bc05b bluetooth module

Last update: Sat Jan 10 23:04:53 2026

Presentation

Principle

Well, I bought that small BC05B module on eBay some times ago, in those moments of "hmmm I might need that one day". And guess what: I need it now (^_^).

Points of interrest

Soldering those tight ass microscoping 0.7mm connectors on the side of the module and taking the decision of never ever again use that kind of modules :) No seriously, it works, it's doable with a bit of time and patience, but it's really not fun.

It worked for a morning, quite well even on my Kenwood CLX-70. I used the jack in and also the red/white composite ones at the back, no problem. Then I tried to stuff it inside, steal some power from the stereo (using a LM317 to feed it with 3.7v) and there catastrophe! Sound went from great to awful, to nothing. Now it's out of the beast, and I just can't get any sound from it. Like zero, just static. The Vol+ also does not seem to work, only Vol- and I fear that my stupid module is stuck at Vol=0 (mute) ... bummer!

EDIT: it's fixed!! There was an invisible short between VOL+ and BACK pins, and that rendered the VOL+ button inefficient and added a big bunch of noise to the board. Now I have it run next to me for one hours to confirm it's all good in term of power regulation. And since I'm a lazy b*stard, instead of shortening and resoldering the ugly air wires I just placed them nicely and drowned the sh*t of that module in hot snort (^_^)v hehehe.

Schematics

Recommended setup (taken from elecfreaks.com site)

Bill of materials

Implementation

Source code

Pictures

The infamous module. Pitch between those pins is very small, it's 0.7mm ! Don't shake while soldering.

Top view: ugliest air wire soldering, a few buttons (blue=power VREG, red=VOL+, yellow=VOL-)

Side view: where that S.o.B. of BACK and VOL+ were shorted. Fixed on this shot before I litterally drowned it under hot glue.

Thought I was joking about being lazy and the mountain of hot snort?

Links

Helpful sources

All one needs to know http://www.elecfreaks.com/wiki/index.php?title=Audio_Bluetooth_Speaker_Module

Inspiration

A project that implemented it

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