In this article, I'll show you how to make a small, wallet-sized device that generates electricity from kinetic energy. The concept is simple: Piezoelectricity is the charge that is produced when certain solid materials (commonly ceramic and crystal) in response to mechanical stress. Piezoelectrics have many applications; in speakers, actuators, sensors, even fuses. For more information, click here.
First, find yourself a couple small, identical LEDs. These are virtually everywhere; in cellphones, remotes, flashlights, most coffee makers, etc. You can find them at most (every) electronics store, or extract them from old electronics. Second, you'll need a piezoelectric disk. These can be found in digital watches, digital clocks, computers, and many other devices. I extracted mine from an old digital watch with an alarm. You'll also need some fluxcore solder.
A soldering iron and some "helping hands" (a little device that sits on your desk, made up of two spring-clips (alligator clips). Not necessary, but makes life easier)
Take your LEDs and identify their polarities. Since its not necessary which polarity is which as long as they are opposite, just look for similarities in the LEDs, and reverse them. Typically, a piezoelectric disk should have a metal outer-rim, and an inner circle made of a less-than-shiny material. That's one polarity, and the outer-rim is the other. Carefully solder the LEDs to your piezoelectric disk WITHOUT overheating them or the disk, and let dry. To test, simply flick the disk NOT aggressively, and observe the blinking LEDs.
- Don't use too much solder, it will look ugly and impair electricity generation
- Use tweezers to place the LEDs on the piezo disk, it makes life easier and saves unnecessary burns
- Use a fine-point soldering iron, it works better for small components
- Soldering irons are hot!! Don't burn yourself
- Don't overheat the piezo disk!! It damages it
- Same goes for the LEDs
- Don't over-stress the piezo disk, they are VERY FRAGILE!