My Progress of PCB Layout

It has been six months since I started doing Schematic design and PCB Layout by myself. I have been working on these things for improving my engineering skills and exhibiting my prototypes in Maker Faire, especially for bone conduction devices that I am developing. I finally could make my own PCB which worked perfectly, so I will show my progress of PCBs.

The first experiment failed…

When I developed my own PCB for the first time, I designed a schematic which was definitely over-skilled for me. Even thought I just wanted to make a PCB which can make sounds through an amplifier, I put BLE for Bluetooth function, and Li-Polymer Charge Management Controller to charge a LiPo Battery. Of course, the PCB did not work because I did not know how to design schematics and PCBs. What I learned from this failure is…

  1. Do not try to design a complicated PCB for the first time.
  2. Increase the difficulty of schematic and PCB layout gradually.
  3. Know how the electronics work better than anybody else.

The second experiment also failed…

From the first failure, I design a easy PC board by eliminating a lot of functions that I was not supposed to use this experiment. And, this is the schematic that I designed.

However, this schematic also did not work because It had three errors.

  1. I did not connect Pin 21 (Thermal Pad) on an amplifier to the GND (ground).
  2. R1, R2, and R3 (resistors) were not working as pull-up resistors.
  3. INL- (Left channel negative audio input) and INR- (Right channel negative audio input) also did not connect to the GND.

In order to fix these errors,

  1. Make a hole on pin 21 using laser cutter and solder pin 21 to GND pin using a tiny wire. (The reason why I made a hole was the package of the amplifier was QFN and needed to be soldered using soldering cream and heat gun).
  2. Connect SDA, SCL, SDZ pins to VDD pin using three jumper wires.
  3. Connect INL- to GND pin using a jumper wire.

After these debugging, my PCB called BCv2.0 finally worked.

BCv2.1 came out!

From previous failure, I redesigned the schematic.

The PCB became much smaller and practical and I removed the external 3.5mm headphone jack and used SMD headphone jack.

By placing components on both side, I could minimize the size a lot.

The Size Comparison

I could successfully minimize the size of PCB. This is the comparison of BCv2.0 (Green), BCv2.1 (Black), and 5 cent coin.

Next challenge I will do is to put more functions such as bluetooth on my own PC Board! See you at next post!

New Bone Conduction glasses 2.1 in San Jose Mini Maker Faire

I have been thinking how I could minimize the size of my prototype and maximize the effect of it. Then, what I came up with was to make my previous bone conduction glasses to the attachable type. Fortunately, there was upcoming maker faire in 9/3/2017 after I came up with this idea so I had a chance to see people’s reactions to my new prototype. 

Fusion 360

In order to make attachable device, I needed 3d printer and some skills of 3d modeling. What I have done was to attach an amplifier PCB (middle), a battery connecter (left) and 3.5 headphone jack (right) on the top side by measuring each PCBs and calculating each positions. Of course, I could not make it only once. I failed to print a couple of times, and I remeasured, recalculated, redesigned, and reprinted many times until it fitted.

On the bottom side was very simple. It just attaches a bone conduction transducer.

In this San Jose Mini Maker Faire, I exhibited two types of my prototypes which are the bone conduction glasses and attachable bone conduction device. I wanted to get any feedback from people.

Previos prototype


New prototype


My Booth

Many people came the booth I was exhibiting my bone conduction devices, and many people told me that these were awesome. Some of them who really were into these took my business card, so these reaction of people and actions really really made me happy like I was grad to make this!

Advantage and Disadvantage of the attachable bone conduction device

These are what I realized and got feedback from people during the Maker Faire.


  • It can attach almost any types of glasses, so the users do not have to buy the glasses itself.
  • It is lighter.


  • It can not make a balance. Either side is heavier.
  • Looks uncool.


Next Step

I cannot tell you the detail but I am currently working on my own PCB to make device itself as lighter as I can. See you in next Maker Faire.

Bone Conduction Glasses 2.0 in Maker Faire Bay Area


Bone Conduction

After testing bone conduction headphone 1.0, I had an issue which the device itself was not stable on user’s head because of the shape that I designed in Fusion 360. However, I got a hint from one of my friend. Why do not you put your prototype onto glasses? I was shocked at what I have not even thought of such a simple solution. After all, I started working on new project called Bone Conduction Sunglasses 2.0. While I am soldering new thing, one of my teachers of electrical engineering recommended me to exhibit my prototype in Maker Faire Bay Area 2017.


I did not expect the prototype accepted, but I got accepted! Therefore, I would be able to introduce my prototype in public. Thank you for everyone involved it, and Maker Faire!



There are two transducers which generate some vibrations based on the audio input from 3.5mm headphone jack.



Basically, these transducers that I am using on the bone conduction sunglasses are called surface transducers. What the surface transducers do is to vibrate any object to make sounds. As you can see on this video, sounds go outside. This is something I need to fix for next prototype.

In Maker Faire

There was a faire for makers from May 19 to 21. I also exhibit my bone conduction sunglasses in my booth. I had a desktop to explain what bone conduction is and how it works with an image.


While I was exhibiting my prototype, I met 9 deaf people. These people gave me really good feedback after they tried. In addition, I got 10 times better result than I expected. Here is the result that I got through the Maker Faire. 8 of them could hear sounds through my device. One man who had an issue of Cochlea could not hear sounds. What I got from them is sounds through the bone conduction was better than some hearing aids that they are using.


After all, I have come up with an idea to next step. I might be able to exhibit the Bone Conduction 2.1 in upcoming mini Maker Faire in San Jose. See you there!

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


・Body of Box


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.


Bone Conduction Headphone Prototype 1.0 is DONE!!!

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


Plus my bone conduction headphone,


equal this…


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.


・Bone Conduction Transducer




・3.5mm Headphone Jack


・3.5mm Audio Cable


・Arduino Uno


・A breadboard


・Some Jumper Wires


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.


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.



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.