Nadia's soft circuit: An occupancy detector for her bathroom
Motivation
I live in a two-bedroom apartment with another girl, and we share a bathroom. Sometimes I'm in my room and I want to use the bathroom (for showering, etc.) but I can't tell if the bathroom is being used. Therefore, I often have to leave my room to check if the bathroom is actually in use. The purpose of this project is to create a sensor that will allow me to determine whether the bathroom is being used from the comfort of my own room.
System overview
When the bathroom door is closed, it completes a circuit to turn on an LED light.
I assume that the bathroom door is only closed when it is being used by someone (from observation, this is a reasonable assumption). Note: The LED light is meant to be placed in my bedroom, but for proof-of-concept purposes (mostly to minimize the amount of material used), I am mounting the LED light right over the bathroom door.
Materials
For the portion of the circuit attached to door frame:
+ Two pieces of conductive fabric (here, circular) serve as the ends of the open circuit
+ Conductive thread is stitched through the open circuit to connect: 1) the two pieces of conductive fabric, 2) the LED light, and 3) the battery.
For the portion of the circuit attached to door:
+ One piece of conductive fabric (here, rectangular) serves as the electrical connection between the two pieces of conductive fabric on the door frame when the door is closed
Results & my experience
My circuit works! I am very pleased with how flexible and robust the system is; because the materials used are so pliable, this system functions successfully over a range of distances between the door and the door frame. I initially thought that I had to add foam backing behind either portions of the circuit that come into contact with each other, but I quickly learned that the circuit can be completed even if the surfaces only lightly contact each other. The circuit can also be tampered with (e.g., by crumpling, scratching, etc.) quite a bit and still work properly
Even with my limited experience with traditional electronics, I often find that creating a "perfect" electrical connection between components is necessary for a properly functioning system. Out of paranoia, while I was constructing the circuit presented here, I very frequently used a multi-meter to make sure I was successfully connecting my components. To my surprise (and extreme joy!), using traditional materials--as simple as conductive threads and conductive fabrics--for nontraditional purposes proved to be very successful, relatively simple (for those of us who are more comfortable with sewing than soldering), and super fun! I especially appreciated the degree of flexibility and creativity that the materials allowed for in making our soft circuits. And, ironically, I think using the textiles medium in this nontraditional fashion is gradually making me comfortable with electronics.