CAPACITIVE SENSING

WHAT CAN YOU SENSE? Distance, displacement, presence, x-y position on a plane, pressure, acceleration, humidity
WHO MAKES THEM?  
WHERE CAN YOU BUY THEM? Hosfelt , Digikey
HOW DO THEY WORK?

The amount of current out of a single electrode is measured. As a hand approaches the electrode, the electrode becomes coupled more strongly to ground (through the person).

Things that typically cause a change of the C:

Something changes the distance between the two plates
Something changes the dielectric constant (i.e. humidity)
Something changes the area (i.e. variable cap)

EXAMPLE CIRCUIT:  
PITFALLS & SOLUTIONS: