For my creative switch project I created two circuits, each consisting of: piezoelectric disk, darlington transistor, 28ohm resistor and blue LED. I then wired these circuits in parallel.
The reasoning for using a piezoelectric disk it that I wanted to create a switch which didn’t require a conventional power source. The piezos themselves create electric energy when mechanical stress is applied to them, meaning they have create the charge to power the LEDs. However, I realized that this wouldn’t suffice. The piezos only created a very small amount of energy. I added transistors to each circuit so that the electrical energy output by the piezos could be amplified in order to make the LED lighting up more visible.
Unfortunately, in its current state my creative switch is not much of a switch. The effect of the piezos is only temporary. However, this is only the first iteration in my design. I eventually hope to hook piezos up to an arduino and create a simple game that, when passed, would turn on/off the LED.
Parts needed:
- 2 LEDs
- 2 28 Ohm Resistors
- 2 Piezoelectric disks
- 2 Darlington Transistors (I used 4123)
- Wire, solder
Each piezo circuit consisted of a piezo disk, LED, transistor and resistor. The piezo ground was attached to the transistors middle pin (collector). Piezos power was attached to the resistor which in turn was attached to the LED ground. The LED power was attached to the transistor right pin (emitter).
At this point, the circuit will work by the power of the piezo alone. However, to amplify the charge generated by the piezo a power source (9v battery) was needed. To attach this batter, the transistor left pin (base) was attached to (-) and the resistor (which was attached to piezo power) was attached the the battery (+). Now the LED will light up more significantly.
Wiring these two circuits together so they could both utilize the power source was simply a matter of soldering together the areas which the circuits connected to the power source.
I ran into a number of issues along the way. Two main issues which really set me back were that one of my transistors pins broke off and the other transistor overheated and began melting.
As you can see in the first picture, my final product also includes two door knockers. I added these so that they could be used to apply mechanical stress to the piezos, which the piezos would turn into electrical energy.
