ultrasonic project

Discussion in 'General Electronics Chat' started by yasir_66, May 9, 2010.

  1. yasir_66

    Thread Starter Active Member

    Jun 25, 2009
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    hi friends,
    plz help me in troubleshooting a problem in my circuit.I made a ultrasonic transmitter & receiver project.I couldnt find SL100 & SK100 transistors so instead of these i used A684 & C1383 transistors.When i energize transmitter & receiver circuits,the relay on receiver circuit switch on instead of receiving transmitted signal by transmitter.Plz held me in analyzing whats wrong with & circuit.
    here the diagrams.[​IMG][​IMG]
    click here to enlarge schematic
     
  2. VoodooMojo

    Active Member

    Nov 28, 2009
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    53
    are your pin-outs correct?

    the A684 and C1383 are low frequency
    is that an issue?
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    I think I recognize this design. The transmitter is brute simple, and sends a simple U/S tone. The receiver is similar to an AM receiver, and picks up sidebands. If anything moves in the area doppler will create sidebands, which triggers the relay.
     
  4. VoodooMojo

    Active Member

    Nov 28, 2009
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    my guess is a wiring issue.
    can happen when components are substituted
    as Bill says, pretty simple and available
    in kit form from many vendors I would
    suspect.
     
  5. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    The receiver will not work. The op amp output needs to be able to swing to the positive rail (vcc) to turn off the PNP. It can only go to about vcc-2V. Also, the input stage is biased into saturation, assuming you are using a piezoelectric transducer.

    The transmitter does not need the transistors, diodes, R3, R4, and R5.

    The receiver (if it was biased correctly) is just an amplifier and peak detector, followed by an op amp that is being used as a comparator. I don't see and sideband detection.

    Where did you get this design?
     
  6. Audioguru

    New Member

    Dec 20, 2007
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    Almost every old circuit from that website in India does not work!.
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    It reminds me strongly of one I saw in Popular Electronics around the mid eighties, (84?).
     
  8. yasir_66

    Thread Starter Active Member

    Jun 25, 2009
    71
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    if there is a equivalent of SL100 & SK100 so plz tell me.I thing these two transistors A684 & C1383 is not suitable for this circuit.plz tell me true & working equivalent for these transistors.
    & also tell that how can i identify the terminals of u.sonic transducer.one terminal is shorted to metal surface of transducer is this a gnd?
     
  9. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    You don't need transistors. A CMOS 555 might give you a little less power output than a bipolar 555. See attachment.

    The receiver won't work.
     
  10. Audioguru

    New Member

    Dec 20, 2007
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    The transistors are used to drive an 8 ohm tweeter through a coupling capacitor. The transistors are not used to drive a piezo transducer.

    The designer of the circuit does not know much about electronics.
     
  11. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    The transmitter has 110 ohms (equivalent) in series with the transducer, which would not give much output into an 8 ohm tweeter, so I was assuming piezo.
     
  12. Audioguru

    New Member

    Dec 20, 2007
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    I think the original article said that the author tested the ultrasonic transmitter with a low power piezo earphone which might explain why the two 220 ohm resistors are there.
     
  13. yasir_66

    Thread Starter Active Member

    Jun 25, 2009
    71
    1
    plz guyz tell me what i have to do for making it working?
     
  14. yasir_66

    Thread Starter Active Member

    Jun 25, 2009
    71
    1
    i think transmitter circuit issue has been solved.i just have to remove transistors & diode & connect transducer directly to 555.Now how my receiver circuit will work correctly & what replacement should i have to do?
     
  15. Audioguru

    New Member

    Dec 20, 2007
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    The receiver circuit needs to be completely re-designed to work properly.
     
  16. Wendy

    Moderator

    Mar 24, 2008
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    Posted as a PM to me...

    Wookie says this best...

    To answer your question, if this is the same or similar to Popular Electronics circuit I mentioned earlier, the output speaker sets up an ultrasonic field, which the input speaker and circuit receives. Note the two diodes in front of the op amp, this is a AM detector. If something moves in this U/S field the U/S frequency is dopplered, which means frequencies slightly above and below the U/S carrier are formed, which means the diodes will have a very low frequency (around 1Hz, give or take, depending on the speed the object is moving) feed into the op amp. This will in turn trigger the relay activating an alarm.

    In other words, it is a simple motion sensor.

    I could also be wrong (but don't think I am).
     
  17. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    @ Bill_Marsden: Did you also get the PM?

    @ yasir_66: I do not answer in PM's.
    This breaks the use of the forum, sharing information.

    What did you use as transducers?

    Here is a link with an other ultrasonic design:
    http://hobby_elec.piclist.com/e_soniarm.htm

    Bertus
     
  18. VoodooMojo

    Active Member

    Nov 28, 2009
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  19. Wendy

    Moderator

    Mar 24, 2008
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    To Bertus:

    What you saw is what I got...

    To Yasr 66:

    One other point, you can safely drop the U/S frequency to just above audible. If you have teenagers, cats, or dogs expect complaints if you do this (since their hearing goes above ours), but the concept is not frequency sensitive. This might help the speakers work better.

    With the Popular Electronics article the speakers were patio speakers, and were very well disguised as to their true purpose.
     
  20. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    @ Yasir_66:
    Take a look at this site, this person has designed a small yet very sensitive Ultrasonic Range finder, this range finder can actually be bought at some online retailers such as sparkfun electronics, I have successfully built my own version based on his design.

    http://www.robot-electronics.co.uk/htm/srf04tech.htm

    My .02
    B. Morse
     
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