This Instructable shows you how to make a USB-powered LED lamp that turns on (and off) via the wave of your hand (and the QT113 IC):
The touch switch circuit is based on the QT-113 integrated circuit. It works by detecting changes in capacitance. When it is first turned on it measures capacitance at its sensor plate. When a human touches or comes near to the metal sensor plate the capacitance is changed and the circuit turns on.
The sensitivity is adjustable so that at a lower setting it will require you to directly touch the sensor plate. At its most sensitive setting, it will detect your finger through paper, plastic, glass, or even a brick.
The larger the sensor plate the more sensitive the switch. The sensor plate is the triangular circuit board at the front bottom of the lamp.
Curved Circuit Board Art: Make a Touchless Touch-Switch LED Lamp
The QTouch chip used in this project is an older one, but certainly works well from the vid above. I like the elegant, clever design of this project. Might have to mod an old lamp I have on hand to turn on/off the same way.
I swear my brain works along the same lines as Make blog. I was looking at the QTouch products from Atmel earlier today. They recently (2008 I think) bought the entire QTouch program. I’m planning on using one of the QMatrix chips in an upcoming project, because I like how good Atmel is about providing free software tools to customers, and that way I can provide all the details of the project without people having to buy expensive software to emulate it. Their QTouch library and QStudio software are both free downloads. And QTouch Library works with a number of Atmel’s AVR microcontrollers, which I know is a fave of a lot of the Makers here.
(Dang, I sound like an advertisement. I should be in the Sales dept for Atmel, lol.)