Breakaway Audio Cable
Having just added headphones to my new snowboarding helmet, I realised I'd need a method of connecting the headphones to my mobile phone (in my jacket) that would be easy to disconnect and reconnect - whilst wearing gloves - when removing and putting on the helmet. As an added concern, I wanted to avoid damage to the phone (or myself) if and when I took a fall on the slopes.
I have used wireless bluetooth adaptors before, but they have a number of problems, including diminished audio quality and a limited run-time. As they are typically designed to be as small as possible, the built-in playback controls they feature are also often not suitable for use with gloves.
Taking inspiration for Apple's MagSafe connector, I devised a modification to an existing headphone extension cable that would provde the break-away functionality, using nothing more than some rare earth magnets and some heatsrhink tubing.
These magnets are easy to source cheaply from eBay. I choose cylindrical neodymium magnets (10mm long, 3mm diameter) as they would allow for a relatively slim connector. They would also be suitable for heat-shrinking together.
The first step was to cut the extension cord I already had in half, then twist and tin the exposed wires. As with most audio cables, it contained red and white insluated wires for the two channels, with a third ground wire wrapped around the two, also acting as a shield. Taking care not to overheat and melt the insulation of the two channel wires, I tinned all three, ready to be soldered to the magnets.
Construction & Use
The plan was to use 6 magnets in total. Each would be individually heatshrink-wrapped to insulate them, then all three would be wrapped together to create a single connector.
Soldering anything to magnets poses a slight problem, as they are affected by heat in a negative way. Once the 'Curie Point' of a particular magnet is reached, it loses its magnetism completely, unless it is re-heated under the influence of a strong magnetic field. I found it best to avoid this by using a higher soldering temperature for a shorter period of time; also sanding/scoring the soldered end of the magnet in an effort to get the solder to meld with the surface as quickly as possible.
This seemed to work well, and I soon had all six magnets in place. I took care to ensure that the polarity of the magnets forced the connector to always seat itself in the right way, so that the three wires always met up correctly without needing a physical notch or keying system at each end of the connector. I ended up applying a couple of layers of heatshrink tubing to the outside of the connector to make it as durable as possible. In hindsight, this made the length of the connector greater than it needed to be. Had I used shorter lengths of tubing and even shorter magnets, I could have made a connection totally only an inch or so in length.
Despite this, the end result works extremely well.
Making the connection is easy with gloves on, as the magnets seat the connectors in the correct orientation. At the same time, a short sharp force (or a snapping motion applied with the thumb) breaks the connection easily and safely.