Re: 555 timer...

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Chip,

You just need to invert the output. Lot's of ways to do that. A low 
cost solution is:

                     vcc
                      |
                      |
                      R
                      R Resistor
                      R
                      |
                      |---------> = Low Output. When the transistor 
is on, this point is low.
High                  /
Output              |/
pin 3 ----->---RRR--| NPN
of 555              |\
                     \>
                      |
                      |
                      |
                     gnd


You could always just use an inverter chip such as a CMOS CD40106BE 
or equivalent or even a simple opto-coupler to do the same thing. I 
have a plethora of chips on hand and usually go that route. But if 
not, the above would do the trick with a simple 2N2222A or similar.

Take care,
Bart
PS: If above ascii-art looks ugly, set email to view in a fixed width 
font (which I "always" view TCML with).

Tesla list wrote:

> Original poster: "Chip Ford" <chipford@xxxxxxxxxxxxxx>
>
> 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 longer 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