Any suggestions for a source of illuminated light switch as a reminder
that the light it feeds is still on? We have a loo under the stairs with
the light switch on the outside and it sometimes gets left switched on
so the fan remains running (as well as the light being on). I don't want
to fit a clunky 20Amp DP mains switch like this
http://www.fastlec.co.uk/mk-20a-dp-s...whi-p-538.html
or this
http://www.fastlec.co.uk/mk-20a-dp-s...whi-p-539.html

What I really want is a basic light switch like this
http://www.fastlec.co.uk/mk-10a-1g-s...whi-p-511.html
but with a neon indicator incorporated. I can't find such a thing, the
nearest being this http://www.tlc-direct.co.uk/Products/DT2503A.html but
it works the wrong way round - the illumination is 'on' when the switch
is 'off' - its so you can find the switch in the dark. I suspect the
wiring could be reversed, but as it's intended to show up in the dark it
may not be bright enough for use in a lighted area.

I also found this
http://www.fastlec.co.uk/mk-neon-loc...041-p-496.html
which is an illuminated section that sits between the switch and the
back-box. Again I'm not sure if its bright enough and it seems a bit of
an overkill.

I'm considering modifying a standard light switch by drilling a hole
into which a small neon or LED is fitted. There is some safety
consideration here so wonder if there is suitable double insulated
neon/led available. Failing that I think I need to create some kind or
perspex window in the switch with the neon/led behind it.

Any thoughts?

Phil

On Sat, 05 Sep 2009 16:25:46 +0100, Phil Addison wrote:

Any suggestions for a source of illuminated light switch as a reminder
that the light it feeds is still on? We have a loo under the stairs with
the light switch on the outside and it sometimes gets left switched on
so the fan remains running (as well as the light being on). I don't want
to fit a clunky 20Amp DP mains switch like this
http://www.fastlec.co.uk/mk-20a-dp-s...whi-p-538.html
or this
http://www.fastlec.co.uk/mk-20a-dp-s...whi-p-539.html

What I really want is a basic light switch like this
http://www.fastlec.co.uk/mk-10a-1g-s...whi-p-511.html
but with a neon indicator incorporated. I can't find such a thing, the
nearest being this http://www.tlc-direct.co.uk/Products/DT2503A.html but
it works the wrong way round - the illumination is 'on' when the switch
is 'off' - its so you can find the switch in the dark. I suspect the
wiring could be reversed, but as it's intended to show up in the dark it
may not be bright enough for use in a lighted area.

I also found this
http://www.fastlec.co.uk/mk-neon-loc...041-p-496.html
which is an illuminated section that sits between the switch and the
back-box. Again I'm not sure if its bright enough and it seems a bit of
an overkill.

I'm considering modifying a standard light switch by drilling a hole
into which a small neon or LED is fitted. There is some safety
consideration here so wonder if there is suitable double insulated
neon/led available. Failing that I think I need to create some kind or
perspex window in the switch with the neon/led behind it.

Any thoughts?

Phil

LEDs do not have insulation deemed suitable for mains, unless you have one
with a surround and lens. The other problem is that you don't normally have
a neutral available at a lightswitch, hence you can light a neon or LED
easily enough when the switch is off (using the switched light as the path
to neutral, as the current is too low to light it), but not when the switch
is on.

SteveW

In article ,
Phil Addison wrote:
What I really want is a basic light switch like this
http://www.fastlec.co.uk/mk-10a-1g-s...whi-p-511.html
but with a neon indicator incorporated. I can't find such a thing, the
nearest being this http://www.tlc-direct.co.uk/Products/DT2503A.html but
it works the wrong way round - the illumination is 'on' when the switch
is 'off' - its so you can find the switch in the dark. I suspect the
wiring could be reversed, but as it's intended to show up in the dark it
may not be bright enough for use in a lighted area.

Snag is light switches don't normally have a neutral available. The type
which is on with the light off gets the neutral via the light - since it
only takes a small current, the lightbulb looks like a short to it and
thus provides the return. I suppose you could run a small neon to earth -
since this is no worse than many SMPS do. But don't tell anyone I
suggested this.

--
*Parenthetical remarks (however relevant) are (usually) unnecessary *

Dave Plowman London SW
To e-mail, change noise into sound.

On 5 Sep, 18:57, Steve Walker wrote:
On Sat, 05 Sep 2009 16:25:46 +0100, Phil Addison wrote:
Any suggestions for a source of illuminated light switch as a reminder
that the light it feeds is still on? We have a loo under the stairs with
the light switch on the outside and it sometimes gets left switched on
so the fan remains running (as well as the light being on). I don't want
to fit a clunky 20Amp DP mains switch like this
http://www.fastlec.co.uk/mk-20a-dp-s...on-k5423d1whi-...
or this
http://www.fastlec.co.uk/mk-20a-dp-s...k5423whwhi-p-5...

What I really want is a basic light switch like this
http://www.fastlec.co.uk/mk-10a-1g-s...-k4870-whi-p-5...
but with a neon indicator incorporated. I can't find such a thing, the
nearest being thishttp://www.tlc-direct.co.uk/Products/DT2503A.htmlbut
it works the wrong way round - the illumination is 'on' when the switch
is 'off' - its so you can find the switch in the dark. I suspect the
wiring could be reversed, but as it's intended to show up in the dark it
may not be bright enough for use in a *lighted area.

I also found this
http://www.fastlec.co.uk/mk-neon-loc...041-p-496.html
which is an illuminated section that sits between the switch and the
back-box. Again I'm not sure if its bright enough and it seems a bit of
an overkill.

I'm considering modifying a standard light switch by drilling a hole
into which a small neon or LED is fitted. There is some safety
consideration here so wonder if there is suitable double insulated
neon/led available. Failing that I think I need to create some kind or
perspex window in the switch with the neon/led behind it.

Any thoughts?

Phil

LEDs do not have insulation deemed suitable for mains, unless you have one
with a surround and lens. The other problem is that you don't normally have
a neutral available at a lightswitch, hence you can light a neon or LED
easily enough when the switch is off (using the switched light as the path
to neutral, as the current is too low to light it), but not when the switch
is on.

SteveW

What the OP wants is a "panel neon", e.g.
http://www.maplin.co.uk/Search.aspx?...neon&source=15 or
LED: http://www.maplin.co.uk/Search.aspx?...0led&source=15
but check that they aren't too deep for the switch box.

However, I wonder whether a neon/LED will be prominent enough in
daylight, or too easy to ignore even if it is.

If the door is visible down a corridor, you could just drill a hole,
or even replace a whole panel with frosted glass, but again it may be
difficult to see in daylight.

A third possibility is to replace the switch by a motion (sorry)
detector as used for security lights.

A delayed-off time switch is another possibility, but would need to be
inside so that it could be reactivated if things take longer than
expected!

Chris

"Dave Plowman (News)" wrote in message
...

Snag is light switches don't normally have a neutral available. The type
which is on with the light off gets the neutral via the light - since it
only takes a small current, the lightbulb looks like a short to it and
thus provides the return. I suppose you could run a small neon to earth -
since this is no worse than many SMPS do. But don't tell anyone I
suggested this.

As long as the rcd, if present, doesn't trip.

On Sat, 5 Sep 2009 10:44:16 -0700 (PDT),
wrote:

A third possibility is to replace the switch by a motion (sorry)
detector as used for security lights.

A PIR is a good solution. I had one in the kitchen of my old flat as
I'd be for ever leaving the lights on (3 x 100W spots) and
forgetting. Has the advantage that the light comes on automagically
when you enter and if it does switch off you just wave to switch it
back on.

An inital thought was a micro switch operated by the door, closed =
off. But that isn't very convenient when the room is in use. I don't
think a two way switching arrangement would solve that either.

--
Cheers
Dave.

On Sat, 5 Sep 2009 10:44:16 -0700 (PDT),
wrote:

On 5 Sep, 18:57, Steve Walker wrote:
On Sat, 05 Sep 2009 16:25:46 +0100, Phil Addison wrote:
Any suggestions for a source of illuminated light switch as a reminder
that the light it feeds is still on? We have a loo under the stairs with
the light switch on the outside and it sometimes gets left switched on
so the fan remains running (as well as the light being on). I don't want
to fit a clunky 20Amp DP mains switch like this
http://www.fastlec.co.uk/mk-20a-dp-s...on-k5423d1whi-...
or this
http://www.fastlec.co.uk/mk-20a-dp-s...k5423whwhi-p-5...

What I really want is a basic light switch like this
http://www.fastlec.co.uk/mk-10a-1g-s...-k4870-whi-p-5...
but with a neon indicator incorporated. I can't find such a thing, the
nearest being this http://www.tlc-direct.co.uk/Products/DT2503A.html but
it works the wrong way round - the illumination is 'on' when the switch
is 'off' - its so you can find the switch in the dark. I suspect the
wiring could be reversed, but as it's intended to show up in the dark it
may not be bright enough for use in a *lighted area.

I also found this
http://www.fastlec.co.uk/mk-neon-loc...041-p-496.html
which is an illuminated section that sits between the switch and the
back-box. Again I'm not sure if its bright enough and it seems a bit of
an overkill.

I'm considering modifying a standard light switch by drilling a hole
into which a small neon or LED is fitted. There is some safety
consideration here so wonder if there is suitable double insulated
neon/led available. Failing that I think I need to create some kind or
perspex window in the switch with the neon/led behind it.

Any thoughts?

Phil

LEDs do not have insulation deemed suitable for mains, unless you have one
with a surround and lens. The other problem is that you don't normally have
a neutral available at a lightswitch, hence you can light a neon or LED
easily enough when the switch is off (using the switched light as the path
to neutral, as the current is too low to light it), but not when the switch
is on.

SteveW

What the OP wants is a "panel neon", e.g.
http://www.maplin.co.uk/Search.aspx?...neon&source=15 or

Thats the one! thank you! enclosed and fully mains rated. The box is
51mm deep from front of switch so the 29mm lamp will fit easily.

LED: http://www.maplin.co.uk/Search.aspx?...0led&source=15
but check that they aren't too deep for the switch box.

However, I wonder whether a neon/LED will be prominent enough in
daylight, or too easy to ignore even if it is.

We walk past it often enough so I think the red neon will be fine.

If the door is visible down a corridor, you could just drill a hole,
or even replace a whole panel with frosted glass, but again it may be
difficult to see in daylight.

A third possibility is to replace the switch by a motion (sorry)
detector as used for security lights.

A delayed-off time switch is another possibility, but would need to be
inside so that it could be reactivated if things take longer than
expected!

I did have the switch inside originally, but of course its dark in there
until you find where the switch is, so moved it outside, where it does
seem more 'convenient' on the whole.

As others pointed out (thank you Steve, Dave) the neutral is absent, but
I can run one in fairly easily, but am inclined to use the earth. IIRC
the series resistor is usually of the order of 220K so only adds a
milliamp to the leakage current. I can always add the neutral later if
leakage is a problem. My CU is due for an upgrade anyway as it is
currently the old fuse-box type.

Phil

coughed up some electrons that declared:

What the OP wants is a "panel neon", e.g.
http://www.maplin.co.uk/Search.aspx?...neon&source=15 or
LED: http://www.maplin.co.uk/Search.aspx?...0led&source=15
but check that they aren't too deep for the switch box.

However, I wonder whether a neon/LED will be prominent enough in
daylight, or too easy to ignore even if it is.

I was going to suggest a grid switch panel (single gang, 2 grid modules),
one 10AX switch and one grid indicator (amber, red or green). Those are all
designed for easy wiring and of course 240V.

The problem remains as to where to get a neutral from. I'm not sure what
current a grid neon takes (largely determined by the series resistor, but I
wouldn't advocate linking it to earth.

B&Q sell the MK range of grid stuff including indicators, but GET do a nice
range with pretty switches and nice panels if you need to match some
existing scheme eg brass or white nickle etc.

Cheers

Tim

On Sep 5, 4:25*pm, Phil Addison wrote:
Any suggestions for a source of illuminated light switch as a reminder
that the light it feeds is still on? We have a loo under the stairs with
the light switch on the outside and it sometimes gets left switched on
so the fan remains running (as well as the light being on). I don't want
to fit a clunky 20Amp DP mains switch like thishttp://www.fastlec.co.uk/mk-20a-dp-switch-bottom-flexneon-k5423d1whi-...
or thishttp://www.fastlec.co.uk/mk-20a-dp-switch-water-heater-k5423whwhi-p-5...

Depending on what aspect of these switches you find clunky, other
brands may be more suitable. Crabtree's DP switch is visually very
similar to the light switch, so the neon version looks like a light
switch with a neon just above the switch.

A

wrote in message
...
On Sep 5, 4:25 pm, Phil Addison wrote:
Any suggestions for a source of illuminated light switch as a reminder
that the light it feeds is still on? We have a loo under the stairs with
the light switch on the outside and it sometimes gets left switched on
so the fan remains running (as well as the light being on). I don't want
to fit a clunky 20Amp DP mains switch like
thishttp://www.fastlec.co.uk/mk-20a-dp-switch-bottom-flexneon-k5423d1whi-...
or
thishttp://www.fastlec.co.uk/mk-20a-dp-switch-water-heater-k5423whwhi-p-5...

Depending on what aspect of these switches you find clunky, other
brands may be more suitable. Crabtree's DP switch is visually very
similar to the light switch, so the neon version looks like a light
switch with a neon just above the switch.

I used
http://www.toolstation.com/shop/Elec...es/d190/sd2723
so i had a light next to the switch in my shed.
They are cheap, but as its been said before you need a neutral.
I suppose it would be possible to retrofit a flashing led into a neon
housing and run it on batteries for months at a time.

A

On Sep 5, 4:25*pm, Phil Addison wrote:
Any suggestions for a source of illuminated light switch as a reminder
that the light it feeds is still on? We have a loo under the stairs with
the light switch on the outside and it sometimes gets left switched on
so the fan remains running (as well as the light being on). I don't want
to fit a clunky 20Amp DP mains switch like thishttp://www.fastlec.co.uk/mk-20a-dp-switch-bottom-flexneon-k5423d1whi-...
or thishttp://www.fastlec.co.uk/mk-20a-dp-switch-water-heater-k5423whwhi-p-5...

What I really want is a basic light switch like thishttp://www.fastlec.co..uk/mk-10a-1g-sp-1-way-plateswitch-k4870-whi-p-5...
but with a neon indicator incorporated. I can't find such a thing, the
nearest being thishttp://www.tlc-direct.co.uk/Products/DT2503A.htmlbut
it works the wrong way round - the illumination is 'on' when the switch
is 'off' - its so you can find the switch in the dark. I suspect the
wiring could be reversed, but as it's intended to show up in the dark it
may not be bright enough for use in a *lighted area.

I also found thishttp://www.fastlec.co.uk/mk-neon-locator-200250v-50hz-k3041-p-496.html
which is an illuminated section that sits between the switch and the
back-box. Again I'm not sure if its bright enough and it seems a bit of
an overkill.

I'm considering modifying a standard light switch by drilling a hole
into which a small neon or LED is fitted. There is some safety
consideration here so wonder if there is suitable double insulated
neon/led available. Failing that I think I need to create some kind or
perspex window in the switch with the neon/led behind it.

Any thoughts?

Phil


Cnnected from L to E a neon on a 220k resistor will add in the region
of 0.7mA. An ultrabright LED can be run off much less than 1mA with
decent light output. And if you run it from a CR dropper the power
diss would be even tinier. The LED would need a rectifier of course.


NT

Cnnected from L to E a neon on a 220k resistor will add in the region
of 0.7mA. An ultrabright LED can be run off much less than 1mA with
decent light output. And if you run it from a CR dropper the power
diss would be even tinier. The LED would need a rectifier of course.


NT
Wouldnt this add to RCD trip current?

Why not wire it between L and N?

And how does the switchlite work?
http://www.tlc-direct.co.uk/Products/DT2503A.html
it glows when not switched on,
but has no Neutral or Earth connection,
is it like my neon mains testing screwdriver?

[g]

george (dicegeorge) coughed up some electrons that declared:




Cnnected from L to E a neon on a 220k resistor will add in the region
of 0.7mA. An ultrabright LED can be run off much less than 1mA with
decent light output. And if you run it from a CR dropper the power
diss would be even tinier. The LED would need a rectifier of course.


NT
Wouldnt this add to RCD trip current?

Why not wire it between L and N?

And how does the switchlite work?
http://www.tlc-direct.co.uk/Products/DT2503A.html
it glows when not switched on,
but has no Neutral or Earth connection,
is it like my neon mains testing screwdriver?

No - that neon goes across the switch and uses the load as a relative
neutral when switched off - which works well with a resistive load.
Electronic loads, eg a CFL are a different story but if the current is low
enough you may get away with it. In other cases you can get weird effects
like the CFL flashing.

In article ,
dennis@home wrote:
Snag is light switches don't normally have a neutral available. The
type which is on with the light off gets the neutral via the light -
since it only takes a small current, the lightbulb looks like a short
to it and thus provides the return. I suppose you could run a small
neon to earth - since this is no worse than many SMPS do. But don't
tell anyone I suggested this.

As long as the rcd, if present, doesn't trip.

It won't from a neon alone - they take near zero current. Otherwise neon
screwdrivers would be a tad dangerous. IIRC, of the order of 1-2 mA. Less
than many SMPS dump onto the earth.

--
*A picture may be worth a thousand words, but it uses up a thousand times more memory.

Dave Plowman London SW
To e-mail, change noise into sound.

In article
,
NT wrote:
The LED would need a rectifier of course.

You just parallel a reverse connected diode to the LED for AC. Plus a
suitable current limiting resistor, of course.

--
*The first rule of holes: If you are in one, stop digging!

Dave Plowman London SW
To e-mail, change noise into sound.

On Sat, 05 Sep 2009 23:06:12 +0100, John Rumm
wrote:

Phil Addison wrote:

I'm considering modifying a standard light switch by drilling a hole
into which a small neon or LED is fitted. There is some safety
consideration here so wonder if there is suitable double insulated
neon/led available. Failing that I think I need to create some kind or
perspex window in the switch with the neon/led behind it.

Any thoughts?

You can get things like:

http://www.tlc-direct.co.uk/Products/GU2011.html

which although designed for heavier loads are not particularly clunky in
use. However, they suffer the usual limitation of requiring a neutral at
the switch position to work.

I don't know this particular one, but the ones I have seen require quite
a lot more pressure than a light switch rocker, and emit a resounding
'click' when operated. That's why I'm looking for an alternative. I'm
off to maplin tomorrow for their red neon as posted by steve, so its
going to be a DIY job!! Must say I was surpprised to find the big names
don't make a SP lighting circuit varient of the 20A DP SW+neon.

Phil

On Sat, 05 Sep 2009 23:59:22 +0100, "Dave Plowman (News)"
wrote:

In article
,
NT wrote:
The LED would need a rectifier of course.

You just parallel a reverse connected diode to the LED for AC. Plus a
suitable current limiting resistor, of course.

That's neat. That will bypasses the LED on the reverse cycle, and is
probably easier to wire in than a series diode. It allows you to use a
tiny low voltage diode whereas the series one needs to be a bigger mains
rated 1N400x series. OTOH it draws twice the current of the series
solution, but still a mA or so.

Doesn't the 1/2 wave rectification halve the brightness though? An
electrolytic capacitor in parallel should solve that if it doesn't need
too many uF's - haven't calculated the size.

Phil

On Sep 5, 11:27*pm, "george (dicegeorge)"
wrote:
Cnnected from L to E a neon on a 220k resistor will add in the region
of 0.7mA. An ultrabright LED can be run off much less than 1mA with
decent light output. And if you run it from a CR dropper the power
diss would be even tinier. The LED would need a rectifier of course.

NT

Wouldnt this add to RCD trip current?

yes, but by very little


Why not wire it between L and N?

there's often no N present


NT

On Sep 5, 11:59*pm, "Dave Plowman (News)"
wrote:
In article
,
* *NT wrote:

The LED would need a rectifier of course.

You just parallel a reverse connected diode to the LED for AC. Plus a
suitable current limiting resistor, of course.

you can, but the resulting flicker is terrible. Worth going for 100Hz
flicker imho. That also gets you half the capacitor size.


NT

On Sep 6, 12:25*am, Phil Addison wrote:
On Sat, 05 Sep 2009 23:59:22 +0100, "Dave Plowman (News)"

wrote:
In article
,
* *NT wrote:
The LED would need a rectifier of course.

You just parallel a reverse connected diode to the LED for AC. Plus a
suitable current limiting resistor, of course.

That's neat. That will bypasses the LED on the reverse cycle, and is
probably easier to wire in than a series diode. It allows you to use a
tiny low voltage diode whereas the series one needs to be a bigger mains
rated 1N400x series. OTOH it draws twice the current of the series
solution, but still a mA or so.

Doesn't the 1/2 wave rectification halve the brightness though? An
electrolytic capacitor in parallel should solve that if it doesn't need
too many uF's - haven't calculated the size.

Phil

Thats another downside of the circuit, you cant smooth the power with
a little reservoir capacitor.


NT

On Sat, 5 Sep 2009 18:24:02 -0700 (PDT), NT wrote:

On Sep 5, 11:27*pm, "george (dicegeorge)"
wrote:
Cnnected from L to E a neon on a 220k resistor will add in the region
of 0.7mA. An ultrabright LED can be run off much less than 1mA with
decent light output. And if you run it from a CR dropper the power
diss would be even tinier. The LED would need a rectifier of course.

NT

Wouldnt this add to RCD trip current?

yes, but by very little

Why not wire it between L and N?

there's often no N present

NT

um, how about a switch with very obvious on and off appearance and just
look at it.
--
Peter.
The head of a pin will hold more angels if
it's been flattened with an angel-grinder.

In uk.d-i-y, NT wrote:
On Sep 5, 11:59*pm, "Dave Plowman (News)"
wrote:
In article
,
* *NT wrote:

The LED would need a rectifier of course.

You just parallel a reverse connected diode to the LED for AC. Plus a
suitable current limiting resistor, of course.

you can, but the resulting flicker is terrible. Worth going for 100Hz
flicker imho. That also gets you half the capacitor size.

How about a pair of LEDs, reversed and paralleled, and mounted very
close to each other (perhaps behind the same diffuser)?

And there must be a reason why you can't connect the diode pair in
series with the load, otherwise it would have been suggested by now.
What's the reason?

--
Mike Barnes

"Phil Addison" wrote in message
...


Doesn't the 1/2 wave rectification halve the brightness though? An
electrolytic capacitor in parallel should solve that if it doesn't need
too many uF's - haven't calculated the size.

It will flicker wont it.

On Sun, 06 Sep 2009 04:36:03 +0100, John Rumm wrote:

One solution you could try:

R1 LED1
-\/\/\--|^---
| |
| D1 D2 D3 | /
Live in ------|--|--|------o o---------- to lamp
| | sw1
| D4 |
-----|-------

Interesting idea. An improvement might be to use back to back zeners
in place of D1 to 4.

On a quick search I can only find 5v1 ones at 5W dissipation so the
upper limit on the lamp load would be 230W (ish) and you'd have 10W
of heat to get rid of at 230W load. Now if there are some 2v zeners
out there at 2W dissipation...

--
Cheers
Dave.

On Sep 6, 9:46*am, Mike Barnes wrote:
In uk.d-i-y, NT wrote:
On Sep 5, 11:59*pm, "Dave Plowman (News)"
wrote:
In article
,
* *NT wrote:

The LED would need a rectifier of course.

You just parallel a reverse connected diode to the LED for AC. Plus a
suitable current limiting resistor, of course.

you can, but the resulting flicker is terrible. Worth going for 100Hz
flicker imho. That also gets you half the capacitor size.

How about a pair of LEDs, reversed and paralleled, and mounted very
close to each other (perhaps behind the same diffuser)?

And there must be a reason why you can't connect the diode pair in
series with the load, otherwise it would have been suggested by now.
What's the reason?

You can put a diode in series with the LED. But... you then need a
leakage resistor across the LED, you get bad flicker, and you can only
use an R dropper, not a CR.


NT

On Sep 6, 1:14*pm, "Dave Liquorice"
wrote:
On Sun, 06 Sep 2009 04:36:03 +0100, John Rumm wrote:
One solution you could try:

* * * * * * * * R1 * *LED1
* * * * * * * -\/\/\--|^---
* * * * * * *| * * * * * * *|
* * * * * * *| *D1 *D2 *D3 *| * */
Live in *------|--|--|------o o---------- to lamp
* * * * * * *| * * * * * * *| * sw1
* * * * * * *| * * *D4 * * *|
* * * * * * * -----|-------

Interesting idea. An improvement might be to use back to back zeners
in place of D1 to 4.

On a quick search I can only find 5v1 ones at 5W dissipation so the
upper limit on the lamp load would be 230W (ish) and you'd have 10W
of heat to get rid of at 230W load. Now if there are some 2v zeners
out there at 2W dissipation...

filament lamps eat around 8x rated current at switch on, but diodes
dont tolerate these overloads. So your real life lamp limit for a 5v
5w 1A zener will be 1/8A apx, or around 30w.


NT

On Sun, 06 Sep 2009 15:52:22 +0100, John Rumm
wrote:

Dave Liquorice wrote:
On Sun, 06 Sep 2009 04:36:03 +0100, John Rumm wrote:

One solution you could try:

R1 LED1
-\/\/\--|^---
| |
| D1 D2 D3 | /
Live in ------|--|--|------o o---------- to lamp
| | sw1
| D4 |
-----|-------

Interesting idea. An improvement might be to use back to back zeners
in place of D1 to 4.

On a quick search I can only find 5v1 ones at 5W dissipation so the
upper limit on the lamp load would be 230W (ish) and you'd have 10W
of heat to get rid of at 230W load. Now if there are some 2v zeners
out there at 2W dissipation...

I had thought of using a zenner but as you say there are difficulties
finding suitable devices, and bog standard rectifier diodes are dirt
cheap and robust. I used a version of this circuit on a battery charger
I built for an "on charger" light. It was a wide ranging charger that
might be dealing with anything from a single 1.2V cell up to about 30V
and currents from 9mA through to over an amp. The circuit above (without
D4 since this was DC) works flawlessly. Three diodes seemed to get
ample voltage to light the LED even if it was a bit below the 2.5V spec.

In the end I opted for simplicity and used the Maplin panel mount red
neon (BK52) which cost 99p, and took the return to earth; it works fine.

Here's the details...

1 Solder flex tail to neon, insulate with heat-shrink, and fit in 6.5mm
hole http://img35.imageshack.us/img35/760...nthewiresz.jpg

2 I soldered the fine wires to the switched load and earth of the mains
cable to guarantee a lasting connection
http://img142.imageshack.us/img142/7...redthefine.jpg

3 Reconnect mains cable to switch and the earth contact of back-box
http://img36.imageshack.us/img36/484...ecttoswitc.jpg

4 The re-fitted switch with its new red neon
http://img42.imageshack.us/img42/373...ittedswitc.jpg

5 Success!! http://img178.imageshack.us/img178/3...861success.jpg

Thanks for all the input and neat LED ideas, but its hard to beat the
neon for simplicity, cost, very low current draw, no visible flicker
(100Hz), all round visibility, and ready availability in panel mount.

Phil

In uk.d-i-y, John Rumm wrote:
Mike Barnes wrote:
In uk.d-i-y, NT wrote:
On Sep 5, 11:59 pm, "Dave Plowman (News)"
wrote:
In article
,
NT wrote:

The LED would need a rectifier of course.
You just parallel a reverse connected diode to the LED for AC. Plus a
suitable current limiting resistor, of course.
you can, but the resulting flicker is terrible. Worth going for 100Hz
flicker imho. That also gets you half the capacitor size.
How about a pair of LEDs, reversed and paralleled, and mounted very
close to each other (perhaps behind the same diffuser)?

That might solve the flicker issue - but TBH, 50Hz flicker is not going
to be an issue for this application.

People do complain about 50Hz flicker. Not me, but some people.

And there must be a reason why you can't connect the diode pair in
series with the load, otherwise it would have been suggested by now.
What's the reason?

What a pair of LEDs? The have a max forward voltage of *significantly*
less than mains, and a max power handling down in the mW range.

I don't understand the relevance of those parameters to the application.
I see a single-LED series circuit being discussed elsewhere in this
thread, which suggests that it's not impossible.

--
Mike Barnes

In article ,
Phil Addison writes:
Any suggestions for a source of illuminated light switch as a reminder
that the light it feeds is still on? We have a loo under the stairs with
the light switch on the outside and it sometimes gets left switched on
so the fan remains running (as well as the light being on). I don't want
to fit a clunky 20Amp DP mains switch like this

Replace the switch with an occupancy sensor (mains PIR)
inside the room, or just leave the switch on all the time
and add the occupancy sensor next to the light, or replace
with a light fitting with a built-in occupancy sensor.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article
,
NT wrote:
On Sep 5, 11:59 pm, "Dave Plowman (News)"
wrote:
In article
,
NT wrote:

The LED would need a rectifier of course.

You just parallel a reverse connected diode to the LED for AC. Plus a
suitable current limiting resistor, of course.

you can, but the resulting flicker is terrible. Worth going for 100Hz
flicker imho. That also gets you half the capacitor size.

I suppose it depends on the individual but I didn't notice it.

--
*Don't worry; it only seems kinky the first time.*

Dave Plowman London SW
To e-mail, change noise into sound.

On Sat, 5 Sep 2009 15:01:58 -0700 (PDT), NT wrote:

An ultrabright LED can be run off much less than 1mA with decent light
output.

Certainly so, got a bit of kit with a blindingly bright blue LED on
the front. It lit the room up at night! Hacked into the wiring to add
a series resistor, the thing would glow with the leakage through my
dry fingers from the 3v supply. IIRC it now taking 60uA and is still
too bright...

--
Cheers
Dave.

On Sep 7, 1:23*am, John Rumm wrote:
Mike Barnes wrote:
In uk.d-i-y, John Rumm wrote:
Mike Barnes wrote:
In uk.d-i-y, NT wrote:
On Sep 5, 11:59 pm, "Dave Plowman (News)"
wrote:
In article
,
* *NT wrote:

The LED would need a rectifier of course.
You just parallel a reverse connected diode to the LED for AC. Plus a
suitable current limiting resistor, of course.
you can, but the resulting flicker is terrible. Worth going for 100Hz
flicker imho. That also gets you half the capacitor size.
*How about a pair of LEDs, reversed and paralleled, and mounted very
close to each other (perhaps behind the same diffuser)?
That might solve the flicker issue - but TBH, 50Hz flicker is not going
to be an issue for this application.

People do complain about 50Hz flicker. Not me, but some people.

I am one of them - especially on TVs and monitors etc, but we are
talking about a power on light here! ;-)


Light bulbs and tv screens behave differently wrt flicker though. TV
screens simply move the position of the light output at 50Hz, whereas
with a bulb the whole lot goes on and off together at 50Hz, causing a
much worse effect.

I just dont see any advantage in a 50Hz flickering circuit. It eats
twice as much power for the same light output, it flickers.


NT

In article
,
NT wrote:
I just dont see any advantage in a 50Hz flickering circuit. It eats
twice as much power for the same light output, it flickers.

For a warning light might be a good thing - draws your attention to it?

I use an LM 317 for this which flashes at 4 times a second.

--
*I used up all my sick days so I called in dead

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article
,
NT wrote:
I just dont see any advantage in a 50Hz flickering circuit. It eats
twice as much power for the same light output, it flickers.

For a warning light might be a good thing - draws your attention to it?

I use an LM 317 for this which flashes at 4 times a second.

I don't see why he doesn't just use a battery powered flashing LED like I
suggested ages ago.
All he needs is a double pole switch, one pole switches the light the other
the LED.
The batteries will last for months/years as the LED on flashes when the
switch is on.
No fancy components required.
The 20A grid switches I posted a link to have more than enough insulation to
do this.

In article ,
dennis@home wrote:
I don't see why he doesn't just use a battery powered flashing LED like
I suggested ages ago. All he needs is a double pole switch, one pole
switches the light the other the LED. The batteries will last for
months/years as the LED on flashes when the switch is on. No fancy
components required. The 20A grid switches I posted a link to have more
than enough insulation to do this.

There wouldn't be room for even a PP3 inside most back boxes. Certainly
not a plaster depth one.

But Phil has already solved his problem.

--
*Rehab is for quitters.

Dave Plowman London SW
To e-mail, change noise into sound.

On Sep 7, 10:10*am, "Dave Plowman (News)"
wrote:
In article
,
* *NT wrote:

I just dont see any advantage in a 50Hz flickering circuit. It eats
twice as much power for the same light output, it flickers.

For a warning light might be a good thing - draws your attention to it?

fair point. I'm not sure this situation counts as a warning light
though, they've got to live with it on for plenty of time once
installed.


NT

John Rumm coughed up some electrons that declared:

Again, its a LED power on indicator, do we care? If so, add another
couple of diodes to the reverse path and a second LED mounted close the
the first; or use a dual chip LED that looks like one indicator but has
two devices internally...


Did anyone say "bridge rectifier"? 4 diodes (or one small package, 4 leads),
1 led and 100Hz flicker, which I'm fairly sure would not be perceivable to
most people.

Cheers

Tim

On Sat, 05 Sep 2009 16:25:46 +0100, Phil Addison wrote:

Any suggestions for a source of illuminated light switch as a reminder
that the light it feeds is still on? We have a loo under the stairs with
the light switch on the outside and it sometimes gets left switched on
so the fan remains running (as well as the light being on). I don't want
to fit a clunky 20Amp DP mains switch like this
http://www.fastlec.co.uk/mk-20a-dp-s...whi-p-538.html
or this
http://www.fastlec.co.uk/mk-20a-dp-s...whi-p-539.html

What I really want is a basic light switch like this
http://www.fastlec.co.uk/mk-10a-1g-s...whi-p-511.html
but with a neon indicator incorporated. I can't find such a thing, the
nearest being this http://www.tlc-direct.co.uk/Products/DT2503A.html but
it works the wrong way round - the illumination is 'on' when the switch
is 'off' - its so you can find the switch in the dark. I suspect the
wiring could be reversed, but as it's intended to show up in the dark it
may not be bright enough for use in a lighted area.

I also found this
http://www.fastlec.co.uk/mk-neon-loc...041-p-496.html
which is an illuminated section that sits between the switch and the
back-box. Again I'm not sure if its bright enough and it seems a bit of
an overkill.

I'm considering modifying a standard light switch by drilling a hole
into which a small neon or LED is fitted. There is some safety
consideration here so wonder if there is suitable double insulated
neon/led available. Failing that I think I need to create some kind or
perspex window in the switch with the neon/led behind it.

Any thoughts?

Idly been watching this thread over the last couple of days looking at some
of the weird and wonderful suggestions.

I did something like this many many years ago for loft lights, back in the
days when I thought I was going to build a model railway - never did
happen! All I did was drill and fit a small neon indicator in one corner of
the switch plate, wired switch terminal to earth on the box. Alright, I
know it was back in the days when rcds weren't commonly used, but taking a
quick look at the Farnell web site, many of their 230v leds have a forward
current of about 3mA so shouldn't present too much of a problem.


--
The Wanderer

All wighy, rho sriyched yhe ket pads on my ketboawd?

On Sun, 06 Sep 2009 19:49:18 +0100, Phil Addison
wrote:

In the end I opted for simplicity and used the Maplin panel mount red
neon (BK52) which cost 99p, and took the return to earth; it works fine.

Here's the details...

1 Solder flex tail to neon, insulate with heat-shrink, and fit in 6.5mm
hole http://img35.imageshack.us/img35/760...nthewiresz.jpg

2 I soldered the fine wires to the switched load and earth of the mains
cable to guarantee a lasting connection
http://img142.imageshack.us/img142/7...redthefine.jpg

3 Reconnect mains cable to switch and the earth contact of back-box
http://img36.imageshack.us/img36/484...ecttoswitc.jpg

4 The re-fitted switch with its new red neon
http://img42.imageshack.us/img42/373...ittedswitc.jpg

5 Success!! http://img178.imageshack.us/img178/3...861success.jpg

Thanks for all the input and neat LED ideas, but its hard to beat the
neon for simplicity, cost, very low current draw, no visible flicker
(100Hz), all round visibility, and ready availability in panel mount.

.... and today we realised it also provides a clear 'engaged' indication.
OK, the LED schemes would do that as well, but the PIR's would not.

Phil

On Sun, 06 Sep 2009 04:36:03 +0100, John Rumm
wrote:

Phil Addison wrote:

Must say I was surprised to find the big names
don't make an SP lighting circuit varient of the 20A DP SW+neon.

The problem being the typical lack of neutral - hence nowhere to put it!

That only applies to (some) retro-fits and, even then, routing in a
neutral is not impossible. Why isn't such an indicator light-switch
available for new builds where the electrician would know in advance
that a neutral is required? Is it so unusual to have the switch on the
outside of the understairs loo?

Phil