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GPS Tracker Rev 3

For a little more information on the build process for this tracker, see the end of this post on 4hv.org, its post on the rocketryforum and Krazed III (the rocket it will fly in).

After the unfortunate death of the GPS tracker rev 2, I decided that the next revision would have a microprocessor on board so that I could fire charges remotely (chicken switch). That then lead to having a few extra sensors, and then I needed some memory to store all of the extra data in, and a new power supply to keep everything running off a single LiPo cell, and I ended up with the following list of requirements:

• Fit in a 38mm tube
• Have at least 2 mile range, and not require a HAM license
• Be able to remotely fire 3 charges (main chute, drogue chute, tracking smoke, etc) while in flight
• Send GPS data back to the pad at least once per second (to find the rocket)
• Run off a single LiPo cell
• Store all data taken during flight in in nonvolatile memory
• Store altitude and acceleration data at 100samples/sec
• Be able to be expanded easily

I then started searching for suitable sensors, and came up with this list:

• lassen IQ GPS
• Ultra Compact Antenna
• XT09-SI 900MHz transceiver
• 900MHz Halfwave Dipole Antenna
• max1763 1.5A 3.3-5v boost converter
• PIC18f2550 Microprocessor
• MMA2002G +/-50G accelerometer
• LIS3LV02DQ +/-6.5G 3axis accelerometer
• MPXA4115 0-15PSI pressure transducer
• MCP3221 12bit A/D converter (for altimeter)
• AT45DB321C 32Mbit FLASH

After those parts came in I spent some time with a breadboard (and some creative ways of hooking all of the surface mount or even leadless parts into my breadboard...) an got some proof of concept code working for them all.

And then drew up a schematic and did a board layout: (note, there are some errors in these, for reference only)

I then tried to etch my on PCB for the tracker, but ran into all sorts of problems. Of course it was not until after I reworked all of the imperfections in the board that I realised I mirrored the wrong side of the board and it was completely useless. Lesson learned, when there are tons of vias, and really small traces, don't try to etch your own board out of 4oz copper clad, just use batchPCB.com
But if you must see it, there was a few days worth of work I really wish I could have skipped...

and populated the board:

Results:
I flew it in Krazed III on 10/13/07, on a I287 2 times, and on a Hypertek J317 once on 4/6/08. Unfortunately, the code to use the flash memory wasn't working, so the only data I have is the 1hz location/altitude/acceleration data. See Krazed III's page for the data.

Code:
I am currently working on the code, and have had a number of sucessful flights on the revision 0 code
If you would like the alpha code, email me.

Licensing:
Everything on this site (pictures, schematics, code, etc) is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License, which essentially states that you can do whatever you want with it, so long as you

• attribute me
• share it under a similar license
• do not sell it

If you need a different license, contact me.

questions? comments? Want to help? email me contact@krazerlasers.com

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