ultrasonic ckt...

Discussion in 'General Electronics Chat' started by reymund, Nov 21, 2008.

  1. reymund

    Thread Starter Member

    Sep 23, 2008
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    Hi!,

    i want to know on this circuit on how far the signal will travel?:confused::confused:
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    There are too many unknown variables to predict the effective range of the circuit in this case. It depends on the transducers, the way they are mounted, environment, target size and composition etc. etc.......

    Can you give an example of the application?
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    Don't use a standard 555, it will fry the transistors.
     
  5. vimmi

    New Member

    Feb 20, 2009
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    is this ultrasonic sensor range meter circuit?
     
  6. thingmaker3

    Retired Moderator

    May 16, 2005
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    No. It is a simple proximity detector.
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    Published in Popular Electronics, I was impressed. It uses doppler U/S to detect movement, but is an extremely simple design. Basically a U/S AM reciever, if it detects low frequencies it is caused by something moving in the oscillator field of sound.
     
  8. Audioguru

    New Member

    Dec 20, 2007
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    The circuit looks pretty old. It uses a lousy old LM324 quad opamp that barely amplifies frequencies as high as ultrasonic. It can't even amplify ordinary audio frequencies.

    The range is determined by the thickness and coverage of the burglar's clothes.
     
  9. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    How did you deduce that it is a motion detector? I don't see any Doppler detection circuitry. It looks like a presence detector to me.
     
  10. Audioguru

    New Member

    Dec 20, 2007
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    Its receiver has an AM detector. Anything that changes the amplitude of reflections will produce a level change which is AM and it will be detected if the sender and receiver are close enough together since the lousy old LM324 opamp is so bad.
     
  11. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    It's just an amplifier, a slow half wave rectifier, and a comparator. The gain is fixed. The comparator threshold is manually adjustable. If the input level is below the threshold set by VR2, the LED is off. If the input is above the threshold, the LED is on. Assuming the LED is off when there is no motion, the only change in amplitude it will detect is an increase. If the amplitude decreases, it will not be detected. If you want to call that an AM detector, well, OK, :rolleyes: but there is no Doppler detection.
     
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