Whistle responder circuit

Discussion in 'General Electronics Chat' started by Motanache, Mar 2, 2015.

  1. Motanache

    Thread Starter Member

    Mar 2, 2015
    70
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    http://www.learningelectronics.net/circuits/whistle-responder-schematic-circuit.html

    [​IMG]

    I want to build this circuit, but his output will go to a micro controller.

    First step
    When I whistle to flash an LED

    a) I not understand, how a logic gate is a use as operational amplifier (IC1A)
    b) How do I change the filter to change the crossover frequency (IC1B)
    c) Know such a scheme with fewer components ?
    d) Instead of 4049 (NOT) can use CD4093(NAND)?
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,529
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    Many logic gates are simply very high gain amplifiers. It is important that you do not substitute another hex inverter for the 4049. This is one of the original CMOS IC's, before the addition of input protection and output buffers. The 4093 is one of my favorite parts, but it is the worst choice for this circuit because it has a buffered output stage (that's why the part number always ends in B) and it has an internal Schmidt trigger stage. This is a very non-linear section that will not pass low level audio.

    When biased correctly, the 4049 makes a decent microphone amplifier. Here is how this type of bandpass filter usually is drawn:
    http://www.circuitdb.com/?p=305
    It is about as low a parts count as you can have for a bandpass filter. The equations to change the two cutoff frequencies are not simple. You can find them on the web if you really want to change things.

    ak
     
  3. Motanache

    Thread Starter Member

    Mar 2, 2015
    70
    4
    <It is important that you do not substitute another hex inverter for the 4049.>
    Thank you very much for your answer

    Unfortunately, I have only one store of electronic component in town and they do not have this IC.
    I have on the table 74LS06.

    Have to find another solution to make the circuit .....

    Other circuit from 40 series tha are finding the store:
    CD4001
    CD4011
    CD4013
    CD4017
    CD4020BE
    CD4026
    CD4030
    CD4040
    CD4060
    CD4066
    CD4066BE
    CD4069
    CD4098BE
    The place where I want to introduce thi circuit is verry small.
    I want tooobtain very small size.

    1. Trying with a microcontroller?
    2. To get an initial microphone signal amplification with transistors ?
    3 And the band pass filter to make it all with a single transistor ?
     
    Last edited: Mar 3, 2015
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
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    This circuit is crying out for opamps. Since you are going into a micro, you do not need the oscillator and buzzer driver IC1 e & f or the transistor, so it could nicely be done with a quad opamp IC.
     
  5. Motanache

    Thread Starter Member

    Mar 2, 2015
    70
    4
    "so it could nicely be done with a quad opamp IC."
    OK.
    I have TL074.
    But power is only 5V.

    I do not know if it will work well at this voltage. GND will be at 2.5V
     
  6. MrChips

    Moderator

    Oct 2, 2009
    12,435
    3,360
    Why not scrap that circuit and create your own with your available components.
    Do you have an LM324?
     
  7. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    stage a is a mic preamp
    stage b is a bridged-T narrow bandpass filter
    stage c makes pulses only when the amplitude of the filtered output is > than a threshold.
    stage d rectifies and filters the pulses to make a logic level when the signal is detected.


    What is the center frequency of the filter?

    The TL074 is not suitable for low-voltage, single supply operation.
     
  8. Motanache

    Thread Starter Member

    Mar 2, 2015
    70
    4
    "What is the center frequency of the filter?"
    2KHz
    "stage c makes pulses only when the amplitude of the filtered output is > than a threshold"
    The amplitude of what?
    At the output of a digital circuit where we have just 0-logical and 1-logical ?:(
    R7/R8=aprox. 1/2

    He expects to charge C4 as a whistle to be sufficiently long in time.

    I probably do not know:
    'before the addition of input protection and output buffers"

    The output of these gates can also take continuous values?:eek:
     
  9. Motanache

    Thread Starter Member

    Mar 2, 2015
    70
    4
    R4/R5=100k/200R ???????????????
    This only to be more efficient filter at low signal?

    After amplify the signal 'we' decrease it?

    I want to understand how it works so I can use another IC
     
  10. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    use a cd4069 hex inverter
     
    Last edited: Mar 3, 2015
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    For the special case of an unbuffered gate, i.e. the CD4049 or CD4069UB, yes. For the other gates in your list, no.
    R3 tries to make the IC1a steady state input voltage the same as the output voltage. Because IC1a is merely an inverting amplifier, this results in both voltages being at the gate switching threshold, i.e. about half the supply voltage. A slight change at the input (due to the mic) results in a big change at the output.
     
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  12. Sensacell

    Well-Known Member

    Jun 19, 2012
    1,128
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    I built a whistle remote control around an LM567 tone decoder IC many years ago, worked well.
    I don't think you will achieve enough reliability with a single stage band pass filter, loud noises will still wreak havoc.
     
  13. Motanache

    Thread Starter Member

    Mar 2, 2015
    70
    4
    Please give me details. I do not want to do unnecessary experiments, if you know how to do.


    What I tried ...:
    - I did a tone generator ~2KHz with a small speaker
    - I did this preamplifier:
    (instead a piezo I used a microphone, powered correctly)
    [​IMG]

    - The result I saw with the soft Visual Analyser:
    [​IMG]

    Only 5 cm away from the transmitter, the reception frequency can be distinguished from the noise !!!!
    And that after using two transistors for amplification !!!!

    An integrated solution would be super!
    LM324 si 4069 remains to try them.
     
  14. Motanache

    Thread Starter Member

    Mar 2, 2015
    70
    4
    I bought HEF4069UBP.
    The first part, signal amplification, goes very well.
    Instead of R3=4M7 I put 1M5, I had no other resistor.

    However, the gain is good, may detect the signal at 2m from the sound source.

    The second stage, the filter did not work. I had no signal output.
     
  15. Motanache

    Thread Starter Member

    Mar 2, 2015
    70
    4
    HEF4069UBP has not been very helpful.
    Voltage gain around 30dB -> approximate 30X

    And LM324 have 30x gain at the frequency of 20KHz.

    I have not to get a "5V" amplitude !
     
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