The phone is a great, compact package that contains almost all of the pieces we need to accomplish our goal, but there’s one piece missing; releasing the tether. Once we’ve reached altitude, there needs to be some way of releasing the balloon and initiating our descent. It’s entirely possible for a balloon to reach a certain altitude and for some reason or other not pop. If this happens, the balloon may float far out of range and get lost. Additionally, even if the balloon does pop, it is still attached with the tether to the payload on the descent, which could cause complications with the descent and either slow it or keep it off balance.
Recent Android phones are capable of communicating via the USB port with other devices, but we can’t rely on that capability existing for older phones.
A common method for interfacing with phones when other means are not available is through the headphone jack. By playing a carefully constructed audio signal, we can have a circuit that detects the audio and triggers an action. This option is cheap, robust, and easy to build, so we’ve designed and built one for you. You can order this component from our store, or if you decide to risk the balloon not popping, you can skip it entirely.
UPDATE: Because of a delay in the production process, our boards will not be arriving in time to test and use. We’re simplifying our design even more and just ignoring the electronics part, relying on the balloon to pop on its own and return to earth.