RE: Triac question

["Ian Davidson" <ian@xxxxxxxxxxxxxxx>]

Hi
=20
You can do it with one changeover relay (SPDT). Connect all three lamps
neu=
trals together. Connect the common of the relay to the centre bulb live.
Th=
en connect the two changeover contacts one each to the end bulbs live.
Conn=
ect the relay coil (240v ac relay) between neutral and one of the live
feed=
s to one of the end lights. Whichever end you attach the coil connection
to=
o must also be the same light going to the NO side of the contacts.
=20
When one side is switch on the relay is not energised and the centre bulb
i=
s effectively in parallel with that bulb and will light. When the other
bul=
b is switched on the relay will energise connecting the centre bulb to the
=
other end and it will also light.
=20
At work at the moment but if that doesn't make sense I can draw it out
toni=
ght.
=20
Ian D
=20

________________________________

From: ukha_d@xxxxxxx [mailto:ukha_d@xxxxxxx] On Behalf Of S=
tuart Meier
Sent: 24 September 2007 12:00
To: Ian
Subject: Re: [ukha_d] Triac question



Thanks Nick, but I think that as shown it will work when BOTH left and
righ=
t=20
are on, but not when EITHER (ie OR!) the left lamp, or the right=20
lamp...hence two relays (or other devices)

Stuart
----- Original Message -----=20
From: "Nick Austin" <nick.w.austin@xxxxxxx <mailto:nick.w.austin%40gmail.=
com> >
To: <ukha_d@xxxxxxx <mailto:ukha_d%40yahoogroups.com>
>
Sent: Monday, September 24, 2007 11:44 AM
Subject: Re: [ukha_d] Triac question

On 9/24/07, Stuart Meier <stuartm2007@xxxxxxx <mailto:stuartm2007%40gmail=
.com> > wrote:
>
> I'm hoping an electronics whizz can help me...
>
> I need several "blocking diodes" for 240ac, but of course
strictly that
> doesn't exist. In essence, the job is to turn a light on in the middle
of
a
> corridor if the light at either end is on, but without the opposing
end
> coming on too, ends being independently switched. I could use some
blocking
> relays, but that would be =A38 each, and significant space. OK, I
could m=
ake
a
> small board for a PCB mounted one but is there a better option...
>
> Can I use some of the triac's I have knocking about, by wiring the
gate t=
o

> the input, perhaps via resistor. Resistor value?

If there is no other control of the middle lamp then you only need one
relay. I tried to do it as ASCII art but failed so here a diagram:
http://xs.to/xs.php?h=3Dxs319&d=3D07391&f=3Dlamp_switch.jpg
<http://xs.to/x=
s.php?h=3Dxs319&d=3D07391&f=3Dlamp_switch.jpg>=20

Nick.

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=20


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