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timer equation drivation

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m_osama

New Member

hello everybody
i hope all of you are fine
i wanna know how to get the equation of the frequency of the square wave
i understand how the circuit work but i can't get the equation
i use ne555 ic
the equation of the freq. is
1.4/((r1+2r2)*c)
thanks at all

 
The equation is readily available on-line. Why do you need its derivation (drivation)?
 
Consequently, if the timer operates in astable, the period is the same with
'T=tH+tL=0.693(RA+RB)C1+0.693RBC1=0.693(RA+2RB)C1' because the period is the sum of the charge time and discharge
time. And since frequency is the reciprocal of the period, the following applies.

Read the bottom of page 7 in this link. It covers how the equation is derived pretty well.

frequency, f = 1/T = 1.44/(RA + 2RB)C1

<EDIT> Beat by Carl........... :) </EDIT>

Ron
 
Last edited:
I was going to save your web page for my 555 files but it will not let me.
Its some nice stuff, do you have it in a saveable format?
Andy

4pyros, It is saveable I already did :).
 
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