We designed a low cost balloon-launch platform that did not require the use of expensive equipment such as radio modems (the total cost of our device did not exceed 150 dollars) or complicated hardware hacking (all of the components of our device were common electronics available off-the-shelf in stores).
The GPS receiver was a Motorola i290 “Boost Mobile” prepaid phone with internet and GPS capability (set up with Accutracking to constantly report its GPS location).
We bought a AA-battery cell phone charger to sustain the phone’s power over the duration of the flight, and we used Energizer lithium batteries (rated to operate at temperatures are low as -40F) to power both this charger as well as our camera.
As a further safeguard against electronic/battery failure due to low temperature, we utilitzed Coleman disposable hand warmers (placed near our electronics) to help keep our equipment warm in the cold of the stratosphere.
We loaded a Canon A470 camera (bought used on Amazon) with CHDK open source software to enable a feature which allowed the camera to take pictures continuously (intervalometer). Using this feature, we set the camera to take a picture every 5 seconds at a 1/800 second shutter speed. With an 8GB card, the camera was able to chronicle the whole journey of the balloon from launch to retrieval. (~5 hours)
Equipment Used in the Launch Capsule
|Sounding Balloon 350g from Kaymont||350g||~$20 +$20 (helium)|
|Motorola i290 Prepaid Cellphone||~90g,||~$50**|
|Styrofoam Beer Cooler||~15g||~$0|
|Canon A470 with 8GB SD card||~165g,||~$40***|
|Insulation material- newspaper||~5g||~$0|
|Duracell USB phone charger powered by AA batteries||~20g 1oz||~$10|
|Instant Hand warmer||~5g||~$2****|
|4 Ultimate Lithium AA batteries||~15g * 4 = 60 g||~$5|
|Radar Reflector (aluminum foil)||~0g||~$0|
|Total||~800g, /w misc.||~$150|
* Two things:
(1) We had one of these laying around, so we’re actually a little unclear about how much it would cost to get a plastic parachute with strings, but we can’t imagine it would be that much. However, we actually created a second launch vehicle using a trash bag as a parachute, so that is one way people could probably cut costs.
(2) It may not even be necessary to attach a parachute. For instance, I think that a large number of streamers dangling off the back of the box might provide enough drag to slow it down to a comparable landing speed.
** Some people have told us (and we have confirmed after some searching online) that the cost of the cell phone (usable for a similar launch) can actually go as low as $30. We paid $50 for ours though.
*** This was a lucky grab for us. One can do the same with a 4GB SD card with picture intervals of 10s each, and that will save you about $10. You can find cheap cameras on ebay or Amazon (used). You probably want to send a used one up anyways, considering the harsh conditions it will be subject to.
**** A packet of 6 handwarmers can be bought for ~$5 from Target. We used two handwarmers for our launch, one pressed against the camera and one pressed against the cell phone.
***** Many people have asked about the antenna in our pictures. It was an extra part from a used wireless router. However, i don’t actually think it’s necessary to have one (and in our second vehicle, we actually didn’t add the antenna.) As long as the cell phone can report its location after landing, one should be okay.