Site Network: freakymousemats | portal | smashingbloke | regenology

the weblog

Occasional musings that fall out of my brain and on to the site. Occasionally more occasional than I'd like. But will try to fix that.

Head in the Clouds

Posted by stephen on Monday, 19th March, 2007 @ 18:00

Conveniently coinciding with my recent discovery of the more practical side of myself with the camera project at work (soldering irons and power drills seem much more usable and useful than they did a week ago) I came across Balloon v1.0 and got rather excited by the notion of launching a weather balloon with a digital camera attached to take pictures of the journey. When you add the GPS, a small Linux x86-based motherboard and interactive control over packet radio you get a dream project for geeks like Chris and me.

And with my knowledge of Linux and his knowledge of radio stuff (usefully including actually having a radio license) and our combined mass of random stuff it turns out it's actually quite conceivable we could successfully undertake such a project. Lots more research about more recent UK launches at the UK High Altitude Society has given us plenty of inspiration.

So here's my current, approximate plan...

  • Purchase a weather balloon of sufficient size to carry the payload once we've determined how heavy it's going to be and what sort of lift we'll be needing. Add to that the helium to make it fly and a sufficient parachute to safely return the payload to earth, most likely one of the commonly sold model rocket parachutes will do.
  • Construct a 'cutdown device' from a small plastic tube and a model rocket ignitor. This would be attached on a cord from the balloon, and a cord to the parachute and payload would run from it. Needs some electronics to allow the flight computer to fire it.

  • Purchase a couple of digital cameras from ASDA or similar. Richard discovered they sell a small 3 megapixel camera that takes a pair of AAAs and an SD card. All that for £18, bargain! Being light will be important and we want two so we can take pictures of the horizon and of the ground. Extra things needed: some simply electronics to activate the shutter at set intervals. SD cards big enough to store the pictures for the duration of the flight. 512Mb or 1Gb will probably do and is ridiculously cheap at around £5 from ebuyer.com.
  • Use my Neuros OSD as the flight computer. It's small and light, runs Linux and has plenty of CPU and RAM while using limited power. Also provides a USB port for the USB GPS dongle I've already got, and an RS232 serial port for talking to a packet modem or controlling any GPIO electronics like the cutdown device. Has audio in and out for transmitting/receiving morse and packet radio at the software level. And one other potential advantage is the onboard hardware MPEG4 encoder. Using the AV output from a camera it's possible to created a video of the flight on a SD or compact flash card in the OSD.
  • Use a USB hub to also attach a spare Nokia phone with data cable. Use Gnokii software on the OSD to send the current GPS co-ordinates via text messages at given intervals. Good backup in case of radio failure or when it's hard to pick up the signal once the payload has landed.
  • Create a simple radio from readily available ICs producing a signal at license-free frequencies and use to transmit the current GPS co-ords and other data by morse or packet radio. Power of transmissions from mobile operator-free devices is legally restricted, so use of a larger antenna on the ground to pick up the signal will be necessary.
  • Build a Linux system for the OSD along with some scripting to log GPS data and transmit it as required via radio and SMS. Create conditions for cutdown, when the balloon gets too high or leaves a certain area that'll make it impractical to recover (e.g. the sea).

It doesn't seem too hard really, so stayed tuned for updates on our progress. I'll probably begin by assembling some of the components I've already got into working systems and go from there.

Made with Django.