Wiring circuit

Energy is becoming ever more expensive, and some fresh ideas are needed. There are already human-powered devices on the market, most of which employ a dynamo to generate power. It is also possible to recover energy from a piezo crystal of the sort found, for example, in the loudspeakers in greetings cards. Making use of this device is relatively straightforward.

Piezo-Powered Lamp Circuit Diagram :

Piezo crystals can generate voltages of many tens of volts when given a firm enough prod with a finger to bend the  baseplate. The charge moved, however, is relatively small and the crystal is effectively a capacitor with a capacitance of only  around 20 nF to 50 nF. This means that we need larger-scale storage in the form of an electrolytic capacitor.

The piezo crystal can be treated as an alternating current source. We therefore need a rectifier and a reservoir capacitor. Pressing the metal surface of the transducer ten or twenty times with a finger will charge the electrolytic in steps to the point where it has enough charge to drive a LED. The circuit is a ‘charge pump’ in the full sense of the term.

When the button is pressed the electrolytic discharges into the LED, which emits a brief, but bright, flash of light.

Author : Burkhard Kainka - Copyright : Elektor