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Old Oct 12, 2012, 04:31 AM
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For lost model use, the coordinates can be truncated to just minutes and seconds, we can safely assume degrees.
This will make the transmissions shorter, and the battery life longer. A nice firmware option anyway.
I hope you sell a kit, I would love to build one!
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Old Oct 12, 2012, 07:51 AM
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One of the benefits of using a PICAXE, and publishing the software, is that its open to all to tinker with and adjust the code. I have done a version of the same idea in complied basic, and there is not a lot of point in publishing the code as you need the compiler ($200) to make changes. Changes to PICAXE code just need a serial lead, the 'compiler' is free.

Making kits is not as simple as it may sound. Getting a locator so small does imply a reasonable level of skill to assemble. There is scope for poor assembly causing the device not to work or components to be destroyed. I would be looking to test all the components before dispatch, such that if a device does not work after assembly its not down to defective parts. This in turn requires various test jigs to be built, a time consuming process.
Old Oct 12, 2012, 01:55 PM
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Out of interest, do forum readers think that the transmission of locators distance and direction from home, as humane readable Morse is useful ?
Old Oct 12, 2012, 08:52 PM
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Given the choice I would pick GPS coordinates. After a crash I only need to receive one set of coordinates to know the location of the airplane, however you need a smart phone with Internet.
The bearing and distance information is nice because you only need a walkie-talkie, but you need a map to plot on.
I vote for the option for either.
Last edited by iskess; Oct 12, 2012 at 08:59 PM.
Old Oct 12, 2012, 09:03 PM
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Quote:
Originally Posted by srnet View Post
One of the benefits of using a PICAXE, and publishing the software, is that its open to all to tinker with and adjust the code. I have done a version of the same idea in complied basic, and there is not a lot of point in publishing the code as you need the compiler ($200) to make changes. Changes to PICAXE code just need a serial lead, the 'compiler' is free.

Making kits is not as simple as it may sound. Getting a locator so small does imply a reasonable level of skill to assemble. There is scope for poor assembly causing the device not to work or components to be destroyed. I would be looking to test all the components before dispatch, such that if a device does not work after assembly its not down to defective parts. This in turn requires various test jigs to be built, a time consuming process.
How about a detailed tutorial video with the parts list and you can just send out the printed circuit boards. Or have a third-party company print and send out the boards. Maybe a slightly larger footprint with less SMT components would make it easier for beginners.
Old Oct 13, 2012, 04:02 AM
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Quote:
Originally Posted by iskess View Post
The bearing and distance information is nice because you only need a walkie-talkie, but you need a map to plot on
As long as its within a 2km or so all you need is a compass and some accurate pacing, that is enough in relatively open country, but in a town a map helps a lot.
Old Oct 13, 2012, 05:32 AM
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Quote:
Originally Posted by iskess View Post
Maybe a slightly larger footprint with less SMT components would make it easier for beginners.
Soldering the SMT components is as not difficult as you might think, assuming you use a soldering iron with a 1mm bit or smaller.

The SMT components help a lot to keep the size down, the pads are on one side only, pin in hole components need pads on both sides, which cuts down the space for routing tracks.

If you can solder the SMT version of the 28X2, then the rest of the SMT components should be easy enough.

If you use the DIP version of the 28X2 you need a much larger PCB, I did do one for the ground station receiver, it uses standard wired components, will run the lost model locator code, but is twice the size, 50x50mm.

If you wire the GPS direct to the PCB pads, and dont use the SMA socket for an antenna the locator PCB shown will cut down to 26x34mm
Old Oct 14, 2012, 11:31 AM
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I've figured out most of the schematic except for the following parts: lk1, lk2, pad1 & PROG.
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Old Oct 14, 2012, 11:49 AM
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Which circuit diagram ?
Old Oct 14, 2012, 12:28 PM
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This one.

Quote:
Originally Posted by srnet View Post
Which circuit diagram ?
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Old Oct 14, 2012, 12:50 PM
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LK1 and LK2 can be ignored.

Pad1 is an isolated pad, useful to secure a piano wire antenna, if that what you are using.
Old Feb 03, 2013, 01:43 AM
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Srnet,
What have you been up to?
You still haven't gotten around to making a tutorial or a PCB for the world to enjoy your brilliant beacon device?
You have the best solution I've ever found, but it's just not accessible to me with me skill set.
How is your space exploration going?
Old Feb 04, 2013, 03:07 AM
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I have been building an improved satellite board that combines a RFM22 and RFM23 on the same PCB. The RFM23 has 30dBm output (1W) and would substantially improve the chances of getting data packets back from a 720kM high orbit. The PCB design is done and it works, undecided whether to take it forward.

For the RFM22 satellite PCB, I have implemented with software FSK RTTY transmission, although this will be a little tricky to receive from space due to doppler issues. Its advantage is that in short distance (4kM) comparison tests the FSK RTTY shows about a 26dBm power advantage over the RFM22 data packets. As the RFM22 data packets were tested LOS to 40kM that would suggest being able to receive data at 1000km mark without complex equipment.

So why would this relate to a lost model locator, 1000km to get back GPS location information seems a bit unnecessary ?

Although the RFM22 data packets will work up to 40km between hilltops, at ground level and in an urban environment that reception range could easily be 1kM or less, so a last resort reception mode with much greater range has to be a good idea, and this code will be added to the lost model locator to transmit the GPS location as FSK RTTY.

I have been looking at the locator this last week, there has been a lull in space related experiments. One thing I need to test is the addition of a charger for the small Lipo backup battery. I am less than impressed with those small red JST connectors, not really reliable enough, so that implies soldering the Lipo permanently to the board, and that requires an on-board charger.

The locator was always envisioned as two PCBs, a small locator (can be cut down to 25mm x 34mm) for a plane and a larger (50mm x 50mm) PCB as a receiver for the data telemetry although both PCBs can be used as transmitter or receiver. The locator is SMT assembly, the larger PCB standard ICs and wired components, a lot easier to assemble.

The smaller locator is never going to be easy for the less experienced to assemble. There are plenty of videos on the net already on how to solder SMT, and a component by component video tutorial would just take to long to do.

I will probably make a few of the larger PCBs available for sale in the next month or so, to see how much interest there is.
Old Feb 10, 2013, 12:29 PM
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@srnet - is it possible to use an arduino instead of picaxe for this project?
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Old Feb 10, 2013, 01:18 PM
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Possible, of course.

With a different PCB and code.

Processor wise its not very demanding, apart from the distance and direction calculation which is a heap easier with floating point maths and proper trig.


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