Introduction: Journey From a Normal Wired Earphone to a Wireless Bluetooth Earphone

Picture of Journey From a Normal Wired Earphone to a Wireless Bluetooth Earphone

Music is a great thing and it really help me in changing my mood. But since I don't want others to peep into my tracks nor I want to disturb my family members with my music, I mostly use those wired apple EarPods for listening music. Though EarPods are loud and sturdy, and provide a quality sound, the biggest problem with them is their cable. That hanging cable is really annoying, when I am trying to focus while listening to my favorite tracks. It gets tangled so easily when I am not using the earphones. Also, while watching movies or youtube videos, I can not go away more than 2 meters from my phone because of that silly cable. Since both of my phones do not have a headphone jack, I have to use a convertor each and every time, to plugin my EarPods to my phone. Buying those new AirPods can solve this problem but I don't want to invest in those $160 earphones. A bluetooth headphone will also do the job but as you know, after using headphones for quiet some time, your ears start paining. Finding out the solution of my problem, I came across this idea of building wireless earphones. Since I had a pair of old earphone lying around, I utilized them in making this DIY bluetooth earphone.

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These earphones are a cheap alternative for those wireless headphones and are able to provide a really loud and quality sound, for a very less price. Since these are DIY earphones, you can chose the specifications and the capacity of the battery, as well as the type of earphones used according to your need. You only need some basic parts and soldering skills to modify your current earphones into a bluetooth earphone.

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Talking about the project, it includes an old cellphone battery which power a bluetooth dongle present inside that red and chrome colored box. The bluetooth dongle used in this project is generally used in those car radio systems, which do not have a bluetooth functionality. In cars, the dongle is firstly connected to the lighter port and is then connected to the car radio system through AUX.

We are going to use this dongle in a similar way, but it will be modified by us in the later part of this project, to fit our requirements. A small switch is also connected to the dongle, to turn it on/off and an LED, to show whether the bluetooth module is working or not. The charging of the battery is done by a normal mobile phone charger. For the enclosure, I have used acrylic sheet, which is further coated with a chrome color.

The range of the bluetooth module is about 8 to 10 meters and the battery life is about 5 hours. Volume of these earphones can be controlled by your phone's volume rockers. Also, there is a clip attached at the back of the earphones which helps you in hanging it, at the back of your shirt.

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For any query and question regarding the project, comment down below. Please vote for me in the contests I have entered in. Your vote is valuable for me.

Step 1: Watch the Video

Before making the project, I advice you to watch the step by step instruction video of this project. This will help you in understanding the things and you would be able to easily tackle the problem you encounter while making the project. Here is the link.

Step 2: Gather Parts

Picture of Gather Parts

These are the parts that you require to build this project. You can buy them from a electronic store or from any online retailer. Description of all parts is given in later part of this project.

PARTS:

  • Bluetooth audio dongle
  • Normal earphones
  • Mobile phone battery(Li-ion)
  • 1N4007 diode
  • Female USB charging port
  • On/Off switch ( slide switch would be better)
  • Green LED
  • Acrylic sheet

TOOLS AND OTHER ITEMS:

  • Soldering iron along with some solder wire
  • Super glue
  • File
  • Saw
  • Hot glue
  • Spray paint
  • Drill machine
  • Wire cutter and stripper

Step 3: Hacking the Bluetooth Module

Picture of Hacking the Bluetooth Module

In this project, we are going to use bluetooth for the transmission of audio signals from our smartphone to our earphones. Since our smartphone has prebuilt bluetooth modules, we only need to equip our receiver unit or the earphones with bluetooth. For this I am going to use a bluetooth dongle which only cost a couple of bucks and can be easily bought online. It is a special type of bluetooth dongle, used to transmit only audio or sound single from a mobile or laptop to an auxiliary port and is generally used in cars and home theater systems which lack bluetooth functionality. You can very easily buy these bluetooth dongle from a car accessory shop.

Since the whole dongle assembly is quiet bulky, we are going to tear it down and keep only necessary parts. Start by opening the case of the dongle and taking out its circuit. To do so, simply take a flat tip screwdriver and pierce it inside the separation line going along the side of the dongle. Once the body is cracked open, you will find a circuit inside it, similar to mine. Take it out and throw away the rest of the body.

Step 4: The Battery

Picture of The Battery

To make this device portable, I am going to use a Li-ion battery as the power source. I salvaged this battery from an old Nokia phone. Till date, the battery works perfectly fine. These types of batteries have an inbuilt charging protection circuit, so you do not need any special charger for them. Connect a 5v mobile charger to the battery with a diode in between and the battery would start charging.

To make a charging circuit for the battery, simply take a 1N4007 diode and connect its negative to the positive of the battery. Connect the positive of the diode to the positive of the female charging port and the negative of the female charging port to the negative of the battery and your charging circuit is complete.

Regarding the use of diode, the diode is connected between the charing port and battery to prevent the back flow of current from battery to the charger and also to drop the voltage of charger from 5V to 4.3V because these mobile phone batteries are generally charged at 4.3v and the 1N4007 diode has a tendency to absorb 0.7V of current, when connected in series in a circuit. Talking about my female charging port, I did not use a micro USB port because the retailer from whom I purchase my part did not have one in stock. I rather had this old female charging port used in previous generation of Nokia phone, lying around my workplace for a while so I used this for my project. Both of them work the same, the only difference is the shape of the connector.

Step 5: Modifying the Bluetooth Dongle

Picture of Modifying the Bluetooth Dongle

After making the power supply circuit, we are going to attach the bluetooth dongle to it. But before that we have to make some adjustment to it. Firstly we have to remove that male USB socket because it takes up a lot of space and we don not have any use of it in our project. Also desolder that female audio jack from the circuit board because we are going to connect our earphones directly to the circuit. After you have done the above adjustments, your bluetooth dongle circuit would look something like mine.

Step 6: Connecting Bluetooth Module to Battery

Picture of Connecting Bluetooth Module to Battery

The power pin or the pin from where your bluetooth module will get the power is located at the place where the male USB port was previously soldered. And the audio output pins are present at the place where the female Audio jack was soldered. Look one the above images to understand the thing.

Now take the slide switch or the on/off switch and connect its 1st pin to the pin 1 or vcc of the bluetooth dongle and the 2nd pin to the positive of the battery. Connect the ground of the battery to the pin 4 or the ground of the bluetooth module.

Step 7: Replacing the LED Indicator

Picture of Replacing the LED Indicator

Now flip your bluetooth module and at the bottom, you will find a SMD LED. Use a multimeter and find out the polarity of the LED. Once you have found out, using a permanent marker, mark it on the circuit board so that you don't forget it later. Now warm up the solder joint of LED and pluck it out with the help of a tweezer. Take a full size green LED, and solder wire on its leads. Now with the help of those wires, solder that green LED to the bluetooth module keeping the polarity in consideration. Switch on the circuit to check whether the LED is soldered properly or not.

Step 8: Preparing the Earphones

Picture of Preparing the Earphones

The main step of this project is connecting your earphones to your bluetooth module. Take your earphones and cut its cable to an optimum length using a wire cutter or knife. You should keep your height in consideration when doing so because a very short or a very long cable will create problems in future. Once you have cut the cable, use a wire stripper to expose the inner insulated copper wires. Inside the cable, you will find four wires of different colors. If your earphones do not have a mic support, there will only be three wires inside the cable. Generally the color of the wires inside the cable is red, green , blue and white(non-insulated copper wire). The red one is the wire for left earphone, green one is for right earphone, blue one is for mic and the white one is for ground. If your headphone has any other colored wire, its better you check the connection of that wire using a multimeter before connecting it to the cirucit.

Using a lighter or a matchstick, burn the nylon threads present inside the wire. Now using your soldering iron, tin the ends of the insulated wire. In the beginning, your solder will not stick to the wires but keep on the heating the wires with your soldering iron until your solder starts sticking to the wire. Its advised to use a good amount of solder otherwise you will face difficulty in tinning the wires. Ones done, connect the red wire to the left audio output of bluetooth module, green wire to right audio output, blue wire in place of positive of microphone, and white one to ground. Once done, switch one the circuit and you will be able to hear the startup sound of the bluetooth module.

Step 9: Creating the Encloser

Picture of Creating the Encloser

The circuit part of this project is complete but still our project is not portable enough to be used on everyday basis. To do that, we have to make an enclosure for it. For the enclosure, I chose 5mm thick acrylic sheet. You can use thin wood or any plastic container to make the box or can even 3D print the box if you have the privilege of owning a 3D printer. Using a aluminum case is prohibited because metals create hinderance in the signals of bluetooth module and also decreased its range.

Start by measuring the size of your battery because your battery is the biggest component is of this project. Size of my battery came out to be 5.2 X 3 x 0.5 cc. Similarly measure the size of other components and decide the size of your box keeping the thickness of acrylic board and some room for parts in consideration. After doing all adjustments, I decide the size of my box to be 8 X 2 X 5 cc. So the size of my acrylic pieces were 8 X 5, 8 X 2 and 4 X 2 cm2.

After that mark these dimensions on the acrylic board and and using a saw cut the out. Create a notch on the box for the slide switch and two holes for the LED and charging port. Also make a small hole for the headphone wires.

Step 10: Mounting Everything Inside the Enclosure

Picture of Mounting Everything Inside the Enclosure

Now peel off the protective cover from the acrylic board. To give my box a good look, I painted the acrylic pieces in chrome color using spray paint. Let the paint dry for some time.Once the paint has dried up, compile the acrylic pieces together using super glue to make a box. While doing these steps, I ruined my paint coating. Instead of painting the box again, I simply sticked a read colored art paper on that particular piece.

Before adding the last piece, hot glue all the parts and components inside the box and finally stick the last piece.

Step 11: Making a Hook for the Project

Picture of Making a Hook for the Project

Now take a metal piece or wire and bend it in form of a clip. Using some super glue, stick it at the back of the box. Make sure the clip is steady enough to hold the box along with all the components. This clip will help you in hanging the project to your shirt. Now your project is complete and is ready to use.

Step 12: The END!

Picture of The END!

This is the end of this video. Hope you liked it. If you have any query, comment down below in the comment section. Watch the step by step instruction video on the below link. And don't forget to subscribe to my youtube channel.

Comments

bhvm (author)2017-09-18

So the BT module works well on LIion 3.7v? I thought they are meant on 5v USB.

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Bio: An electronic hobbist and a tech-savvy. Love to know and publish good electronic projects. I use some popular micro controller like raspberry pi, arduino, linkit ... More »
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