Hi,

I have discovered the fatal flaw in my pull switch and humidistat bathroom
fan.

I cannot tell if the humidiatat is on or the pull switch is on.

I have worked out the wiring (which is how I first proved that the
humidistat was on most of the time) but I would like to fit a small LED
which only lights when current is passing through the switch.

To do this I need a 240v LED which can be mounted in a small hole in a
plastic casing.

Looked in Maplins but can't find a 240v LED - although most don't seem to
have a voltage rating.

Any ideas/sources?

TIA
Dave R

--

In article , David W.E.
Roberts writes
Hi,

I have discovered the fatal flaw in my pull switch and humidistat bathroom
fan.

I cannot tell if the humidiatat is on or the pull switch is on.

I have worked out the wiring (which is how I first proved that the
humidistat was on most of the time) but I would like to fit a small LED
which only lights when current is passing through the switch.

To do this I need a 240v LED which can be mounted in a small hole in a
plastic casing.

Looked in Maplins but can't find a 240v LED - although most don't seem to
have a voltage rating.

Any ideas/sources?

use a neon, not an LED. You can wire up LEDs to work at 240V but it
would be far simpler to use a mains neon, which would give a very
similar effect.
--
Tim Mitchell

Looked in Maplins but can't find a 240v LED - although most don't seem to
have a voltage rating.

Any ideas/sources?

Try looking for Neon rather than LED

Sean

"Sean Delere" wrote in message
...
Looked in Maplins but can't find a 240v LED - although most don't seem
to
have a voltage rating.

Any ideas/sources?

Try looking for Neon rather than LED

Sean



Thanks guys - will do

In article ,
David W.E. Roberts wrote:
Looked in Maplins but can't find a 240v LED - although most don't seem to
have a voltage rating.

That's because an LED is a DC current operated device. For normal DC
operation they require a series resistor the value of which depends on the
voltage it's running off and the current you wish to drive it with. For AC
use, you require a diode as well.

It's more normal to use a neon indicator, but if you'd prefer the look of
an LED it's easy enough if you can solder.

I *think* RS components do mains LED indicators ready made - they
certainly exist, I've got some.

--
*Change is inevitable, except from a vending machine.

Dave Plowman London SW 12
RIP Acorn

"David W.E. Roberts" wrote in
:


What I want to do is modify the casing of the fan so that an indicator
light shows when the switch is on.
If the switch is off, it is reasonable to assume that if the fan is
running this is due to the humidistat.

It would work equally well if a light came on when the humidistat was
active.

I just have two posssible reasons for the fan to be running and no way
of telling which.

Wire a mains neon ie one *with* a series resistor, between the switched
contact and neutral; connect the series resistor end to the live (switched
wire) side. Modify the case so you can see the neon, obseve safety at the
live end.

A LED would have to have 228V dropped across it's resistor, at about 10
mill thats about 2.3 watts - definitely not the way to go

mike r

Mike Ring wrote:

A LED would have to have 228V dropped across it's resistor, at about 10
mill thats about 2.3 watts - definitely not the way to go

You could use 3 or 4 series rectifier diodes and wire the LED + resistor
across these - that would give you a suitable voltage drop to power a
small LED. You would also need a reverse diode to bypass the LED so that
when the reverse phase comes along your LED does not go pop!


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article 0, Mike
Ring writes
John Rumm wrote in
:

Mike Ring wrote:

A LED would have to have 228V dropped across it's resistor, at about 10
mill thats about 2.3 watts - definitely not the way to go

. You would also need a reverse diode to bypass the LED so that
when the reverse phase comes along your LED does not go pop!


I am told the LED will not pop, the reverse current is limited by the
resistor to the forward current, and it can take this quite happily like a
xener.

In my working days I have been known to wire LEDs the wrong way round,
(Noooh?....well, once or twice), and it never hurt them.

Not true, LED's are only tolerant to a small reverse voltage, much less
than a normal diode. If you are working from a 9 volt PP3 then they will
be OK connected backwards. At 240V mains they will be destroyed by the
reverse polarity.
--
Tim Mitchell

Mike Ring wrote:

when the reverse phase comes along your LED does not go pop!



I am told the LED will not pop, the reverse current is limited by the
resistor to the forward current, and it can take this quite happily like a
xener.

Think you will find you want the reverse diode anyway, otherwise you are
going to be running your whole circuit half wave rectified since there
will be no path for the return phase!


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote in
:


Think you will find you want the reverse diode anyway, otherwise you
are going to be running your whole circuit half wave rectified since
there will be no path for the return phase!

The resultant 50Hz flicker gives a greater apparent brightness, like
strobed bike lamps for half the power dissipation!

Mike r

The resultant 50Hz flicker gives a greater apparent brightness, like
strobed bike lamps for half the power dissipation!

I thought we were talking about a supply to a fan here..... not sure
what it will make of half wave DC even if the LED can cope!

Yup, way back we decided it wasn't the way to go, this is just philosophy.

BTW, someone chucked a googly when they said some fans have a sort of
pulsed control, so the user's "mains on" state is fleeting.

I dunno what you do then....

mike r

mike ring wrote:

BTW, someone chucked a googly when they said some fans have a sort of
pulsed control, so the user's "mains on" state is fleeting.

I dunno what you do then....

Use a bi-stable circuit to act as a latching toggle control.....

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

mike ring writes:

The resultant 50Hz flicker gives a greater apparent brightness, like
strobed bike lamps for half the power dissipation!
I thought we were talking about a supply to a fan here..... not sure
what it will make of half wave DC even if the LED can cope!
Yup, way back we decided it wasn't the way to go, this is just philosophy.

Surprising that no one uses a bidirectional LED (i.e. one containing two
back-to-back diodes), so that the 100 Hz flicker isn't apparent.

They're available with both diodes being of the same colour if desired,
and not expensive.

Just add in series one of those interference-suppressor devices
(actually 0.1 uF / 250VAC with 100 ohms in series) and you've got some
protection against current surges caused by spikes on the line.

A fairly cheap, non-dimming, non-flickering substitute for a neon.

Works for me in the occasional home-built contraption; maybe some
manufacturers actually use this arrangement?

--
Roy Millar, Use m o u l i n e t @

(Roy Millar) wrote in
:



Just add in series one of those interference-suppressor devices
(actually 0.1 uF / 250VAC with 100 ohms in series) and you've got some
protection against current surges caused by spikes on the line.

A fairly cheap, non-dimming, non-flickering substitute for a neon.

Works for me in the occasional home-built contraption; maybe some
manufacturers actually use this arrangement?

Sounds like a good idea, but google and maplin came up dry (well on google
the first umpteen hits), so who's gottem; also what sort of suppressor -
how would I know what's in it from it's description, or to measure it

mike r

In message , Roy Millar
wrote

Maplin sold me some a while ago, but now that they're reinventing
themselves as a kind of UK version of Tandy,

Tandy were cheap - Maplin is expensive even after the 'price
reductions'.

--
Alan

In message , Alan
writes
In message , Roy Millar
wrote

Maplin sold me some a while ago, but now that they're reinventing
themselves as a kind of UK version of Tandy,

Tandy were cheap - Maplin is expensive even after the 'price
reductions'.

They are currently selling a fart machine with 5 different noises for
£3.99 - that's cheap (the idea)
--
geoff

geoff wrote:
In message , Alan
writes
In message , Roy Millar
wrote

Maplin sold me some a while ago, but now that they're reinventing
themselves as a kind of UK version of Tandy,

Tandy were cheap - Maplin is expensive even after the 'price
reductions'.

They are currently selling a fart machine with 5 different noises for
£3.99 - that's cheap (the idea)

I got one! Couldn't resist it as colleague bought one a year ago for £19.
Its very realistic. Even makes swmbo laugh. Instructions say not to use it
at serious occasions such a weddings, restaurants etc. Why?

mike ring writes:

Sounds like a good idea, but google and maplin came up dry (well on google
the first umpteen hits), so who's gottem; also what sort of suppressor -
how would I know what's in it from it's description, or to measure it

Maplin still sell them as 'contact suppressors', I found.

Their part no. RG22Y

Described as consisting of an 0.1uF capacitor in series with a 100 ohm
resistor (those values have been rule-of-thumb for this purpose since
before the dawn of time).

Also suitable as snubbers in SCR and triac circuits, they say, so
should be capable of handling large surge currents. Which you could
sometimes get when turning on power to a device which used this part
plus a bipolar LED instead of a neon.

Most LEDs seem quite happy with a high initial surge current which
quickly decays with a time constant of only 10 microseconds, but YMMV.

As for the bipolar LEDs, Digikey is still the only supplier I can think
of who sell these with two diodes of the same colour (thus being more
suitable for use on AC) as opposed to the common arrangement of one
red, one green, which would likely blend to produce some shade of
yellow if used on AC.
But others must sell two red or two green combinations.



--
Roy Millar, Use m o u l i n e t @

BillR wrote:
geoff wrote:
In message , Alan
writes
In message , Roy Millar
wrote

Maplin sold me some a while ago, but now that they're reinventing
themselves as a kind of UK version of Tandy,

Tandy were cheap - Maplin is expensive even after the 'price
reductions'.

They are currently selling a fart machine with 5 different noises for
£3.99 - that's cheap (the idea)

I got one! Couldn't resist it as colleague bought one a year ago for
£19. Its very realistic. Even makes swmbo laugh. Instructions say not
to use it at serious occasions such a weddings, restaurants etc. Why?

A pub landlord I knew had one that was remote controlled, he used to hide it
in various places around the bar (it cropped up once hanging off the dog's
collar) and have a right old laugh with the regulars, can't say a lot of the
passing trade really knew what was happening.

--
James...
http://www.jameshart.co.uk/

"Frisket" wrote in message ...
"Mike Ring" wrote in message
52.50...
"David W.E. Roberts" wrote in
:


What I want to do is modify the casing of the fan so that an indicator
light shows when the switch is on.
If the switch is off, it is reasonable to assume that if the fan is
running this is due to the humidistat.

It would work equally well if a light came on when the humidistat was
active.

I just have two posssible reasons for the fan to be running and no way
of telling which.

Wire a mains neon ie one *with* a series resistor, between the switched
contact and neutral; connect the series resistor end to the live (switched
wire) side. Modify the case so you can see the neon, obseve safety at the
live end.

A LED would have to have 228V dropped across it's resistor, at about 10
mill thats about 2.3 watts - definitely not the way to go

mike r

What make of fan is it? Quite a few these days (Greenwood for example) use a
normally open contact for switching - that is, it only gives a pulse when
pulled rather than actually staying "on" so doing what you describe would be
quite difficult.

Richard

If the electrical option is too complex for this reason, there may be
a mechanical solution. The last time we were in the US, the ceiling
fans had a little mechanical doodah on the pull cord to show what
state the fan was in. Although now that I think about it, the fans
(and the doodahs) were designed with 1 off state and 3 on states for
the different speeds. So even if you could find them here (unlikely)
they probably wouldn't be much use for a 2 state device... Sorry!

"MarkM" wrote in message
om...
"Frisket" wrote in message
...
"Mike Ring" wrote in message
52.50...
"David W.E. Roberts" wrote in
:


What I want to do is modify the casing of the fan so that an
indicator
light shows when the switch is on.
If the switch is off, it is reasonable to assume that if the fan is
running this is due to the humidistat.

It would work equally well if a light came on when the humidistat
was
active.

I just have two posssible reasons for the fan to be running and no
way
of telling which.
snip
If the electrical option is too complex for this reason, there may be
a mechanical solution. The last time we were in the US, the ceiling
fans had a little mechanical doodah on the pull cord to show what
state the fan was in. Although now that I think about it, the fans
(and the doodahs) were designed with 1 off state and 3 on states for
the different speeds. So even if you could find them here (unlikely)
they probably wouldn't be much use for a 2 state device... Sorry!

[See previous posts]
I already have an external on/off switch with both neon and mechanical
indicators.
The issue is the internal switch (tiny) within the fan body.
I need a very small indicator light to show if power is coming via the
switch or the humidistat - both of which are built into the compact fan
body.
So the indicator has to be integrated into the fan body.

"David W.E. Roberts" wrote in message ...
"MarkM" wrote in message
om...
"Frisket" wrote in message
...
"Mike Ring" wrote in message
52.50...
"David W.E. Roberts" wrote in
:


What I want to do is modify the casing of the fan so that an
indicator
light shows when the switch is on.
If the switch is off, it is reasonable to assume that if the fan is
running this is due to the humidistat.

It would work equally well if a light came on when the humidistat
was
active.

I just have two posssible reasons for the fan to be running and no
way
of telling which.
snip
If the electrical option is too complex for this reason, there may be
a mechanical solution. The last time we were in the US, the ceiling
fans had a little mechanical doodah on the pull cord to show what
state the fan was in. Although now that I think about it, the fans
(and the doodahs) were designed with 1 off state and 3 on states for
the different speeds. So even if you could find them here (unlikely)
they probably wouldn't be much use for a 2 state device... Sorry!

[See previous posts]
I already have an external on/off switch with both neon and mechanical
indicators.
The issue is the internal switch (tiny) within the fan body.
I need a very small indicator light to show if power is coming via the
switch or the humidistat - both of which are built into the compact fan
body.
So the indicator has to be integrated into the fan body.

Maybe I didn't explain myself well... The mechanical indicator is
attached to the pull string of the internal fan switch, so that it
would track (and indicate) the state of this internal switch. So it
would indicate whether the humidistat was being over-ridden by the
manual switch. Sounds very clunky, but actually worked fine on the
overhead fans. I expect these are an over-the-counter accessory sold
in the US, but may not be available in a two-state on-off form.

"MarkM" wrote in message
m...
snip
Maybe I didn't explain myself well... The mechanical indicator is
attached to the pull string of the internal fan switch, so that it
would track (and indicate) the state of this internal switch. So it
would indicate whether the humidistat was being over-ridden by the
manual switch. Sounds very clunky, but actually worked fine on the
overhead fans. I expect these are an over-the-counter accessory sold
in the US, but may not be available in a two-state on-off form.

Things become clearer :-)
Does this replace the plastic toggle at the bottom of the pull cord?
I guess I could always order one from the US.

Cheers
Dave R

"David W.E. Roberts" wrote in message ...
"MarkM" wrote in message
m...
snip
Maybe I didn't explain myself well... The mechanical indicator is
attached to the pull string of the internal fan switch, so that it
would track (and indicate) the state of this internal switch. So it
would indicate whether the humidistat was being over-ridden by the
manual switch. Sounds very clunky, but actually worked fine on the
overhead fans. I expect these are an over-the-counter accessory sold
in the US, but may not be available in a two-state on-off form.

Things become clearer :-)
Does this replace the plastic toggle at the bottom of the pull cord?
I guess I could always order one from the US.

Cheers
Dave R

The ones I saw were fitted about half way up the pull cord, around eye
level. I have no idea if these came as standard with the fans or were
after-market.

I have worked out the wiring (which is how I first proved that the
humidistat was on most of the time) but I would like to fit a small LED
which only lights when current is passing through the switch.


Did you get your answer yet, David W.E.?

I read most of the thread but couldn't see any simple answer...

As far as I am concerned, you need to look at the *current* flowing
through the switch (or the humidistat), as I guess they are connected
in parallel...

I saw a circuit using a LED and a few diodes, which in effect will
monitor the current. It was used as an indicator for a normal (no
neutral) 240V light switch.

Quote: (for 'Lamp' read 'Motor')

fixed width font
LED
----RES180R---||----
| |
SWITCHED-FEED----||--||--||--||------LAMP
| |
---------||---------

--||-- = DIODE

A bit heavy on component count but lights evenly independent of lamp
load, choose diodes to match full lamp current. LED is low current
(5mA).

All parts are live, including the LED. For safety don't poke the led
thro the panel, use a plastic holder.

Extra components would be required to meet BS/VDE safety.

Unquote... (from uk.diy - "Power an LED from a light switch?")

"Abdullah Eyles" wrote in message
om...
I have worked out the wiring (which is how I first proved that the
humidistat was on most of the time) but I would like to fit a small LED
which only lights when current is passing through the switch.


Did you get your answer yet, David W.E.?

I read most of the thread but couldn't see any simple answer...

Main answer I got was that I asked the wrong question.

The lights in switches are apparently neons not LEDs.