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

harvestmouse

New Member
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

New Member
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

Super Moderator
Most Helpful Member
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

New Member
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

Super Moderator
Most Helpful Member
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 :D
 

harvestmouse

New Member
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

New Member
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

Super Moderator
Most Helpful Member
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.
 

rjenkinsgb

Well-Known Member
Most Helpful Member
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

New Member
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

Well-Known Member
Most Helpful Member
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

New Member
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

New Member
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

Super Moderator
Most Helpful Member
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

New Member
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:


Does anyone have a design of their own?
 

audioguru

Well-Known Member
Most Helpful Member
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.
 

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