XPost: sci.electronics.basics, sci.engr.lighting   
   From: freddywilliams@btinternet.com   
      
   operator jay wrote:   
   >   
   > "Frederick Williams"  wrote in message   
   > news:512E90AC.163CAAFC@btinternet.com...   
   > >I know one can dim filament bulbs with triacs (or similar).   
   > > I think I know that one used not to be able to dim fluorescent lamps by   
   > > the same or similar means.   
   > > But can one dim low power lamps _of some kind_ by _some means_?   
   > > What is a low power lamp?  Is it (at present) a fluorescent lamp?   
   > > Etc.   
   > >   
   > > The questions are prompted by strip lights outside a brach of Sainsburys   
   > > that are on all day even in bright sunlight.  I would have thought that   
   > > lamps could be installed the brightness of which could be controlled (in   
   > > an inverse fashion) by the brightness of the incident sunshine.  But   
   > > would that require the strip lights to be replaced as well?   
   > >   
   > > Please not that my knowledge of things electrical is limited.   
   > > --   
   > > When a true genius appears in the world, you may know him by   
   > > this sign, that the dunces are all in confederacy against him.   
   > > Jonathan Swift: Thoughts on Various Subjects, Moral and Diverting   
   >   
   > 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   
      
   A popular beat combo m'lud.  Oh, no, sorry: a supermarket chain well   
   known in the UK.   
      
   > (and I am assuming that 'brach' is just a typo for 'branch'),   
      
   Yes.   
      
   > 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.   
      
   Thank you.   
      
      
   --   
   When a true genius appears in the world, you may know him by   
   this sign, that the dunces are all in confederacy against him.   
   Jonathan Swift: Thoughts on Various Subjects, Moral and Diverting   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)