types of light sensor

[Suz]

I first subscribed to this newsgroup about 4 years ago when we forst thought about doing a renovation. Plans are now finally submitted and I'm making a list of things to include for builder's quotes. The house will get a full height extension to the side and a roof space conversion. With a kitchen, two bathrooms and two bedrooms to sort I'll have loadsa questions in the near future.

Can all those wonderful people that have answered questions for me over the years, please keep an eye to my posts in the next month? (TIA).

First question: Thinking of a door activated sensor for the attic bathroom as it will have a fire door and I won't be passing to notice the light left on. Is this possible? Not motion sensor only because my girls won't go in if the light isn't on already. But it would need a motion sensor too so it doesn't go dark while they are parked reading the Beano. Can't put a motion senor outside the door as it is at the very top of the stairs and would get triggered too often.

Any example of a 'door' switch and motion sensor in operation together?

Thanks, Suzanne.

[meow2222]

I dont understand what youre trying to achieve, or to put it another way, why you want a light rigged to the door.

NT

[Owain]

Bathrooms don't usually need fire doors even on loft conversions, because they are classed as being a low risk source of ignition or fuel.

Why not have a light switch with neon indicator outside the bathroom door, with a repeater neon indicator somewhere downstairs?

Owain

[SirBenjamin]

His girls won't go into the bathroom unless the light is on first.

What he needs is something like a passive infared outdoor light with a timer of say 4 or 5 minutes?

I suppose really he could take the innards out of the outdoor passive light encase them into a metal box and mount the sensor also in the box.

[Roger Mills]

I think she wants the light to come on and go off automatically while the bathroom is occupied so that it cannot be left on accidentally.

To the OP: You probably need *two* switches wired in parallel - so that when either or both are closed the light will be on. The first is the sort of switch which is often used in stairwells in blocks of flats. It's a spring loaded button rather than a toggle switch, plus a timer. When the button is pressed, the light comes on and stays on for a pre-determined time - maybe one minute. The second is a PIR (passive infra-red) switch as used on outside lights etc. This needs to be inside the bathroom.

All you have then to do is the press the button before going into the bathroom. The light will come on immediately and remain on for as long as there is someone in the bathroom.

[John Rumm]

A bathroom is a "non habitable" room for building regs purposes, so you can do without a firedoor if you want. This would allow use of a door with a frosted glass panel for example.

You could do all sorts of nifty stuff, although I expect a switch with neon indicator would do well enough. You could make it two way switched so that you can turn the light off without having to go up there.

[David Hansen]

On Sun, 3 Dec 2006 13:27:13 -0000 someone who may be "Suz" wrote this:-

How will it detect that the bathroom is in use? One that goes on and off sequentially could be fooled by opening and closing the door. One that goes on when the door is locked means the light would not be on until one shut and locked the door.

As others have said a neon indicate somewhere would be useful for you to see what is going on. You are going to use energy saving bulbs?

[nightjar]

How about a push to operate time switch outside the door and a motion sensor switch in the bathroom, wired in parallel? The girls could push the switch before opening the door and, if they are still inside after the timer runs out, the motion sensor should keep the light on.

Colin Bignell

[John Rumm]

nightjar How about a push to operate time switch outside the door and a motion sensor

The difficulty with motion sensors (the phrase takes on a whow new meaning in a loo!), is what happens whey you stop moving... Bit disconcerting if you are sat on the loo at the lights go off.

[meow2222]

the motion sensor goes in the bowl, then it tells you when youre done. Serously, this thread isnt making any sense in my brain yet. Is the problem fear of ghosts?

NT

[Roger Mills]

I wouldn't use a motion sensor - I'd simply use a PIR detector which detects the presence of a warm body.

[Ian Stirling]

I would be looking at an extractor timer, that's designed to time extractor fans. You connect up the extractor timer to a momentry switch, and a switched output from the PIR in parallel, to a momentary switch. This way, you get an extra 5 mins (or whatever you set it to) whenever the PIR triggers, or whenever the light is pressed). Run the fan from the same circuit.

Easy alternative.

1W LED light, on all the time, that's enough to see where you are going to turn the main switch on.

[Bob Eager]

And there might not be any motions if you're constipated...

[John Rumm]

IME, they still stop triggering unless the warm body is moving (at least some of the time)

[Alan]

In message , Roger Mills wrote

PIR work by detecting a change in radiation (heat) falling on the sensor

- they are motion detectors.

[David Hansen]

On Sun, 3 Dec 2006 18:22:11 -0000 someone who may be "Roger Mills" wrote this:-

Not quite. They detect the movement of a warm body.

[Guy King]

The message from John Rumm contains these words:

Quite. If you look at a PIR sensor you'll see there's a moulded plastic fresnel lens that's split into many patches. The idea is that the sensor only sees strips of the coverage area, only those parts focussed by the lens. The bits in between aren't visible to the sensor. The detector works by seeing a sudden change as you walk from a bit that's covered to a bit that isn't - or vice versa.

[Dave Liquorice]

You don't have to do that you can get stand alone PIRs. I think one of the recent CPC flyers had a ceiling mounted 360 deg jobbie.

But the big snag is that PIRs do need movement to keep 'em triggered. Stand or sit still long enough and the lights go out. I fitted a PIR to the kitchen light in my flat so I didn't leave the 180W of light burning away every evening. Worked very well, light came on as I entered and a wave when it goes off whilst doing the washing up.

Donno if an intruder alarm PIR with the "anti creep" feature would be of any use, would need an interface and power supply though.

Education of daughters to enter darkened rooms would be better in the long term but appreciate that in the short term the technological solution has a lot going for it. Darkness mid wee excepted... I can hear the scream from here!

[David Hansen]

On Sun, 3 Dec 2006 21:47:33 GMT someone who may be Guy King wrote this:-

Provided the warm object is moving at more than the minimum speed which the detector will detect. If the warm object is stationary or moving slowly enough it will not be detected. That is why sophisticated alarm systems tend not to use such sensors.

[Guy King]

The message from David Hansen contains these words:

Because of the way the lens works it's very hard to move slowly enough to not trigger the sensor. What does work is a thermal blanket. Even a carboard sheild will work in most cases.