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FASTEST FINGER FIRST

Discussion in 'General Electronics Discussion' started by michy005, Mar 18, 2015.

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  1. michy005

    michy005

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    Mar 17, 2015
    Can anyone post the project "fastest finger first" used in quiz competition with buzzer using D flip flop (explained in detail).
     
  2. Gryd3

    Gryd3

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    Jun 25, 2014
    Do you have any examples you want to base your project on?
    Do you have any parts currently?

    How far have you made it in your own design?


    Link
     
  3. michy005

    michy005

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    Mar 17, 2015
    i am about to start it. I even don't know which components are required. Basic design is required.
     
  4. Gryd3

    Gryd3

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    Jun 25, 2014
    Well, you obviously have some kind of idea asking for a design based on a D Flip Flop.
    If you like, you can start on the 'link' from my first response. Get some ideas and get back to us.
    Please note that these forums seem to be a lot more helpful and receptive if it is obvious you have made some kind of effort to either learn or build about the project.

     
    Arouse1973 likes this.
  5. michy005

    michy005

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    Mar 17, 2015
    i worked on this and i have successfully implemented this project Meanwhile i had a doubt regarding LM7805 voltage regulator. Is it necessary to apply capacitors with LM7805 or it directly gives 5V output.
     
  6. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
    QUIZ-TIMER.gif
    Here is the simplest circuit
     
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  7. Gryd3

    Gryd3

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    Jun 25, 2014
    I've used the LM780X series regulators without capacitors before with success, but it is a good practice to follow to use capacitors on the input and output side of the regulator. Depending on the other components involved, additional much smaller capacitors are placed as close to possible to certain ICs to help filter out any noise that may be present on the power traces.
     
  8. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
    "much smaller capacitors are placed as close to possible to certain ICs to help filter out any noise that may be present on the power traces."

    Capacitors are needed, not to reduce noise on the supply rails but to reduce noise produced by the 3-terminal regulator itself.
    That's why they are needed, even when you use a battery.
     
    michy005 likes this.
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    This is often used when you have digital logic as the chips themselves create noise on the supply rails. The chips tend to draw a much higher current when switching that they do in a static state. The capacitors across the power supply connections provide a low impedance source for these brief, but comparatively high, current demands.
     
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  10. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
    The 3-terminal regulators are so badly designed that they can produce their own noise (1MHz etc) and draw excess current, even when the load is small. That's why the capacitors have to be positioned very close to the leads.
    • It's nothing to do with noise from external circuitry.
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Colin, capacitors on the output of the terminal regulators are there to help control noise from the regulator.

    Caps placed close to the power supply pins of ICs (especially logic) are there to help prevent noise from switching affecting this or other ICs.

    Anyone in doubt should Google "why put capacitors close to power supply pins of ics?"
     
  12. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
    That's exactly what I am saying.
     
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