Friday, November 22, 2013

Let's make a Wireless Speaker

Found some unused parts laying in the box, let's make something.
How about battery powered wireless speaker, portable speaker for your phone or player. What wireless technology I going to use? Bluetooth ofcourse.

Let's take cheap speakers like this for example Pyle PLMR24. I bought these to use outside, but...
look inside:

"Completely Water Proof" with a big hole in the front. I thought it should be sealed. Do you see advertised "Capacitor Crossover Network"? I don't. Just wires. Those "1.75" Wide Dispersion Cone Midrange" and "1" Super Dome Tweeter" made of 2 identical piezoelectric transducers, have a spare.
I'm going to listen mostly talk podcasts on this wireless speaker, so, doesn't matter much.

As a bluetooth A2DP receiver I'm going to use KRC 86A/B V3.2 but any other A2DP bluetooth modue will do. KRC has CSR BlueCore5 bluetooth chip and making a bit of hiss noise when connecting.

Next I need a sound amplifier. I took TPA2005D1 ic known from my GBAmp project. It's only 1.4W power but for my purporse it is enough. And it is class-d very efficient amplifier, good for batteries. I'm going to use 18650 li-on single cell battery.

I measured width of the bluetooth module pcb and designed amplifier pcb to be glued on top of module pcb. Then I made a couple of amplifier pcbs at home with most working method, one for backup.
There are many capacitors with small capacity, I have not any bigger capacity caps in stock.

Then glue it with double sticky tape on top of bluetooth module. And connect wires.
As you can see the final amplifier version configured to 18dB gain.

Add a battery holder, tape and glue it all to the speaker back.
You can see blue led glowing, means it is conneceted. I'm thining to put it all insude and add charger pcb and a swith, that will look much better. But for now, it works s is. Battery will last for several days I guess. I already used it for 10 or so hours.

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