TIme delays using 555 timers

Thread Starter

kaz21

Joined Jun 11, 2011
5
I am trying to make a delay using a 555 timer. The delay should be 20second off and 1us on!!i tried all the calculation but i couldn't get the output from the multisim oscilloscope!!can some one please help me with this??
thank you!!:D
 

Bernard

Joined Aug 7, 2008
5,784
Not brillian, or tried, but maybe simple: A 555 one shot can give a positive 20 sec. pulse, but maybe you could differentiate trailing edge with .001 cap & 1k resistor, cleaning up neg spike with an inverting schmitt trigger or a comparator.??
 
Last edited:

Bernard

Joined Aug 7, 2008
5,784
As I said : .001 & 1k into a 40106 and out came a flat topped 1.2μs + pulse. It was sure a skinney little thing tacked onto end of 21 m + pulse.
 
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