Wireless Bone Conduction Headset (headphones)

In this Instructable we are going to make a solar wireless headphones that use bone conduction speakers to play music. This headphones are capable of control the multimedia player basic functions and also have a built in microphone to allow take calls.
The solar panel will provide an extra power boost, is not too much but is enough to give 15 extra minutes of music and recharge the battery while the headphones are off. The lipo battery itself can power the headphones for around 50 minutes. And also you can provide external power via de mini usb connector, when you do this you can continue using the headphones while the battery is recharging. The battery status indicator only will be on while the battery is recharging over USB, in solar recharge mode the led remains off all the time to save energy. The bone conduction allow to listen your music while you still hearing your surroundings, so this headphones are nice when you are outside and you want to continue paying attention to the external world.

This is a work in progress so there is a lot of improvements that can be done!

Lets get started, shall we?

Step 1: Materials

To make this fantastic build you will need this components:

Flexible 5v solar panel, small enough to fit in the headband.( my solar panel only generate 4.8V@22 ma)
Plastic headband. (the ones girls uses for the hair)
Aluminum tape.
Double side tape.
A sheet of thin craft foam.
Hot glue and of course hot glue gun.
Some flat wire.
Electret microphone.
Small 3.7v lithium polymer battery. Mine is 450maH.
2 Bone conduction transducer (got myne from Adafruit, they are the 8 ohm small type)
A bluetooth audio module ( I used XS3868, but if you can buy a better one like the RN52 do it!)
Two small audio transformers (I used DA101MC)
Two 33 ohm resistors.
The rest of the electronic components can be seen on the Eagle designs that I include with the PCB and schematic. Most of them are SMD.

Keep in mind that this proyect uses SMD components, so be ready to solder this tiny things!

Wireless solar headset.rar
Download

Step 2: Making the Boards

For this step you need to download the eagle designs from the previous step. And you need to make and assemble this boards. I am assuming that you know how to interpret the designs and get things done. So i will be short in this step.

Note: I used a JST connector for the lipo battery. The 3.6v regulator is not necessary, I included it for powering the bluetooth module but it give me a lot of brown out power problems.

Step 3: Getting Done the Tranducers

The first thing you get in mind when you receive the bone conduction transducers is that the wires are fragile. So I wrap the wires around the body of the transducer and used some hot glue for secure it.
Then I used a cross shape piece of foam to cover the transducer and protect it. Then I used some aluminum tape to keep in place the foami. Then I put a piece on double side tape in the other side of the transducer and braid the wires. Now you can solder the transducer to the amplifier board. Repeat this process two times, you will need to of this.

Step 4: Placing the Modules in the Headband

Now is time for remove the backing of the double side tape and start placing the boards. I make A little slot in the headband for the tranductor wires.
Place all the boards, but consider to save space between the boards for the soldering job. You need to be patient, this take a bit of time and effort. When you are sure of the placing stick it using double side tape. Don't glue the solar panel in this step, just save the space for later. This way you can pass the wires under the solar panel.

Step 5: Make the Connections

Ok. This part is probably the most challenging, you need to solder all the wires in place. Follow the schematic of the picture and use flat wire to get this done. Be careful!