1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

High Frequency Kid Repellent

Discussion in 'Members Lounge' started by Analog, Feb 13, 2008.

  1. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,449
    Likes:
    937
    Location:
    Canada, of course!
    ONLINE
    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.
     
  2. HerbertMunch

    HerbertMunch New Member

    Joined:
    Aug 11, 2007
    Messages:
    285
    Likes:
    0
    Location:
    England
    where would you find a piezo that would resonate happily(and loudly) at 20kHZ?
     
  3. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,449
    Likes:
    937
    Location:
    Canada, of course!
    ONLINE
    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:
     

    Attached Files:

  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. HerbertMunch

    HerbertMunch New Member

    Joined:
    Aug 11, 2007
    Messages:
    285
    Likes:
    0
    Location:
    England

    nice one cheers mate.
     
  6. Hero999

    Hero999 Banned

    Joined:
    Apr 6, 2006
    Messages:
    14,902
    Likes:
    79
    Location:
    England
    20kHz is still audio for young people but it's ultrasonic for older people.
     
  7. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,449
    Likes:
    937
    Location:
    Canada, of course!
    ONLINE
    3kHz is ultrasonic for some old people. That is why they like AM radio.
     
  8. shokjok

    shokjok Member

    Joined:
    May 14, 2008
    Messages:
    452
    Likes:
    3
    Location:
    Alberta, Canada
    Isn't classical music, or the threat of boot camp, an effective kid deterrent?
     
  9. Thunderchild

    Thunderchild New Member

    Joined:
    Jul 3, 2005
    Messages:
    2,294
    Likes:
    9
    Location:
    UK
    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 ?
     
  10. shokjok

    shokjok Member

    Joined:
    May 14, 2008
    Messages:
    452
    Likes:
    3
    Location:
    Alberta, Canada
    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.
     
    Last edited: Jun 28, 2008
  11. Juan

    Juan New Member

    Joined:
    Nov 1, 2008
    Messages:
    2
    Likes:
    1
    Location:
    Australia Land of the Hitler youth
    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.
     
    Last edited: Nov 1, 2008
    • Like Like x 1
  12. HarveyH42

    HarveyH42 Banned

    Joined:
    Feb 25, 2006
    Messages:
    3,442
    Likes:
    18
    Location:
    Not Here
    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.
     

    Attached Files:

    • 555.jpg
      555.jpg
      File size:
      89.3 KB
      Views:
      587
  13. Papabravo

    Papabravo Well-Known Member

    Joined:
    Mar 9, 2006
    Messages:
    2,889
    Likes:
    25
    Location:
    Michigan, USA (GMT-5)
    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.
     
  14. shokjok

    shokjok Member

    Joined:
    May 14, 2008
    Messages:
    452
    Likes:
    3
    Location:
    Alberta, Canada
    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!
     
  15. HarveyH42

    HarveyH42 Banned

    Joined:
    Feb 25, 2006
    Messages:
    3,442
    Likes:
    18
    Location:
    Not Here
    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.
     
  16. Leftyretro

    Leftyretro New Member

    Joined:
    Mar 11, 2007
    Messages:
    1,420
    Likes:
    13
    Location:
    Hercules, California
    Take that and get off my lawn.... ;)
     
  17. Juan

    Juan New Member

    Joined:
    Nov 1, 2008
    Messages:
    2
    Likes:
    1
    Location:
    Australia Land of the Hitler youth
    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 .
     
    Last edited: Nov 5, 2008
  18. Mike Jobe

    Mike Jobe New Member

    Joined:
    Jan 30, 2016
    Messages:
    19
    Likes:
    0
    Can anyone suggest a kit??
     
  19. Ian Rogers

    Ian Rogers Super Moderator Most Helpful Member

    Joined:
    Mar 28, 2011
    Messages:
    9,170
    Likes:
    910
    Location:
    Rochdale UK
    9 year old thread.... Only AG left I'm afraid... I doubt anyone will answer....
     
  20. cowboybob

    cowboybob Well-Known Member Most Helpful Member

    Joined:
    Oct 22, 2011
    Messages:
    3,026
    Likes:
    477
    Location:
    James Island, SC
    MJ,

    Kit here.

    DIY here. (Haven't built it myself - schematic is poor...)
     
    • Like Like x 1
  21. Mike Jobe

    Mike Jobe New Member

    Joined:
    Jan 30, 2016
    Messages:
    19
    Likes:
    0
    Thank you for the link!!...Mike Jobe
     

Share This Page