Build Your Own True Wireless Stereo Adaptors for Under $10!

Hello fellow makers,

For a while now I've been looking for some bluetooth adapters that I could use for multi-room/wireless stereo throughout my home, unfortunately systems like the Sonos are very expensive plus I want to use the speakers I already have and love, next you can use something like an Amazon Alexa device for this but I also didn't want one at every speakers (and they're not officially supported in my country).

So I went on a search for an alternative, there are a lot of small portable speakers out there that are now TWS (true wireless stereo) but I didn't just want to rip some of these apart as you'll be stuck with their low power amplifier.

Then the market started being flooded with earpod knock-offs commonly called I12 earpods, these looked like good contenders.

I bought a lot of 10x "broken" pairs off a local auction site for only $0.50 a pair and started experimenting.

These tend to stop working because of the charging case design this causes the buds not charge anymore and leads to a load of these being thrown away...good for us tinkerers though!!

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Step 1: What You Will Need:

To make your own you will need the following:

I12 or similar earpods

Amazon - I12 TWS Wireless Earbuds

Access to a 3D printer

Amazon - Creality Resin 3D Printer Halot-Mage 8K

3.5mm AUX jack

Amazon - 3.5 mm Audio Jack Connector PCB Mount

Soldering iron and solder

Amazon - 60W Digital Display Soldering Iron Station Kit

Some thin wire

Amazon - Striveday™ 28 AWG 1007 Tinned Copper Wire Electric Wire kit

Optional:

A larger LiPo battery for the adaptors

I used some of the 300mah batteries from the extra charging cases for mine.

Amazon - Lithium Polymer Battery 3.7V 250mAh 502030

An old USB cable if you don't want to use the one included with the earpods

Step 2: The Donor Buds:

The first thing we will need to do is disassemble our donor earbuds.

Thankfully for us longevity wasn't a main concern when they made these as the enclosures simply clip together. Starting at the speaker end you can pop the speaker off by simply pulling it apart, don't worry if the leads of the speaker break off.

Clip the battery off one wire at a time, cutting them at the same time will case a short.

Next using a hobby knife pry off the chrome piece at the charging end, this will give you access to the main PCB that can be grabbed with some tweezers and simply pulled out.

On the PCB you'll find a microphone for calls next to the main bluetooth circuit that also handles the Lithium battery charging at 30ma.

The two brass rods at the one end is the charging pads and the chrome pad on the opposite end is the capacitive touch pad.

There are four solder pads for battery positive/negative and speaker positive/negative.

Now onto the charging case.

The charging case is held together with two clips on the side, as we won't use the case again I usually just break the two edges and slide the electronics out as it is nearly impossible to get it out without damaging the case.

Remember to salvage all of the silver neodymium magnets from inside the buds and charging case.

Step 3: Design and Print:

Now we will need to design an enclosure and charging dock for our new wireless audio adaptors.

As always I hopped onto Fusion 360 to design the enclosure, the idea behind the design is to fit the larger LiPo battery along with the AUX jack in as small as possible enclosure whist only being able to fit one way into the charging dock.

I think the final design turned out rather elegant, I ended up printing all of the parts on my SLA printer to get dimensionally accurate parts and for all the small details.

Refining the prints:

To give the adaptors a more "off the shelf" look I decided to spray them using some charcoal metallic paint and the charging dock was sprayed in antique gold which fits into the color scheme of my speakers.

Being a resin print there is no real prep work necessary before painting, I simply sanded the printed parts with some 400 grit wetted sandpaper to get rid of any nibs left over from the supports.

TWS Aux

Step 4: The Electronics:

Time to assemble the electronics.

Although the soldering tabs on the PCB is small this was actually quite easy to get all soldered together.

There are four connections on each board to be made, the red wire from the battery goes to the B+ tab, the black/blue wire from the battery goes to the B- tab.

Next we need to solder on some thin wires onto the L+ and L- tabs, these wire now go to the 3.5mm AUX jack. The L+ wire needs to be soldered onto both the left and right pins on the AUX jack and the L- wire gets soldered onto the GND pin on the jack.

Step 5: Assembly:

Onto the last step, assembling the adaptors.

To ensure a good connection when in the charging dock I decided to add back the magnets that were originally in the earbuds. I simply used some 2-part CA glue(superglue) to adhere the magnets into the adaptor, just double check that the polarity of both adaptors are the same.

Each component has it's own dedicated slot and can be secured with a drop of CA glue after placement.

We will need to extend the reach of the capacitive touch button in order to control the devices, the easiest solution I found for this is to have a small piece of copper wire that simply presses against the capacitive tab and then extends to the outside of the enclosure.

I cut off a 2mm piece of copper household grounding wire that was then pressed into the hole in the enclosure above the capacitive tab and filed flush with the enclosure (wait a minute or so before testing the new touch button as I found they take a few seconds to calibrate and work correctly).

You can now adhere the AUX jack into place and test the adaptor to make sure it connects and plays correctly as well as pairing with the second adaptor.

Once confirmed working you can snap the two pieces together and your adaptors are done.

The charging dock:

With the adaptors done we need a charging dock.

We will be reusing the spring connectors from the original charging board for the new dock, so I desoldered them from the old PCB and pushed them into the dedicated holes. With resin prints I always heat up the part with a heatgun set to about 120degC or a hairdryer before inserting pins as this prevents fractures and give a great friction fit.

We will need to connect the pins opposite each other together, for this I used a sturdy copper wire as it gives the spring pins some extra support and makes soldering the charger easier. Simply solder both pins together as pictured below.

For the power source I will be reusing the charging cable supplied with the I12 earpods that I snipped off the lightning connector and stripped away the insulation to reveal the two wires.

The positive red wire from the USB gets soldered onto the pins that are furthest away from each other (next to the magnets) and the negative blue/black/white wire gets soldered to the pins that are closest to each other (on the edge).

Finally we just need to adhere two more magnets into the round slots, place the adaptors into the dock to make sure the magnet orientation is correct before adhering them into place.

When finished I like to just pot the entire cavity of the dock with some hotmelt glue, this protect the charging cable connections and also adds some weight.