When we kicked off this project back in October with "StratoBalloon, A Teaser" Katherine and I mentioned that we didn’t want to just launch a camera, we wanted to log temperature and pressure readings along the way. We also needed to be able to capture GPS tracking signals, and transmit those (and ideally some data) back to Earth during the flight.
To do all that we needed a microprocessor, and we settled on an Arduino Uno. We got our feet wet in "Arduino: First Exposure", and then got a little more serious when we built a compatible snap-on circuit board, or "shield" in "Shield’s Up!".
The next step was to lay out how all of our components would fit onto the shield. Here is what we planning to fly with:
- One Wire Digital Temperature Sensor (https://www.sparkfun.com/products/245 )
- Barometric Pressure Sensor (https://www.sparkfun.com/products/9694 )
- OpenLog data logger (https://www.sparkfun.com/products/9530 )
- Venus GPS with SMA Connector (https://www.sparkfun.com/products/11058 )
- RadioMetrix HX1 VHF Transmitter (http://www.radiometrix.com/content/hx1 )
We are going to add the components to the shield one at a time, writing the control program for them as we went. The first challenge, then, was to make sure that these five components would actually all fit on the board, and to sort out any pin conflicts.
To make things a little more modular, the components would each be soldered to what we’re calling a "socket" (https://www.sparkfun.com/products/9919 ). The socket would attach to the shield, and allow us to plug and unplug the component if we needed to.
The shield we’re using is called a protoshield, and it’s really meant to have a breadboard plugged into it on top so you can prototype with it. That won’t work for our purposes – we need the components actually soldered down – so we had to come up with another way to make connections. What we’re going to do is treat the shield like perfboard, and make the connections between adjacent holes using solder. In the diagrams below, a pair of holes connected like this are "jumpered holes".
Now, without further ado, here are the components laid out in 5 major steps. On the second and subsequent diagram, you will see holes blackened out from the previous steps. That should give you an idea of how this instrument pack will get built up over time:
I was pleasantly surprised to see the out-of-the-box wiring instructions for these five components had zero conflicts with any of the data lines, and I think the five sockets are spaced out far enough to allow us to work on each.
In our next podcast, Katherine and I will hook up the Temperature Sensor. Stay tuned!