Alex Alty, Chad Miller, Kristian Gjika, Will Smith - Section B

General Description

The weather balloon logger and cutdown system uses 10 peripherals to record near space weather balloon flight. It uses a GlobalSat EM 406 GPS Module, MPL3115A2 Altimeter, SparkFun microSD Transflash, 16Ch MT8870 DTMF Audio Decoder, and multiple 3.3 analog sensors. It records GPS coordinates, altitude data, temperature data, two analog sensors, and the 2, 4, and 6 signals from a touch-tone phone (or in our case a ham radio). The system logs this data with the SD card along with time stamps and uses programmed logic to trigger cutdown if the GPS senses the balloon leaves a pre-defined box, reaches to 100,000 feet, a 2 tone is dialed on an attached radio, or if the system runs for two hours. The system has two jumpers, a 3.3 volt that goes high if the cutdown sequence has to start, and ground, both of which can be inserted into any cutdown mechanism.

Interfacing With mbed

The system uses 4 main peripherals, the GPS, altimeter, SD logger, and DTMF decoder. Information on each can be found below.

Sample Program

The following program logs GPS, altitude, temperature, 2 analog sensors and 3 boolean values from DTMF 2,4, and 6 to an SD card. If the GPS leaves a defined box, altimeter hits a set value, 2 hours pass, or if DTMF 2 is triggered, the cutdown sequence begins by turning the jumper attached to pin 14 high.

Pin Hookups

mbed to EM 406 GPS Module

mbed to MPL3115A2 Altimeter

• needs 1k ohm pull up resistor

mbed to SparkFun microSD Transflash

mbed to 16Ch MT8870 DTMF Audio Decoder

3 analog sensors on pins 18, 19, and 20

Cutdown logic is pin 14

Video