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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.

Sunday, October 13, 2013

TI LaunchPad RDA5807P (TEA5767) FM Radio inside a pc speaker

This is about my old project when I firstly received TI LaunchPad kits.

An encoder used for tuning to frequency. I'm using an encoder with push button which used as search function to auto tune in fm station. Couple of caps used for debounce..

I used old pc speakers, which already has amplifier inside and a transformet to power this fm radio. Just added 3.3v linear regulator in dead bug style.

I had RDA5807P fm radio module from china. RDA5807P is a clone of TEA5767 including i2c commands and functions etc. Read the datasheets for rda5807p and tea5767. Any similiar module will do.

I then wrote a driver for rda5807p and application code to control frequency with encoder etc. As for PLL tunning I had to precalculate a table for fm radio spectrum because my msp430 chips only had 2kb of flash.
Cram it all inside the speaker housing.

And the whole look.
Antenna wire goes out from speaker's "phase inverter" hole.

RDA5807P driver and application is open source and available at: TI LaunchPad FM Radio repository.

Wednesday, July 24, 2013

Gameboy Color Quality Sound Mod update

Update: new version available for order

Here we go again about sound in the Gameboy Color handheld.

I've made new pcb with new smaller amp ic. So this is a new leaf style cut pcb and it will fit just over speaker in the speaker cutout. Virtually takes no space.
I've already tested it, sounds great. Set to 12db gain.

Here how it looks when wired up. Needs only 3 wires to install (+2 for speaker).

I can make it into a kit now.

Monday, January 21, 2013

Chinese electronics recycle fun or what's inside gsm to landline phone terminal

Here we go. I have a simple gsm terminal for landline phones, so I can call from regular analog phones through gsm network. I'm using it in low signal area with external antenna.
So one day I decided to look what's inside of it. I was thinking there would be some kind of gsm modem inside and analog support electronics etc. But found some interesting stuff.
Here how this thing looks, nothing important just grey box with gold antenna output sma socket.

Now let's take a look inside:

Yes, it is a gsm cell phone pcb inside! With phone battery for backup power. This thing is powered by nuvoTon W78E052DDG mcu. Which has 80C51(52) core. Never heared of them yet, but they make Cortex-M0 mcu and other ARMs too. I guess it is connected to the phones serial port.

Wires soldered directly to pcb connector.

Looks like Nokia or SE connector to me.

Wires soldered directly to phone external connector.
Phone pcb screwed to terminal housing posts, so this housing is made for this particular phone pcb on purporse. It means some kind of cellphones recycling =) Chips on phone pcb has date codes leading to 1999.

Wires soldered to the phones sim socket leads to a new sim socket on bottom side of terminal main pcb.

Some unknown chip under pcb.

Here must be some know-how, otherwise I don't know why they sand those chips markings.

LCD board glued in place =) This LCD board is connected through serial data line, may easily be reused. There is a black blob lcd controller on pcb.

LCD itself actually has a good contrast.

I had used a cell phone as wireless terminal to send sms alerts. But I never though this would be used in actual manufacturing =)

Update: as requested I pictured main pcb bottom side: