I bought this Stereo Bluetooth Receiver from DealExtreme.Com. It's a nice receiver, but it has a few flaws. First, the battery life is mediocre, and when it is about to die, it interrupts your audio with these really annoying beeps. Second, the darn thing charges through the headphone jack. This means that you can't charge it and use it at the same time.
With this in mind, I sought out in search of a solution. I found a great thread in the DX forums. One of the suggestions was to get a headphone splitter and simultaneously charge and use it. Sadly, the thing has some sort of switch that automatically turns off the audio when it is charging. The other idea was to connect an external power supply to the internal battery. I thought that this was interesting, but I don't like the idea of continuously sending power through the battery. Maybe this is fine, but I just didn't like it.
Finally, and this fit what I had been thinking, someone suggested that you remove the internal battery and simply hook up a power supply. One poster used a multimeter to check the battery's voltage and clocked it at 3.7 V.
Thus, the plan would be to get an adjustable power supply, adjust it to 3.7 V (or whatever the battery's voltage is), remove the battery, and hook up the power supply.
Instrucables.Com had some interesting plans to build your own Adjustable Power Supply, but I ended up taking the easy route and building one that LadyAda.Net offered for sale (as a kit).
Let's begin. Here is a shot inside of the Bluetooth receiver.
And a better look at how the battery is attached to the circuit board. I did my own reading of the voltage at this point and measured the battery at 4.1 volts. I was slightly confused at why my reading would be different, but I wasn't concerned. I trusted my reading and figured that I would use that as a start.
Here is the my adjustable power supply kit.
I am consistently impressed with LadyAda.Net, and that didn't let me down this time. The kits and the instructions that come with them are excellent. I really liked the multiple steps that were included in this kit's instructions that let you test the board to make sure that it was working correctly.
I now have a working adjustable power supply. As such, I can take a 9v power adapter and tone it down to 1.25 volts. Even if this project doesn't work, this is definitely going to come in handy.
The next step was to remove the battery from the Bluetooth receiver and solder in some new wires.
Here is a picture of the whole ensemble. The power supply is plugged in to the receiver and I have my headphones plugged in.
Did it work? Well, the blog title probably clues you in to the answer. At first, it did work. The first thing that I did was to adjust the power supply to 4.1 volts. I tried turning it on, and it didn't work. Next, I tried using a lower voltage (3.3v, one of the set voltages that comes with the board.) This worked, but I was constantly getting the beep that accompanies the lower battery signal from the receiver. Finally, I tried using 5 volts. AND IT WORKED!!! I was pretty excited at this point. I had to leave for the day, so I packed things up for the moment.
Later, I tried to show my friend Jef my DIY prowess. And....it didn't work....at first. And then it did. But it was running really hot. I didn't like this, so I turned things off and again had to leave to do some other things.
The next morning, I set aside some time to fiddle with this and tried to figure out what was wrong. It wouldn't consistently turn on, unless I turned the voltage up higher than the 4.1 v that I clocked the battery at. I didn't like doing this, but it didn't seem to turn on otherwise. Then it would work, but it still ran hot. Both the power supply and the receiver were getting toasty.
Then something happened. I don't know what, but the receiver just stopped working. It would turn on, but all I heard from it was fizz and crackling. And that was that.
I would love to try this again, but I'm afraid to drop another $20 on a receiver without having any idea what I did incorrectly. If anyone has any suggestions, please feel free to let me know!
Anyhow, with the Bluetooth project done, I decided to finish my "Breadboard" power supply and hook it up into my breadboard. Here is the finished result. A very nice Breadboard adjustable power supply.
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