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555 Timer Problem

Discussion in 'General Electronics Discussion' started by Muhasaresa, Jan 12, 2012.

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  1. Muhasaresa

    Muhasaresa

    45
    2
    Jan 2, 2012
    Hi everyone, :)

    I have a slight problem understanding how part of the 555 timer works. I was using http://www.williamson-labs.com/pu-aa-555-timer_med.htm to help me and it is a very good diagram, but when the capacitor is in the process of charging up, why does current go through the trigger comparator only and not the threshold comparator as well?

    I would greatly appreciate any help.:D

    Muhasaresa
     
    Last edited: Jan 12, 2012
  2. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Current does not go through them (or in them); they are voltage comparators - changing states only for a moment at 1/3rd and 2/3rds of Vcc.
    I don't find that animation to be a very good educational tool.
     
  3. duke37

    duke37

    5,364
    772
    Jan 9, 2011
    Very little current (negligible) goes in or out of the trigger comparator (pin 2) or the threshold comparator (pin 6).
    Current comes from the positive supply through a resistor to the capacitor and pin 7. When the IC triggers, a transistor connects pin 7 to ground, discharging the capacitor.
     
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