Microtrak Testing

Lead Author: Nathaniel Franklin

Goals

            The goals for this test were to make sure our Microtrak 300 was operating properly.  This included proper wiring of the GPS transmitter, programming, connection to a GPS receiver and finally, taking the GPS unit outdoors for proper testing.

Wiring and Programming

            To begin, below is an image of the Microtrak 300.  It is a simple GPS transmitter, that when attached to a GPS receiver, will transmit its coordinates in latitude and longitude.

Figure 1- Micro Trak 300

            The screw on the left hand side is where the antenna attaches for tracking.  The green relay on the right hand side is where a 9-volt battery is connected to supply the microtrak can and receiver with power. The 5 wiring plates for connecting it to a computer for programming can be seen on the right hand side.  These plates allow wiring to be easily soldered to the board.  Going from top to bottom, the plates are numbered 5-1.

Pin Number	Function	DB-9 Pin
1	No connection
2	Serial Data IN (From GPS Trans. or computer for programming) (White)	2
3	Serial Data OUT (Green)	3
4	+5 Regulated output (For GPS power) (red)	4
5	Ground (black)	5

The plates were soldered with different colored wires just to allow us easily tell which wire represented each output.  After soldering these wires to the plate, the other ends were attached to a DB-9 solder cup female cup.

Figure 2-DB-9 Connector

Looking at the DB-9 connector, each solder cup is labeled with a number.  The number that each wire coming from a plate is the same number as the plate (i.e plate 2 is soldering to solder cup 2 on the DB-9 connector).  To program the microtrak through a computer, a null modem had to be placed between this DB-9 connector and the computer.  This involved taking two male DB-9 connectors and soldering them together with the green and white wires (pins 2 and 3) reversed as they go from one male connector to the next.  This was then plugged into a computer for programming.  The program used for programming is from the developers of the microtrak 300 (Bionics) and is very easy to use.  Below you can see what the program looks like.

Figure 3- Microtrak 300 programming

While it looks a bit complicated, only a few options need to be changed and programmed into the microtrak for the flight.  With power supplied to the micro trak, we opened up the program and entered the callsign for our balloon (the highlighted portion you see in Figure 3).  We also had to make sure the Auto Transmit Rate was set to 120 seconds, so the microtrak transmits every 2 minutes.  Finally, the COM port had to be properly selected so that we could communicated with the microtrak.  Once the proper COM was selected, we clicked the “Send 1200Hz” button to send a test tone.  It was successful as the LED bulb on the microtrack lit up and blinked until we stopped sending the tone.  We then simply clicked “Write Configuration” to send the proper programming (Callsign and transmit frequency) to the microtrak.  Finally, we disconnected the microtrak from the computer and the null modem and attached it to our GPS receiver, which is shown below.

Figure 4- Garmin 18x GPS Receiver

With it connected to the GPS receiver and power supplied, we took it outside to make sure it was transmitting and tracking properly

Transmission Testing

            To begin transmission testing, we took the microtrak attached to the receiver outdoors.  When the microtrak gained GPS lock, its LED when from blinking to solid green.  From here, we turned on our radio for our ground station and picked up the following GPS location for our transmitter.  Below is an image of the radio screen containing the coordinates as well as an image from google maps to show it was located outside Strong Hall at Eastern Michigan University.  The location transmitted by the GPS transmitter is the location of the green arrow.


1.

After getting the first location, I had another group member walk across campus to show that the microtrak would track my group member as he walked to Pray Harold (another building on campus).  Below are the sequential photos and google maps images to show that the microtrak was able to properly transmit his location as he traveled around campus from Strong Hall to Pray Harold.

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Recommendations

            With the GPS operational, we have to make the final adjustments to the payload and sensors.  The GPS needs to be mounted inside the payload as well as the other sensors.