In article ,
Bill Wright wrote:
The cupboard has two doors, which open independently. The plan is to fit
two push switches of the type sold for this purpose, one for each door.
The switches will control a light that will shine into the cupboard,
which is rather deep and gloomy. These switches are 'on' when the
plunger is out, so the light comes on when the door is open. I also
intend to use a timer so that if the door or doors are left open the
light will eventually go out. The timer will commence timing when the
supply is applied (the door(s) are opened) and if the door or doors are
left open the light will eventually go out. If the doors are closed
during the timing period the light will go out immediately. In order to
initiate a timing period and turn the light on the door must be closed,
then the timing period starts when the door opens. I've sorted the
timer out. It's a multifunction one, and it does what I want. But
ideally I'd like the light to come on if either or both doors are
opened, and stay on for the full duration of the timing period even if
one of the two doors is shut. With one door it's simple. The one switch
controls the timer perfectly. But with two doors and two switches the
best I've done is to have the switches in series, so that both doors
have to be open to initiate the timing period. With the switches in
parallel, if one door has been left open the timing period will not
commence when the other door is opened. It is necesssary for both doors
to be closed, then either to be opened. If the switches are in series,
for the timing period to start one or both doors must be shut, then
both must be open.

Suggestions anyone?

There's probably a way of doing it with logic - but since you're using a
timer to switch the load I'd fit two reed burglar alarm switches per side
- the type with changeover contacts. Some clever wiring of those should
give you the logic you need. They'll be more reliable in operation too
than those pukka door switches which are quite critical in how they're
installed.

--
He who laughs last, thinks slowest*

Dave Plowman London SW
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