This is a short instructable on how to use the Qprox IC (QT113G) as a touch sensor. Using this IC, you can essentially turn any object into a touch switch. This simple circuit may be hooked up to a microcontroller (in this case I used the MAKE controller board).
Step 1: Gather All the Necessary Parts
1. QT113 - can be ordered at Digikey DigikeyDigikey. Each one costs around $2.
2. 10mF capacitor
5. breadboard or perfboard (if you choose to perf, you will obviously need a soldering iron and some solder)
Step 2: Build Your Circuit
wire up your circuit according to the following diagram:
pin 1: Power (3.3-5V)
pin 2: Output (in this case I used a red LED)
pin 3: Ground
pin 4: Power
pin 5: Power
pin 6-7: 10 micro Farad capacitor. These pins also connect to the input wire.
pin 8: Ground
Step 3: Input Wire
You can see how the light turns on and off when my finger touches the wire.
Step 4: Connect to a Microcontroller
In this case I used the MAKE controller - connected the output wire from Step 2 (which was an LED there) into the 4th Input pin of the controller board. When touched, the pin goes low, otherwise its state is high.
In this example, I used the NET connect software to create a flash animation that changes its shape according to a user's touch.