This is a pretty simple switch design that senses when an object is lifted off a flat surface. To demonstrate it, I put the components inside a cardboard box. The operation is easy to understand. Basically, the switch circuit is composed of a battery, a resistor, an LED, a metal clothes hanger, a spring, and conductive foil. When the object is resting on a surface, the spring holds the hanger above the foil (the spring pokes through a hole in the bottom of the box). When the object is lifted, the spring falls through the hole, pulling the clothes hanger down onto the foil. This completes the circuit, as shown below.
Here’s a video showing what the switch action/response time was like. This was a basic prototype, and can obviously be applied to a much smaller scale with more careful design.
Also, I was bored and thought of a design for a switch with no obvious purpose. I call it a puffer — basically, you blow up a balloon with a wire attached to it, and once the balloon has expanded that wire makes contact with another wire. Here’s a sketch, sorry for my feeble attempts at drawing:
Like I said, I can’t think of a use for it, but I figured it was worth posting anyway for a laugh at least.
And the sketches:
Arduino Sketch: <a title=”Arduino Sketch: David_DIO1″ href=”http://code.arc.cmu.edu/~cheng/uploads/David_DIO1.pde” target=”_blank”>David_DIO1</a>
Arduino Sketch: <a title=”Arduino Sketch: David_DIO2″ href=”http://code.arc.cmu.edu/~cheng/uploads/David_DIO2.pde” target=”_blank”>David_DIO2</a>
Arduino Sketch: <a title=”Arduino Sketch: David_DIO3″ href=”http://code.arc.cmu.edu/~cheng/uploads/David_DIO3.pde” target=”_blank”>David_DIO3</a>