Science Buddies: "Ask an Expert"

How to generate enough piezoelectricity to light up a fluor4escent lamp?
I am a 14 year old Malaysian student and I am working on a project(mentioned above). I am researching on how enough piezo can be generated in order to light up our class during the school hours. Malaysian students sit in the class for an average of 5 hrs daily and I am trying to utilize the weight of my class to generate piezoelectricity. I am planning to incoperate piezoelectric films along with Rochelle salts or other piezoelectric materials into a chair so that when a student sits on it, piezoelectricity would be generated. With this, I am planning to light up the class .However, I am faced with the problem on How to generate enough piezoelectricity to light up the fluorescent lights. I know that the voltage produced is high but the current is small. How do I step up the current produced so that it is enough to light up one fluorescent lamp.
Please help me.

Hi lee hock huat!

Hate to be the person breaking this news, but I hate to say I'm skeptical that it can be done.

If you supply "piezoelectricity" to answers.com, you get back a list of applications of piezoelectricity. None of these are as practical as keeping a light bulb on as you specify.

Of course, I'd love to be proved wrong in this opinion.

davidkallman wrote:Hi lee hock huat!

Hate to be the person breaking this news, but I hate to say I'm skeptical that it can be done.

If you supply "piezoelectricity" to answers.com, you get back a list of applications of piezoelectricity. None of these are as practical as keeping a light bulb on as you specify.

Of course, I'd love to be proved wrong in this opinion.

I agree that lighting a bulb is quite unlikely. In a previous job, I used piezoelectric quartz transducers to measure the forces exerted on a tool in lathes and mills, a very heavy-duty application. The forces involved were much greater than what could be expected from a student taking a seat in a chair.

To light a lamp, current flow is required. The piezoelectric output is essentially charge, not current. Special circuitry that can measure the charge without bleeding off the electrons are required.

In our application, we built an amplifier that converted the charge into a voltage and current signal that we could use for our measurements. Something you could consider is building an amplifier like this and use the output of the amplifier to light the lamp.

Also, if I'm not mistaken, flourescent lighting requires AC current. In any case, I think you'd be much better off trying to light a flashlight bulb or an LED.

I hope this helps!

I have read your mail.
Please explain about the amplifier that converts charge into voltage and current signals since its output can be used to light a DC current appliance. I am eager to know how it works. Please reply soon.
Another question: Can piezoelectricity be stored?

Can you send a diagram or a picture of the amplifier including its cross section, if possible?
How do I, if possible, set it up?

lee hock huat wrote:Can you send a diagram or a picture of the amplifier including its cross section, if possible?
How do I, if possible, set it up?

The kind of curcuit I was referring to is called either a "high-impedance amplifier" or a "charge amplifier". Searching on Google or other such engines for these terms plus the word "circuit" or "schematic" will yield some designs. The circuit design you use will have to match the type of sensor you use.

Here is an example of an application note describing a circuit similar to the one I was referring to:

http://www.maxim-ic.com/appnotes.cfm/ap ... umber/1127

Note that the components to construct such an amplifer can be expensive. As a student, you may be able to convince manufacturers to donate parts to your effort if price is an obsticle.

You should also consider using a strain gauge instead of piezoelectrics. Strain gauges are simpler and less expensive. They can be used to measure weight, so you could do something like have the brightness of the lamp be proportional to the weight of the person in the class. Search for "strain gauge applications" and so on for additional information.

Note that any amplifier you build will need power. The act of sitting in a chair can be measured, but it won't be enough to power the amplifier. You'll need some kind of DC power source, such as batteries.

Have you considered other ways to produce energy while sitting in class for 5 hours?