A colleague in our office had an old pair of Bluetooth headphones with a slightly broken, tarnished shell and badly worn out ear pads. Fortunately for him, the headset was working perfectly with all functionalities in place. When he approached us to have them fixed, we told him that the shell couldn’t be repaired and that the ear pads were not easily replaceable. He’d simply have to opt for a new one. Then we thought of an alternative - why not convert the same working Bluetooth headset into an audio module, which can be used with any stereo headphones of his choice?!
The Bluetooth module would also have multiple uses, thereafter. For example, he could use them with regular headphones, to connect it to his home theatre and have a wireless Bluetooth audio speaker system, connect it to a car stereo auxiliary input and have a BT hands-free for the car, use it to stream audio from a PC or laptop to an external speaker set, and many other options. The method of hacking into a unit and modifying the circuit was a bit of a task and needed a few hours of thinking - how could we simplify the work? This is what we did, and you can implement the similar idea with your BT headset, if you have a slightly damaged one just lying around.
The main ingredients
Getting down to the nitty-gritty
Firstly, to get to know the whole circuitry, internal parts and its connections, we had to get inside the headset. We started by carefully studying the headset and separating the ear units from the head loop. We had to remove the ear pad foam cushions because the screws to the shell were underneath.
What the innards look like
Once open, we separated the shell from the circuitry. Here’s what we found—the right earphone had the main BT module circuit board, along with the control panel buttons over it. Below the circuit board was the right speaker or driver. Four wires were carried along the head loop to the other side which connects to the left speaker, and the main battery was enclosed inside.
What you'll need to get this going
Since the speakers would not be required anymore, we cut-off the wires and separated the battery from the left side. We disconnected the head loop and the right speaker. Now we were left with the shell, the button pads, the battery and the main circuit. We had to retain the shell as it helped mount and keep in place the control panel buttons. This part of the shell (the right ear side) was ideal for housing all relevant tech. If the shell were damaged, we would have to hunt for a similar-sized shell or plastic box to mount the whole circuit inside, which would make it more complicated and also a bit unappealing in terms of looks.
The battery could be placed comfortably where the speaker was initially housed—this took care of the power section. Next we needed to hunt for space to mount the 3.5-mm female audio jack. This was tricky as it would need drilling and sanding in a few areas. We thought it best to get rid of the power socket and use a USB connector, instead. This would make it even more ideal as the charger could be eliminated completely, and the BT module could now be charged from any USB port or USB wall charger. We placed the USB connector at the edge where the right ear unit was joined to the head loop. We made use of a USB connector hacked from an old pen drive. The power jack was removed and the audio jack took its place. This area needed a little cutting and sanding to accommodate the connector comfortably. Shell was finally re-designed; we now had to tackle the circuit board.
Inside the headset shell
Carefully checking out the circuit board, we found the necessary connections neatly marked. We de-soldered all the existing wires and made use of some thin flexible wires obtained from an unused IDE HDD cable. We cropped out the necessary wire lengths and kept them ready. Next, we began soldering all the essential components—the audio jack, USB power connector and battery. We gave it a test and found everything was connected properly and working fine.
Test the system
Before we finally mounted the circuit onto the now modified shell, we had to disconnect the battery, pass the wires through the shell and then glue the battery down on the other side. We used hot glue, as it is non-conductive and also hardens in a few seconds. Next the audio jack and the USB connector were glued down carefully. Since the built-in microphone was not touched, we did not modify anything in this section. Finally, after all the connectors were glued down and once everything was in place, we glued down the wires to a blank areas on the circuit board. This prevented the wires from getting loose and possibly breaking because the solder joints were quite minute and feeble. Finally, with everything in place, we put the shell together, inserted the screws and then applied some more hot glue to secure it with the USB port. That’s it! Our Bluetooth module was ready for use.
If you intend making one for yourself, you can simply pair it with your Bluetooth-enabled phone, tablet or PC and stream your audio. You’ll just need to connect a pair of standard stereo headphones to enjoy your music. You can also connect it to your home stereo system or your in-car entertainment via the Aux-In to have yourself a BT hands-free kit as well.
Fitting the circuit board and components
Note: While disconnecting any wires and replacing them with new ones, note down the polarity and double check it before re-soldering them to avoid damage and other hazards. Use of the soldering iron and the hot glue gun should be done with extreme care. If you do not have any idea about how to handle circuits and/or a soldering iron, we recommend you take the help of a friend or electronics engineer or do not attempt this at all. This workshop is for educational purposes only and we are not responsible for any damage caused, while attempting the same. Do this at your own risk.
Published Date: May 30, 2012 09:42 am | Updated Date: May 30, 2012 09:42 am