Re: 555 timer...

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: mileswaldron@xxxxxxxxxxx 

The 555 charges up through 2 of the voltage divider resistors and 
discharges through one of them, or the other way around, so there is 
no way to make a > or < 50% duty cycle with a 555. You have to use 
the first 555 to make the impulse train, and trigger another astable 
one to make the proper duty cycle. I use a a SHOTKEY invertor fed 
back to itself with an RC network for an adjustable duty cycle TTL circuit.

Check this circuit out:
<http://www.gravitymagnet.com/images/Nv_3.gif>http://www.gravitymagnet.com/images/Nv_3.gif



--
<a href=http://www.gravitymagnet.com>gravity magnet</a>

-------------- Original message --------------
From: "Tesla list" <tesla@xxxxxxxxxx>

> Original poster: David Speck
>
> Chip,
>
> Simple approach is to put a NPN inverting transistor on the output
> and use it that way. I think there is an inherent feature of the way
> that the 555 works internally that makes it hard to do what you 
want directly.
> There are, however, lots of web sites that have all kinds of exotic
> 555 circuits if you want to go for a more elegant solution.
>
> Dave
>
> Tesla list wrote:
> >Original poster: "Chip Ford"
> >
> >This is kinda off topic but, can someone please help me with
> >this...I am trying to get a 555 timer rectangle pulse (Basic
> >Astable) to stay low longe r then it is high...Is this possible? I
> >have achieved near equal (square) but never longer low then it is
> >high?? Thanks for any help.
> >
> >Chip Ford
> >
> >
>
>
>
>