This is one of the most frequently asked questions regarding our project on the headphone jack : I have an old headphone, how do I configure it to do all the stuff that you feature on your blog ? This post will be a pictorial DIY edition of it.
One of the first steps is to procure an old headphone ( in working condition or otherwise).
And then cut off the mic and the rest of the earphones with it. ( But don’t throw it away! ) The reason why we do this is because when you want to hack into a device, its a boon to have accessibility to the Input/Output ports.
When you strip open the wire that you have, in the case of a TRRS headphone jack you will find 4 wires (Left,Right,Mic and ground) and with a TRS (Left, Right and Ground). The next step is to attach female jumper wires to them so we can plug in anything we want.
These wires are not your conventional “plug and play” type i.e If you take these wires and plug them into anything it won’t work. This is because they have a non-conductive plastic-like coating in them that prevents the wires from shorting.
Therefore soldering them to the jumper wire is a bit tricky. But in our experience it helps to preheat the wires before soldering and also to wrap the wire in a braid fashion for longer life.
And similarly you solder the rest of the wires as well. Now in order to find out which wire corresponds to what, connect a speaker between the Left/Right and the ground, plug it into your computer and start playing tones.
If you are asking where am I going to find a speaker ? Well just use the speaker from your headphone that you stripped off in step 1 and solder two wires to its terminals like the picture above and you are all set.