider an alteration of this project as follows:
Sorry, the idea is to make an independent, simple and robust emergency system, nothing else...But anyone is free to modify it and share the results
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Old Oct 04, 2010, 11:30 AM
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Originally Posted by nabazul View Post
this looks indeed very interesting! Problem is that i dont have the tools to make my own pcb.
The only tool you need is a laser jet printer. If you dont have one your local copy shop should have one.

***Oops forgot one, a drill or Drumel, but you should already have one of those***
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Last edited by Williwaw; Oct 04, 2010 at 11:34 AM. Reason: Forgot a tool
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Old Oct 04, 2010, 01:27 PM
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I am having problems finding all of the material needed from a few vendors. Do you have any recommendations on vendors to buy the material from?
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Old Oct 04, 2010, 02:13 PM
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Originally Posted by Williwaw View Post
I am having problems finding all of the material needed from a few vendors. Do you have any recommendations on vendors to buy the material from?
Ah forgot the display, bought on ebay, just make a search for "16X2 LCD display"
The transistor is from digikey, the modules may be ordered directly from radiometrix or farnell.
I think everything else is very common and components are not critical .
Here are 2 pictures of the RX part, as you can see not ver "professional" but works perfectly, and easy to build.
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Last edited by Fred.; Oct 04, 2010 at 06:19 PM. Reason: lcd
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