need a quick ultrasonic noisemaker

The speaker will have the final say on what frequencies you get from this. This is a generally bad design if you are using a conventional (voice coil and magnet) speaker, since it applies DC to it and tends to move its voice coil out of the proper centered position.

But that's immaterial here, since you will have a hard time finding a conventional speaker with much ultrasonic output. Special tweeters are available, but they are not cheap.

You could look into piezo tweeters, which are not only cheap, but are usually used with a DC blocking cap anyway... and some do go to the ultrasonic range. The problem is getting enough power for your purpose. (Actually, the first problem is getting a data sheet that even mentions the power output and has a frequency response plot!)

You could see if there are pre-tuned piezo oscillators for this type of use. But I think this is going to be a lot tougher job than you think. For one thing, how will you know how much (if any) ultrasonic sound you are getting from your gadget? If you thought ultrasonic speakers were expensive, ultrasonic mics are in the $1000+ range!

Best regards,

Bob Masta DAQARTA v4.51 Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Sound Level Meter FREE Signal Generator Science with your sound card!

+1 on the piezo, and use a reflector to direct the sound in the general direction you want. Use a wok or something. A parabola's focus lies halfway between its apex and the center of curvature at the apex. So if you use a spherical surface to approximate a parabolic reflector, put the piezo halfway between the center of the sphere and its surface. You don't want a super tight focus. You can spread the beam by moving the piezo in or out a little bit. You can also put it off to the side, like they do with tv receiving dishes.

The 6.5" car speaker I've got (actually, I've got two) has tweeters on- board. $20 from Wal-Mart, IIRC. It's pretty much surplus anyway - unless I can finish building a 10W amplifier... :D

If the dog shuts up, I guess it's enough power.

I thought 12V would be an improvement over this, which according to the comments, uses a single 9V battery:

Thanks,

Michael

The 6.5" car speaker I've got (actually, I've got two) has tweeters on- board. $20 from Wal-Mart, IIRC. It's pretty much surplus anyway - unless I can finish building a 10W amplifier... :D

If the dog shuts up, I guess it's enough power.

I thought 12V would be an improvement over this, which according to the comments, uses a single 9V battery:

Thanks,

Michael

Here is a link to the device your looking for :

use a 2N3055 transistor instead of the D40D5 since they're hard to get ahold of and use 12 volts. The inductor needs to be a big one to handle the current. use a horn piezo instead of the small one in the article.

Shaun

.com/media/pdf/1281.pdf

old

Thanks. I'll study that circuit. Two inductors, huh?

Did you buy the kit? I was looking for an embedded magazine title but didn't see one.

Michael

Thanks. I'll study that circuit. Two inductors, huh?

Did you buy the kit? I was looking for an embedded magazine title but didn't see one.

Michael

I didn't buy the kit, just built it from a book "Build you own laser phaser ion ray gun" many years ago. You should know that using one of these will affect you too, even though it's pointed away from you, so use with caution!

BTW: the inductor closest to the transistor is a small transformer, I think it 8 ohm to 1000 Ohm impedance matching transformer. You used to be able to get them from Radio Shack.

Shaun

That range is audio. Go for about 40kHz.

Think about an ultrasonic dog whistle and then figure out how you are going to blow air through it. That might be easier.

R

In a bit of a hurry at the moment, so no C, R1

What I have usually heard for getting attention of dogs is 25 KHz, not

1. You want the frequency to be barely too high to be audible to humans.

Meanwhile, I would try one of those piezoelectric type loudspeakers rather than a 4 ohm one. The piezoelectric ones usually do well at 25 KHz or even higher, preferably the ones smaller than the larger 2.5 by 6.5 inch or whatever horn one. Loudspeakers with voice coils tend to not do as well at frequencies that high, even if they are tweeters. And I have found small fullrange loudspeakers such as 2.25 inch "transistor radio" ones to do poorly even in upper audio frequencies.

A piezoelectric loudspeaker is a primarily capacitive load, and you should have a 10 ohm resistor in parallel with it to discharge its series capacitance if you use the above circuit.

- Don Klipstein ( snipped-for-privacy@misty.com)

Don,

If you put a 10 ohm resistor in parallel with the piezo tweeter you'll use up all the available energy and waste it in heat. If you've followed with thread, I posted a link to a schematic that uses series / parallel resonance (using inductors) with the piezo to amplify the voltage across it. A 10 Ohm resistor would kill the resonance. Try following the thread completely.

Shaun

Sorry, I do not have fullest monitoring of threads here, because I have to spend a lot of time working for a living.

Meanwhile, I think so far here that I have done a goodly 75%-plus attribution for my comment here in this thread, and I need help to see how I failed to mention you.

Can you help me out here?

- Don Klipstein ( snipped-for-privacy@misty.com)

Your English is very poor, is English your second language? or are you just stupid? I can't understand what you're trying to say.

Shaun

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I finally found a piezo element from a door alarm from the 99 Cent store. Took it apart, and it looks like this one:

/APS4812B-LW100-R.pdf

Are those specs typical?

I'm wondering if I can wind my own 500 uH inductor L1 using the inductor design equation.

Would a TIP31A work, or must I use a 2N3055?

Thanks,

Michael

I finally found a piezo element from a door alarm from the 99 Cent store. Took it apart, and it looks like this one:

Are those specs typical?

I'm wondering if I can wind my own 500 uH inductor L1 using the inductor design equation.

Would a TIP31A work, or must I use a 2N3055?

Thanks,

Michael

I don't think that piezo speaker will work. The one's I used I could buy from radio shack in there car audio or home audio section. Or another place I found (which has gone out of business) was an electronics supply store that had car audio stuff (speakers). These piezo speakers are meant to replace the tweeter with a speaker that can reproduce really high frequencies.

do a google search for "motorola piezo tweeter" it comes up with several. One place to buy them is ebay.

then 500 uH inductors could be hand wound, but that's allot of winding or buy them from a store that sells speaker parts, they're used in crossovers.

The transistor......... I don't know if it will work.

Shaun