What are they?

They could be transducers or maybe flux capacitors. No one will be able to tell you how they are used until it is known what they are. Do you know anyone with a DeLorean?

I've got a Mr. Fusion. There are no such parts in it.

Bob

Sounds like you have the version that was neutered.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

That would be eunuclear fusion ?

-- "Electricity is of two kinds, positive and negative. The difference is, I presume, that one comes a little more expensive, but is more durable; the other is a cheaper thing, but the moths get into it." (Stephen Leacock)

Yep, surplussed from the Vienna Boy's nuclear power plant. They didn't work worth a damn. ;-)

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Hi, Roger. Seriously, they sound like they're a little too big to be a microphone. If the cylindrical cans are black thermoplastic, your parts may be piezoelectric beepers. There are three basic kinds of beepers:

1) Those that have all the drive circuitry enclosed, and just require that vThey sound like they're too small to have enclosed drive circuitry, so you'll have to drive them yourself. 2) Those that have an internal transistor and a couple of resistors -- you have to add a transistor and one or two parts to make them work, and 3) the bare piezoelectric element.

The best way to tell if you've got a 1) is to just apply a low DC voltage, and see if it beeps (option 1) or just clicks (probably option

3). Judging from size, I'd guess you've got #3. The piezo concept means that a change in applied voltage causes the piezo element to flex, and that flexing the element produces a change in voltage. You can use piezo discs as sensors (flex causes voltage), and you can also use them as beepers (voltage causes flexing like a tiny speaker) by applying an AC voltage to them of the recommended mechanically resonant frequency (usually 3KHz or so for the smaller units).

For most applications, a digital drive signal is applied to both sides of the device to produce the "AC". For the really small ones (like yours), you might be able to do something like this if you've got a

74HC14 and a 5V power supply (view in fixed font or M$ Notepad):

| ___ | .--|___|--. Piezo | | R | Beeper | | | | | | |.-.| | | |\\ | |\\ A || || B | o---| >O--o--| >O-----|| ||-------. | | |/ | |/ || || | | | | |'-'| | | --- | | | C --- | | | | | | | | | |\\ |\\ | | === '-----| >O--| >O-----------' | GND |/ |/ | | (created by AACircuit v1.28.6 beta 04/19/05

The 74HC14 is an inverer IC with schmitt trigger inputs. You can use that with an R and a C to produce an audio frequency square wave as shown, with R and C chosen for the appropriate frequency (again, usually around 3KHz for the smaller piezo elements). This is fed to the other gates, so that when A is high, B will be low, and vice-versa.

This means that, for a 5V supply, you're applying a 10V peak-to-peak square wave to the piezo transducer. If you've chosen a frequency close to mechanical resonance, and the capacitance of the piezo element is small enough to be effectively driven by the HC14, you'll get an audio tone.

This drive method is only recommended for the smallest piezo speakers. Larger ones can be driven by an LM556 or even a capacitive bridge driver for the larger piezo elements. This bridge-type switched DC is much more efficient than sine wave AC, because the fast rate of change of the square wave produces a much faster flex of the piezo element (and hence, more sound).

I hope this has been helpful. As to your specific part, I believe there are about 4 or 5 manufacturers of these little piezo buzzers in Taiwan, and everyone puts their own numbers on and sells them under their own trade name. Can't help you there.

If you're interested in designing one into a project, you just might want to buy one or two. The smaller ones are very inexpensive even in small quantities.

Good luck Chris

does that generate the required Jigga Watts?

--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

130

think

are

These are in small aluminium cans. I bought them years ago in a Dick Smith sale but without any documentation. I think that they are ultrasonic devices of some sort.

Roger

Can you post a picture to news:alt.binaries.schematics.electronic

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Put one on a signal generator with a 1k R in series and sweep it up to

40khz.... the volts across the R will peak at the resonance freq. Or maybe dip. Anyway, look for a maximum or minimum around there.... real helpful, huh?

by your description they sound like ultrasonic transducers, but could be electret microphones etc...

Bye. Jasen

An electret mic will have a kind of 'black felt' on the opposite end from the pins.

Graham

130

think

are

I think that is what they are. Which is which and how do I use them in a circuit?

R

Hi, Roger. Can't help you on the "which is which" side (possibly try DSE?) but here's an older EDN article on a minimum parts count uC-based ultrasonic rangefinder using parts similar to yours:

Look at the second article (p. 2).

Good luck Chris

Hi Roger, Try these links, might be useful for the SCS-401 at least:

Arch