piezo transducer; polarity; current

Rated Voltage (Vp-p) Max 30 Current Consumption (mA) Max. 10 @10Vp-p, square wave, 4.8Hz

and it has two leads: one black and one red.

I was wondering whether it would work in a double-555 multivibrator (powered by a 9V battery) described as having push-pull output, and it does (I think I had some resistance in series just to be careful). So I wondered whether the implied polarity in the lead colors was significant.

AFAICT from trying it turned both ways in a single-555 multivibrator (between the ground and 9V square wave output), I suspect it isn't actually polarized. Comments?

Also, does the specification mean that the actual current when you apply 10Vp-p voltage is 10 mA, so (unlike LEDs, for example) it doesn't need any protective series resistance at that voltage?

(I have 5 of these and they were cheap, so I don't mind burning a couple out for educational purposes.)

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Reply to
Adam Funk
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Piezo ceramics are poled, i.e. formed at high temperature with a large bias voltage. That's the piezoelectric/pyroelectric equivalent of rubbing a magnet against a screwdriver to magnetize it.

Leaving them with a DC bias in the direction opposite to their poling can eventually depole them, so many of them have polarity marked.

Cheers

Phil Hobbs

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Reply to
Phil Hobbs

"Adam Funk"

** Beep, beep beep beep .....
Reply to
Phil Allison

is it this one?

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another reason to colour the leads is that if you have two and want the both to be in phase you can match the leads up

Phil H says thet y can be damaged by prolonged exposue to reverse polarity. Phil A seems to have the part confused with a different part.

that's right. it doesn't need any. these devices behave like lossy capacitors each time they get a voltage change they will only accept a small amount of charge

with the 556 you can make a louder noise by using a bridged configuration:

. . . . . . . . .O . . . [. . . .]--+ . . | . . | +--------[. .] | C1 | . . | || | . . | +--||--+ [. 556 .]-----+ | || | . . | | | | . . | | | +-----------[. .] | | | | | . . | | | | +-[R1]-+ . . | +----- | | | +-[. .]--+ | | | | | . . | | to piezo | | | | . . | | | | +------|-[. .]----------- | | | . . | | | | | . . | | +---------------[. .]--|--+ | | | . . | | | | | . . . . . . . . | | | | | | | | | +--------------------|--+ | | | o o------------------------------+ - + 9V battery

or you can produce a varying tone by driving the CV pin of the cecond astable from the first.

+---------------------------------. | | |+ . . . . . . . . | ===== .O . . . | | C1 [. . . .]---+ | | . . | | | . . | | +--------[. .] | | | . . | | | . . | | | [. 556 .]-----+ | | . . | | | | . . | | | +-----------[. .]--------+ | | . . | | | | . . | | | +--[R1]--[. .]--+ | | | . . | | | | . . | | | +--------[. .]--------------+ | . . | | | | . . | | | +---------------[. .]--|--+-+-[R2]-+--- + | | . . | | | | . . . . . . . . | ===== to piezo | | | C2 | | +------------------------------+ +----------- | | | +---------------------------------------+ | | o o - + 9V battery R1 47K C1 10uF R2 3.3K C2 10nF

I expect that will make a horrible racket.

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Reply to
Jasen Betts

It's a passive ceramic on metal transducer and it's "poled" rather than polarized.

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http://www.morganelectroceramics.com/resources/piezo-ceramic-tutorials/piezoelectric-actions/
Reply to
John Fields

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http://www.kingstate.com.tw/eng/Products/Products/ProductItem/tabid/186/rtab/187/Default.aspx?ItemId=22
Reply to
John Fields

"John Fields" "Phil Allison"

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** See the OP's post.

" Current Consumption (mA) Max. 10 @10Vp-p, square wave, 4.8Hz "

That error PLUS the pic and description fitted an electronic buzzer.

.... Phil

Reply to
Phil Allison

I think so. The data sheet I have is only in English and just has the information corresponding to parts B, C, & D in that example.

Oh, that's given me an interesting idea to play with.

Thanks for the other information and suggestions!

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Reply to
Adam Funk

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Interesting, thanks.

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Reply to
Adam Funk

The piezo stages that I worked with were rated for about ten times more voltage in the + direction than - -- it was something like +200, -30, but I can't remember back that far to know the specific voltages.

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Reply to
Tim Wescott

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This shows their line of piezo active and passive devices:

http://www.kingstate.com.tw/eng/Products/Products/SubCatalogType/tabid/185/CatSubTypeId/21/rtab/184/Default.aspx
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Reply to
John Fields

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I disagree since, from the link above, an electrostatic capacitance
spec. would only be meaningful for a device with a passive piezo
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Reply to
John Fields

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Yes, I'm sure that's the one. For some reason the data sheet from RS calls it "KPE-163" without the "G".

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Reply to
Adam Funk

"John Fields" "Phil Allison"

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** Irrelevant.

Your link was not available to me.

I found a pic and an ambiguous description.

Did you SEE the error in the OP's post at all ??

..... Phil

Reply to
Phil Allison

What was my error? (The RS website calls it a "Piezo electric transducer", and the specs were all copied & pasted from the data sheet.)

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Reply to
Adam Funk

There's a difference in the specs between the datasheet at the link John Fields posted and the spec you posted: Your post says "square wave, 4.8Hz" Datasheet says "square wave, 4.8KHz"

Ed

Reply to
ehsjr

Oops, I just checked the PDF I have from RS, and it must just be a scan: the text is not copy-and-pastable.

Aha, that's my typing error; the PDF I have does actually say "4.8KHz". You're right.

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Reply to
Adam Funk

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