Materials (touch sensing)
The interactions with the Peabody quilt are touch based – the user presses on a square and the LED lights up. Thus, parts of the quilt must be sensitive to touch. There are two potential ways to include touch sensitivity in the quilt: pressure sensors or capacitive touch.
Capacitive touch sensing is a type of sensing that doesn’t require much force, if any, to trigger. Any conductive material can be a capacitive touch sensor. You just need to add power, a resistor and your touch! Here’s a great video that explains the physics behind capacitive touch: https://www.youtube.com/watch?v=jco-uU5ZgEU
Why capacitive touch?
- avoids unnecessary roughness with the quilt (in an extreme example, you don’t even have to touch it if you have a strong enough resistor)
- can work with conductive fabric so the quilt itself can be the sensor
- can detect touch through any insulating material (like the LED’s silicone casing) which would allow us to conceal a sensor if needed
- each sensor only needs one wire
- relatively inexpensive (cheaper to buy conductive fabric and cut it than to buy 900 pressure sensors)
- there is an existing capacitive touch sense library for arduino
Potential Material for the capacitive sensor
- conductive fabric (knitted superlight conductive fabric is transparent to allow the LED to shine through)
- silver ink (the ink could be painted in a circle on the quilt around the LED so as not to block the light)
Things to consider with capacitive sensing
- LED must be able to shine through the quilt
- the quilt cannot be used if it is laying on a metal or static dissipative surface. The capacitive touch-sensing circuit must be insulated
- the resistor value affects the sensitivity of the touch sensor– at the low end (1 mega-ohm) the sensor will only be activated by absolute touch, and on the high end the sensor can be activated from a distance of 12 inches or more
- each sensor requires one wire which means there will be 900 wires running through the quilt. A possible solution is to 900 pieces of conductive thread that go to a central exit point on the quilt connecting to actual wires
Hi I was planning to build an Arduino based capacitive touch circuit to control a concrete lamp.
Will the touch work through 8mm thick concrete slab
Hi! Capacitive touch relies on conductivity and/or pressure (resulting in additional conductivity/completion of circuit). I’m not entirely sure how conductive concrete would be, as in whether it would complete a circuit through the concrete as a medium. Now, if there were a conductive pad on the underside of the slab and the control mechanism is of you pressing down on the slab, it could complete a circuit if the conductive pad were to touch another conductive pad. Hope that helps!
— Courtney