Types of Piezoelectric Crystals to Harvest Sound

ninja.lion

I am in the process of building a piezoelectric device to harvest sound with a frequency generator at one side of a plastic/glass tube which sends out a low frequency which is then picked up by a piezo disk which send the energy to an led which demonstrates hoe sound can be converted to electricity. what type of disk should i use.

please reply because i have holiday and want to work on my project

Bobbywhy

ninja.lion, Welcome here to Physics Forums!

Your same question has been frequently raised here. Two examples are:
http://physicsforums.com/showthread....ctrical+energy

http://physicsforums.com/showthread....ctrical+energy

I recommend you read these threads thoroughly before you begin your project.
In all these cases folks wanted to “harvest sound energy”. You must be aware that
Piezo-electric crystals, when used to receive acoustic energy, output tiny amounts of power, often measured in microwatts. This means you should not expect to convert acoustic pressure waves into any more than tiny amounts of electrical energy. Lighting up loads like LEDS requires milliwatts. Of course, you already know in the system you describe the crystal will output an AC voltage at the frequency of its vibration. To light your LED you’ll need to rectify it into DC.

For an overview and a good starting point for learning about piezo-electric crystals is here at Wikipedia:
http://en.wikipedia.org/wiki/Piezoelectricity

Here is how you could make your own:
http://blog.makezine.com/2008/07/31/...piezo-crystal/

One of many sellers:
http://www.alibaba.com/showroom/piez...-for-sale.html

As for selecting your Piezo-electric transducer, the most efficient conversion of acoustic energy to electrical energy will occur when the Piezo-electric element is resonant with the driving acoustic frequency. Generally speaking, the smaller the crystal (or disc) the higher its resonant frequency. Look at the transducer inside of a Piezo-electric “tweeter” speaker. It’s small size is proportional to the frequency it emits…in the region of fifteen kilohertz. You mentioned in your post you plan to use a “low frequency” source. Since this will require a “larger” sized transducer, you may want to reconsider that parameter.

There is another way to demonstrate the conversion of sound to electrical energy. Use a Piezo-electric microphone connected to an oscilloscope. Speak into the microphone and see the voice acoustic signal displayed.

Let us know here on Physics Forums about the progress of your project, and ask members here if you have any questions or doubts.

Cheers,
Bobbywhy

ninja.lion

thank you so much for you help i may change the idea of a low frequency, here is the model of sound generator i have it was supposedly good for piezoelectricty
HT2844 4-Sound Generator
and thanks again for the help