NAND Gate

Discussion in 'The Projects Forum' started by alchemist13, Dec 8, 2011.

  1. alchemist13

    Thread Starter New Member

    Dec 8, 2011
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    Hi, I am quite new in the electronics field and I came across a water level alarm circuit with nand gates that is connected in this way:
    [​IMG]
    My question is, what would be the input of the 1st nand gate if it is connected on the 2nd nand gate? Also, the 2nd nand gate's input will be based on the 1st nand gate's output which will also be based on the 2nd nand gate's output.

    I am really confused right now.:( :confused: please help me.

    Here is a picture of the complete circuit, if it helps..

    [​IMG]
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,449
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    Gates 1 and 2 constitute an oscillator running at about 1Hz.
    Gates 3 and 4 constitute an oscillator running at about 200Hz.
    The net result will be a signal that makes the buzzer beep at about once every second...
    beep...beep...beep...beep...
     
  3. alchemist13

    Thread Starter New Member

    Dec 8, 2011
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    Thanks a lot :D
     
  4. alchemist13

    Thread Starter New Member

    Dec 8, 2011
    8
    0
    Um.. I have another question. Why does the circuit need nand gates for the piezo buzzer?
    Wouldn't it work without the nand gates?

    I mean, just connect the wires directly to the buzzer.
    Wouldn't that work perfectly as well?
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,449
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    The buzzer is just a simple transducer. You need an oscillating signal in order to produce audible sound.
     
  6. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    I thought there existed buzzers for DC power supply operation, unlike common speakers.
    Are you sure the oscillator isn't there just to provide an alarm-like on-off sound?
     
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