Wireless GPS tracking thoughts

[shafferm]

After reading about DaGriz's problems with theft, I got to thinking and reading a bit into how to make a gps bug that would not depend on cell phone service or costly monthly access fees and software.

Here is what I came up with for tracking with gps out in areas without cell phone coverage.
With some additions and modifications from a gps rc plane locator such as this,

http://www.rcgroups.com/forums/showthread.php?t=993165

it should be possible to make a gps to rf tracking bug that does not require cell phone service, plus there are no monthly service fees for tracking to pay. The downside is the fairly high up front cost for the parts.
I wanted to use readily available components to handle the wireless communication, especially as they already have FCC approval.

Here is what would be needed for the "bug" it basically would attach to the battery pack of a game came and would pulse out its location a few times per hour using RF, you will also need a receiver hooked to a laptop to capture the signal and display the latitude and longitude of the bug. The microcontroller is used to turn on the gps receiver and the 900 mhz transmitter for around three minutes (this gives the gps module time to startup, determine its position, and then transmit the position using the xbee module) on approximately 20 minute intervals. You could vary the on time when you set the timing in the PIC microcontroller depending on how long of battery runtimes were needed. The more often it broadcasts, the faster you are going to run down the batteries. Here is the parts list for the bug portion, it is a gps receiver module, and xbee 900 mhz transmitter, xbee voltage regulator board,microcontroller, voltage regulator, and relay.

XBee Pro 900 XSC Wire http://www.sparkfun.com/products/9085
$66.95
EM-411 GPS Engine Board Module with SiRF Star III Chipset http://www.dealextreme.com/p/em-411-gps ... pset-80037
$28.3
XBee Explorer Regulated http://www.sparkfun.com/products/9132
$9.95

reed relay http://www.hobbyengineering.com/H4537.html
$4
PIC 12F629 microcontroller http://www.hobbyengineering.com/H1757.html $2.25
voltage regulator LM2940T-5.0 http://www.hobbyengineering.com/H1590.html
$1.8

The total price on the bug side comes to around $113 before adding on shipping.

The receiver side is a little cheaper, as you just need the 900 mhz xbee module and an adapter board to interface to a laptop. The price for the two comes to around $92.

XBee Explorer USB http://www.sparkfun.com/products/8687
$24.95
XBee Pro 900 XSC Wire http://www.sparkfun.com/products/9085
$66.95

The grand total would be around $205 for parts before tacking on shipping. You will also need to figure out how to shoehorn the bug into the game cam while not making it obvious that something is a bit different. You could also add in a small battery pack if you were worried about someone pulling the batteries from the game cam. The 900 mhz modules are supposed to be capable of transmitting up to 15 miles under ideal conditions for line of sight, however I would guess that it should be able to make 1 to 2 miles with a fair amount of trees etc. in the way.

I have not built and prototyped this personally, although the design is based primarily using off the shelf components to make it relatively easy to build. If anyone is interested in building one, let me know.

[rayman]

Sounds kind of like an EPIRB or personal locator beacon. Don't know much about how that stuff works though.

[GaryM]

I dunno. How good would the thing work? You spend $200 for a GPS you have to build from parts to track a $200 camera. If the gizmo doesn't work you're out $400! Things like this I call "rich hero stuff". Gary

[shafferm]

It would work fairly similarly to a locator beacon, not sure what frequency they are using to transmit the location.

Gary,
I agree it doesn't seem to make financial sense to dump $200 into electronics to recover a game cam that may cost less than that. Although there is something to be said for being able to catch whoever is stealing from you, as they are likely to keep on stealing. The other factor driving the cost up are the transmitter/receivers. The ones I picked should give a very long range, if you had a suspect and were able to get within a few hundred yards of them from the road, then much lower power transmitters should be able to do the job. I did find some line of sight transmitters that were claiming around 1000 yards, they were running about $25 each. Going with these you could get the total price down to around $100. The breakdown is then around $60 of parts to add to the game camera and the other $40 stays with you for the receiving end.

Without actually buying the parts and putting one together it is hard to say definitively how well it would work.

The other question would deal with the legal aspect, is having a gps signal indicating where your stolen property has moved to enough to get a search warrant? I can't say for certain.

[BigNasty]

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