Semi OT: LED traffic light failures

This summer when out driving, I've been noticing more and more partial failures of LED traffic lights. It's always the green signal - the failures seem to range from a few "knockout" failures of the green LEDs where a half dozen LEDs on the signal are dead or so, to weird failures where an entire "pie slice" chunk of the signal has gone dark.

Some of the failed LEDs will also blink at about 5-10 Hz or so on and off, or even an entire section will flicker.

I've now seen this on at least 8 different traffic signals within a 10 mile radius. Always the green - never seen it with the red or yellow lights.

What's going on here? I'm in the Boston, Massachusetts area, if for some reason that's required information...

Reply to
bitrex
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Same thing here in AZ, so it's heat/moisture independent. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

Someone's fired!!!!! :-D

Reply to
bitrex

Havent noticed any this year, but will keep an eye out the next couple of days fo 90+ temps.

Cheers

Reply to
Martin Riddle

Are green LED's operated such that there's more power dissipated per device than red and yellow? Or something about the green LED chemistry that's corrosive? ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

I don't know a lot about LED semiconductors, but if I had to guess both the reds and the yellows would be gallium arsenide phosphide or something, while the high brightness greens are probably similar to blue leds - indium gallium nitride.

Reply to
bitrex

Moisture independent, but it gets warm in Boston.

I've seen that, too, but I haven't noticed any this year.

May be a particular brand.

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Reply to
Tim Wescott

Ten or so years ago, I worked for a company who manufactured those LED lamps as replacements for the incandescent lamps.

The LEDs are wired in a series-parallel combination and if only one LED begins to act up, that whole series string acts up.

We had problems. Occasionally the green LEDs would lose an internal connection at elevated temperatures and when they cooled, would reconnect, we surmised. Sort of like an oscillator due to temperature changes. I don't remember if we ever proved that. The red LEDs were more robust. You will see more green ones giving trouble than red ones and especially in the summer months.

The yellow ones last much longer because they don't stay on long enough for the heat to build up.

The warranty at that time was 5 years, I think. And, when you add in the savings in power (they were power-factor corrected) of less than 50% over incandescent, it means a significant savings to the cities. Additionally, since the LEDs last longer than incandescent (supposedly), the cost of sending out the bucket trucks for replacement would be reduced. Lots of advantages there.

In my opinion, it has not worked out that way. I see signs of signals going back to incandescent. I suspect that the manufacturers can't keep up with the warranty replacements and the city is using the incandescents to keep going. Bucket trucks are still needed.

Reply to
John S

It sure does. From the forecast it looks like the next week is shaping up to be brutal; mid 90s every day...after our record-breaking winter with 110 inches of snowfall.

New England is an interesting place.

Reply to
bitrex

Green and blue LEDs run a higher voltage than the red or yellow ones. Maybe that's the issue.

I can see a section of the disk going out. I don't know how many they use total, but there may be enough in a single pie slice that in series they can be run directly off of the line voltage with an appropriate limiting resistor. I expect a voltage dropping/regulator circuit would have a shorter MTBF than do the LEDs.

I am guessing that the failures are related to the signal manufacturer. I guess some do a better job of getting rid of the heat and blocking surges.

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Rick
Reply to
rickman

Lower efficiency? I don't know what they use, but I don't think its the same as the early style that suffered failures, which I have seen.

We have new LED street lights installed around here, and so far they are with out failures.

Cheers

Reply to
Martin Riddle

On Mon, 27 Jul 2015 19:47:03 -0400, bitrex Gave us:

Look around. I noticed in many such instances that there is a nearby cop controlling the light, trying to catch folks who anticipate a light change or speed through. It is truly sad what pigs do these days.

Yep... pigs in the wings.

Instead of making 'safe' traffic control systems, they made/make "controllable" systems where cops can attempt to cause a violation, then press a charge of said violation.

Reply to
DecadentLinuxUserNumeroUno

On Mon, 27 Jul 2015 21:10:59 -0400, bitrex Gave us:

The pulsing comes from the controller cabinet, and has NOTHING to do with the hanging signals or the conditions they are hung in.

Reply to
DecadentLinuxUserNumeroUno

On Mon, 27 Jul 2015 17:25:26 -0700, Jim Thompson Gave us:

More like something about the local PIGGERY that is corrosive to our society.

Reply to
DecadentLinuxUserNumeroUno

On Mon, 27 Jul 2015 21:14:52 -0400, rickman Gave us:

There are not that many signal makers in the US. All 50 states use the same asshole company who STILL uses the same broke dick day/night sensor on street lamps, despite RTCs being around for decades now.

The controllers STILL use hard contact relays in the controllers instead of SSRs too.

Now, the idiots even offer "LED street lamps" and the idiot STILL incorporated the same broke dick day/night sensor into them.

The idiots who buy these things (city planners) are about as stupid as a home stereo salesman. They likely pay hundreds of dollars for the "new" LED versions too. It is a truly sad, greedy bastard world.

And the idiots still pipe the full 600VAC feed up the poles.

Reply to
DecadentLinuxUserNumeroUno

On Mon, 27 Jul 2015 20:06:26 -0500, John S Gave us:

They are not made that way at all any more.

Reply to
DecadentLinuxUserNumeroUno

I'm not sure how a few knocked-out LEDs among dozens and dozens could cause a traffic violation.

Reply to
bitrex

DecadentLoser is a troll (and a village idiot on the par with rickman and krw)... don't feed the troll. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

We have the same thing here in SF, maybe a third of the greens have something wrong with them, usually a funny-shaped region out, sometimes blinking erratically. Rarely a red will have something wrong.

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John Larkin         Highland Technology, Inc 
lunatic fringe electronics 
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Reply to
John Larkin

When I first read this I thought it was a political statement. lol

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Rick
Reply to
rickman

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