This board will contain a Magnetic sensor that will be used to detect apogee. It will also contain a pressure sensor and A/D convertor. The Magnetic sensor output will be fed to the A/D convertor and also to a comparitor. The comparitor output will go to the Interupt line of the controller. When the controller receives this interupt it will read the altitude and store it. It will also start comparing the read altitude to the AGL main deployment altitude. When that altitude is reached it deploys the main chute.
Basically what this allows is a dual deployment Magnetic sensor design. This design could be mounted in the nose cone with the sensor vent on the curve of the cone. Since the sensor wont be reading pressure till after apogee there is no problem with vent placement. There will also be no concern of mach pressure.
This could also be accomplished with the sensor board and a wireing harness that reads the output of a seperate MAD unit and uses this input for the above function.
The design of the comparitor circuit uses a digital potentiometer that will
allow you to calibrate it. If you hold down the calibration button when you turn
it on it will go into calibration mode and beep at you.
Then whenever you
press the button the controller reads the current mag sensor output and adjusts
the digital pot. to switch on the comparitor at this new value. Then you just
tip it up and back to test while watching the LED. This value is stored in the
internal EEPROM and will be used until you change it.
