ERU2 – Winter 2015: James’ Results

Wearable electronics are becoming widespread as electronic components become smaller, flexible, and more durable. I have prototyped a clothing item integrating some simple sensors and a lighting system for use in outdoor exercise, scientific field work, and camping. This device is integrated into a waterproof jacket. One function is a pair of glasses-mounted RGB LEDs, controlled by a potentiometer to adjust between white light and red light. The device also uses a temperature sensor and heart rate monitor to determine basic data about the wearer’s vital signs and display these through micro LEDs in a wrist strap.

The creation of the initial prototype on using an Arduino Uno and breadboard was quite quick; the stitching of the conductive thread circuits into the coat, and the subsequent tweaking and calibration took a much greater amount of time and effort. A particular problem I encountered was that due to a lack of thread and some poor planning, some circuits needed to cross. I eventually I had to protect many of the crossings using electrical tape to prevent short circuits. Furthermore, while I thought I had only created parallel circuits, it seems that I had actually created a few series circuits, as the voltage readings from some of my sensors dropped when other lights turned on. In order to overcome this, I added correction factors for each light into my code, with whether or not the correction factor was used being determined by whether each light was on. Another issue I faced was a lot of noise in my sensor readings. To overcome this, I designed a noise filter: the behaviour of my lights varied depending on which portion of the range of readings was sensed, so I required that 20 consecutive readings in a particular range be read before that action was carried out. This was accomplished by adding variables that could be increased by 1 each time the reading was in the same range, or reset to zero every time the reading was in a different range from the previous one.

In terms of physical difficulties, I used more thread than I thought I would, completely depleting a spool of conductive thread. Furthermore, while I made my stitches quite flat, the fact that interior parts of the coat may touch when I bend or move caused circuits to come in contact, which led to undesired behaviour like outputs from one pin affecting the wrong light.

The final product was quite close to as it was imagined. The wiring was not as neat as hoped for, and in general, it does not look as aesthetically pleasing as hoped for. However, its core functionalities all work in general. Poor connections for some of the LEDs result in shifting colours or intensity, however. One major shortcoming was that I could not get the battery to power the Lilypad. As of submission time, I still had not determined what the problem was. The battery was capable of powering a circuit of one LED with the circuit going through the Lilypad, but the Lilypad would not turn on either with the battery in the battery holder or even when connected directly to the battery with wires. The following are pictures of the final product, and of myself wearing the final product.

ERUIIFinalpics

Here is also a link where I give an overview of the product’s functionalities:

Overall, this was an interesting experience for me. While my final product was not perfect, I gained valuable skills in both programming and problem solving. I was also able to apply my knowledge of some other disciplines of science to this, such as understanding the infrared reflectance of blood and how this is used by the pulse sensor to detect the pulse. I had a lot of experience with problem solving over the course of this project, as I encountered problem after problem, requiring me to troubleshoot in a systematic manner, testing each component of the circuit to isolate the part that is causing the problem, then coming up with ways to overcome the problem. It was a lot of fun for me because it allowed me to use my imagination and build a device similar to ones that are often portrayed in science fiction and which I had always wanted one of.

Overall, this was a great experience. While I would like to continue developing this prototype, access to more thread, and continued access to the FTDI board used to connect the Lilypad to the computer may be necessary for that. Furthermore, I would need to consult others for help, as I cannot determine the reason the battery will not power the Lilypad.

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