### Re: Can a vibrating unit be made from piezo ceramics?

Date: Sun May 19 23:47:43 2002
Posted By: Aurelio Ramos, Grad student, Computer Engineering, Not a member of any institution
Area of science: Engineering
ID: 1021780852.Eg
Message:
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It seems like you are on the right track.

By "similar vibration to that of an insect" I assume you mean the type of
sound made by insect wings (such as flies) it is conceivable you may
design a device to imitate a cricket as well, although that may be more
difficult.

Assuming you want to emmulate a fly, the maximum dimensions force you to
use a piezo powered by one or two watch batteries. The piece of the
puzzle that remains is the circuit. The sound of a fly is comparable to
that of a saw tooth wave with varying pitch and amplitude. So you need to
build a very small saw wave sinthesizer, powered by a watch battery,
coupled to a piezo. Depending on how far you go in sophistication, you
may reduce the project to simply producing a sawtooth wave, and make the
pitch or amplitude variable externally (make a mini theremin) or simply
fixed. Yet, a higher level of sophistication would involve varying the
pitch and amplitude automatically in a random fashion.

Because the circuit needs to be very small I will just give you some tips
on how to make a fixed pitch/amplitude sawtooth sinthesizer using a small
integrated circuit: the 555 timer. It's small enough (just an 8 pin DIP
package), takes little power, and it only needs a few additional
components.

By just putting the words '555' and 'sawtooth' in www.google.com I found
http://www.electronic-circuits-
diagrams.com/oscillatorsimages/oscillatorsckt2.shtml

They have full schematics and instructions on how to select the resistor
and capacitor for a desired frequency (something between 200 and 400 Hz
seems reasonable). Although the schematics suggest a supply voltage of
5.0V you might succeed with just 4.5 (a voltage commonly attained with
batteries) Three 1.5 volt batteries (or one 4.5V) will be needed
(hopefully it will still fit within the specified dimensions.) You could
power the circuit with slightly higher voltage with no adverse effects.

Remember to try your prototype out on a bread board first, and good luck!

```

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