High Frequency Kid Repellent

[audioguru]

A big fan can make infra-sonic waves to blow birds off a roof. Just make the fan go forwards then backwards then forwards again then backwards again over and over.

 

[HerbertMunch]

where would you find a piezo that would resonate happily(and loudly) at 20kHZ?

 

[audioguru]

where would you find a piezo that would resonate happily(and loudly) at 20kHZ?

20kHz is still audio. Ultrasonic piezo transducers operate at 40kHz and have a flat wide frequency response.

Audio piezo transducers have their ouput level all over the place at different resonating frequencies. If your oscillator is slightly off frequency then the output is in a low level notch instead of a high level resonance.

Here is the frequency response of a typical piezo transducer and a typical piezo high power horn tweeter:

 

[HerbertMunch]

nice one cheers mate.

 

[Hero999]

20kHz is still audio for young people but it's ultrasonic for older people.

 

[audioguru]

3kHz is ultrasonic for some old people. That is why they like AM radio.

 

[shokjok]

Isn't classical music, or the threat of boot camp, an effective kid deterrent?

 

[Thunderchild]

Isn't classical music, or the threat of boot camp, an effective kid deterrent?

thats a very good idea yobs hate good music and I like it where as we both hate that horrible noise those things make. is it my fault my hearing at 25 is as good as the hearing of a 25 year old yob and I have to puit up with it ?

 

[shokjok]

Classical music played by artists whose names they cannot pronounce! Profanity is non-existent, no reference to evils that they openly worship ( sex, drugs, money, partying).
Making the local area look uninviting may also work.

 

[Juan]

Take an astable 555 timer tuned for 18kHz and connect it to a piezo tweeter.

I don't really agree with the use of child repellers because they'll cause problems for people with good hearing and for dogs and cats. I also think that children should have the right to be on the street.

Also there's nothing stopping them getting ear plugs or a ghetto blaster that pumps out a loud enough bass line to cancel out the near ultrasonic tone.

My first post on this forum and maybe my last.
Could you post a circuit with all values as I am in desperate need of such a device. I am a disabled person and I am being harrased by kids.
They are breaking my windows and vandalising my property. They know I can't go after them. The Police will do nothing as they are all underage and only caution them. I can't aford the commercial unit as I am on a pension.
I had some electronics experience in the forces so I think I can make it but I need the circuit information. Please help.
To the people who say they should be banned well you would soon change your tune if this was happening to you . Please help.

 

[HarveyH42]

Did a quick design. Search for '555 Wizard', you should find a bunch.

Usually, I mess around until I find standard values. You can use trim pots to fine tune, or experiment with higher/lower frequencies.

This is an old thread (last summer). I thought it was interesting, and some of the comments and opinions amusing. Anyway, I built something similar a few years ago to scare off cats. The circuit posted is just for a constant 18k 50% duty cycle square wave. My has 2 timers and only gives short bursts ever 10 seconds or so. 555 timers are very temperature sensitive, and drift quite a bit. Mine ranges from just a click from the speaker (actually over 20k signal), to an audible tone. Not very effective on cats, but leave it running anyway.

The output isn't too bad at 12 volts, but you might want to amplify it some.

It's only a minor annoyance, might not bother anyone enough to make much difference, as with the cats. Doubt it's going to damage anyone's hearing, or be a huge problem for the neighbors. The sound doesn't carry that far.

 

[Papabravo]

It probably won't work so don't get your hopes up. My advice is to get yourself a varmint rifle and wing one of the little miscreants. You can say he looked like a hedgehog.

 

[shokjok]

If audio doesn't work, try graphic mural images of crashes, war, famine or misery. These misfits may get the message that their chosen neighborhood is unappealing, encouraging them to move on to other areas or GET A LIFE!

 

[HarveyH42]

A security camera (real or simulated) is usually a great deterrent. Nobody wants to be acting like a fool on camera, and have no control over who watches it. Might end up on the evening news, youtube, or might be good enough evidence for a judge to lock them up, or reward damages. For me, I have the real deal, one in my carport, one one the back porch, and one in my living room. Just got a awesome DVR/switcher, slightly used/abused, but fully functional. Recording 24/7, and motion events.

 

[Leftyretro]

Take that and get off my lawn....

 

[Juan]

Sorry for the slow reply I have been so stressed that my Doctor put me in hospital for a few days.
Thanks for the efforts but none of the replys realy helps. I need a simple but complete circuit . I am not experienced enough to substitute too much.
I will keep saving for some cameras though.
In this twisted screwed up country they don't even lock a kid up for murder and they don't award damages against a kid because they will not charge them in the first place. I think they have to be over 10 before they will do anything at all which is usually only for murder and vicious assualts.
What is needed is laws to make parents more liable for some of their kids actions which are clearly a result of lack of proper parental control .

 

[Mike Jobe]

Can anyone suggest a kit??

 

[Ian Rogers]

9 year old thread.... Only AG left I'm afraid... I doubt anyone will answer....

 

[cowboybob]

MJ,

Kit here.

DIY here. (Haven't built it myself - schematic is poor...)

 

[Mike Jobe]

Thank you for the link!!...Mike Jobe