sensing and responding to pressure
The initial hypothesis of the project was that conductive yarn could be used as a means to regulate resistance within a circuit. As the yarn is stretched, the resistance linearly changes and then returns to a base value. This change in resistance can then be used as a sensor via voltage division to interpolate stretch within a textile.
With the ability to read the amount of pressure applied to a textile along with a coordinated location of the touch, we hoped to achieve a tactile and visual sensory response with the combination of a micro-lilypad LED system. The LED system would respond with a different light color in coordination with the amount of pressure applied to the textile. The goal of the reading would be to visually equate the amount of pressure a user is applying to the textile while becoming more attuned to the sense of touch and pressure.
The initial testing phases of the research focused on finding a base information line for reading a resistance change in a knit textile. Several setups and knit types were used in an attempt to find a stable reading method. The general outcome of all examples seen in this chapter was overall an inconsistent reading of resistance changes. After the first test, the subsequent knit structures developed on the hand knitting machine sought to create a more stable integration of the conductive yarn in order to increase repeatability in the pressure reading.
In place of meaningfully accurate stretch sensors within the textile, off the shelf flex sensors were used in the final prototype. Unlike the conductive yarn tests, these sensors give completely repeatable and reliable results and yield a resilient and durable prototype. By mounting them within an acrylic frame under a tensioned elastic textile, the flex sensors displace with the stretch of the material and signal a reliable interpretation of that stretch. From this data, a relatively simple program was written to signal various colors of LEDs to light, depending on material stretch.