Hi,
I'm rewiring at the moment and have come across this system of wiring
up two lights, the first with one-way switching and the second with
two-way switching:

http://i598.photobucket.com/albums/t...es/circuit.jpg

Hopefully you can make out how it works from the circuit diagram!

Essentially the one-way light is fed from three core and earth, with
the third core used as the switched live for the second (two-way)
light. The Live for both lights is shared at the twin switch, by means
of a "jumper cable" whic I hope is clear in the picture. I *think* it
was done this way to save disturbing decoration as it would have
impossible to squeeze 2 twin and earths and 1 three core and earth
down to the twin switch, in the usual fashion. As you can see, the
system illustrated relies on just 2 three core and earths to the twin
switch instead.

My causes for concern a
A: One three core and earth cable is acting as the switched live for
two DIFFERENT luminaires.
B: The switched live for Light A is joined together with a crimp
connector within the ceiling rose for Light B.

Is this setup perfectly acceptable? If so, I will simply ignore,
otherwise I will cut out a new chase to accommodate the more standard
switching practice.

Thanks in advance

Luke

Luke wrote:
Hi,
I'm rewiring at the moment and have come across this system of wiring
up two lights, the first with one-way switching and the second with
two-way switching:

http://i598.photobucket.com/albums/t...es/circuit.jpg

Hopefully you can make out how it works from the circuit diagram!

Essentially the one-way light is fed from three core and earth, with
the third core used as the switched live for the second (two-way)
light. The Live for both lights is shared at the twin switch, by means
of a "jumper cable" whic I hope is clear in the picture. I *think* it
was done this way to save disturbing decoration as it would have
impossible to squeeze 2 twin and earths and 1 three core and earth
down to the twin switch, in the usual fashion. As you can see, the
system illustrated relies on just 2 three core and earths to the twin
switch instead.

My causes for concern a
A: One three core and earth cable is acting as the switched live for
two DIFFERENT luminaires.
B: The switched live for Light A is joined together with a crimp
connector within the ceiling rose for Light B.

Is this setup perfectly acceptable? If so, I will simply ignore,
otherwise I will cut out a new chase to accommodate the more standard
switching practice.

Thanks in advance

It would not work with the drawing you gave. Try

http://i428.photobucket.com/albums/q...2020/light.jpg

It is unconventional not unsafe IMHO.

--
Adam

On Mar 24, 2:10*pm, Luke wrote:
Hi,
I'm rewiring at the moment and have come across this system of wiring
up two lights, the first with one-way switching and the second with
two-way switching:

http://i598.photobucket.com/albums/t...es/circuit.jpg

Hopefully you can make out how it works from the circuit diagram!

Essentially the one-way light is fed from three core and earth, with
the third core used as the switched live for the second (two-way)
light. The Live for both lights is shared at the twin switch, by means
of a "jumper cable" whic I hope is clear in the picture. I *think* it
was done this way to save disturbing decoration as it would have
impossible to squeeze 2 twin and earths and 1 three core and earth
down to the twin switch, in the usual fashion. As you can see, the
system illustrated relies on just 2 three core and earths to the twin
switch instead.

My causes for concern a
A: One three core and earth cable is acting as the switched live for
two DIFFERENT luminaires.
B: The switched live for Light A is joined together with a crimp
connector within the ceiling rose for Light B.

Is this setup perfectly acceptable? If so, I will simply ignore,
otherwise I will cut out a new chase to accommodate the more standard
switching practice.

Thanks in advance

Luke

What you have here is the standard method of converting a one way
switched light into a two way.
The one way switch is removed & discarded.
A bit of three-core wire is run from this wsitch postiion to the
additional position.
The commons on the switches are link by one core.
The other two terminals (L1&L2 /"strappers") in the two switches are
linked by the remaining two cores.
The wires that fed te original one way switch are connected toL1&L2
terminals on the switch that replaced the one way switch.
Finish.

harry wrote:

What you have here is the standard method of converting a one way
switched light into a two way.
The one way switch is removed & discarded.
A bit of three-core wire is run from this wsitch postiion to the
additional position.
The commons on the switches are link by one core.
The other two terminals (L1&L2 /"strappers") in the two switches are
linked by the remaining two cores.
The wires that fed te original one way switch are connected toL1&L2
terminals on the switch that replaced the one way switch.
Finish.

That's a very odd "standard method", given that the more orthodox
method requires no more wires. Why the heck wasn't the new 3-core
wire wired as follows instead?

Use two of the cores to connect the two strappers of the two switches.
This is the same as above.

Connect the third core to the common of the remote switch. Then use
the local end of that third core, and the common of the local switch,
as the replacement for the original one way switch.

I.e. either connect the local end of the third core (which is the common
of the remote switch) to the live feed, and then connect the common of
the local switch to the live end of the light bulb, or the other way
round.

Apart from anything else, the circuit is easier to understand.

Though I do see the inherent simplicity of wiring the thing up by
using the three cores to parallel up all three terminals on both
switches.


So here's a wee exercise for you. You have two lamps up a pole.
Call them lamp A and lamp B. You never want both of them on at
once, i.e. you want either both off, or A on with B off, or A off
with B on.

There is only a 2 core cable going up the pole, but that's OK
because they are on a DC supply and there are a couple of diodes
up there, wired so that the polarity of the supply determines
which bulb comes on.

Question 1 (easy): You are given a two pole changeover switch
with a centre off position. How do you wire the battery supply,
the switch's 6 terminals, and the cable to the pole to get what
you need?

Question 2 (more difficult): You don't like the changeover switch
and decide you would rather have two separate switches, one for
lamp A and one for lamp B. What types of switch do you need and
how do you wire them? The obvious solution involving two double
pole one way switches will short-circuit the battery if you are
stupid enough to turn both switches on at once. So you need a
safer solution which avoids that.

On Mar 24, 2:10*pm, Luke wrote:
Hi,
I'm rewiring at the moment and have come across this system of wiring
up two lights, the first with one-way switching and the second with
two-way switching:

http://i598.photobucket.com/albums/t...es/circuit.jpg

Hopefully you can make out how it works from the circuit diagram!
Essentially the one-way light is fed from three core and earth, with
the third core used as the switched live for the second (two-way)
light. The Live for both lights is shared at the twin switch, by means
of a "jumper cable" whic I hope is clear in the picture. I *think* it
was done this way to save disturbing decoration as it would have
impossible to squeeze 2 twin and earths and 1 three core and earth
down to the twin switch, in the usual fashion. As you can see, the
system illustrated relies on just 2 three core and earths to the twin
switch instead.

My causes for concern a
A: One three core and earth cable is acting as the switched live for
two DIFFERENT luminaires.

not a problem

B: The switched live for Light A is joined together with a crimp
connector within the ceiling rose for Light B.

not a problem

Is this setup perfectly acceptable? If so, I will simply ignore,
otherwise I will cut out a new chase to accommodate the more standard
switching practice.

Thanks in advance

Luke

Ronald Raygun wrote:
harry wrote:

What you have here is the standard method of converting a one way
switched light into a two way.
The one way switch is removed & discarded.
A bit of three-core wire is run from this wsitch postiion to the
additional position.
The commons on the switches are link by one core.
The other two terminals (L1&L2 /"strappers") in the two switches are
linked by the remaining two cores.
The wires that fed te original one way switch are connected toL1&L2
terminals on the switch that replaced the one way switch.
Finish.

That's a very odd "standard method", given that the more orthodox
method requires no more wires. Why the heck wasn't the new 3-core
wire wired as follows instead?

Use two of the cores to connect the two strappers of the two switches.
This is the same as above.

Connect the third core to the common of the remote switch. Then use
the local end of that third core, and the common of the local switch,
as the replacement for the original one way switch.

I.e. either connect the local end of the third core (which is the
common of the remote switch) to the live feed, and then connect the
common of the local switch to the live end of the light bulb, or the
other way round.

Apart from anything else, the circuit is easier to understand.

Though I do see the inherent simplicity of wiring the thing up by
using the three cores to parallel up all three terminals on both
switches.

Because that is how numpties wire switches up.

--
Adam

harry wrote:
On Mar 24, 2:10 pm, Luke wrote:
Hi,
I'm rewiring at the moment and have come across this system of wiring
up two lights, the first with one-way switching and the second with
two-way switching:

http://i598.photobucket.com/albums/t...es/circuit.jpg

Hopefully you can make out how it works from the circuit diagram!

Essentially the one-way light is fed from three core and earth, with
the third core used as the switched live for the second (two-way)
light. The Live for both lights is shared at the twin switch, by
means of a "jumper cable" whic I hope is clear in the picture. I
*think* it was done this way to save disturbing decoration as it
would have impossible to squeeze 2 twin and earths and 1 three core
and earth down to the twin switch, in the usual fashion. As you can
see, the system illustrated relies on just 2 three core and earths
to the twin switch instead.

My causes for concern a
A: One three core and earth cable is acting as the switched live for
two DIFFERENT luminaires.
B: The switched live for Light A is joined together with a crimp
connector within the ceiling rose for Light B.

Is this setup perfectly acceptable? If so, I will simply ignore,
otherwise I will cut out a new chase to accommodate the more standard
switching practice.

Thanks in advance

Luke

What you have here is the standard method of converting a one way
switched light into a two way.

Standard in what way?

1. The lights would not be switched correctly if the lights were wired up
like that.

or

2. The OPs main concern is the use of a 3 core and earth cable used as the
supply and two switched feeds


The one way switch is removed & discarded.
A bit of three-core wire is run from this wsitch postiion to the
additional position.
The commons on the switches are link by one core.
The other two terminals (L1&L2 /"strappers") in the two switches are
linked by the remaining two cores.
The wires that fed te original one way switch are connected toL1&L2
terminals on the switch that replaced the one way switch.
Finish.

Well that is not what the OP asked is it?

--
Adam

On Mar 24, 7:16*pm, "ARWadsworth"
wrote:
harry wrote:
On Mar 24, 2:10 pm, Luke wrote:
Hi,
I'm rewiring at the moment and have come across this system of wiring
up two lights, the first with one-way switching and the second with
two-way switching:

http://i598.photobucket.com/albums/t...es/circuit.jpg

Hopefully you can make out how it works from the circuit diagram!

SNIP LIGHT EXPLANATION
Luke

What you have here is the standard method of converting a one way
switched light into a two way.

Standard in what way?

1. The lights would not be switched correctly if the lights were wired up
like that.

or

2. The OPs main concern is the use of a 3 core and earth cable used as the
supply and two switched feeds


Well that is not what the OP asked is it?

--
Adam- Hide quoted text -

Thanks for your input everyone, and thanks for Adam for pointing out
the error in my diagram and yes, it is wired up as you depicted - I
just didn't quite get the picture right.

I see that Harry's system would work but does not, I think, quite
grasp the situation I have as it still would need a total of 3 lengths
of wire down to the twin switch shown in the picture, and this is the
situation which had been explicitly avoided.

It is all wired up in old colours as the house was rewired in 1997 so
predates the new cable. I have the floor up in the room above as I'm
adding new sockets and thought I might as well ask about the lighting
wiring from the floor below in case it would be a good idea to renew
it whilst I had the boards up and prior to laying a new carpet.

As it stands, bearing in mind the advice, I will leave it as it is. I
did try the wiring puzzler involving the lights up a pole but drew a
blank.

Thanks

Luke

Luke wrote:

I
did try the wiring puzzler involving the lights up a pole but drew a
blank.

Well the question did not make sense. The obvious solution using two double
pole switches works fine depending on how RR wants to place the switches,
cables and diodes and more importantly, he never gave a rule on switch
positions and which lights should be on depending upon the switch positions.

If it is

battery =={2 core cable}==switches== [2 core cable] == [2 LEDS wired in
parallel in opposite directions] then it is easy.


--
Adam

ARWadsworth wrote:
What you have here is the standard method of converting a one way
switched light into a two way.

Standard in what way?

It's /a/ standard method: http://www.diyhowto.co.uk/projects/two-way-lighting.htm
I prefer to avoid it unless I have can't, as having five wires
coming out of the switchplate backbox can confuse future
maintainers, even more than a loop-in ceiling rose can.

JGH

jgharston wrote:
ARWadsworth wrote:
What you have here is the standard method of converting a one way
switched light into a two way.

Standard in what way?

It's /a/ standard method:
http://www.diyhowto.co.uk/projects/two-way-lighting.htm I prefer to
avoid it unless I have can't, as having five wires
coming out of the switchplate backbox can confuse future
maintainers, even more than a loop-in ceiling rose can.


It is not a standard method that the OP referred to and gave a diagram for.
His concern was not the 3 core and earth cable used for the two way
switching but the three core and earth cable used for the switched drop that
used one core for permanent live and two different switched lives on the
other cores.

Read the OPs question and not Harrys waffle.

--
Adam

ARWadsworth wrote:

Luke wrote:

I
did try the wiring puzzler involving the lights up a pole but drew a
blank.

Well the question did not make sense.

I thought it did, but perhaps I unwittingly left out some detail.

Perhaps it would help if I give some background. See below.

The obvious solution using two
double pole switches works fine

No it doesn't, I'll explain below why not.

depending on how RR wants to place the
switches, cables and diodes and more importantly, he never gave a rule on
switch positions and which lights should be on depending upon the switch
positions.

If it is

battery =={2 core cable}==switches== [2 core cable] == [2 LEDS wired in
parallel in opposite directions] then it is easy.

I meant the cable which runs up the pole is 2 core, the two lamps and diodes
are up on top of the pole. The battery and switches are at the bottom of
the pole where you can do anything you like.

The "pole" is actually a mast on a sailing boat and the two lamps are
navigation lights. Lamp A is an anchor light which shines white all
round (in a 360 degree arc). It is used to warn other boats of your
presence when you are at anchor. Think of it as a "parking light".
When sailing, boats are expected to exhibit sidelights (red to port
(the left), green to starboard (the right), and white astern (backwards)).
Sailing boats below a certain size are permitted to combine these lights
into a single tricolour (which uses a single light bulb inside a multi
coloured housing) at the top of the mast. This is lamp B.

Imagine a boat which was originally fitted with only an anchor light
(and which previously used ordinary side and stern lights at deck level),
or alternatively was fitted with only a mast top tricolour, with other
arrangements for anchor light being made at deck level. Therefore a
two core cable would have been used in the original installation.

Now the boat is upgraded to use one of these combined tricolour/anchor
lights which are normally fed by 3-core cable because it contains two
bulbs. But the cable is threaded up the inside of the mast and it would
be a major operation to rip out the 2-core and thread a 3-core in its
place. Hence the trick with the diodes, mounted inside the mast top unit,
so that if you label the two cable ends at the bottom X and Y, if you
connect XY to +- you light lamp A, and if you connect XY to -+ you light
lamp B.

The wiring question simply concerns how you wire up a switch or two,
to make XY either +- or -+ or something else (++ or -- or 00) when you
want both lamps to be off.

Problem 1 with a two pole changeover switch:

The switch has three positions, namely a centre off, and two "on"s.
The idea is that in one "on" position it lights the anchor light, in
the other it lights the tricolour.

The switch has six terminals: two commons A and B, which it connects
either to A1 and B1, or to A2 and B2, or to neither in the centre off
position.

The obvious and correct solution is to cross-wire A1 to B2 and B1 to A2.
You then either wire B2 to X and A2 to Y, and A to + and B to -; or
else you wire A to X and B to Y, and A1 to + and B1 to -.

Problem 2 is that you want one switch to turn on the anchor light,
and a separate switch to turn on the tricolour. If you use double
pole one way switches for this, then the obvious way to wire them
up is as follows. Switch 1 has poles A and B which it either
connects to A1 and B1 or not; switch 2 likewise connects C and D
to C1 and D1 or not.

Wire + to A and C, and - to B and D.
Wire A1 to D1 to X, and B1 to C1 to Y.

Then if switch 1 (with A and B) is on, XY is +-.
If switch 2 (with C and D) is on, XY is -+.
But if you switch both switches on, then you short + to -,
because A1 is connected to D1 and also because B1 is connected
to C1.

To prevent this, you could of course deploy an extra four diodes,
but you will then get 3 diode voltage drops in the line, which on
a 12V system will dim the lamps rathe more than a single one will,
which is already bad enough.

However, there is a solution involving two double pole changeover
switches.

When both switches are on, you don't want a short, nor do you want
both lamps on (which they can't be anyway), so the safe option is
to have both lamps off in this case.

On Mar 24, 5:41*pm, Ronald Raygun
wrote:
harry wrote:
What you have here is the standard method of converting a one way
switched light into a two way.
The one way switch is removed & discarded.
A bit of three-core wire is run from this wsitch postiion to the
additional position.
The commons on the switches are link by one core.
The other two terminals (L1&L2 /"strappers") in the two switches are
linked by the remaining two cores.
The wires that fed te original one way switch are connected toL1&L2
terminals on the switch that replaced the one way switch.
Finish.

That's a very odd "standard method", given that the more orthodox
method requires no more wires. *Why the heck wasn't the new 3-core
wire wired as follows instead?

Use two of the cores to connect the two strappers of the two switches.
This is the same as above.

Connect the third core to the common of the remote switch. *Then use
the local end of that third core, and the common of the local switch,
as the replacement for the original one way switch.

I.e. either connect the local end of the third core (which is the common
of the remote switch) to the live feed, and then connect the common of
the local switch to the live end of the light bulb, or the other way
round.

Apart from anything else, the circuit is easier to understand.

Though I do see the inherent simplicity of wiring the thing up by
using the three cores to parallel up all three terminals on both
switches.

So here's a wee exercise for you. *You have two lamps up a pole.
Call them lamp A and lamp B. *You never want both of them on at
once, i.e. you want either both off, or A on with B off, or A off
with B on.

There is only a 2 core cable going up the pole, but that's OK
because they are on a DC supply and there are a couple of diodes
up there, wired so that the polarity of the supply determines
which bulb comes on.

Question 1 (easy): *You are given a two pole changeover switch
with a centre off position. *How do you wire the battery supply,
the switch's 6 terminals, and the cable to the pole to get what
you need?

Question 2 (more difficult): *You don't like the changeover switch
and decide you would rather have two separate switches, one for
lamp A and one for lamp B. *What types of switch do you need and
how do you wire them? *The obvious solution involving two double
pole one way switches will short-circuit the battery if you are
stupid enough to turn both switches on at once. *So you need a
safer solution which avoids that.

It's the normal method from year dot. No external joins in the cabe
are required.
Since the adoption of the three plate cieling rose system of wiring,
it has become common as original fix too. It's themain reason forthe
existence of three core wire which was uncommon years ago except for
3phase work.

On Mar 24, 5:41*pm, Ronald Raygun
wrote:
harry wrote:
What you have here is the standard method of converting a one way
switched light into a two way.
The one way switch is removed & discarded.
A bit of three-core wire is run from this wsitch postiion to the
additional position.
The commons on the switches are link by one core.
The other two terminals (L1&L2 /"strappers") in the two switches are
linked by the remaining two cores.
The wires that fed te original one way switch are connected toL1&L2
terminals on the switch that replaced the one way switch.
Finish.

That's a very odd "standard method", given that the more orthodox
method requires no more wires. *Why the heck wasn't the new 3-core
wire wired as follows instead?

Use two of the cores to connect the two strappers of the two switches.
This is the same as above.

Connect the third core to the common of the remote switch. *Then use
the local end of that third core, and the common of the local switch,
as the replacement for the original one way switch.

I.e. either connect the local end of the third core (which is the common
of the remote switch) to the live feed, and then connect the common of
the local switch to the live end of the light bulb, or the other way
round.

Apart from anything else, the circuit is easier to understand.

Though I do see the inherent simplicity of wiring the thing up by
using the three cores to parallel up all three terminals on both
switches.

So here's a wee exercise for you. *You have two lamps up a pole.
Call them lamp A and lamp B. *You never want both of them on at
once, i.e. you want either both off, or A on with B off, or A off
with B on.

There is only a 2 core cable going up the pole, but that's OK
because they are on a DC supply and there are a couple of diodes
up there, wired so that the polarity of the supply determines
which bulb comes on.

Question 1 (easy): *You are given a two pole changeover switch
with a centre off position. *How do you wire the battery supply,
the switch's 6 terminals, and the cable to the pole to get what
you need?

Question 2 (more difficult): *You don't like the changeover switch
and decide you would rather have two separate switches, one for
lamp A and one for lamp B. *What types of switch do you need and
how do you wire them? *The obvious solution involving two double
pole one way switches will short-circuit the battery if you are
stupid enough to turn both switches on at once. *So you need a
safer solution which avoids that.

I never heard such drivel. Where would you find DC lighting up a pole
these days?

harry wrote:

On Mar 24, 5:41 pm, Ronald Raygun
wrote:

So here's a wee exercise for you. You have two lamps up a pole.
Call them lamp A and lamp B. You never want both of them on at
once, i.e. you want either both off, or A on with B off, or A off
with B on.

There is only a 2 core cable going up the pole, but that's OK
because they are on a DC supply and there are a couple of diodes
up there, wired so that the polarity of the supply determines
which bulb comes on.

Question 1 (easy): You are given a two pole changeover switch
with a centre off position. How do you wire the battery supply,
the switch's 6 terminals, and the cable to the pole to get what
you need?

Question 2 (more difficult): You don't like the changeover switch
and decide you would rather have two separate switches, one for
lamp A and one for lamp B. What types of switch do you need and
how do you wire them? The obvious solution involving two double
pole one way switches will short-circuit the battery if you are
stupid enough to turn both switches on at once. So you need a
safer solution which avoids that.

I never heard such drivel. Where would you find DC lighting up a pole
these days?

Firstly, I said this is an exercise. You can't dismiss exercises on
the basis of them "being drivel" because they are often contrived.

Secondly, it isn't drivel, and in this instance isn't contrived. As
I have explained elsewhere, it's on a boat.

Now just answer the question, if you can.

Ronald Raygun wrote:
harry wrote:

On Mar 24, 5:41 pm, Ronald Raygun
wrote:

So here's a wee exercise for you. You have two lamps up a pole.
Call them lamp A and lamp B. You never want both of them on at
once, i.e. you want either both off, or A on with B off, or A off
with B on.

There is only a 2 core cable going up the pole, but that's OK
because they are on a DC supply and there are a couple of diodes
up there, wired so that the polarity of the supply determines
which bulb comes on.

Question 1 (easy): You are given a two pole changeover switch
with a centre off position. How do you wire the battery supply,
the switch's 6 terminals, and the cable to the pole to get what
you need?

Question 2 (more difficult): You don't like the changeover switch
and decide you would rather have two separate switches, one for
lamp A and one for lamp B. What types of switch do you need and
how do you wire them? The obvious solution involving two double
pole one way switches will short-circuit the battery if you are
stupid enough to turn both switches on at once. So you need a
safer solution which avoids that.

I never heard such drivel. Where would you find DC lighting up a pole
these days?

Firstly, I said this is an exercise. You can't dismiss exercises on
the basis of them "being drivel" because they are often contrived.

Secondly, it isn't drivel, and in this instance isn't contrived. As
I have explained elsewhere, it's on a boat.

Now just answer the question, if you can.

Well I used 2g 2way light switch.

Is there a prize?

--
Adam

On 24/03/2011 23:22, Ronald Raygun wrote:
However, there is a solution involving two double pole changeover
switches.

Surely you can do it with two single-pole changeover (SPDT) switches.
Using your terminal naming, so SW1 has 'fixed' contacts A1 & A2 and
common or moving contact A (and SW2 similarly has B1, B2 and B). Now
connect

- A1 and B1 to -ve supply
- A2 and B2 to +ve supply
- A and B to the outgoing wires X and Y.

If both switches are 'up' or 'down' X & Y are connected to the same
supply pole, so both lights are off. If one is up and the other down
there will be an output to X & Y, with the polarity dependent on which
switch is up.

QEF
--
Andy

ARWadsworth wrote:

Ronald Raygun wrote:
harry wrote:

On Mar 24, 5:41 pm, Ronald Raygun
wrote:

So here's a wee exercise for you. You have two lamps up a pole.
Call them lamp A and lamp B. You never want both of them on at
once, i.e. you want either both off, or A on with B off, or A off
with B on.

There is only a 2 core cable going up the pole, but that's OK
because they are on a DC supply and there are a couple of diodes
up there, wired so that the polarity of the supply determines
which bulb comes on.

Question 1 (easy): You are given a two pole changeover switch
with a centre off position. How do you wire the battery supply,
the switch's 6 terminals, and the cable to the pole to get what
you need?

Question 2 (more difficult): You don't like the changeover switch
and decide you would rather have two separate switches, one for
lamp A and one for lamp B. What types of switch do you need and
how do you wire them? The obvious solution involving two double
pole one way switches will short-circuit the battery if you are
stupid enough to turn both switches on at once. So you need a
safer solution which avoids that.

I never heard such drivel. Where would you find DC lighting up a pole
these days?

Firstly, I said this is an exercise. You can't dismiss exercises on
the basis of them "being drivel" because they are often contrived.

Secondly, it isn't drivel, and in this instance isn't contrived. As
I have explained elsewhere, it's on a boat.

Now just answer the question, if you can.

Well I used 2g 2way light switch.

Is there a prize?

There is no prize other than your own satisfaction, but if there were
a prize, you would be disqualified on grounds of being too expert. I
was interested in whether harry could do it. :-)

Presuming that the "g" in your "2g 2way" stands for "gang", i.e. that the
switch has two poles, each of which can be switched 2 ways, in what is
commonly referred to as a DPDT switch, then yes, that's the answer to Q1.
Indeed I have already given wiring solution for that one.

But Q2 explicitly specifies that you must use two switches, one to operate
each lamp. I find I need two DPDT switches for that (I don't know if there
is a simpler solution), and the puzzle lies in working out how to wire them
up so that when switch A is on and B is off, then the two cores X and Y of
the cable are connected to + and -, respectively, whereas when switch B is
on and A is off, you want X and Y to be - and +, respectively, instead.

When you turn both switches on, you don't want to short out the battery, or
blow your fuse if there is one, as you would if your solution were based on
two 2g 1way (DPST) switches.

Turning both switches on simultaneously is an operator error condition,
since you can't turn both lamps on together. What gets connected to X and Y
in those circumstances may be undefined if you wish, but preferably it
should be that X and Y are both disconnected from the battery, same as when
both switches are off.

Andy Wade wrote:

On 24/03/2011 23:22, Ronald Raygun wrote:
However, there is a solution involving two double pole changeover
switches.

Surely you can do it with two single-pole changeover (SPDT) switches.
Using your terminal naming, so SW1 has 'fixed' contacts A1 & A2 and
common or moving contact A (and SW2 similarly has B1, B2 and B). Now
connect

- A1 and B1 to -ve supply
- A2 and B2 to +ve supply
- A and B to the outgoing wires X and Y.

If both switches are 'up' or 'down' X & Y are connected to the same
supply pole, so both lights are off. If one is up and the other down
there will be an output to X & Y, with the polarity dependent on which
switch is up.

QEF

Ah yes, well done. Why didn't I think of that?

What I had was two DPDT switches. Using the same notation, one switch
has moving contacts A and B which it switches either to A1 and B1 or to
A2 and B2, with the other switch using the letters C and D correspondingly.

I connect A1 and C1 to +, and B1 and D1 to -.
I connect A to C, and B to D.
I connect X to A2 and D2, and Y to B2 and C2.

Call each switch "off" when it is in the "1" position, i.e. A=A1, etc,
and "on" when in the "2" position, i.e. A=A2, etc.

When both switches are "off", X and Y are not connected to anything.
When both switches are "on", + and - are not connected to anything,
but X and Y are conncted harmlessly to each other.
When at least one switch is "off", A and C are connected to +, and
B and D are connected to -.
When at least one switch is "on", X is connected either to A and hence +
or else to D and hence -, depending on whether switch AB or CD is on.
Correspondingly Y would be connected to B and hence - or to C and hence +.

QEF, eh? I like it.

Ronald Raygun wrote:
Well I used 2g 2way light switch.

Is there a prize?

There is no prize other than your own satisfaction, but if there were
a prize, you would be disqualified on grounds of being too expert. I
was interested in whether harry could do it. :-)

Presuming that the "g" in your "2g 2way" stands for "gang", i.e. that
the switch has two poles, each of which can be switched 2 ways, in
what is commonly referred to as a DPDT switch, then yes, that's the
answer to Q1. Indeed I have already given wiring solution for that
one.

A 2g 2way switch is two seperate SPDT switches with SPDT defined here

http://en.wikipedia.org/wiki/Switch

But Q2 explicitly specifies that you must use two switches, one to
operate each lamp.

I did a 2g means two switches on the same faceplate:-)

I find I need two DPDT switches for that (I don't
know if there is a simpler solution), and the puzzle lies in working
out how to wire them up so that when switch A is on and B is off,
then the two cores X and Y of the cable are connected to + and -,
respectively, whereas when switch B is on and A is off, you want X
and Y to be - and +, respectively, instead.

When you turn both switches on, you don't want to short out the
battery, or blow your fuse if there is one, as you would if your
solution were based on two 2g 1way (DPST) switches.

Turning both switches on simultaneously is an operator error
condition, since you can't turn both lamps on together. What gets
connected to X and Y in those circumstances may be undefined if you
wish, but preferably it should be that X and Y are both disconnected
from the battery, same as when both switches are off.

Ah, now you adding bits to make it harder. My setup does not disconnect the
lights from the battery.

--
Adam

Andy Wade wrote:
On 24/03/2011 23:22, Ronald Raygun wrote:
However, there is a solution involving two double pole changeover
switches.

Surely you can do it with two single-pole changeover (SPDT) switches.
Using your terminal naming, so SW1 has 'fixed' contacts A1 & A2 and
common or moving contact A (and SW2 similarly has B1, B2 and B). Now
connect

- A1 and B1 to -ve supply
- A2 and B2 to +ve supply
- A and B to the outgoing wires X and Y.

If both switches are 'up' or 'down' X & Y are connected to the same
supply pole, so both lights are off. If one is up and the other down
there will be an output to X & Y, with the polarity dependent on which
switch is up.


I was going the make Ronald work it out for himself as he likes a challenge.

--
Adam

ARWadsworth wrote:

Ronald Raygun wrote:
Well I used 2g 2way light switch.

Is there a prize?

There is no prize other than your own satisfaction, but if there were
a prize, you would be disqualified on grounds of being too expert. I
was interested in whether harry could do it. :-)

Presuming that the "g" in your "2g 2way" stands for "gang", i.e. that
the switch has two poles, each of which can be switched 2 ways, in
what is commonly referred to as a DPDT switch, then yes, that's the
answer to Q1. Indeed I have already given wiring solution for that
one.

A 2g 2way switch is two seperate SPDT switches with SPDT defined here

http://en.wikipedia.org/wiki/Switch

But Q2 explicitly specifies that you must use two switches, one to
operate each lamp.

I did a 2g means two switches on the same faceplate:-)

I know what SPDT etc means, it's the "2g" part that was unfamiliar. It's
also misleading if you use a term containing the word "switch" in the
singular to denote what is in fact two independent switches. That's what
led me to the wrong conclusion above about what you meant.

Turning both switches on simultaneously is an operator error
condition, since you can't turn both lamps on together. What gets
connected to X and Y in those circumstances may be undefined if you
wish, but preferably it should be that X and Y are both disconnected
from the battery, same as when both switches are off.

Ah, now you adding bits to make it harder.

I didn't mean to make it harder.

My setup does not disconnect the lights from the battery.

That's fair enough, I only said "preferably". That X and Y are at the
same potential is good enough.

Ronald Raygun wrote:
ARWadsworth wrote:

Ronald Raygun wrote:
Well I used 2g 2way light switch.

Is there a prize?

There is no prize other than your own satisfaction, but if there
were a prize, you would be disqualified on grounds of being too
expert. I was interested in whether harry could do it. :-)

Presuming that the "g" in your "2g 2way" stands for "gang", i.e.
that the switch has two poles, each of which can be switched 2
ways, in what is commonly referred to as a DPDT switch, then yes,
that's the answer to Q1. Indeed I have already given wiring
solution for that one.

A 2g 2way switch is two seperate SPDT switches with SPDT defined here

http://en.wikipedia.org/wiki/Switch

But Q2 explicitly specifies that you must use two switches, one to
operate each lamp.

I did a 2g means two switches on the same faceplate:-)

I know what SPDT etc means, it's the "2g" part that was unfamiliar.

A UK terminology. But never mind, we got there in the end and you can now
impress your mates with the "new" answer.

Personally I love puzzles.

--
Adam