Motion sensor light switches

[A.Clews]

I've just bought two of these from windtrap.co.uk - see

I fitted these (replacing the manual switches) in my kitchen and hallway, both of which are lit by compact fluorescent lamps. The blurb on the website clearly says that the switch can be used with "all light bulbs, including energy saving ones".

However, I found that even with the lux adjuster set to minimum, the lamps flickered very faintly, showing that the switch is always allowing some current through. Strange, I thought the switch was supposed to be on or off? That's no good to me, thought I, so off came the switches again.

Before I return them for refund, does anyone else here have this experience with these switches, and did you find a solution?

[Andrew Gabriel]

I don't see how this could work with energy saving lamps. You would need one with a neutral connection so it doesn't power itself through the lamp. That would make it difficult to fit as a direct swap for most light switches, where there is no neutral available.

[davey]

I agree with Andrew. I was under the impression that these motion switches ONLY work with energy saving lights, when wired through a relay. I have tried one also, and it did not work with the energy saving bulbs - then I read the blurb and it stated that they only worked with incandescent bulbs. When in doubt, RTFM! I must admit that I was surprised to read the blurb in the advert for YOUR switch. It clearly includes energy saving lights. Strange.

[Peter Parry]

Most CFL's have a 0,1uF capacitor- choke in series - 0.1uF capacitor noise filter on the input. That will allow a couple of milliamps to flow by itself. Design the sensor so that it doesn't draw enough current to allow the HF oscillator to operate properly and allow the lamp to strike and you should be able to get a few tens of milliamps through the noise filter and input rectifiers.

The downside is that the lamps will flicker faintly all the time and that a small amount of current will be drawn all the time. The latter of course is also going to be true of any sensor switch - it must always consume some energy to work at all.

[T i m]

It's funny, the missus and I were talking of 'automatic light switches' just last night as her sister was asking into similar for use in her house and that and this thread got me thinking re us.

So, say we wanted to have the 2 x 6' twin flouro's in the kitchen turn on an off automatically (and to stay on during the continuing presence of movement) with the idea of energy saving, is there a device that would provide said but with the ability to be overridden without having to add much (any?) extra circuitry outside any gadget etc (and not a human hand of course) ;-)

In the case of our kitchen lights I can fairly easily get to the ceiling space and have access to live and neutral but would prefer any 'override switching' of a solution to be done via the existing 2-way pull switches (or similar sized replacements if we need more features etc).

I guess with 4 x ~80W and there being many instances where the lights should really be turned off but aren't, there would be some energy saving?

All the best ..

T i m

[Pete Verdon]

Make sure that the sensor can see you wherever you are in the kitchen. In my last year of school we had a refurbishment which included loads of motion-sensor lights. Thing is, they also built the new toilet cubicles with proper brick walls[1], and the sensors were only in the main room. So if you lingered too long on the bog you'd be plunged into darkness, and have to open the door and wave your legs about to get the light on again.

Pete

[1] After some less than successful building[2] in the recent past, they took a lot of input from some of the old, experienced teachers. I'm pretty sure the solid cubicles were in response to the practice of chucking cups of water or clumps of wet bogroll over the partitions into occupied traps. [2] Plasterboard and large groups of teenage boys don't go together very well. One wall had people go through it three times to my knowledge.

[A.Clews]

Thus spake Andrew Gabriel ( [e-mail]) unto the assembled multitudes:

Well, the notes that came with the switches clearly state that they can be used with energ-saving lamps, and they also state that you don't need to worry which way round to connect the live and neutral.

[Richard Russell]

I'm afraid you can't believe everything you read. I purchased one of these because they also clearly state they can be used with CFLs (in a given range of wattage):

in practice although it would turn the CFLs *off* (and there was no trace of flicker) it wouldn't turn them *on* again. The CFLs were those horrible MEM BC3 types fitted in new-build properties; the evidence was that the off-on transitions from the timeswitch didn't trigger the CFL's starter.

As an off-topic comment, these Timeguard switches also claim to be '2- way compatible'. It's true that they have L1 and L2 connections, but they can only switch the lights on if all the other switches are in the correct 'on' state; I don't call that '2-way compatible'! An old Superswitch timeswitch (unfortunately no longer available it would seem) does it properly - it can turn the lights on (or off) whatever the state of the other 2-way and intermediate switches.

Richard.

reply by email change 'news' to my forename.

[T i m]

Ok, well we have a fairly small 'galley style' kitchen 3m long x 2.25m wide x 2.5m high. I was thinking of fitting a sensor in the middle of the ceiling. I have access to one end of the ceiling space and should be able to get to the back of the one of the 2 way light switches and the t&e from light feed and could pickup the cable from the back of the sensor with my rods.

Where I worked last was designed as an open_plan floor and was then sub-divided into smaller rooms. This did for the ventilation / heating what your walls did for the ir sensor. :-(

Kids

All the best ..

T i m

[mlv]

Sir Jestalot * provided us with some light entertainment when he scribed:

A motion detector from Windtrap? Surely these should be installed in your toilet bowl? :-)

Yes and yes!

When I had a similar problem, the circuit was actually switching three corridor lights, all of which were CFLs. I changed one of the CFLs to a low wattage incandescent lamp, and the problem was solved.

Not ideal, I know, but a reasonable workaround. And not much use if there's only one CFL in your circuit.

These devices have to pass a small, continuous operating current through the load, due to the absence of a neutral at the switch location.

[A.Clews]

Thus spake Sir Breakalot (*) unto the assembled multitudes:

You'd think that they'd have thought of a more sensible name than "Windtrap", wouldn't you?

That's gonna create problems when the government bans the use of incandescents, then. Would LED lamps provide the same solution?

Thanks (all) for your help, and especially Sir Breakalot.

• sorry; another in-joke from the golden days of uk.media.radio.bbc-r2 :-)

[Andrew Gabriel]

That won't do the tube life any favours. Trickling a small current through a tube with cold electrodes wears the filament coating much faster than when operating the tube at full power.

[Peter Parry]

I've removed the sensors from the commonly available floodlights for this. They can usually be switched on permanently by switching off and back on within a short time so no extra wiring needed. I'm not sure if any of the ceiling mounted sensors can do the same.

One point to remember is that PIR motion detectors are sensitive to radial movement but not very sensitive to axial movement. Movement across the sensor arc is quickly detected but motion to and from the sensor less so. If you have a long thin kitchen this can mean that the sensor often fails to detect motion and the lights go out when someone is working there - generally not a good idea in a kitchen.

[T i m]

I believe they can.

Hmm. Ok, so even though our kitchen is nearly square the 'walkway' is long / thin(ish), soooo, what if I had two sensors wired in parallel, mounted so as to split their rage equally?

Also, if they were set to stay on for say 10 mins (still better than them being left on for hours) would there would be less chance of them cutting off when they shouldn't (I assume the timer would be reset every time movement was detected)? If they are overrideable I guess I can turn them to 'ON' in any case?

All the best ..

T i m

[PCPaul]

BTDT. We've also had to track down an issue with occasional super-cold air conditioning. Turned out that the monitor for a reliable server was on top of a filing cabinet right under the main temperature sensor.

Whenever that monitor was turned on the sensor registered a lovely hot day and turned up the aircon to compensate...