GPS Tracking

Here is my work on a GPS only tracking device for my rockets. I wanted to modularize it so I could the same parts in different designs. This would allow me to use my GPS module in as a GPS for my car, then use the same module in my GPS rocket tracking device etc. This way I can use the same item across several projects. You will notice the satin phone cable and RJ11/14 on the GPS module this is how I made it movable.
So here is how I made my rocket GPS tracking device. After doing some research on the web and looking at what certain equipment could do, I bought the Maxstream 9xtend developers kit which happened to be on sale for $249.00. This kit comes with two Maxstream 9xtend RF modems, two interface developers boards, two serial cables, two power supplies and several serial adapters. I also bought a USB interface board so when I was out in the field I could use the USB to power the board and not have to have a separate power supply. Now I had the radios that could do the job. These units with the high gain antennas are good for 20 miles line of sight. I know they have been tested even further in rockets. Maxstream has another product that goes up to 40 miles but I didn't see the need for them at this time.
Next was the GPS unit. I wanted to get something that work inside a rocket. I found the EM-406 GPS unit that had some respectable GPS specs and uses the SiRF III chip set. With the built in antenna the unit works to -159 db. So when I first tested it in my house in the sub level basement, I was able to pick up between five and eight satellites. From there is just used parts and stuff I had in my electronic parts box like phone cable and connectors etc.
The first project was to get test the GPS. Since the board puts out 2.85 volts TTL, I needed to convert it to RS232 electrical signals. For the first test I used a shifter board just to test the unit. The shifter board (from Sparks Fun Electronics) will convert any input voltage to 5 volts out. So all I did was match the input voltage to the shifter board with 2.85 volts and I had GPS serial data. So I wanted to build a car box to use with Microsoft Streets and trips. Using a MAX232 chip and some 1uF caps, I was able to hook up my GPS to output true RS232 for any computer or laptop. This works great with the 2006 version of MS Streets. It gives you Direction elevation, speed, lat & long as well as tracking. I have used the integrated voice directions to go to work a couple of times and it works great. One thing not on the schematic is I added a external power jack to use in a car with a cigarette lighter. Ok One project out of the way, on to the next.
The next project was to make the GPS work with the Maxstream modems to use for actual rocket tracking. Using the manual for the GPS and Maxstream modems I hooked up the units and did some testing of the signals to see if I needed to use a MAX232 or not. Turns out I did not so the hookup was real easy. With just a 5 volt regulator, as couple or resisters for the power/TX LED and some wire, I had a working GPS unit with the Maxstream modems. I will build a box shortly for the prototype board shortly.

Car Box Schematic PDF
GPS Rocket Tracker PDF

GPS Schematic JPEG

Coming soon