Father creates proximity touch switch for his son

“I knew that he would be able to operate a capacitive proximity sensor, since it only requires that he touch the sensor. I did some searching and did find a few assistive products, but they were all remote switches and rather expensive. We thought that it would be better for him cognitively if the device he operates is the same as the one that he touches. Hence the birth of the Touch Switch. The Touch Switch is an extremely sensitive capacitive proximity sensor switch. It is a small two-sided circuit board, designed to be as small and cheap as possible so that it can easily be embedded in just about anything for modification (e.g. electronic toy). The Touch Switch works by detecting a change in capacitance between a sensing plate and ground. The sensing plate is just a conductor with a large surface area (eg. piece of metal foil). When the sensing plate is approached by a finger the capacitance rises and the switch is closed. When the finger is removed the capacitance drops and the switch is opened”, the father explained.

Adapted from: http://www.hackingsma.com/?p=51