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

Dog stopping: Finding a Piezo buzzer/transducer?

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by DigiTan, Mar 5, 2007.

  1. DigiTan

    DigiTan New Member

    Joined:
    Apr 19, 2004
    Messages:
    797
    Likes:
    3
    Location:
    Dallas. USA
    I'm searching for a very loud and compact piezo buzzer to use for a current project.

    The resonant frequency needs to be in the range of 16kHz to 22kHz, but the only ones I found fitting that description have 106dB @ 30cm sound pressure or lower, and I was hoping for 120dB and up. I checked digikey, mouser, and currently allied but no luck. Does anyone know of a place that specializes in loud, borderline-ultrasonic piezos?
     
  2. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,585
    Likes:
    950
    Location:
    Canada, of course!
    Companies don't make powerful ultrasonic transducers that are only useful for scaring dogs. They make more popular and more important stuff.

    Ultrasonic transducers are fragile so can't operate at high power. Use hundreds of them.
     
  3. DigiTan

    DigiTan New Member

    Joined:
    Apr 19, 2004
    Messages:
    797
    Likes:
    3
    Location:
    Dallas. USA
    You might want let the people who built this one, this one, and this one in on that secret. If a specialized peizo isn't available, I want to try using an audible one outside its resonant frequency. I know it wastes energy, but until I can find a datasheet with the piezo's transfer function I can only guess what the loss is. The search continues..
     
  4. dave

    Dave New Member

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


     
  5. Torben

    Torben Well-Known Member

    Joined:
    Oct 6, 2006
    Messages:
    2,507
    Likes:
    34
    Location:
    B.C., Canada

    Check out the parts lists for some of the sound generator projects from the Evil Genius books: http://www.amazing1.com/evil_genius.htm

    They have some high-power transducers which I believe are made specially for Information Unlimited by Motran, about which I know pretty much nothing else except that they also make high-temperature speakers for use in vehicle engines for sound control.

    The first Evil Genius book actually has plans for some stuff which might work for you out of the box; pain field generators and sonic shock waves etc. I think you can buy the plans, the kit, the kit assembled for you, or the piezo transducer by itself. The piezo I'm looking at is $14.95 US.


    Good luck!

    Torben
     
  6. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,585
    Likes:
    950
    Location:
    Canada, of course!
    Murata make many ultrasonic piezo transducers. A few would scare a dog if they are as close as in the picture. The dog is afraid of being hit with it.

    Years ago, Motorola made a piezo horn tweeter for very bad sounding cheap speakers. I called it "a whistle, not a tweeter". It worked at frequencies up to about 25kHz but the response was all over the place, like a whistle. You could feed one 22kHz and its output would be 11kHz. Weird.
     
  7. chemelec

    chemelec Well-Known Member

    Joined:
    Apr 4, 2004
    Messages:
    2,123
    Likes:
    77
    Location:
    Hedley, B.C. Canada
    You Might try using a Pizo Tweeter, Aimed into a Good Parabloic Dish, thats than Aimed at the Dog.
     
  8. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,585
    Likes:
    950
    Location:
    Canada, of course!
    Ha, ha. It will scare away the parabolic dishes that come to piss on your lawn.
     
  9. on1aag

    on1aag New Member

    Joined:
    Jul 31, 2006
    Messages:
    512
    Likes:
    8
    Dog repeller.

    Why invent something that is already invented. This will stop all
    dogs, cats and other domestic cattle, even annoying neighbours.

    http://www.fnherstal.com/html/Index.htm

    And if this isn't enough they've got bigger ! :D

    on1aag.
     
  10. Sceadwian

    Sceadwian Banned

    Joined:
    Oct 27, 2006
    Messages:
    14,047
    Likes:
    141
    Location:
    Rochester, US
    Every extra transducer you use increases your effective output 3db's doesn't it? Just use 5 of the ones you're looking at. Would allow you to phase steer the signal if you wanted as well.
     
  11. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,585
    Likes:
    950
    Location:
    Canada, of course!
    Two transducers are 3dB louder than one. Four transducers are 3dB louder than two. Eight transducers are 3dB louder than four. So eight transducers are less than double the loudness. Use hundreds of them.

    You must select a frequency that the transducers work well at. How? Ask the dogs.
    You must get to within only 30cm from the dogs because these transducers are wimpy little things.
     
  12. Papabravo

    Papabravo Well-Known Member

    Joined:
    Mar 9, 2006
    Messages:
    2,889
    Likes:
    25
    Location:
    Michigan, USA (GMT-5)
    I have nothing but contempt for a person that would want to do this to an animal. You should be ashamed of yourself.
     
  13. DigiTan

    DigiTan New Member

    Joined:
    Apr 19, 2004
    Messages:
    797
    Likes:
    3
    Location:
    Dallas. USA
    [​IMG]

    Due to size restrictions, I can only use 1 transducer/tweeter. I'll keep the +3db option in mind though. It makes me wonder if I should spring for the $25 on ebay for a complete circuit, pop out the transducer, and just mod the living daylights out of it.

    Murata does sound vaguley familar though and I'm checking out their product line.

    On a similar topic, I'm looking for a super-efficient multivibrator to replace a 555 chip in this one. Preferably a surface-mount device. Is the CMOS equivalent of that chip any good?
     
  14. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,585
    Likes:
    950
    Location:
    Canada, of course!
    An ordinary 555 has a max output current of 200ma. A Cmos 555 can source (output high) only 10mA and can sink (output low) only 50ma.

    An ordinary 555 has a minimum supply voltage of 4.5V. A Cmos 555 is guaranteed to work with a supply voltage as low as 1.5V.

    An ordinary 555 has a supply current of about 3mA at 5V. A Cmos 555 has a supply current of 100ua at 5V.

    The piezo transducer has a fairly high capacitance that will need a fairly high current to charge and discharge at 25kHz.
     
  15. Papabravo

    Papabravo Well-Known Member

    Joined:
    Mar 9, 2006
    Messages:
    2,889
    Likes:
    25
    Location:
    Michigan, USA (GMT-5)
    Yes but I do, and that's the difference between you and me.
     
  16. DigiTan

    DigiTan New Member

    Joined:
    Apr 19, 2004
    Messages:
    797
    Likes:
    3
    Location:
    Dallas. USA
    Aw, well aren't you the little altruist? Unfortunately you're no mod, so BTFU and quit acting like one.

    @audio: I guess 555 CMOS will work then. I have a nice switching PMOS transistor I can use for an inverter on the output. So since the piezo has high capacitance, will I be needing a coil on the output of this inverter?
     
  17. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,585
    Likes:
    950
    Location:
    Canada, of course!
    You don't need a coil to drive a high capacitance piezo, you need a bridge amplifier made with two complimentary pairs of emitter-followers to supply the high charging and discharging currents.
     
  18. DigiTan

    DigiTan New Member

    Joined:
    Apr 19, 2004
    Messages:
    797
    Likes:
    3
    Location:
    Dallas. USA
    Okay, I think I will have room for that. Since distortion won't be a factor, can I use a single emitter-follower stage but with really high gain or will that cause a new problem?
     
  19. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,585
    Likes:
    950
    Location:
    Canada, of course!
    The piezo transducer needs to be driven push-pull. They have a max signal voltage of 24V so a bridge driver could be used with a 12V supply to get about 21V p-p output like this:
     

    Attached Files:

  20. DigiTan

    DigiTan New Member

    Joined:
    Apr 19, 2004
    Messages:
    797
    Likes:
    3
    Location:
    Dallas. USA
    Are there 24 Volts between the "+" symbol and ground or is it like a charge pump situation where I can use 12V? I can can probably start testing this with my 40kHz transducers. In the meantime, I'll just order a circuit off ebay, I can't find a single transducer with the right transfer function.
     
  21. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,585
    Likes:
    950
    Location:
    Canada, of course!
    My circuit has the transducer in a bridge. The bridge nearly doubles the voltage across the transducer. Use a 12V supply because the Cmos IC has 18V max.
     

Share This Page