From: Terry Pinnell
Subject: Re: Another 12V project Help needed
Date: Mon, 16 Dec 2002 08:17:32 +0000
NNTP-Posting-Date: Mon, 16 Dec 2002 08:17:55 +0000 (UTC)
X-Newsreader: Forte Agent 1.92/32.572
"Steve Barker" wrote:
>Yes, exactly. I have the latching relays all laid out, I can do that much.
>I just need the adjustable timer part designed.
You didn't clarify why you said the trigger could be applied for 'up
to a minute'?
That aside, you just need the same circuit I drew for you in reply to
your post on 13th Dec, i.e the one at
except that you should raise the value of Ct to say 22 uF and change
Rt to a pot of 470k (plus a series resistor of say 1k to establish a
very brief minimum period). Or use any other convenient values as
already explained in the notes with that schematic.
If you also need details of how to connect it to your relay, refer to
I've never used a snow plow, but I'm curious why you wouldn't instead
want the greater manual control of a simple toggle switch with UP and
DOWN positions? Or is it a matter of wanting to use your hands for
plow control for the absolute minimum time, so as to concentrate on
steering? If so, maybe a foot-switch or button could be an
Also, I've assumed a nice clean 12 V supply. At the very least add a
47 uF cap across the supply, close to the 555 pins. And if that proves
inadequate, add the fuller noise suppression precautions recommended
by Fred Bloggs in the previous thread.
Hobbyist, West Sussex, UK