Bluetooth Knee Monitor

Hi, my name is Ashley and my project is the Bluetooth Knee Monitor, which uses a flex sensor, Arduino, accelerometer, and Bluetooth module to send information about how your knee is bending, accelerating and rotating. This device is useful because it can tell you if you’re bending your knee wrong and allow you to correct it.


Ashley Kwong

Area of Interest


Evergreen Valley High School


Incoming Senior

Final Milestone

My final milestone is the increased reliability and accuracy of my robot. I ameliorated the sagging and fixed the reliability of the finger. As discussed in my second milestone, the arm sags because of weight. I put in a block of wood at the base to hold up the upper arm; this has reverberating positive effects throughout the arm. I also realized that the forearm was getting disconnected from the elbow servo’s horn because of the weight stress on the joint. Now, I make sure to constantly tighten the screws at that joint.

Third Milestone

third milestone paragraph

Second Milestone

First Milestone

Ashley's First Milestone

Code Used for Flex Sensor, Click for link to Github!

My first milestone was connecting the flex sensor to my Arduino then having the Bluetooth module send the data wirelessly to my computer. Admittedly, this process was probably the longest and toughest for me, just because I had to learn a lot about how circuits work, how a breadboard works, and coding in Arduino Serial. My first order of business was to connect my flex sensor to the Arduino. A flex sensor is a variable resistor, whose resistance increases the more it’s bent. When the substrate inside the flex sensor is bent, the sensor produces a resistance output correlated to the bend radius. When the radius is smaller, the resistance increases. In order to connect the flex sensor in a circuit, I had to learn about voltage dividers, which controls a large voltage input and turns it into a small output, this mechanism, based on Ohms Law helps the Arduino read the information from the flex sensor. I then used the code I found on Sparkfun and edited it to fit my purposes (ie calibrating the resistance values to get the correct bend values). In addition, I had to connect the Bluetooth module HC 05 to the Arduino to get my data to send wirelessly. Using a library called software serial, I had to change the RX (receiving)and TX pins(transmitting) from the digital pins to pins 10 and 11 in order to allow the Bluetooth and computer to communicate with each other. Doing this opens to the two serial enabled devices and adds serial ports. After that, I had to do another voltage divider, to control the amount of voltage going into the Bluetooth’s RX pin. Afterward, I downloaded Bluetooth Serial Terminal and got the data to appear on the computer.

Starter Project:TV B Gone!

Ashley's Starter Project TV B Gone

For my starter project, I decided to do the TV B Gone, which is a small universal remote that has the ability to shut off any TV through infrared light waves. Most remote controls for electronic devices operate with invisible infrared light, usually about 940 nm, and picked up from an LED receiver in the designated object. My project works with the same mechanics, using the LED’s at the top, the small bulbs emit pulses of infrared light, and when pointed at a TV, has the capacity to send a signal to shut the TV off. With the little microcontroller, the TV B Gone has the ability to send specific wavelengths through pulses, which will shut off a TV depending on the wavelength the TV operates on. From this project, I learned a lot about the hardware aspect of things, such as the purpose of resistors, what soldering was and how to do it. I think the part I enjoyed the most about the project was that I had the ability to learn and develop new skills. For me, I definitely enjoyed soldering, and plus I learned something new about how remote controllers actually work, spoiler, it’s not magic 🙁

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