Piezo Transducers with Feedback Electrodes - Short Circuits 4

[lastfuture]

I accidentally bought one of those piezo transducers when I meant to buy a regular two-pole one and didn't know the difference. I've wired it up to use the metal base plus the small part of the top electrode, the part that you use for feedback. It sounded pretty quiet. Would it sound louder if I used the bigger part of the top electrode instead? and would it sound even louder if I connected both?

[vasuthinkbig]

Nice explanation. Thanks for the video :)

[lotec11]

Also, can you talk about why I might want one of these? Self oscillation ... hmmm ... what can I do with self oscillation as opposed to altering the driver pattern?

[jeriellsworth]

@lotec11 I will try to do this sometime in the future, but I don't have much time for a few months.

[lotec11]

@jeriellsworth thanks!

[lotec11]

Hi Jerri - can you talk a bit about the driver circuitry? Piezoelectric devices typically operate at high voltages right?

[raindogred]

piezoelectric phenomena is fascinating. I started out wanting make a contact guitar pickup then I find that they are used in phones, alarms, seismic, pingers, sonar and of most interest energy harvesting under roads - currently doing this israel. anyone got a good schemo for piezo guitar preamp please pm me

[dubeyanupam]

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[madamerotten]

I really like this video. You gave a great explanation. You may want to correct the erroneous reference to "PNP" transistor at 2:26.

[efiscp]

Good test circuit for piezo, works perfectly.

[chukchee]

Women are the best!  Women rule!

[iorixs]

@chukchee not all women are the best. some women dont have any control over themselves just like a lot of men

[lotec11]

@iorixs rephrase sentence plz

[johnnytheprick]

....women have NO business in science.

[joeteejoetee]

VERY, very well done Jeri. This video was

short, sweet, and succint! Bravo baby!

[chickenmcnoodle]

I play cello in a band, and I've been using the element from a RadioShack piezo buzzer as a pickup. I've been meaning to build an impedance buffer for it, but currently it gives a really hot signal, and is extremely prone to (audio) feedback. Is there some way to use a 3-tap element so that it reduces this feedback buildup? I love playing around with electronics, but I'm lacking in much theory.

These vids are cool little snippets of electronics knowledge. Thanks for putting them together.

[4833504F]

"and how to make two wire piezo transducer to have feedback by cutting the top electrode"

did i miss anything? this would be really interesting.

[jeriellsworth]

I'll have to check. I may have left out that you can cut a triangle in the top electrode and solder a wire to it. The size of the electrode you cut out determines the frequency it likes to resonate at.

[4833504F]

But how could one cut the electrode without damaging the crystal?

[jeriellsworth]

The electrode is very thin. I scratch it with an exacto knife.

There are some guys cutting disk piezo disks for microscopy.

[wbeaty]

It's not really crystal. It's piezo-ceramic, barium titanate long ago, but nowdays always Lead Zirconate Titanate (PZT).

Piezoceramic is barium titanate, while "Piezo crystal" would be quartz.

For playing with such things, a great source for large thick cheap and high-power piezo transducers is "Ultrasonic Stain Remover" from Harbor Freight Tools, $10 each right now (being discontinued, I think.) A similar transducer on eBay ("piezo store") goes for forty bucks!

[tttuberc]

Thanks for posting this informative video. Looks like you have a lots of interesting videos. I've used these self driven piezo a lot, kind of knew how it would work, but never look at them closely to see what goes inside. I was trying to modify one of these to operate at lower voltage, but that didn't come out well.

[wbeaty]

> I was trying to modify one of these to operate at lower voltage

We need some way to create the necessary large voltages. Traditionally they add an enormous inductor in series, with RLC resonance equal to piezo res. (So series resonance converts high current into high voltage.) That might work fine at 50KHz, but not at 2KHz.

Perhaps a piezo-disk "electrostatic transformer?" Slice the disk into 2 unequal electrodes. Drive one at resonance. Large voltage appears on the other electrode!

[Afrotechmods]

Your videos are awesome because you talk about parts that most people haven't got experience with. Did you know that the Roomba uses a piezo disc as a dirt sensor? When vacuumed particles hit it, a voltage is generated that they measure.

[jeriellsworth]

Thanks. My goal is to do uncommon circuits when possible.

I didn't know that about the Roomba. Wonder what other application this can be used for.

[wbeaty]

Someone sells a "piezo motor" prototyping kit, where the "motor" is a plastic wheel with a vibrating piezo rod pushed against it. I guess the rod's sharp edge pushes on the wheel when it expands, but can't pull as it contracts again.

I've had visions of making tiny robots with piezo-disk vibrated angled whiskers (steerable bristlebots with high-tech active bristles!)

But google shows a few old grad-student projects where people have been building exactly that. Rats! Already Been Done!