q:for the masters of electronics of the web a problem with n

[st_yar@yahoo.com]

hi
I have a problem with ne555 I connect the ne555 in astable mode with
(vcc=5volt) I connect pin 2,6&7 together with 2Mohm
variable resistance & cap 220uf to get the maximum required time
(~150sec)but when I shorted the variable leads to get the minimum
required time ( ~.001 sec or less if it possible) I connect 1 ohm
resistor series with the variable to catch my goal but ne555 is
freezing with high level output
my goal: when I short the variable leads ne555 give my as small as
possible pulse ( pulse width .001 sec or less )

thank you for helps
yar

 

[Ban]

st_yar@yahoo.com wrote:

hi
I have a problem with ne555 I connect the ne555 in astable mode with
(vcc=5volt) I connect pin 2,6&7 together with 2Mohm
variable resistance & cap 220uf to get the maximum required time
(~150sec)but when I shorted the variable leads to get the minimum
required time ( ~.001 sec or less if it possible) I connect 1 ohm
resistor series with the variable to catch my goal but ne555 is
freezing with high level output
my goal: when I short the variable leads ne555 give my as small as
possible pulse ( pulse width .001 sec or less )

thank you for helps
yar

It doesn't need a master to understand a 555, ask John Fields, but don't
mess with Texas.
I would suggest you read the datasheet first
http://www.fairchildsemi.com/ds/NE/NE555.pdf
have a look at figure6 where you find a minimum value of 1k. You will have
to switch in different capacitors for shorter times. you can automatize
switching with transistors (BJT or FET). Only this way you can resolve those
short times on your pot anyway.
--
ciao Ban
Bordighera, Italy

 

[martin griffith]

On Thu, 24 Mar 2005 06:12:16 GMT, in sci.electronics.design "Ban"
<bansuri@web.de> wrote:
snip

It doesn't need a master to understand a 555, ask John Fields, but don't
mess with Texas.

Texas or Texas Instruments?

I would have thought that TI could make a descent 555 by now


martin


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