It’s been a while… So I just competed in HackDFW - which was pretty awesome. My team worked really well together, and we did really well (placed second overall). We designed a cell phone controlled TENS device over 24 hours. Half of the team worked on the hardware portions of it, the other half (the half I was on) worked on the Android side of things. This’ll be short because I’m still tired.

Hardware

The hardware side of the team worked on boost circuitry to boost the signal coming from the phone. They simulated the circuit using LTSpice, built a prototype using protoboards, then designed and manufactured a professional looking PCB (all within 24 hours). While the circuit was remarkably simple, it was a really impressive feat for them to have done. I have some pictures that I hope to upload soon.

Software

We made an Android app to actually control the device, though it honestly could run on anything with an audio jack. At first we worked on just getting something that could reliably output a sine wave, which proved more annoying that I originally thought it would have been. At first we wanted to use Androids audio looping so that we wouldn’t have to continually generate more of the signal, but there were some issues that made this not work amazingly well. After this, we went on to just using the streaming mode (I may post about this later, but wont go into details about it right now). In terms of outputting a signal this worked really well.

We then ran into some issues with getting the signal correct. This was mostly a matter with getting the units correct for the functions we were using. Once that was done, it worked perfectly. Afterwards, we worked on getting the actual waveform, which was mostly just a math problem.

Results

Our final prototype was well executed and worked amazingly well for something that was designed and built in 24 hours. We pitched our product to a panel of celebrity judges, and placed 2nd.