Third Eye for the Blind

The Third Eye for the Blind is an ultrasonic sensor that can be worn anywhere on the body. The sensor vibrates to alert the wearer of any nearby obstacles.

Engineer

Naomi C.

Area of Interest

Software Engineering

Robotics

Aerospace Engineering

School

Lowell HS

Grade

Rising Junior

Reflection

I had a solid plan all laid out when I first started working on my Third Eye for the Blind. I would follow the instructions I found online, finish my base project in only a couple days, then spend the rest of my time working on modifications. Instead, my base project required more thought than I expected and took much longer to program. After I had figured out the basics of electronics and finished deleting and rewriting half the code I found online, I could finally move on to modifications. My first thought was implementing a bluetooth module, but that would take more time than I had. I was disappointed, but I settled for what I thought was the next best thing- adding  a GPS. It was actually my second modification that excited me the most. I designed my own PCB and held it in my hand. Unfortunately I had designed one of my Arduino headers backwards and wasn’t able to use it during my presentation. Despite that disappointment, designing my PCB sparked my interest in electrical engineering, a field I had previously thought of as boring and unsatisfying. That excitement made my entire project worth the six weeks of struggle.

Modification 2

My second modification was by far the most enjoyable element of my project. I designed my own PCB using Autodesk Eagle and ordered it through OSH Park. The most difficult concept to grasp before I could make any real progress on my design was Eagle’s disregard of dimensions or position while designing a schematic. I spent a fair portion of time struggling to find dimension settings for my schematic before learning that the dimensions of parts only matter while designing the board. The most critical part of designing a schematic is confirming that the footprints on your schematic match the actual footprints of your parts. A footprint is the physical blueprint for each through hole you will be using to solder each part to your PCB. After I added the correct parts to my schematic, the next step was connecting each part with the correct wiring. After optimizing my wiring to include as few right angles as possible and the shortest routes possible, I generated my board in Eagle. Here was where dimensions and placement mattered. I measured the physical space my parts would require on the board and adjusted my design accordingly. After adding a silkscreen with my name and year, I ordered my PCB.

Modification 1

My first modification is the addition of a GPS tracker to my Third Eye design. I wanted to be able to track where the wearer of my Third Eye had been and view that information on my serial monitor. I soldered a GPS onto my perfboard and added the necessary code. Initially, finding the correct code and rewriting parts of it to integrate correctly with my existing Third Eye code was a tediously difficult process, but it became easier with time. After I managed to correctly add the right code, my GPS activated, but wouldn’t display on the serial monitor. After some lengthy online research, I realized my mistake was that I had been using the incorrect BAUD rate for my serial monitor. BAUD rate is how quickly information is transmitted through a channel of communication, and up until that point, I had been using a BAUD rate too high to receive data from the GPS. After correcting my code, my GPS was fully functional.

Code

Final Milestone

My final milestone is the more permanent version of my Third Eye. I soldered my third eye design onto a perfboard and stitched together an elastic band to be comfortably worn around the user’s hand. I created a schematic for the Third Eye design and used that to transfer my project onto perfboard. After several rounds of soldering and resoldering, the result of creating unintentional connections where they shouldn’t be, I finally managed to produce a working model. I struggled with my switch, having it turn on but not off and vice versa, even after learning the reason behind having to use a specific orientation. Eventually I reasoned that the solder between the furthest pins of the switch must be touching, even if I couldn’t see it. I desoldered the pin on the switch that connected to my arduino and used a wire to connect the two directly. The Third Eye finally worked as designed, and I began planning my modifications.

Schematics

First Milestone

My first milestone is the completion of my first working third eye for the blind model. I struggled trying to understand the relationship between the placement of wires on my breadboard and the code I wanted executed. I researched the meaning of the pins on my Arduino and got a better understanding of each pin’s purpose. All of the objects I wanted to execute my code had to be grounded (connected to the GND pin), then connected to whichever digital pin I had assigned them in my code. The ultrasonic sensor itself had four wires that had to be connected in specific places- the ground pin(GND), voltage supply pin(VCC), and a pair of input/output wires that had to be connected to digital pins only. Analog pins are also included on the Arduino, but unlike digital pins, they have more values than HIGH/LOW and can only act as input connectors. After uploading my code to the Arduino through a USB cord, the last task I had was to connect my battery and switch. My third eye for the blind model worked correctly when powered by my laptop, but had to be extremely portable to operate as a handheld device. I connected my 3.7V battery to the ground and VIN(voltage control) pin, but it failed to power my sensor for some unknown reason.

Code

Minty Boost 3.0

My starter project is the Minty Boost 3.0, boosting a 3V battery to 5V and capable of charging anything from phones to GoPros. The Minty Boost is built up of a PCB circuit board, resistors, ceramic bypass capacitors(0.1uF), electrolytic capacitors(220 uF), power inductor(10uH), 8-pin socket, female USB jack, and 5V boost converter. The completed circuit board is connected to two 1.5V AA batteries through two wires which connect to the two 1.5V batteries. The charge in the batteries travels to the board and is boosted from 3V to 5V as it travels across the board. The resistors limit the current passing through them, ensuring the board doesn’t short circuit. The ceramic and electrolytic capacitors store charge in their electric fields, which they will destroy to compensate for any voltage drop. The inductor works similarly, storing charge in a magnetic field which it will destroy to compensate for any change in current. Next to the inductor is the diode, which ensures current only flows in one direction, towards the USB connector. In the center of the board is the IC socket, protecting the boost convertor chip and making it easier to replace the chip when necessary. The initial soldering was the easiest part and I was able to quickly solder each part into the correct place. While mounting my board onto the tin case, I realized that the solder from the underside of my board would touch the tin case and cause a short circuit. I corrected myself and insulated my board with electrical tape, then tested the charger. The case quickly overheated and short circuited. I couldn’t understand why it short circuited, as everything was in the correct place and I had insulated the board with tape. I realized that while the tape looked intact in my hand, it would be firmly pressed down when in the tin case, which might have led to some of the solder puncturing the tape. I added more layers of tape and tested it again- my Minty Boost worked.
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