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555 timer with 50% duty cycle question

P

panfilero

Jan 1, 1970
0
Hi, does anyone know how I could get a 555 timer to operate in astable
mode at a 50% duty cycle? All the circuits I've seen are always for
greater than 50%. thanks.
 
J

Jim Thompson

Jan 1, 1970
0
Hi, does anyone know how I could get a 555 timer to operate in astable
mode at a 50% duty cycle? All the circuits I've seen are always for
greater than 50%. thanks.

It's easy with the CMOS version of the 555 timer...

Tie Threshold and Trigger together, capacitor to ground from this
node, likewise a resistor to output... voila, 50%.

...Jim Thompson
 
J

John B

Jan 1, 1970
0
Hi, does anyone know how I could get a 555 timer to operate in astable
mode at a 50% duty cycle? All the circuits I've seen are always for
greater than 50%. thanks.

Yes. Go here:

http://www.national.com/pf/LM/LM555.html

and download the data sheet. Look at page 10 (figure 14). IT shows you
exactly how to do it.

GIYF.
 
M

Michael Black

Jan 1, 1970
0
panfilero" ([email protected]) said:
Hi, does anyone know how I could get a 555 timer to operate in astable
mode at a 50% duty cycle? All the circuits I've seen are always for
greater than 50%. thanks.
You go to sci.electronics.basics where this sort of question belongs,
and you look for the answers to your post asking the very same thing
there.

Michael
 
panfilero said:
Hi, does anyone know how I could get a 555 timer to operate in astable
mode at a 50% duty cycle?

While there are ways to get close with feedback, one can get closer
with
a flip/flop set to toggle. With two flip/flops, you can get four
phases of
quadrature output. The '555 has to run at 2 or 4 times the desired
output
frequency, though.
 
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