On 19/05/2011 3:14 PM, Jack. wrote:
On May 19, 4:22 pm, wrote:
On 19/05/2011 1:27 PM, Jack. wrote:





On May 19, 2:38 pm, wrote:
On Thu, 19 May 2011 08:41:59 -0400, Hairy wrote:
In ,
says...

On Wed, 18 May 2011 14:07:45 -0400,
wrote:

Canuck57 wrote:
On 17/05/2011 8:27 PM, wrote:
On Tue, 17 May 2011 21:41:50 -0400, Wayne B
wrote:

On Tue, 17 May 2011 14:09:47 -0400, I_am_Tosk
wrote:

F*ck you Al Gore you hypocritical piece of ****...

Scott, with all due respect, energy efficiency is something we should
all be interested in. It turns out that high efficiency bulbs,
especially LEDs, are a good long term investment. Yes, they cost
more, and yes, they still have a few rough edges, but over the useful
life of the bulb the cost per hour is a lot lower. That should be of
interest to anyone who is thrifty. Costs will drop as volume builds
and the technology improves. It's already happening.

That is only true if you actually get the expected life out of them. I
am still waiting. Most LEDs in light bulbs are driven at such high
currents that I do not see them lasting as long as the prediction.

I am not having wonderful experiences with CFLs and I went for them
big time. I seem to be having early end of life at something like
10-15 % based on 20 - 30 lamps. I have had at least 5 bad ones.

No I didn't call EPA when I threw them away. I did break one (not in
the 5) and I cleaned it up with a big wad of wet paper towel.
I threw everything in the trash

I find the batches and brands of CFLs have different lifetimes. Some
lots, they last only a year maybe two. But have some now 7 years old.
Seems to vary quit a bit in the quality and longevity.

I bought some CFL floodlight bulbs for a trio of recessed ceiling
fixtures. They seem to be working out ok...low wattage, brighter than
the incandescent bulbs they replaced, seemingly cooler, whiter white.

I had a couple of those in my motion lights and they both died an
early death. My electrical folks say it is because the ballast is
above the reflector so the heat does not get radiated out of the bell.
They say they are having the same trouble with "R" style CFLs in
recessed cans.

BTW one thing I notice with the LEDs I have is (the decora night light
thing) that they "strobe" when you have motion across them. It is 60hz
so you don't notice it most of the time but if you are walking past
one you definitely get the 80s disco thing going on.

Any light strobes at 60Hz because that's the way our A.C. current works!

The difference is how fast the lamp responds to that change. A
tungsten filament has a large amount of latency and you can select
phosphors in a fluorescent to mitigate the effect but a LED is
instant. If you rectified and filtered the AC you could eliminate the
problem. I am curious about how long these LEDs will last since my
line voltage is on the high side of nominal at 124V. They drive them
pretty hard.

See my post elsewhere in this thread... the LED's aren't being driven
by a simple half or full wave rectifier, they are being driven by a
chip that regulates their drive signal. That's why these AC bulbs are
so expensive... they aren't just a string of LEDs, they also have a
heat sink and drive circuitry to control them.

Huh? Not at all. A LED is a rectifier, a diode that emits light.
Simple resister on the end is all they have.

--resister---forward led-----forward led.....----
\-reverse led-/ \-reverse led..../

Just pairs of LEDs opposed to each other in a series and a resistor on
the end, so if the phase is positive one lights, on the opposite phase
the other one lights. At 60 hertz each, 120 hertz pulsed light. The
most common way to build them.

You could also get fancy, a 2 cent bridge rectifier, 2 cent small cap,
one cent resister and again the sequence of LED (not pairs) if you want
to get rid of the 60/120 hertz thing. But not usually done for a few
reasons as the current drive is sustained and more burn out might occur.

Either way, early 1970's basic electronic components from radio shack.
But the new LEDs are brighter and white.

No reason they shouldn't be cheap.


I'm quite aware of how LED's work, I'm an Electronics Engineer. You
are technically correct that you *could* build an LED lamp that would
run from 120v AC with a minimum of components, but it's operation,
life, and effeciency would be very marginal. We're not talking about
lighting up a simple single LED, these modern 100w LED lamps use
active thermal management, switching power supplies, and other tricks
to provide a light that people can tolerate in a home setting for
their primary source of light. Take a look at:

http://www.earthled.com/evolux-led-light-bulb.html

This is why the bulbs are so expensive. It's not as simple as you
think.

EarthLED charges far too much. Costco has them here much cheaper than that.

You will see the prices drop to $3 a bulb in a year or two, US inflation
excluded. Say about 20 Yuan.
--
Take a look at ANY country, more debt is more problems. So why do we
allow our governments more debt? Selfishness, greed, denial, ignorance?