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555 Timer Problem

Muhasaresa

Jan 2, 2012
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Jan 2, 2012
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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:

Resqueline

Jul 31, 2009
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Jul 31, 2009
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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.
 

duke37

Jan 9, 2011
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Jan 9, 2011
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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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