Bluetooth Audio Glasses

This project was inspired by bose's audio sunglasses, (link) which usually cost around 200USD, and meant as a gift to a close friend of mine. I wanted to experiment and see if I could replicate a model at a cheaper cost.

There were no previous Instructables or tutorials I could really find on audio glasses so this project was quite challenging to navigate. But in the end, the design turned out quite nice, the circuit was relatively simple, and it works very well.

As for the actual project, to summarise it briefly, it is a pair of glasses with a hollowed-out frame in which the circuitry for Bluetooth earphones fit into. Therefore you can listen to music wirelessly while wearing the glasses.

Rough cost of the project: 10-12 USD

Time taken: 3-4 days

Complexity: 3/5

Supplies

There are a lot of parts required for this project however they are relatively accessible.

1) 1 x Male to Male Jumper Cable 40pcs. (link)

2) 1 x Old/unused earphones lying around the house. Aeroplane earphones will also work.

3) 2 x 150-ohm resistors (link)

4) 1 x 3.3k ohm resistor (link)

5) 1 x PAM8403 Audio amplifier board (link)

6) 1 x Bluetooth audio module. I used this (link), however afterwards I found out that this is a cheaper and newer alternative (link).

7) 1 x TP4056 charging module with protection. The model you buy should have over-discharge protection (link)

8) 1 x 300mAh small Li-po battery. I used this (link), but a thinner battery like this would be better (link)

9) 1 x Small Slider switch. I got mine from an old RC car. The width of the switch has to be 6mm or less

10) 10cm x 1.5mmHeat shrink tube (link)

11) 1 x Male berg strip 40pcs (link)

Tools and Equipment:

1) Soldering Iron + Soldering wire

2) Desoldering pump

3) Pliers

4) Wire cutters + Wire Strippers

5) 3D printer or access to a 3D printing service provider

Step 1: Supplies Photos

Step 2: Understanding the Circuit

There are only main parts to this circuit: Audio amplifier circuit, Bluetooth module, and charging module.

1) Charging module:

The TP4056 acts as the charging module, and it is connected to the rechargeable battery through B+ and B-. The output pins on the charging module (OUT+ and OUT-) are connected to the Vcc and ground pins of the Bluetooth and audio amplifier module. This is how the circuit is powered.

Since the glasses are cordless, they will have to have a rechargeable battery in them, and hence, an appropriate circuit to charge and discharge the battery safely is also required, which is what the TP4056 does.

The board then changes the current and voltage to optimize charging up the battery. There is also a protection feature in the TP4056 board that prevents the rechargeable battery's voltage from becoming too high or too low.

Here is a good video explanation: link.

2) Bluetooth Audio module:

The Bluetooth module allows your device (phone/laptop/tablet) to connect wirelessly to the glasses through Bluetooth.

It has a Vcc and ground pin for power and 3 output pins corresponding to the left earphone, right earphone, and ground. These three pins are connected to the audio amplifier for the signal to be amplified and usable for earphones.

Once the Bluetooth audio module is powered up, it should appear on your phone's Bluetooth scanner as 3.0 BT or VIRE BT.

3) Audio amplifier:

The PAM8403 board is perhaps the cheapest and most effective audio amplifier board out there. It has three input pins that are connected to the Bluetoothmodule's three output pins. It also has 4 output pins, two for each speaker/earphone corresponding to the left and right side.

The output from the Bluetooth module is at a relatively high impedance while the speakers have a relatively low impedance. Therefore you were to connect the Bluetooth module directly to the earphones, without an audio amplifier, it would spoil the Bluetooth module's internal circuitry.

The earphones will try and draw way too much current from the Bluetooth module and there won't be enough voltage to power the speaker. That is why we need an audio amplifier. To provide the right intensity of current to the speaker.

The audio amplifier also has Vcc and GND pins to connect to a power source. It draws current from this to power the Speakers. Good website for explanation: https://www.headphonezone.in/blogs/audiophile-gui...

Step 3: Circuit Schematic

Notes:

1) Switch is used to turn on and off the power supply to the main circuit. This is to save power when the glasses aren't being used.

2) PAM8403 board has two earphones connected to them. Left and right side. Each earphone has a positive and negative terminal.

3) The PAM8403 board and the Bluetooth audio module are connected in parallel to the TP4056 output. This is to ensure both boards receive sufficient voltage.

Step 4: Soldering Battery to TP4056

1) Red (positive) wire to B+

2) Black (negative) wire to B-

Step 5: Adjusting TP4056 Charging Rate

A store-bought TP4056 board will charge your battery with a current of 1A. However, this amount of current is too much for the small 300mAh battery. Therefore the charging current has to be decreased.

If the charging current is not decreased it can lead to the Li-po battery heating excessively or even exploding. Therefore this step is very important.

The charging current can be decreased by changing the value of R3 on the board. This resistor is also called Rprog in datasheets. The resistance is normally 1.22k, however, this has to be increased to 3k or 4k by changing the R3 resistor.

Steps:

1) Using a soldering iron I desoldered and removed the 1.22k SMD resistor.

2) With helping hands and pliers I soldered on the 3.3K resistor, which had its legs shortened.

Step 6: Soldering Audio Pins on Bluetooth Module and Audio Amplifier Board

1) Cut up 3 pieces of the male berg strip, and remove the plastic bit.

2) Align the three output pins of the Bluetooth module over the three input pins of the audio amplifier and push the metal pins into each hole.

3) Solder the onto the pad for both the boards. Make sure you have pushed them together as close as possible. The holes don't align perfectly, so you will have to apply pressure with pliers.

4) After soldering, snip off any metal pins that are excess and protruding out significantly.

Step 7: Soldering Vcc and Ground Pins on Bluetooth and Audio Amplifier Board

1) Using pliers bend one metal pin from the male berg strip to form roughly a 90-degree angle.

2) Cut out a short piece of wire (~2cm) and strip its end to expose the copper.

3) Use the wire to solder the Vcc/Vin pins of the two boards together. Use the bent metal pin to solder the GND pins of the two boards together. Remember that this forms a parallel circuit.

Step 8: Preparing Wires to Deliver Power From TP4056 to Bluetooth and Audio Boards

The TP4056 and battery will be close to the right ear, and the Bluetooth and audio boards will be close to the left ear. Therefore two long wires have to be made so that they can deliver power (Vcc and GND) from one end of the frame to the other.

1) Cut one of the jumper cables in half and form two sets of wires. Each set has 2 full wires and one, half, cut wire. Each wire should be roughly 18cm.

2) Strip the ends of all the wires to expose the copper

3) Solder the ends of the wires together in each set. This should give you 2 wires, which are each roughly 45cm long. (18+ 18 + 9)

4) Cut up some heat shrink into lengths of 5mm-8mm and coverup the solder joints at each wire.

Step 9: Connecting Wires to TP4056 Output Pins

If you recall the circuit schematic, there is also a switch involved to turn on and off the circuit.

1) Solder a short lead (8-10cm) to the middle pin of the slider switch

2) Solder the long wire prepared in the previous step to any of the remaining pins on the switch.

3) Solder the other long wire prepared in the previous step to the OUT+ pin of the TP4056.

4) Solder the short lead to the OUT- pin of the TP4056.

Step 10: Connecting Wires to the Power Pins of the Bluetooth and Audio Boards

1) From the previous step the wire connected to OUT+ is positive, and the wire connected to the switch or OUT- indirectly is negative.

2) Using this connect the positive wire to the Vcc pin of the audio amplifier module.

3) Solder the negative wire to the GNDpin of the audio amplifier module.

Note: Steps 2 and 3 are easiest done when soldering to the bottom side of the audio amplifier module. (check images)

Step 11: Soldering Resistors to Audio Amplifier Output Pins

The audio amplifier is designed for large speakers. The board delivers 3W for each speaker/earphone side. This is too much for the much smaller earphones.

The problem can be rectified by soldering a resistor in series with the earphones to reduce the power being delivered to the earphone. The resistance value I found to be optimal is anywhere between 100-150 Ohms.

Since I only had 150ohm resistors available, I used them for this project.

Steps:

1) Bend and shorten the legs of the two resistors as shown in the image.

2) Solder one leg of the resistor to the positive (+) terminal of the output. Leave the other one free for now.

3) Repeat for the other side earphones.

Step 12: Preparing the Earphones

1) Cut the cables of the individual earphones as seen in the photo. One side can be short (~10cm) the other side has to be quite long (~45cm) as it has to travel from one end of the glasses to the other.

2) Using some wire cutters cut off the plastic shell around the earphone speaker. Be slow and careful as you may accidentally cut the speaker or the very thin and delicate copper wires.

3) Strip the ends of the wires to reveal two single-strand copper cables. The coloured cable (red/blue) is positive. The uncoloured cable (copper) is negative.

Step 13: Soldering Earphones to the Audio Amplifier

1) Solder negative wire (copper coloured) to the negative terminal of the audio amplifier output.

2) Solder positive wires (red/blue coloured) to the other leg of the 150 Ohm resistor

3) Repeat for the other side.

Note: Make sure the terminal do not touch each other as this could lead to shorts. You could bend the resistors back to the board's backside.

The circuit is complete!!!

Step 14: Designing the Glasses on Onshape

I used Onshape to design the knives. It is free I believe. Here is the link: https://www.onshape.com/en/

The glasses consist of three parts.

1. The main frame

2. Two long pieces that cover the hollow section of the frame from the top.

The dimensions of the glasses are 50mm*165mm*185mm

They are quite big so they would only fit on an adult.

Step 15: 3D Printing the Design Pieces

1) Ultimaker Cura was used as the slicer. Ender 3 was the 3D printer used for this project.

2) The .stl files for all three pieces have been attached to this step. Here is the link to the file on Onshape: link

3) The main frame took roughly 6 hours while the covers took 1.5 hours to print. The total print time was about 7.5 hours.

Note: If you don't have a 3D printer, or if your 3D printer is too small to print such a large object, then you can try reaching out to 3D printing services in your community or a Design technology lab at school if you are a student.

Step 16: Printing and Finishing the 3D Printing Pieces

1) Printing temperature was 210°C for the nozzle and 60°C for the bed

2) I added a brim to improve adhesion.

3) Using pliers and some box cutters, I cutoff the supports, brims, and smoothened the edges.

Step 17: Inserting Circuitry Into the Glasses' Frame (1)

1) Insert the TP4056 board and the Li-po battery back-to-back into the right end of the frame. This is quite a challenging fit so it will take some force.

Make sure to not puncture the battery. Also, ensure that the solder on the bottom side of the TP4056 is not sharp as to not poke the battery.

2) Place the earphone with the longer connecting wire on the right-side grill.

3) Place switch next to the earphone. If it is 6mm wide (which mine was) it should be a snug fit. The wire to the adjacent earphone speaker should passunder the switch. Therefore there are 3 wires coming out of the right side of the earphone: Vcc, GND, and Right earphone.

Step 18: Inserting Circuitry Into the Glasses' Frame (2)

1) Wrap the wires tight and secure using some tape. Make sure to not wrap the wire for the second earphone speaker.

2) Insert the bluetooth+audio amplifier piece into the thick end of the other side.

3) Place the other earphone speaker under the thick wrapped connecting wires at the position of the left-side grill.

Step 19: Hot Glueing All Circuitry

1) Switch and right-side earphone speaker

2) TP4056 board. You will have to be careful to not bring the hot glue gun close to the battery

3) Left side earphone speaker

4) Audio amplifier board

Step 20: Hot Glueing on the Cover

1) Left side is very straightforward. You can place the cover over and apply how much hot glue you need.

2) For the right side you have to cut the cover into two parts to accommodate for the protruding switch. Then you can hot glue the cover on.

3) For additional security and a bit of colour I used some electricaltape to tape the middle of the glasses as well as the ends of the glasses near the ears.

4) Finally using the wire cutters I trimmed off any excess hot glue or uneven surfaces.

Step 21: Testing and Photos

Notes:

When you turn on the switch the speakers will say power on.

When your phone connects or disconnects with the Bluetooth audio module the speakers will say connected or disconnected, respectively.

It takes about 20-25 minutes to charge the battery fully. It can then run the speaker for 2.5-3 hours. The battery can be charged through the TP4056's MicroUSB port.

There is a slight design flaw in the model. The speaker grills actually sit slightly above the ear and in a loud-crowded place the sound doesn't come through easily. However, if you bring the speaker grills slightly down so that they are resting on the top of your ears, the sound is significantly louder and clearer.

When the LED on the TP4056 is red, that means the battery is charging. When the LED turns blue then the battery has been chargedcompletely.