555 timer circuit

[John Winstead]

I'm trying to build a 555 or 556 timing circuit that creates a 5 second
pulse to activate a small reed relay once every 5 or 6 minutes. Can anyone
help me with that?
Thank You.
John

 

[Terry Pinnell]

"John Winstead" <jlwin@carolina.rr.com> wrote:

I'm trying to build a 555 or 556 timing circuit that creates a 5 second
pulse to activate a small reed relay once every 5 or 6 minutes. Can anyone
help me with that?
Thank You.
John

Here's a circuit to do it.
http://www.terrypin.dial.pipex.com/Images/555Astable5s5m.gif

A simple 555 astable cannot give a duty cycle of under 50%. Your
requirement is for about 2% (1/60). However, a standard astable with
any of the combinations below gives an output that is approximately 5s
low and 5 mins high. You then simply invert that, or (easier) use a
reed relay which gives the required action, as shown in my schematic.
IOW, instead of using normally open contacts, use normally closed or
vice-versa as appropriate to your intended application.

You didn't specify voltage supply. I've assumed 12V, but the identical
circuit is good for 5 - 15V.

If you want reasonable precision, ensure Ct is a good quality, low
leakage cap. Use a pot or preset in series with one or both timing
resistors to adjust High and Low times by trial and error if you wish.

Ct R(Upper) R(Lower)
--- ------ --------
82uF 5.2M 88k
47uF 10.0M 154k
100uF 4.7M 72k
220uF 2.2M 33k
330uF 1.3M 22k
470uF 1.0M 15k
1000uF 470k 8k

--
Terry Pinnell
Hobbyist, West Sussex, UK

 

[John Fields]

On Fri, 13 May 2005 12:31:01 GMT, "John Winstead"
<jlwin@carolina.rr.com> wrote:

I'm trying to build a 555 or 556 timing circuit that creates a 5 second
pulse to activate a small reed relay once every 5 or 6 minutes. Can anyone
help me with that?

---
Check s.e.d. and, next time, crosspost.

--
John Fields
Professional Circuit Designer