Re: 555 timer circuit

From: Brian Lyons (Nospam_at_nowhere.com)
Date: 12/29/04 

Date: Wed, 29 Dec 2004 10:18:33 -0500

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

Cheers