High frequency 25-45kHz sound generator circuit, where to buy ready made?

[harvestmouse]

Hello All. First post here. Forgive me if it's in the wrong place. My knowledge of electronics can be written on the back of a stamp.

I have a project in mind. Need to generate sound between 25 and 45kHz. Variable DC voltage, say 3-15v (if my understanding of Piezo is correct in that if you want it louder, you give it more volts). I can sort out the power at one end and the Piezo buzzers at the other end, but I need to buy the middle bit.

Where can I get (in Europe) the required circuitry ready made? Doesn't have to be in a case, just with nothing to solder.

Thanks in advance. I can rewire a house and mig-weld cars, but you can see what's going on there, unlike electronics.

 

[harvestmouse]

Try what I have? I don't have anything yet, on account of not knowing what to buy.

The long range aspect is the most important, to avoid having to rely on batteries. This would have to be on a DC adaptor from a plug in the house.

 

[Nigel Goodwin]

Sorry, I thought you'd got something? - I see looking back it was from Amazon and you returned it.

However, if that didn't work at short range, why would you think something more powerful would at a longer range?.

Don't forget, the inverse square law applies as well - you need ten times as much power to get twice the range - and I suspect losses at high frequencies would make that even worse.

 

[harvestmouse]

I thought that it didn't work because it was cheap Chin*se rubbish built down to a price and that its power would be limited by the unit's cheap small power source.

Ref DC voltage, I was reading about someone who claims to have used a dc-dc step up convertor, which increased the voltage to 35v dc, to boost a piezo signal. It may well have worked for a lower frequency. The person described it as deafening, which suggests even to me that it wasn't 25kHz.

 

[Nigel Goodwin]

I thought that it didn't work because it was cheap Chin*se rubbish built down to a price and that its power would be limited by the unit's cheap small power source.

Power would be limited, but I suspect it's more likely that the whole idea doesn't work - you never hear of anyone who has had one working.

But assuming it was 1W output, and didn't work at 6 feet, then a 10W output device wouldn't work at 12 feet, and a 100W device wouldn't work at 24 feet. Also assuming, of course, that any such device would work anyway.

Ref DC voltage, I was reading about someone who claims to have used a dc-dc step up convertor, which increased the voltage to 35v dc, to boost a piezo signal. It may well have worked for a lower frequency. The person described it as deafening, which suggests even to me that it wasn't 25kHz.

Obviously not

 

[harvestmouse]

Some reviews on Amazon claim that some ultrasonic devices work, hence my hope that it might be possible.

 

[Nigel Goodwin]

Some reviews on Amazon claim that some ultrasonic devices work, hence my hope that it might be possible.

What percentage?, and how many of them are honest reviews by purchasers, and not just spoof reviews by the sellers.

Why not buy one that has 'some' positive reviews?.

 

[harvestmouse]

Point 1: I completely agree. Can't be sure who left the reviews.

Point 2: I did buy one that had some positive reviews. That's why I bought it. It was the one I sent back.

To return to the start menu, press 0.....

 

[harvestmouse]

I'm still happy to try to build something that might work. Might try with the MO48N (12-15v dc) . Could it run more than one buzzer and if so would there be an advantage to doing so?

The advice of Mr Goodwin, for which I am grateful, does contain what appears to be conflicting info in that

"you never hear of anyone who has had one working" and

"Why not buy one that has 'some' positive reviews?.

I have someone who can make the timer circuit (555) but I wanted to see if the sound part worked first.

Thanks to all so far, I have already learned some things.

 

[Nigel Goodwin]

I'm still happy to try to build something that might work. Might try with the MO48N (12-15v dc) . Could it run more than one buzzer and if so would there be an advantage to doing so?

The advice of Mr Goodwin, for which I am grateful, does contain what appears to be conflicting info in that

"you never hear of anyone who has had one working" and

"Why not buy one that has 'some' positive reviews?.

Not really, I was suggesting that the reviews are less than honest - and presumably the one you tried had some positive reviews? - which rather proves the point.

I have someone who can make the timer circuit (555) but I wanted to see if the sound part worked first.

Thanks to all so far, I have already learned some things.

Well disregarding the issue that the whole premise probably doesn't work, then your first snag is finding high power HF transducers, that will project a fairly narrow beam to try and get a decent range. I don't know of any?, or even where to look?.

'If' you can source something suitable, then it's a question of a high power, high frequency, amplifier - which should be fairly easy to do by modifying the HF filtering used to restrict high frequencies to the audio range. I would also suggest a sinewave, rather than a nasty 555 signal.

 

[harvestmouse]

What, does anyone know, is the highest frequency that could travel 25 metres and sound loud when it gets there?

 

[Nigel Goodwin]

What, does anyone know, is the highest frequency that could travel 25 metres and sound loud when it gets there?

It's rather difficult to know, because you can't hear it.

 

[rjenkinsgb]

What, does anyone know, is the highest frequency that could travel 25 metres and sound loud when it gets there?

It very much depends how well it's focussed.

As I mentioned earlier, a parabolic reflector good for ultrasonic signals. The short wavelength means a smallish dish can have quite high gain and be extremely directional.

 

[harvestmouse]

Am researching parabolic reflectors. It's quite confusing with lots of references to microphones or medical stuff. Unless someone has a link to the right one, for sale, ready to connect, I'll keep researching.

 

[rjenkinsgb]

Am researching parabolic reflectors. It's quite confusing with lots of references to microphones

Anything that will work for a microphone should also work for ultrasonics, as long as the parabola is accurate enough.

In fact, the best way I can think of to find the correct focus is to the a microphone and find the point that gives the best audio from a distant source. It's like the reflector is pretty much the same between some types of spotlights and telescopes.

 

[harvestmouse]

The Inverse Square law has convinced me why this wouldn't work, at least not with 25kHz and above, at the required distance. Bin that one.

I have been reading about Long Range Acoustic Devices, used for civilian crowd control and against approaching pirates. These do work, but aren't as easy to buy on Amazon, nor has the manufacturer been good enough to post a circuit diagram online.

 

[harvestmouse]

Hello again. Not given up hope, even if not much progress made yet. Although I have learned things, so it has been worthwhile.

A product called Dog Silencer Max  claims to work on a dog 90 metres away.

Does anyone here know what's in the box? And if it really works?

 

[Nigel Goodwin]

The Inverse Square law has convinced me why this wouldn't work, at least not with 25kHz and above, at the required distance. Bin that one.

I have been reading about Long Range Acoustic Devices, used for civilian crowd control and against approaching pirates. These do work, but aren't as easy to buy on Amazon, nor has the manufacturer been good enough to post a circuit diagram online.

As far as I'm aware those use extremely LOW frequencies, and very high powers.

 

[harvestmouse]

Am not planning on buying a Dog Silencer Max, but would be interested to know how / if it works.

Back to my original plan..... How about just the dog bark detector circuit ?

There are a few designs here:

How to Make Dog Barking Preventer Circuit using High Frequency Deterance | Homemade Circuit Projects

The discussed circuit is designed to discourage dogs from barking in the selected zone by the generation of a synchronized ultrasonic sound waves in response to a few initial barking […]

www.homemade-circuits.com

Does anyone have a design of their own?

 

[audioguru]

What brains are inside a "dog bark detector" to prevent it from detecting any noise like people laughing, a motor cycle or an ambulance siren??

You found a circuit that plays ultrasonic frequencies into "a speaker". Most speakers do not work at ultrasonic frequencies and the DC in it from the circuit might mute the speaker anyway.

 

[harvestmouse]

I'd still be interested to know how the D.S.Max functions, if anyone knows.