Penny for Your Thoughts: Biofeedback Lie Detector

Biofeedback sensors: I was really excited to explore the biofeedback realm this week. As a retired track athlete, I have always loved the overlap of technology and kinesiology because of the potentially enormous impact these sensors can have on someone’s life. Going into college I was planning on majoring in Kinesiology and minoring in Fashion Design because I love exploring where science and art overlap. This semester I am also taking Intro to Engineering and my group is prototyping a footwear insole that would be able to identify biomechancial imbalances in a person’s gait. My passion is footwear design so to finally be able to pursue projects like these make me so excited to learn more.

I wanted to mess around with a DHT11 Temperature and Humidity Module 1PC to see how to communicate these factors in an unconventional way. After some research I found some code that prototyped a makeshift “lie detector” using a temperature sensor, a breadboard, an LCD screen, pennies, and a potentiometer. It was pretty funny to think about reducing something that often times is used to make immensely important life decisions to something as simple as a penny.

I started out by placing the LCD module onto the breadboard and then connecting this to an Arduino Mega 2560 Controller Board and the potentiometer. In my research I discovered how important it is to test out the LCD before connecting it to the DIY GSR Sensor and Temp Sensor. This way any problems that arise can be addressed before making the circuitry more complex. Learning about the mapping needed to use an LCD was also really interest to see. I would have never thought that something like that would be reduced down to simple (0,0) coordinates in order to communicate text. After I set up the first part of this project, I ran a test sketch to make sure that the LCD was working. The first time I verified the sketch, I got the error “stray 342”. It took me the longest time to figure out but funny enough the problem was that when I copied the code from the blog, the quotations marks were not ready as such so once I retyped those marks that error went away. I also had to create a “const int” to establish the pins for the board and for the LCD. Once I made these two changes the code verified and uploaded to the LCD. The test readout on the LCD said “Congrats LCD works!”. This was really exciting since I’ve never coded an LCD before and I knew that I had correctly connected the project thus far.

Now that the LCD was working properly, I could now attach the temp/humidity sensor and make the GSR sensors. I connected the temp sensor to the breadboard, 220 ohms resistor, and analog pin A0. Once that was connected I could make a homemade GSR sensor. To do this I cut open two jumper cables exposing the copper wires. I wrapped the copper in aluminum foil and then hot glued that wrap to a penny. I did not have solder, so I used the aluminum to increase the metallic contact to the penny. This way there would still be a good connection from the penny to the wire even though I used hot glue. These GSR sensors would give biofeedback that would print on the LCD as well as the information from the temp sensor. I connected the GSRs to the breadboard and then copied the final code into the sketch. Reading through the code, it was very well laid out explaining exactly where the various sensors were being defined and then looped together.

After a few adjustments to the code, the sensor was able to detect my body temperature as well as fluctuations from the GSR. The LCD printed out a timer, the temperature, and results from the GSR. It was so cool to see something as simple as a penny be transformed into operational “lie detector”.

With the excitement from building an operational biofeedback sensor, I wanted to build something else. I had failed last week trying to connect a MIDI to my Arduino so I wanted to

attempt a mini synthesizer. I found a simple prototype and started plugging away. I connected the Arduino to a Photoresistor, a passive buzzer (used instead of Piezo), and a bread board. This had a more simple layout than the lie detector sensor, but I had to download a few different libraries to get this to work properly. In the sketch, a segment of code was dedicated to creating a calibration period. The sensor would take five seconds to calibrate its surroundings and then output sound based on fluctuations in light caused my contact with my hand. It took a few minutes to get to run properly because I misidentified the Output pin in the sketch so it but I eventually got it to work. I don’t think I got the calibration factor to fully perform, but the buzzer did output sound and change pitch based on movement. When it did work, the sound was terrible but when I touched either the buzzer or the Photoresistor the fluctuations made really interesting tones, almost like a symphony of crickets chirping at night.