In article , Josepi wrote:
Incandescents were not so acceptable. They were experiemtning with LEDS to
lower the maintenance on incandescent systems.

Somebody ehre was roght about the lack of heat too. Snow storms can fill the
lamp projector lens in and the status cannot be told during the day. (No we
aren't moving to Florida, Robert...LOL)

Hasn't been much of an actual problem in Philadelphia PA USA.

After a debate on the job, we ran into a traffic light maintenance crew and
pulled over to chat with them. IIRC, they informed me they replace the
incandescents every year or on report. We always have multiple lamps for
out traffic lights. I assume you are in the USA where they classically may
have only one traffic head facing each way.

My experience in Philadelphia and its suburbs in 2 states is that
minimum of 2 face each way.

We have at least two and on big intersection, three or four,
sometimes. (we get lower sun in the winter. There always seems to be the
main one with a sunset right beside it)

I would imagine an incandescent, pushed and heated that hard and then
blinked on and off would wear the filiament out (thermal shock) very
quickly, too.

Incandescent filaments suffering significant damage from thermal shock
is mostly myth, despite existence of devices to remedy this. What mainly
happens is that an aging filament becomes unable to survive a cold start a
little before it becomes unable to survive continuous operation.

I even tried an experiment with a soft-starting device claimed to double
life of incandescents. It was a NTC thermistor, and when fully warmed up
it dimmed an incandescent enough to multiply its life by at least 1.5.

- Don Klipstein )

"Don Klipstein" wrote in message
...
I meant being kept in service for 5-10 years. Most of Philadelphia's
red ones installed in the 1990's and using an LED chemistry since
superseded in traffic signal use are still working and in service, not
relaced just for a few LEDs being out.

Now that they are making them with power consumption as low as 7 watts
for ones 8 inches in diameter and 8 watts for the ones 12 inches in
diameter, heat is not that big a deal in traffic signals that had
incandescents of 92 or 116 watts. Such huge reduction in power
consumption occurs in part from not having 70-75% of the light blocked
by red and green filters.

If any failure is so intolerable, then why were incandescents
acceptable?

- Don Klipstein )