where should i put the resistors in this ttl clock schematic??

Discussion in 'Homework Help' started by pr1111, Aug 29, 2010.

  1. pr1111

    Thread Starter Member

    Jul 8, 2010
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    0
    i need to make it in a pcb... tia


    [​IMG]
     
  2. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    The only place I see the need of resistors, is in series with the 7-seg LED's. These are the ones you are talking about? If so, the place to put them is after each output of the 7447.
    Also a good idea is to put a pull-up resistor between ground and the reset input of the 7432's, as if you leave it hanging you can't tell for sure if it will stay to 0 or be raised to 1 by internal voltages, leading to unexpected behaviour. A 5k resistor will do the job I think. But if it doesn's experiment between 1k and 10k.
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    The clock source is fine as it. You will need a pull down resistor for the reset line so the input is not floating when the switch is open.

    You will also need current limiting resistors for the LEDs in the displays.

    LEDs, 555s, Flashers, and Light Chasers
     
  4. pr1111

    Thread Starter Member

    Jul 8, 2010
    35
    0
    ok... my vcc is 5V...
     
  5. pr1111

    Thread Starter Member

    Jul 8, 2010
    35
    0
    i will make it with a 5 V VCC
     
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