Illuminated switch to show that cloakroom light and fan is still on

[NT]

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]

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...

The advantage is a mains powered light source that does not require any kludge like using the earth as a neutral. It also maintenance free saves the risk of having someone having to change batteries on potentially live circuit.

Twice the power? half the power and less light I would expect...

Either way we are talking insignificant loads compared to the lamp itself, you are probably dissipating as much as the LED in the wires of the circuit!

[John Rumm]

It would work, however there are a couple of issues to be aware of. The first would be that you will need to construct the arrangement in such a way as to not pose any risk of exposing an untrained user to mains potential when they have it off the wall to replace the battery. Something that is doable with a properly designed and tested enclosure etc, but not easy to achieve as a quick lashup.

Therein the other problem, you can't use matching switchgear etc (unless you already have grid switches!)

You could also bear in mind the OPs original requirement about the switch still feeling and sounding light a 6A light switch in operation - and many 20A DPST switches don't.

[Tim S]

John Rumm coughed up some electrons that declared:

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

[The Wanderer]

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.

[Phil Addison]

... 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

[Phil Addison]

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

[Dave Plowman (News)]

Easy enough to make one using grid switch components. Plus the fact it would have to be a posh new build to think of something so obvious and use a mm more of wire than they can get away with. ;-)

In my own house I ran the switch feed in triple and earth in most rooms. Handy if you decide you want floor outlet lamps switched from the same place.

[Dave Plowman (News)]

Dunno - presumably ordinary fluorescent would have 100 Hz flicker, and plenty complain about those.

[Owain]

If you've got a fan with a run-on timer you could extend a second neon from that. Then you'd have separate indicators for 'engaged' and 'proceed with caution'

Owain

[John Rumm]

Not sure how you get the three diodes in series configuration needed to get you enough voltage drop to light the led though...?

[John Rumm]

If you had the PIR *and* your switch it would... the light would only come on when both switches are "on".

[John Rumm]

Probably not, but is not the switch being "down" enough indication anyway? (unless you have two way switching for your loo!) ;-)

[Phil Addison]

That's true, and being sat there waving your arms around to keep the light on you could dispense with the fan :O)

[Phil Addison]

Nope, already tried that solition and it doesn't work! see OP "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)." :=/

Phil

[Phil Addison]

We've done the 'making' bit, I'm on to the 'why don't they' bit now :))

LOL

Phil

[Phil Addison]

But 'engaged' and 'proceed with caution' showing together would be inconvenient.

Phil

[Phil Addison]

[Owain]

I was wondering whether you'd spot that deliberate mistake.

Obviously some interlocking relays would be required ...

Owain

[John Rumm]

No, I meant was the switch being down not enough of an occupancy indication rather than a warning the light was left on. Obviously it would leave scope for sitting there with your legs crossed waiting for the emergence of the phantom occupant, which could take a while.