In article , Jimmie D wrote:

"Mark Lloyd" wrote in message
.. .
On Thu, 13 Mar 2008 02:36:47 +0000 (UTC), (Don
Klipstein) wrote:

Keep in mind the life expectancy of traffic signal incandescents in
traffic signal use.

- Don Klipstein )

I notice that all (or almost al) traffic signals around here use LED
arrays.

Same here, and most of them have a lot of burned out and flickering LEDs.
I thought they would last longer han this.

Philadelphia converted nearly all of their red traffic signals to LED
sometime in the late 1990's, at a time when red LED traffic signals had
GaAlAsP LEDs instead of InGaAlN ones. (The older chemistry glowed a
deeper shade of red, and was less efficient - red traffic signals of that
type consumed something like 30 watts, and the newer LED chemistry got
that down to something like 11-15 watts.)

A few percent, maybe several percent of Philadelphia's red traffic
signals have some LEDs out, but they are still largely working after
something like a decade.

Many of Upper Darby's red and green traffic signals were converted to
LED a few years ago. A couple of the green ones have a few LEDs out.

I seem to think that the LED ones are greatly outlasting incandescent
ones.

- Don Klipstein )

In article , HaLiGoOn wrote in part:

MythBusters did a short segment regarding light bulbs.

Lights On or Off

Myth: You save on energy bills by leaving lights on. Some people believe
that the energy to turn on lights exceeds savings of turning lights off.

They talked to Mark Reisfelt, manager of the Independent Electric Supply
where they purchased their light bulbs. He felt that it was best to turn
the lights off.

To test the myth, they needed to measure energy usage during startup,
maintenance (steady state), and shutdown.

For steady state energy consumption, they turned on several different
types of bulbs for 60 minutes and measured their consumption using a
Kill A Watt: * Incandescent 90 Wh * Compact Fluorescent (CFL): 10 Wh *
Halogen: 70 Wh * Metal halide 60 Wh * LED: 1 Wh * Fluorescent: 10 Wh

For startup energy consumption, Grant hooked up an inductive current
loop to a computer and measured the amount of energy used when the
turned on the bulbs. With an inductive current loop, you run a wire
through the center, which induces a current in the loop. This current is
then measured by a digital sampling oscilloscope.

Based on the amount of energy consumed turning on the bulb, they were
able calculated how long the bulb would have to be turned off in order
to make it worth the energy savings, i.e. "It's best to turn off the
bulb if you are leaving the room for":

* Incandescent: 0.36 seconds
* CFL: 0.015 seconds
* Halogen: .51 seconds
* LED: 1.28 seconds
* Fluorescent: 23.3 seconds

In other words, its almost always best to turn the bulb off. Even the 23
seconds for the fluorescent lights isn't very long, and the rest of the
times are pretty much blinks of an eye.

The 23.3 seconds is more than the actual truth for fluorescents.
Fluorescent fixtures that draw increased current during starting also have
their power factor reduced during starting, and the above setup appears to
me to measure only current consumption.

- Don Klipstein )

In article , HaLiGoOn wrote:

MythBusters did a short segment regarding light bulbs.

Lights On or Off

SNIP
Bulb Longevity

They tested one final element of this myth: frequently turning lights on
and off decreases their life span, thus leading to greater costs. Grant
setup a timer and relay to turn the bulbs on and off repeatedly every 2
minutes. After six weeks, only the LED bulb was still working. Based on
this test, they extrapolated that it would take five years of ordinary
usage to cause the bulbs to burn out.

Fluorescents and HID lamps (such as metal halide) do suffer wear from
starting. Halogen and HID lamps can also age badly if they spend a lot of
"on time" incompletely warmed up.

2 weeks being on half the time is 504 hours. Many incandescents are
only rated to have average life expectancy of 750 hours.

* busted *
Side-note: 105-year bulb

Grant and Kari visited the Livermore/Pleasanton Fire Department to view
their light bulb that has been burning for 105 years. It has a carbon
filament that is much thicker than modern bulbs and also burns much
cooler/darker. You can check on the light using the bulb's webcam.

I have seen the webcam picture. Based on this and web searching, I
suspect teh filament is indeed running at an unusually low temperature,
and with much less energy efficiency than that of modern incandescents.

You can get 230V lightbulbs. Some electrical/lighting supply places, as
well as online outfits such as bulbs.com, sell them. At 120V, they should
easily last a century. A 200W 230V lightbulb at 120V consumes about 75
watts, and produces about 2/3 the light output of better 40 watt 120V
incandescents. A "century bulb" is easy to achieve, but no bargain.

- Don Klipstein )