Piezo Tweeters - diyAudio
Go Back   Home > Forums > General Interest > Everything Else

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 13th August 2002, 04:58 PM   #1
subwo1 is offline subwo1  United States
diyAudio Member
 
subwo1's Avatar
 
Join Date: Jan 2002
Location: North American Continent
Default Piezo Tweeters

Hi Everyone. I thought I would get some opinions on a project I am
working on. I am working on an ultrasonic varmint repeller to discourage
cats, racoons, oppossums, etc. and am not sure how loud I
can make it before blowing the tweeters. I remember a rather universally
characteristic figure of around 28 VRMS.

I think I could drive one at a few hundred watts if I had a transducer
that could withstand it. however, I don't want to run up my power bill,
and I want to maintain simplicity, so I don't want to bother with a
proximity detector. The present version runs on a standard 120 VAC timer
set to run dusk to dawn.

Therefore, I am considering driving it with only around 40 volts peak to
peak, but tuning the physical sonic area around the piezo element so
that it can resonate somewhere around 17 or 20 Kilohertz.

So the main thing I am wondering about is whether peaking the output for
a certain frequency will physically damage the piezo element inside the
tweeter. If the effect is anything like a cone speaker in a speaker box,
then my impression is there should be no problem. Howerver, the piezo
element is a crystaline structure, and I suspect that it may crack.
Thanks in advance, everyone.
  Reply With Quote
Old 16th August 2002, 11:54 AM   #2
alfsch is offline alfsch  Germany
diyAudio Member
 
Join Date: Jan 2002
Location: augsburg
Hi,
the piezo has high impedanze, so you need not much power to drive , but i ve seen some cracks in heavy used piezos...but you should take them, because theres nothing cheaper, i think, to make high sound pressure at >20kHz.
greetings
alf
  Reply With Quote
Old 16th August 2002, 12:11 PM   #3
diyAudio Member
 
Circlotron's Avatar
 
Join Date: Jun 2002
Location: Melbourne, Australia
Since the tweeter will appear predominantly capacitive, you could try putting a suitable value inductor in series with the tweeter and driving it from a pair of mosfets in a half-bridge configuration. Use a square wave drive - the LC combination will turn it into quite a reasonable sinewave. Start with 10v p/p squarewave. Monitor the sinewave voltage across the tweeter with a scope and start from above resonance and work downward till you get the the required amount of voltage drive across it as you tune up the resonant slope. (i.e. decreasing frequency) If you run above the LC resonant frequency it will enable the mosfets to soft-switch but that's not really an issue at these power levels, just nice to have if all it needs is a stroke of the pen. You can put extra capacitance across the tweeter if you need to for the sake of tuning. Use a polypropylene (FKP or MKP) or polycarbonate (FKC or MKC) rather than a more lossy polyester (FKS or MKS) for both the series resonant cap and the tweeter shunt cap.

GP.
  Reply With Quote
Old 16th August 2002, 09:58 PM   #4
tiroth is offline tiroth  United States
diyAudio Member
 
Join Date: Dec 2001
Location: Pittsburgh, PA, USA
Default Re: Piezo Tweeters

Quote:
Originally posted by subwo1
Therefore, I am considering driving it with only around 40 volts peak to
peak, but tuning the physical sonic area around the piezo element so
that it can resonate somewhere around 17 or 20 Kilohertz.
Man, that would also be an effective me-repeller.
  Reply With Quote
Old 17th August 2002, 03:19 PM   #5
diyAudio Member
 
Bill Fitzpatrick's Avatar
 
Join Date: Jun 2001
Location: Eugene, OR
It's my understanding that ultrasonic varmit repellers don't work.

You might want to do an internet search on the subject before you waste a lot of your time.
  Reply With Quote
Old 17th August 2002, 04:59 PM   #6
subwo1 is offline subwo1  United States
diyAudio Member
 
subwo1's Avatar
 
Join Date: Jan 2002
Location: North American Continent
Bill,
so far, it appears to be helping some.

tiroth,
sorry.

Circlotron.
that soft switching explains why a switching power supply I am working on keeps the mosfets cooler.


alfsch,
makes sense.
  Reply With Quote
Old 23rd August 2002, 12:46 AM   #7
diyAudio Member
 
Join Date: Apr 2002
Ultrasonic repellers that uses peizo speakers don't work because they are directional. The best way is use an inductor and oscillating it.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
How do these piezo tweeters work? Datinker Multi-Way 48 5th August 2013 08:05 PM
How well do piezo tweeters do skooter Car Audio 2 2nd September 2008 10:05 PM
Piezo vs electromechanical tweeters polsol Multi-Way 50 6th June 2006 10:07 PM
Using piezo tweeters Rory Multi-Way 15 6th November 2001 09:46 PM


New To Site? Need Help?

All times are GMT. The time now is 10:23 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2