Help Required For Project !!!

Discussion in 'The Projects Forum' started by bilalsaeed, Mar 30, 2008.

  1. bilalsaeed

    Thread Starter Member

    Mar 30, 2008
    22
    0
    Hi, I have to design a circuit which take input in terms of sound like on or off and switches on the electrical components like fan etc.. Help me in designing such circuit by only using logic gates. ​
     
  2. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    Not specific enough. Clarify.. It is impossible to answer your question.
     
  3. bilalsaeed

    Thread Starter Member

    Mar 30, 2008
    22
    0
    see i have to design a circuit which take some voice as an input and switch on/off the fan take fan for an example !!! but the condition is that i have to use only the gates !
     
  4. bilalsaeed

    Thread Starter Member

    Mar 30, 2008
    22
    0
    i dont know ho to be more precise....
     
  5. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    I have a way you can be more precise..

    "which take some voice as an input"

    Does this mean through a microphone? Through a standard audio cable at audio signal levels? What voltage do you have peak to peak? At what level do you need to trigger a fan?

    "switch on/off the fan"

    What voltage/current is the load/fan? At what condition does the voice signal trigger the load/fan?

    I don't see the correlation between using an analog signal input and logic gates. This lends itself to a filter/comparator type circuit, not using logic gates that work at specific voltage levels.

    Steve
     
  6. S_lannan

    Active Member

    Jun 20, 2007
    247
    2
    years ago i had to build a sound activated switch. The circuit i was given was a little useless because it did nothing to de-bounce the switching.

    The first problem you will face is the small signal from a microphone will not be able to properly trigger a logic gate.
     
  7. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Is "use of only logic gates" an instructor imposed limitation, or does a valid reason exist?
     
  8. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    You can make a Cmos logic gate or logic inverter into a mic preamplifier by adding a resistor in series with the input and a negative feedback resistor.

    You can "cheat" a little by counting the spoken words instead of decoding the words:
    Turn fan on. Fan off. But then the fan will turn on if somebody says, "Three Blind Mice".
     
  9. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    Very interesting! Does anyone have a link to related material?

    Steve
     
  10. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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