LED Traffic Light Question

[jsmith]

Any of you familiar with LED traffic signal design? The "bulbs" are powered
from 120VAC so they must have some sort of DC power supply built into the
package. Any idea of how much variation in AC input voltage can be
tolerated?

 

[Harry Dellamano]

Any of you familiar with LED traffic signal design? The "bulbs" are
powered
from 120VAC so they must have some sort of DC power supply built into the
package. Any idea of how much variation in AC input voltage can be
tolerated?

80Vac to 135 Vac input, 50/60HZ, 20 watts, PFC.
All done with one stage.
cheers,
Harry

 

[jtaylor]

Any of you familiar with LED traffic signal design? The "bulbs" are powered
from 120VAC so they must have some sort of DC power supply built into the
package. Any idea of how much variation in AC input voltage can be
tolerated?

Not your answer, but I have noticed that the LED traffic lights around here
sometimes get covered in snow and stay that way - the old-fashioned ones
must be warm enough to melt snow...

 

[Michael]

Not your answer, but I have noticed that the LED traffic lights around here
sometimes get covered in snow and stay that way - the old-fashioned ones
must be warm enough to melt snow...

Cool! One more situation to add to the Unexpected Consequences list.

Replace incandescents with LEDs => conserve power and decrease maint.
Snow comes along. OOPS! OK, add a heater. => Conserve less power than expected
.... and decrease maint.

I wonder how much of a problem snow and slush are to LED automotive tail lights.

 

[Spehro Pefhany]

Cool! One more situation to add to the Unexpected Consequences list.

Replace incandescents with LEDs => conserve power and decrease maint.
Snow comes along. OOPS! OK, add a heater. => Conserve less power than expected
... and decrease maint.

I wonder how much of a problem snow and slush are to LED automotive tail lights.

Or, perhaps more critically, things like HID headlamps. The plastic
fronts on most headlights these days don't get as warm so they don't
tend to create as much of that dry crust that you get from driving
with lights on in the right conditions (the same conditions that can
cause you to go through a container of washer fluid in a single
trip)**, so they are actually better in those conditions, but I'd
imagine they might be worse where ice was building up.

** Typically, when the road is wet, in the winter after sand/salt has
been distributed, and in heavy, but fast traffic conditions on a big
expressway. The dirty water on the road is flung up into the air by
all those tires front, back and across 16 lanes of high-speed road,
and it comes down all over your windshield and dries there. It only
occurs a few days in a given year IME.

Of course if you have a Volvo or MB, you just turn on the little
headlamp wipers/washers. ;-)


Best regards,
Spehro Pefhany

 

[Dave]

Any of you familiar with LED traffic signal design? The "bulbs"
are powered from 120VAC so they must have some sort of DC power
supply built into the package. Any idea of how much variation in
AC input voltage can be tolerated?

Whatever they use it seems to sometimes take a noticeable number of
milliseconds to light the LEDs. I'd guess several hundred milliseconds
in some cases.

 

[jtaylor]

lights.

Or, perhaps more critically, things like HID headlamps. The plastic
fronts on most headlights these days don't get as warm so they don't
tend to create as much of that dry crust that you get from driving
with lights on in the right conditions (the same conditions that can
cause you to go through a container of washer fluid in a single
trip)**, so they are actually better in those conditions, but I'd
imagine they might be worse where ice was building up.

I drove a car in a sort of snow/rain/freezing rain mix once; the stuff would
stick to the front glass of the light, melt and slide to the outside edge,
where it would freeze again. After about 4 hours there was a vertical sheet
of ice the height of the lens and about 5 inches wide attached to the
outside edge. The lights were in a pop-up module so the airflow and room
available helped this to happen, I'm sure.

 

[Jim Thompson]

Not your answer, but I have noticed that the LED traffic lights around here
sometimes get covered in snow and stay that way - the old-fashioned ones
must be warm enough to melt snow...

What's this phrase, "snow" ?

...Jim Thompson

 

[Keith Williams]

What's this phrase, "snow" ?

Look outside. Oh, wait. Nevermind! ;-)

 

[Guy Macon]

What's this phrase, "snow" ?

I think they are all making up stories about this mythical
"snow." I just went outside to get the newspaper and it's
about 65 degrees F (pre-dawn) here in Los Angeles outside,
and the high today will be around 85. Snow is a myth.

Earthquakes, mudslides and wildfires; *those* are real!

 

[Keith Williams]

I think they are all making up stories about this mythical
"snow." I just went outside to get the newspaper and it's
about 65 degrees F (pre-dawn) here in Los Angeles outside,
and the high today will be around 85. Snow is a myth.

It's now 2:45PM and I'm looking out at a foot or so of 14F and blowing
myth (mythed yesterday, cold and blowing myth today).

Earthquakes, mudslides and wildfires; *those* are real!

I remember an earthquake. A 6.0 IIRC on the other side of the lake.
Woke me up, but that and a few roads at the epicenter were about the
extent of the damage.

A mudslide is vodka, Kaluha, and Bailey's, no?

 

[Michael A. Terrell]

I think they are all making up stories about this mythical
"snow." I just went outside to get the newspaper and it's
about 65 degrees F (pre-dawn) here in Los Angeles outside,
and the high today will be around 85. Snow is a myth.

Earthquakes, mudslides and wildfires; *those* are real!

Sorry, but I've seen it snow about 30 miles north of Orlando,
Florida. On the other hand, go to Alaska in the wintertime and you'll
see it for months.

 

[Bob Stephens]

Jim Thompson wrote:




I think they are all making up stories about this mythical
"snow." I just went outside to get the newspaper and it's
about 65 degrees F (pre-dawn) here in Los Angeles outside,
and the high today will be around 85. Snow is a myth.

Earthquakes, mudslides and wildfires; *those* are real!

Not to mention 3 times our yearly allocation of *RAIN*

Bob

 

[Jim Thompson]

Not to mention 3 times our yearly allocation of *RAIN*

Bob

My whole hillside is populated with yellow flowers.

Makes for a bad fire season, particularly in California.

...Jim Thompson