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Ultrasonic Metronome, or rangefinder transmitter

Discussion in 'General Electronics Discussion' started by Ext1jdh, Nov 15, 2015.

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  1. Ext1jdh

    Ext1jdh

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    Nov 15, 2015
    I'm looking to make a circuit that will produce a regular ultrasonic ping. I'm thinking that a 555 metronome circuit would be a good base for this, but would I be able to tune an ultrasonic transducer to 20khz?
     
  2. dorke

    dorke

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    Jun 20, 2015
    Which transducer do you have?
    post it's datasheet please .

    .
     
  3. Ext1jdh

    Ext1jdh

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    Nov 15, 2015
    I have no components yet.
     
  4. Alec_t

    Alec_t

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    Jul 7, 2015
    Readily-available transducers generally operate at around 40kHz. For maximum efficiency it is better to let the transducer dictate (control) the operating frequency, rather than try to force it to vibrate at some frequency you determine. Try googling 'self-resonant ultrasonic' for a suitable circuit which can be gated on/off to give pulsed ultrasonic signals.
     
    hevans1944 likes this.
  5. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    Some Polaroid cameras had ultrasonic range finders that were used to adjust the camera focus for nearby objects. If you can find one on Ebay it could be a useful reverse-engineering experience. Radio Shack sells ultrasonic range finders, and they are also available on Amazon, but distance is limited to about thirteen feet.

    What is your intended application?

    As @Alec_t said, most ultrasonic transducers are mechanically resonant and must be used at their resonant frequency to be efficient. This caveat applies mainly to the receiving transducer, since pulsing the transmitter transducer will be equivalent to "ringing a bell". It would be difficult to pulse the transmitter at its resonant frequency without some feedback mechanism to ensure each pulse adds to the "ringing" instead of destructively interfering with it.
     
  6. Ext1jdh

    Ext1jdh

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    Nov 15, 2015
    intended application is a strange one - my dog recently went blind and I'm looking into the options to create an echolocation device for her. There's an existing one out there at jordycanid.com, but it's $600.

    Basically, it sends an ultrasonic ping somewhere around 20khz about once every 3/4 or 1 second. The dog uses her ears to do the echolocating on her own. So it's basically half of an ultrasonic rangefinder.
     
  7. AnalogKid

    AnalogKid

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    Jun 10, 2015
    So two astable multivibrators, or oscillators. One slow, and it gates the fast one briefly. Two CMOS 555's will do this, or a CD4093 or CD40106, etc. First thing is to decide on the transducer. Everything flows from that.

    aj
     
  8. Ext1jdh

    Ext1jdh

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    Nov 15, 2015
    I'm open to recommendations
     
  9. dorke

    dorke

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    Jun 20, 2015
    1. First thing to do would be to check your dogs frequency range of hearing.
    It is very likely your dog can hear 40Khz(reports say up to 60Khz depending on breed and age).
    I guess that can be checked with a variable dog whistle

    2.If your dog can indeed hear at 40KHz,
    you can work directly with a "standard "40KHZ transducer.
    makes life easier and cheaper.

    3.To create a Ping you need to drive the transducer with a "burst"/"keyed" 40KHz Oscillator.
    That isn't difficult thing to do. PING.JPG
     
    hevans1944 likes this.
  10. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    You could try this one. Inexpensive and waterproof.

    I would purchase two of them, one for generating ultrasonic pulses and the other to receive them. Then use a variable-frequency oscillator to find the resonant frequency of the transmitting transducer by sweeping the frequency near 40 kHz and observing the received echo amplitude. Of course the receiving transducer is also resonant, but hopefully this procedure will get you into the "ball park" of what you want the transmitter to do. When you find the maximum amplitude at the receiver transducer, record that frequency and use it when you pulse the transmitter. Gating out about 100 cycles at a frequency close to 40 KHz will give you a two and a half millisecond "chirp" which any dog should be able to hear and locate the reflection of.

    You might consider adapting this concept to blind people. You would need two transducers for receivers, located near each ear, and electronics to change the received ultrasonic pulses to audible pulses sent to earbuds. Perhaps this could all be integrated into an "in the ear" device, one for each ear, but the prototype could be mounted on a head-band and worn like stereo head-phones. You might want to make the transmitter hand-held (like a flashlight) for better localization of the reflected ultrasonic pulses.

    There is a huge market in prosthetic appliances to aid the handicapped, and 21st Century technology is just beginning to address that need.

    Good luck with improving the life of your dog.
     
    dorke likes this.
  11. GPG

    GPG

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    Sep 18, 2015
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