How might I make a basic capacitive touch sensor for the Beaglebone Black that is capable of sitting behind an insulating material? I would like to make it as basic as possible, and without any sort of "breakout board", or specialized IC, using only the Beaglebone to interpret data received as might the specialized IC would. The Beaglebone has digital IO pins, a 12-bit ADC, and PWMs (for reference), and is very similar to the Raspberry Pi. Is it do-able? (With only the Beaglebone, breadboard, jumper cables, copper tape, and resistors of any value)
Answer to that: It is doable. Same as in the circuit schematic, it would seem! Can be done with the digital pins. You put a large-value resistor between the send pin and the receive pin, set the send pin to high, and time how long it takes for the receive pin to be brought up. The sensor acts as a capacitor, storing charge, so that the receive pin takes a longer amount of time to be brought up.
How does such a sensor operate, and how does the sensor itself affect this circuit? (shown below, representing a touch sensor)
There is only one source of charge, through the resistor. So if you increase the room for storage of charge by adding the capacitance of the finger it will take longer to fill.
(and thus the differences in time indicate whether or not the finger is there)