Dimming low power light bulbs

When you say strip lights, it leads me to think you are talking about LED strip lights? If that being the case, yes, they can be regulated but not with a conventional voltage control unit. You need to get at the string of LEDs and put a current limit device in there and maybe a photo cell with some electronics to automate it abit.

Jamie

A common, but by all means not the only, approach to "dimming" LED lights is to use PWM. The wider the pulse width, the more fully "on" they are. This can be quite efficiently done.

I don't know much about TRIACS, but from what I read on wikipedia, it looks like using one to dim an LED strip would be reasonable.

Pretty much any commonly used lighting technology (incandescent, fluorescent (T8, T12, T5, T5HO), compact fluorescent, metal halide, LED, high pressure sodium, etc.) has means to do dimming. The costliness varies. Sometimes special 'dimming ballasts' are needed wiht the fixtures, and very often, special dimmers are needed. And yes, lighting can be controlled based on daylight (search 'daylight harvesting'). While I do not know what Sainsburys is (and I am assuming that 'brach' is just a typo for 'branch'), in a scenario with outdoor fixtures mounted on a building exterior it would be typical to do less intelligent controls. At least it would be typical in much of north america. Either photocell control, or a timeclock, or a combination of photocell and timeclock, might be used. The lights would just be turned off and on in a more or less 'dusk til dawn' manner. Astrological timeclocks are available that can accommodate changing sunrise/sunset times with the seasons, and beyond that they can be programmed with routines for weekdays, weeknds, holidays, and all sorts of stuff. And they're not that expensive.

'Low power' may not be a well defined term, maybe 'efficient' is a better term (depending on what you are actually asing, of course). Certain technologies are more efficient than others, but if you want lots and lots of light out of an efficient luminaire, you still need lots of power. All of the lighting technologies mentioned above are OK for efficiency, except for incandescent which is not good for efficiency. As rough numbers, I'd say you can get 70 lumens per Watt to 140 lumens per Watt out of the efficient technologies above. Fluorescent is probably around 100, and widely used in normal indoor commercial applications. High pressure sodium and metal halide are often used outdoors, with efficiencies between say 80 Lumens/W and 140. Incandescent is probably 10-20 lumens per watt. LED lighting is changing fast. There is a ton of research money and effort going into LED and it may well be the future of lighting. I don't think it is king of efficiency yet for bulk lighting, generally speaking. Though for some people it is the go-to technology. And the marketing hyping it is at times perhaps a little ... zealous.

There are other newsgroups where you might get a better response on a question like this. I'm a little rusty on them but alt.enegineering.electrical might be one, sci.engr.lighting another. I'll crosspost them in this reply.

No, fluorescent strip lamps. The things common in commercial premisses. Sorry for not being clearer.

I take it you mean the eight foot long ones that are ubiquitous in shopping centers and the like?

They could be dimmed to maintain a minimum level, but the type of dimmer it requires would be fairly sophisticated and the parts and retro-fitting them would probably be too expensive - particularly when LEDs are promising to be more efficient and eventually less costly with lower maintenance.

They do something similar to what you suggest in some HDTVs and computer monitors with fluorescent back lights.

Yes, those.

That is what I was wondering. Thank you.

A popular beat combo m'lud. Oh, no, sorry: a supermarket chain well known in the UK.

Yes.

Thank you.

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Dimming fluorescent lamps is not all that easy. The following is probably more than you want to know,

The easist way to 'dim' a bunch of fluorescents may be to just turn some off.

George H.

I think I heard that some years ago, hence my question and my wondering whether more recent dimmer technology (or, perhaps, lamp technology) allowed it or made it easier.

I'll read it. Thank you.

I may write a letter to the shop manager to that effect.

I was thinking how I'd go about doing that - and I suspect it isn't as trivial as it may seem (other than cost and time). For instance if you want each light to monitor a certain area to maintain a specific level of intensity you may still have to slave them to a single controller or slave banks to a controller. Independent controllers on each lamp may "talk" to the others and you'd have a hodge podge of flickering lights all trying to maintain some average illumination down at the floor level.