Soldering to castellated half through-holes (Bluetooth Audio Modules)

[BobW]

Before I go ahead and make a mess of this, I thought I'd better ask for advice. I bought a bunch of these tiny Bluetooth audio modules, and am wondering what is the best way to connect to it. The connection spacing is 0.05" centre to centre—half of the usual DIP pin spacing. Any suggestions, short of making a PCB?

Edit: Nevermind. I decided to make a printed circuit breakout board. It's probably the fastest way to get the connections done.

 

[BobW]

Done!

 

[gophert]

Any suggestions, short of making a PCB?

Done!

hey, you cheated.

 

[Nigel Goodwin]

hey, you cheated.

It depends if his outside holes are 0.1" spaced

But nice job 'BobW'.

 

[BobW]

hey, you cheated

Well, I'm still interested in other ideas.

It depends if his outside holes are 0.1" spaced

When I designed the layout, I thought the spacing of the castellated through-holes was 0.05", but when I printed it out, the Bluetooth module didn't quite line up. Checking the datasheet, I realized that the spacing was 1.3mm rather than 1.27mm, so I just scaled up by a factor of 1.3/1.27, but that also scaled up the spacing of the outside holes. So, they're not exactly 0.1" spacing anymore. Still, they're close enough that if I solder on reasonably long pins, they'll still fit in a protoboard.

This one is just for debugging anyway. I have four more of these BT audio modules. Once I get the first one working, I'll design new boards with the additional necessary components on them.

 

[gophert]

Which bluetooth module is that? And do you know how long the battery lasts in idle mode?

 

[BobW]

Module type number is XS-3868 (Version 3.0), and it uses an OVC3860 Bluetooth chip. Quite a bit of info is available on the Internet.
I haven't found any info on battery life, but then I wasn't really looking. I intend to power these from a USB power supply or other non-battery source. So, battery life isn't an issue for me.

I'm just in the process of soldering some leads onto the breakout board so that I can give it its first smoke test. I'll report back later.

 

[unclejed613]

in consumer audio devices, these BT modules are soldered directly to a PCB much like what you have done... just don't try unsoldering it though the castellated connections make it difficult to get all the solder out.

 

[BobW]

I connected some headphones and fired it up. No smoke so far. It made a bloopity-bloop chime in the phones. So, it appeared to be working, but it took forever for it to show up on the list of devices on my phone and computer. Eventually though, I got it connected, and had audio coming out of the phones.

Every 10-15 seconds it would make another little chime sound. What the heck? Then it occurred to me that it was giving me a low battery signal. Checking the supply voltage it was at the bottom end of the allowable range. I'd just stuck a couple of 1N4007 diodes in series with the 5V USB adapter to drop the supply voltage down. A single diode gave a supply voltage of 4.2 V, which is at the top of the allowable supply range, and I thought that would be borderline. So I'd added the second diode, but obviously that made it too low. I changed to a single UF4007 which gave about 4.0V. That made the low battery chime disappear, and it now shows up quickly on the computer and phone, and connects quickly. So, it definitely doesn't like to operate at the low end of the power supply range.

Audio quality seems pretty good. And, I'm happy that I didn't need to do any configuration of the chip. Basically, it worked right out of the box.

 

[BobW]

Update:
After getting the Bluetooth module working with the breakout board, I made another board with the power supply components and LEDs on it, and installed it in a small 2½" x 2½" box.

As somewhat of an afterthought, I added volume up and down buttons (on separate perfboard). I didn't think I'd need them until something weird happened, and the volume set itself to minimum. I couldn't reset it back to normal without the volume buttons.

I'll be using these modules to add Bluetooth capabilities to a couple of older hifi audio amplifiers that I have.

 

[gophert]

Excellent!