I’m part of a students association and we’ve had a helium tank in our place since 2003 which is still almost full. None of the current members knew where it came from until recently (turned out that we had a RC blimp of some sort back in those days…). So some time ago a member proposed that we could spend it in a high altitude balloon. Being electronics enthusiasts we thought about building our own electronics for the payload, trying to fit as much as possible in as few grams as possible. For now it’s planned that the probe will have an APRS tracker, an emergency 433MHz tracker, a GPS module of course, a GSM module for sending a SMS with the landing position if network is available, a board with lots of sensors (temperatures, atmospheric pressure, light intensity, gamma/cosmic radiation, 3D acc+gyro+mag, humidity and probably wind speed (we’re still not sure if that would be possible with a cheap, lightweight sensor). The whole thing will be controlled by a PIC32 and powered by 3xAA Lithium energizer batteries which are safer than lipos and tolerate very well low temperatures. It will log all its data into a microSD card.
Via the project log forum.