Quiz lockout circuit review help

Discussion in 'The Projects Forum' started by Blacksmith, May 28, 2014.

  1. Blacksmith

    Thread Starter New Member

    May 26, 2014
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    Last edited: May 28, 2014
  2. inwo

    Well-Known Member

    Nov 7, 2013
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  3. crutschow

    Expert

    Mar 14, 2008
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    One option is to replace the D FF's with JK FF's which eliminates the need for the input AND gates. The output of the AND gate at the FF outputs goes to all the J inputs. The K inputs go to ground. The PB outputs go to the respective FF clocks.
     
  4. Blacksmith

    Thread Starter New Member

    May 26, 2014
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    Is it necessary to use a power and decoupling capacitors?
    I'm powering the circuit by a 9-volt battery or a wall adapter.
     
  5. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Yes. Those capacitors are meant to compensate for poorly regulated power sources like 9V batteries and wall warts under fast transient loads in digital circuits.

    Ken
     
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  6. Blacksmith

    Thread Starter New Member

    May 26, 2014
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    Is there a specific formula to determine the capacitance required?
     
  7. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    I used "typical" values. 0.1μF for decoupling capacitors between Gnd and Vcc at each chip.

    I also used 47μF for my power supply filter cap.

    There is a sticky on the forum which discusses decoupling and power cap usage. Click this link
     
  8. Blacksmith

    Thread Starter New Member

    May 26, 2014
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    Also I have seen different values of resistance on the triggering side of the circuit, I have planned to use 1K resistors.
    will this work?
     
  9. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    I used 4k7 resistors and they worked. 10k is more typical for CMOS gates. 1k will use more power if you're running this from batteries.
     
  10. Blacksmith

    Thread Starter New Member

    May 26, 2014
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    ok thank you.
    I just made a purchase of both the 1K and the 4.7K resistors
     
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