"Lostgallifreyan" wrote in message
...
"Arfa Daily" wrote in
:
I could see, that for the most part, it was filled with the LEDs,
which looked like 5mm types, and their support plate. So that leaves
very little space for any drive electronics - certainly not a switch
mode PSU, or even for a smoothing cap on the end of a simple reccy /
resistor combination. Not that there would have been room even, for a
resistor of a sufficient power rating to handle this kind of drop.
There might.. First, it needs to control a fixed current, and an efficient
power converter can be tiny, flat, like this: http://tinyurl.com/ypenut
That's 95% efficient at converting voltage ranging from 5~32 VDC into a
current source that can manage up to 7 LED's in series. A converter from
240 VAC to low volt DC can be had with similar efficiency (I hope), to
feed
what I already have. Ideally I can find a single module that does the
entire power conversion at 95% or better.
Next question. There were two types on offer, one rated at 1 watt, and
one at 1.3 watts, both with a quoted lifetime of 50k hours. So what
exactly is being said here ? Is that 1 watt input from the mains
supply, or 1 watt used by the LEDs or 1 watt of visible luminous
output power ? A website that I looked at quoted the output of a 0.62
watt one, at 20-30 l - I'm assuming that to be 'lumens'. If correct,
and not a misprint, that seems to be a piddling amount compared to the
950 lumens quoted for an incandescent 240v 50 watt GU10, and yet the
text suggests that they are only 'slightly dimmer'. It also says that
these lamps give off almost no heat, and that they consume only around
10% of the energy of a conventional equivalent halogen GU10. So for a
50 watt type, that's about 5 watts, suggesting that around 4 watts is
lost in ballasting ??
That one sounds like a marketing hype. The first thing is that it has lots
of standard 5mm LED's. Avoid like the PLAGUE, seriously. All that voltage
drop, and no cooling to speak off, what kind of thermal coupling can be
had
for a 5mm LED?
The ones to look for are the Cree and Luxeon types. The easiest way to
look
for them is a single emitter, or at least very few of them, with high
output claims. Look into one (unlit!, they WILL damage your eyes if you do
that to lit ones at close range), amd you'll see a distinctive fluorecent
dayglo green yellow cast to the phosphor unlike the chalky phosphors of
weaker white LED's.
Re wattage claims, it's hard to say, without evaluating all the evidence
you can find together. In short, a lamp that needs several emitters to
manage 30 lumens is a joke, when you can cheaply get a single emitter that
puts out 200 lumens with 1 amp pushed through a voltage drop of around 3
volts.
Setting aside the issues of colour temperature and CRI, which I am
sure will shortly be overcome, it seems to me that these halogen
replacement lamps are even now on their way to bettering CFLs in that
they are already exactly the same pattern as the lamps that they are
replacing, so must have sorted the ballasting problem. And yet there
are no plans to phase out the incandescent version. This flies
directly in the face of the proposals to ban standard incandescents,
when the advocated replacement technology (CFLs) is far from being a
satisfactory replacement, on several counts.
I think the ban is 'being seen to be done' kind of reaction. It's got more
to do with trashing an icon known for inefficiency, but there are better
ways to make people change than all-stick-no-carrot.
If governments really want to reduce power consumption I think they should
be subsidising the public to buy computer mainboards based on Nehemiah
CPU's and such. Turning a domestic computer into a fan heater just to run
Windows Vista as a private office is a sick joke! Far more worrying than a
few lightbulbs.
I don't have a problem with a switch mode converter being small - just with
the front end to get from 240v AC down to some realistic DC level, also
being small. I work with switch mode power supplies of every size on a daily
basis, but I've yet to see the front-end electrolytic, which would fit in
any space that was closed in so that you couldn't see it, on one of those
GU10-s.
As far as 5mm LEDs needing a lot of cooling, I've played with all manner of
superbright emitters from white thru' traffic light colours all the way to
red, in 'standard' packages, and never found cooling to be especially a
problem. Although these are not hyper bright Luxeon-style emitters that I'm
talking here, which I know *do* require external cooling, They are
never-the-less still bright enough to hurt your eyes, and light a dark room
up quite well. Where I have found theremal issues, is in the current control
circuitry, even if just a simple resistor.
I agree that the potential ban on incandescents is just a government
knee-jerk reaction, brought on by hysterical claims from their 'scientific
advisors' that these things are going to bring about the end of the world,
but not if we use the marvelous direct replacement CFLs instead (ha!) ...
I was just interested what others' opinions on this were.
So, I'm still no closer to knowing how the multi-LED GU10-s or even single
LED types, are actually ballasted for 240v AC use, and whether the claim
that "these lamps put out almost no heat at all" is at least basically true
overall, in which case the ballasting arrangement must be *very* efficient,
or refers specifically to forward IR radiation in the same direction as the
light, which obviously will be minimal, or is a fundamental marketing hype
lie. Maybe I'll just buy one, and see if I can figure out just what its guts
are.
Arfa