My Bone Conduction Headphone 1.0 !!!

Since I started working on many bone conduction experiments and learning the details of the bone conduction, I have finally done my first prototype of the bone conduction headphone.

Struggling with Fusion 360

First thing I did was to make the box to cover the sensitive materials because the wires I soldered were really easy to torn. In order to make the box and fix that problems, I needed to study how to use a CAD called Fusion 360. In addition, what I wanted to output from my 3D printer was the top of the box and the body of the box, so it was really difficult to make these fit perfectly. After I failed it more than 10times, I finally could make these fit!!!

・Top of box

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・Body of Box

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Probably my 3d design is not good enough yet, but at least, it is ok because my objective which I want these to fit perfectly was accomplished.

My 3D printer, Da Vinci Jr 1.0w, worked perfectly like this picture below. Thanks.

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Bone Conduction Headphone Prototype 1.0 is DONE!!!

After I made the box for my bone conduction headphone, I got my awesome dude.

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Plus my bone conduction headphone,

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equal this…

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I feel like I should have made the flame of speakers and wires… But it will be next time!

What I will do to improve my prototype from now

・Design the better and more beautiful box, and design the flame for these two speakers.

・Design my own PCB layout to make the device lighter and smaller.

・Study deep learning (Maybe Tensorflow) to make something interesting happen.

 

The result of my bone conduction headphone 1.0

Bone Conduction Speaker Experiment using I2C

The more things I studied about TPA2016, the further curiosity I had got such as what is going to happen what if I connect bone conduction speaker instead of a speaker. In addition, while reading the data sheet of TPA2016D2, I had been stuck on some words which were Automatic Gain Control (AGC) and Dynamic Range Compression (DRC) because I have never heard of these words before. However, these words DRC and AGC seem to be really important to know to do the further experiment like the aim of this tutorial which is the experiment of bone conduction speaker using I2C.


○About AGC and DRC

Automatic Gain Control is able to make an output signal constant despite its input signal. For example, when multiple people use a microphone at the same time, the sound input levels are different because some of them might be farther than other people, but some of them might be using the microphone closer. In this case, AGC automatically adjusts the input level and makes the output level constant. The point is, the weaker input signal is, the stronger output signal is, and the stronger input signal is, the weaker output signal is. In addition, the gain on the TPA2016D2 can be selected -28dB to +30dB. Of course, -28dB outputs a silent sound and +30dB can output a louder sound.

Dynamic Range Compression is able to prevent a clipping noise when the sound volume is extremely high by compressing the dynamic range of audio signal and speaker. In addition, DRC can automatically adjust the audio signal level for the sound range that you want.


Once you understood these words, let’s get started with bone conduction speaker using I2C experiment.

○Requirements

・Bone Conduction Transducer

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・TPA2016

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・3.5mm Headphone Jack

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・3.5mm Audio Cable

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・Arduino Uno

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・A breadboard

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・Some Jumper Wires

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○Circuit Diagram

bone-conduction-speaker-circuit-diagram

Assembly the components by following this circuit diagram. Remember that the goal of this experiment is to use I2C. I2C pins on the Arduino are A4 pin (SDA) and A5 pin (SCL), so connect each pin to the pins on TPA2016.


○Programming

Before you look up the code below, you should download two libraries which are wire library and TPA2016 library. (Go to Arduino IDE -> Sketch -> Include library -> Manage Libraries -> Search these libraries and download them). After restarting Arduino IDE, go to File -> Example -> then you see “Adafruit TPA2016 Library and click on it. You will get the exactly same code below.

In the serial monitor, you should get this result.

TPA2016 Audio Test
Gain = -28
Gain = -27
Gain = -26
Gain = -25
Gain = -24
Gain = -23
Gain = -22
Gain = -21
Gain = -20
Gain = -19
Gain = -18
Gain = -17
Gain = -16
Gain = -15
Gain = -14
Gain = -13
Gain = -12
Gain = -11
Gain = -10
Gain = -9
Gain = -8
Gain = -7
Gain = -6
Gain = -5
Gain = -4
Gain = -3
Gain = -2
Gain = -1
Gain = 0
Gain = 1
Gain = 2
Gain = 3
Gain = 4
Gain = 5
Gain = 6
Gain = 7
Gain = 8
Gain = 9
Gain = 10
Gain = 11
Gain = 12
Gain = 13
Gain = 14
Gain = 15
Gain = 16
Gain = 17
Gain = 18
Gain = 19
Gain = 20
Gain = 21
Gain = 22
Gain = 23
Gain = 24
Gain = 25
Gain = 26
Gain = 27
Gain = 28
Gain = 29
Gain = 30
Left off
Left On, Right off
Left On, Right On
Setting AGC Compression
Setting Limit Level
Setting AGC Attack
Setting AGC Hold
Setting AGC Release


○Result

The sound from bone conduction speaker worked well! While the gain increases from -28dB to +30dB, the sound correspondingly becomes louder and when the speaker does not touch anywhere, you cannot hear any sound. Which means I2C also worked well between TPA2016 and Arduino. Pretty cool!

Lastly, check and watch the result video below.

Soldering SMD Tutorial

Soldering is one of the indispensable skills for making your own electronic device. In addition, whenever you make a new device, you may have to practice or consider about the soldering for SMD on PCB. In the time I have been working on soldering while learning how to do it, I could find out some tricks to get it done beautifully. Before it gets started, I would like to explore some important words that I used in the introduction.

According to Wikipedia, SMD (SMT) is…

a method for producing electronic circuits in which the components are mounted or placed directly onto the surface of printed circuit boards (PCBs)

Also, SMD is the abbreviation of a surface-mount device (surface-mount technology)

Once you got the meaning, let’s see the tutorial.

○List of Requirements

Of course, if you are new to do it, you might have to buy some materials from the list.

  1. Your own board

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This is called PCB (Printed Circuit Board). I ordered my PCB in Elecrow  and the cost was $41.95 for 10pcs, including the shipping fees.

    2. Hot Air Gun

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I highly recommend you to use this device rather than using the soldering iron like this picture below.

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Because this soldering iron is not good at soldering super little components like 0402 resistors.

    3. Tweezer

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For picking the small components up and drop them off on PCB correctly.

    4. Solder Paste and Flux

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○Optional requirements.

These materials are not that needed but it would make your project easier if you had them.

  1. Helping Hand with Magnifying Glass

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    2. A couple of toothpicks

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To mix the solder paste and flux up.

○Soldering Time!

When you got these things, you finally could get the soldering started.

First of all, what you are going to do is mix the solder paste and flux together. In some Youtube I watched, they were just using a solder paste. However, my friends, who have more soldering experiences than me, told me that it has to be mixed up because by mixing them up, the paste will be stable on your PCB when you solder. So, I want to follow my friend’s advice rather than the Youtube videos.

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Once you got the mixed solder paste, you set your PCB up by using the helping hand with a magnifying glass.

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Paste the mixed solder paste evenly on the silver area on PCB. It does not matter even if your paste messed up a little bit because when it is being hot by the hot air gun, the paste, which had messed up, will automatically gather to the each pin bases on the surface tension.

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Put a component on the area you pasted them. Be careful of the dimension of your component. Each of components has the exact dimension and pins. You should see the date sheet of them.

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Take the hot air gun and set up the appropriate temperature (I am using 300 ℃). The component and PCB can usually be connected in 20 seconds. However, please make sure you should keep making it hot until the paste starts gathering.

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And continue the same things until you finish soldering SMD on PCB.

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The last thing you should do is make sure whether it is able to work what you wanted it to work. In order to do that, you are going to code to make it work.

Once you understand how to do soldering SMD on PCB, you can make your own product by yourself. I hope my soldering SMD tutorial can help your project out.