Building the Final Device Hardware

Today Roy and Karly were able to complete construction of the hardware for the hip connecting device. The perfboard was sheared and drilled to about the size of an iPhone. It is slightly larger than anticipated but this is because to power the arduino separately from the computer, you need a 9V battery which can take up a significant portion of the board.

It took us a few days to get the circuit to fully function because of issues with the soldering. Initially we used large wires with several soldering point connections. The issue with this is that there was a lot of potential for a poor connections leading to loss of power to the components. Additionally, when soldering the large wires, we applied heat longer to make the connection and we think this may have caused one of our LE bluetooth components to break. Our next solution was to use smaller wires that could be threaded through the perfboard to secure the connections to reduce breakage. We thought less solder would be needed to make a connection which means less heat applied to the device. This means that there may be less risk of blowing out a component. The issue was that there was not heat shrink small enough to insulate the connections. As a result, the connections were even more fragile than before meaning more connections broke with smaller movements.

In the end, we decided it would be best to go with 22 gauge wires. We realized that larger wires would absorb more heat from the soldering iron thus protecting the components and decreasing the risk of them breaking. Additionally, we realized we needed to reduce the number of connection points to make the circuit more durable and avoid power loss. To do this, we removed the pin headers and directly soldered the wires to the printed circuit boards. We secured the components to the perfboard by using hot glue and pin headers in holes on the printed cicuit board that were unused. We soldered each component to the board and then tested that it was functioning. The final step was connecting the battery with the switch and testing that the device could function without connecting to the computer... and it worked!

The next steps in hardware design is to continue to work on connecting the device to SAMI. We are currently having issues with this and are looking to connect it to MatLab directly via a computer. Also, we need to design and 3D print a case for the device to protect it.