Re: 555 timer circuit

From: Dominic-Luc Webb (dlwebb_at_canit.se)
Date: 12/30/04 

Date: Thu, 30 Dec 2004 17:15:51 +0100

On Wed, 29 Dec 2004, Brian Lyons wrote:

> On 29 Dec 2004 03:22:31 -0800, burtonfamily@dodo.com.au wrote:
>
> >Hello,I made a simple astable 555 timer circuit the same as the one on
> >the 555 web site,but im having trouble working out the values of the
> >two resistors and the capacitor so it will turn on for 3 minuts and off
> >for 5 minuts.Could someone please point me in the right direction as i
> >found the data *** a bit confusing.thankyou in advance
>
>
> Try the following values:
>
> R1 = 430K
> R2 = 630K
> C = 1000uf
>
> T1= about 300 sec
> T2 = about 180 sec
>
> Total = about 8 mins (because of component tolerances, it is difficult
> to obtain precisian with long durations)
>
> Use single transistor to invert logic levels for T1 & T2
>
> A good 555 tutorial may be found at
>
> http://www.uoguelph.ca/~antoon/gadgets/555/555.html

Hmmmm,

Maybe this, together with one or more Johnson counters (4017) so that a
higher frequency cap can be used? Also, maybe still higher values of
R1 and R2 could be used (4.3 and 6.3 MOhm) with a 100 uF cap?

Dominic