Space balloon is a popular hobby among makers.Usually they hook an action camera to the balloon take amazing photos over 10km above earth and it is really amazing. At first I believe these photos took our attention. Sending something to sky is extremely fun. But this fun is limited. Because a few hours later balloon is blowing up. So we searched for a long term fun. We want to send something to sky but we don’t want it to blow up and land in a few hours. So our searches lead us to pico ballooning. Pico ballooning is about sending a small sensor package nearly 50 grams with a helium balloon. Generally they use qualatex foil balloon like this one. We fill 1/3 of them with helium.These balloons are not elastic so they are not expanding as they go up in the sky thus they stay in same height after reaching their final volume.
Lets get to our pico balloons. We have sent two pico balloons ,one of them is with a AA battery and one of them is with a solar battery.
Our first balloon is built with a habduino shield. But we did small modifications. Habduino shield includes every sensor we need such as temperature sensor , battery voltage sensor and a gps. However Habduino is built for Arduino uno and it was too heavy for our balloons. We did some modifications to reduce its weight and it was really useful.Our complete system was about 45 grams.
- Removed antenna ports
- Changed gps antenna with passive antenna instead of its active antenna
- Removed arduino uno shield pins
After altering physical parts we need to change software too. Software is designed to work on Arduino uno and it can work on arduino pro too obviously. But the habduino code was missing telemetry functions. It means it can’t send telemetry data. So I added telemetry send function.It can be found on my github : https://github.com/clkasd/HABduino
We sent it with a single AA battery. The result was really satisfying. But after our first try we want build a solar cell – powered system so we could track it for days. Thus we started to build second pico balloon. But this time we did not used a habduino shield. Instead , we used three different sensors to build something that is like habduino but smaller and lighter.
In our second try, following sensors and modules were used :
Because of we did not get as much as sun as we did in summer our energy was so limited that we could only power our system for a few minutes. We need to use power more efficient so we ended up using four 10F , 2.7V capacitor to store solar power. And also we found an interesting module which is responsible for turning off the system when power is too low. With this module(https://www.pololu.com/product/2120) our system turns itself off when power is about 5.2V and turns itself on when it reaches to 5.8V. By this advantage we make sure that it stored enough power before turning itself on.
I used the same library I used on habduino shield. But I wrote a wrapper to make it easy for other people to use it. You can get it from github : https://github.com/clkasd/picoBalloons
And there is an example in the folder. You can look at it and use it. It is designed for a temperature sensored pico balloon sensor box with arduino mini 3.3v and a GPS Sensor (UBLOX M8).
Our second flight lasted 2 days. We don’t exactly know what happened after 2 days but our next flight will be more stable.
You can get more detailed information about our flights from http://picoballoon.ist