On Thu, 27 Aug 2009 17:53:00 +0000 (UTC), Gordon Henderson
wrote:

Unfortunately it is unlikely that we will see LED lights that are
plug-in replacements for incandecent bulbs any time soon - except
perhaps a type that compromises so greatly on efficiency that they are
poor substitutes. There are some tricky technical problems that will
need to be overcome first. So you'll need to replace the entire
fitting.

As an experiment, I got a couple of the 3W ones of these:

http://www.tlc-direct.co.uk/Main_Ind...Led/index.html

some time back to replace 2 x 50W GU10 halogen spots. TLC had them on
offer at a fiver each at the time.

As an experiment, I deemed it a success and wished now I'd bought more at
that price! They're not quite the same in terms of coverage and light -
they only had one type at the time and I'm guessing it's the "cool white"
version. I think the "warm white" might be better suited for my test
- kitchen to illuminate the cooker area. Curiously enough, there is a
start-up delay too - fraction of a second (1/4 to 1/2?), but it's still
there. I guess they have some sort of fancy PSU that needs to stabilise
first.

LEDs are inherently more directional than other forms of lighting.
That is in fact a good thing, because any light that is illuminating
areas you don't *need* to be illuminated is wasted energy. Coverage
angles are increased either by mounting several LEDs at different
angles, or with suitable optics (usually diffuser/lens combination,
which increases the price).

The PSU is a major part of the system. Some companies have brought
out LED lighting without an adequate PSU design, and as a result they
are either very dim, or will not last 5 minutes. LEDs are very
particular about their current supply if you want to operate them at
peak brightness, and also have a maximum operating temperature that
must not be exceeded - so have to be adequately heatsinked or
otherwise protected for all conceivable ambient temperatures. Some
PSUs are suitable for connection to a dimmer-fed light, but most are
not because they are essentially switch-mode power supplies. If you
want dimmable lighting, it is best to get an LED fitting where the PSU
has a dimmer input rather than using an existing dimmer that operates
on the mains. Some PSUs are switch-mode (and so unaffected by input
voltage), but have a separate sensing circuit that detects the fact
that a dimmer is being used and applies the neccesary changes to the
output to dim the LEDs (usually constant current PWM).

I recon that I actually need 3 of these to fully illuminate the same
area as 2 x GU10 50W halogens, so at some point soon I'll get another
and a fitting, however 9W to replace 100W is good in my book.

Yes - it is definitely the way forward, and I don't see much of a
future for CFLs. OTOH I must declare a vested commercial interest in
LED lighting (but not domestic lights - industrial and streetlighting
only).

--
Cynic