# LED traffic lights fading, LED's not working.



## unique (Nov 14, 2008)

In my City there are a lot of LED traffic lights. A lot of these were installed about 2 years ago. But now I see a lot of them are not as bright as they used to be and big chunks of LED are not operating. I would have thought LED would have been more reliable then the old traffic lights with just a light bulb in them?
This is a pretty big safety concern with only sections of the lights working... To change or fix the traffic light you would need to replace the whole thing which would cost more wouldn't it?


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## KD7EIR (Nov 14, 2008)

unique said:


> In my City there are a lot of LED traffic lights. A lot of these were installed about 2 years ago. But now I see a lot of them are not as bright as they used to be and big chunks of LED are not operating. I would have thought LED would have been more reliable then the old traffic lights with just a light bulb in them?
> This is a pretty big safety concern with only sections of the lights working... To change or fix the traffic light you would need to replace the whole thing which would cost more wouldn't it?



My city has been using LED traffic lights for a few years now, and we have not had any problems.


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## NightFlyer (Nov 14, 2008)

unique said:


> In my City there are a lot of LED traffic lights. A lot of these were installed about 2 years ago. But now I see a lot of them are not as bright as they used to be and big chunks of LED are not operating. I would have thought LED would have been more reliable then the old traffic lights with just a light bulb in them?
> This is a pretty big safety concern with only sections of the lights working... To change or fix the traffic light you would need to replace the whole thing which would cost more wouldn't it?



Actually the red yellow and green modules are just that - modules. Yes they cost more per unit but the ones in my city rarely show any issues. The ones they originally put up years ago are still working fine and are still very bright. Going from 125+ watts to 7-17 watts per bulb saves huge money on power cost. I do not know the cost of each module or how long it would take in power savings to offset the extra cost of the LED modules.

Now, I have heard of some of them getting shot at, which would cause all or part of the module to fail, but to my knowledge, most intersections use more than one traffic light per direction, so even if one module were to fail, the other(s) are still working.

Some intersections in parts of town still use the old traditional incandescent bulb/reflector/lenses.


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## unique (Nov 14, 2008)

Even with the lights that are still operating without any problem. I still see few dead LED's. Not sure if this is normal for some to not work.
Yeah, they are definitely better then the older incandescent bulb but was shocked to see a chunk of the LED's not working on one of the lights.


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## greenlight (Nov 14, 2008)

Write to the Dept of public works and ask them to stop skimping with the budget traffic lamps.


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## Jarl (Nov 14, 2008)

Like with anything, there's cheap crap and quality. Quality would be far less likely to break, chances are those in charge used the cheap stuff. Think KD vs surefire; one is a lot more likely to break/malfunction than another.

I'm a cynic, shoot me


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## senecaripple (Nov 14, 2008)

i too noticed some of ours are out! our city/state are in a financial crisis, so, i doubt they'll be repairing/replacing them anytime soon! our politicians are more concerned about free healthcare than public safety!


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## WadeF (Nov 14, 2008)

Could people be throwing bottles, rocks, or who knows what at the lights and damaging them?


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## rockz4532 (Nov 14, 2008)

maybe the 50000 hours have gone past?


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## LukeA (Nov 14, 2008)

I think all the LEDs are driven with the same voltage so the reds get more current. (the vast majority of failures in my town are in the reds)


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## ikendu (Nov 14, 2008)

I've been watching the LED lights in our city since I joined CPF years ago.

I've never seen any problems with burned out LEDs or diminished brightness.

There might be some... but I've not seen them and I've been paying attention all that time.


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## gillestugan (Nov 14, 2008)

The first LED traffic lights were installed 1997here in Sweden. Now almost all of them have LEDs. I have never seen any dim lights, or heard they have had top change any of them.


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## matrixshaman (Nov 14, 2008)

rockz4532 said:


> maybe the 50000 hours have gone past?



Assuming they are on 50% of the time 365 days a year that would take about 11 years to reach a 50,000 hour usage. I doubt that is the problem. They probably bought the LED modules from a cheap manufacturer.


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## PhotonWrangler (Nov 14, 2008)

I've seen LED traffic lights in this area for a couple of years now, and I think I've only seen one that had a problem. It's a far, far better record than I've seen with the incandescents they replaced.

And they tend to not fail catastrophically like incandescents do. If an incandescent fails, it can cause an accident. If a single LED or a section of them fails, the lamp still lights and drivers can still determine who has the right of way. That, to me, is priceless.


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## LukeA (Nov 14, 2008)

PhotonWrangler said:


> I've seen LED traffic lights in this area for a couple of years now, and I think I've only seen one that had a problem. It's a far, far better record than I've seen with the incandescents they replaced.
> 
> And they tend to not fail catastrophically like incandescents do. If an incandescent fails, it can cause an accident. If a single LED or a section of them fails, the lamp still lights and drivers can still determine who has the right of way. That, to me, is priceless.



That's true, the chance of a failure resulting in every LED going out at once is 1/(50000^150) or so per hour. (if 150 is the number of LEDs)


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## Illum (Nov 14, 2008)

I guess no one took heatsinking seriously while designing the LEDs to sit so close to each other:shrug:


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## csshih (Nov 14, 2008)

I see many, many, lights with broken patches of LEDs. :shrug:


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## Mr Happy (Nov 15, 2008)

This is an interesting story. I don't think I recall seeing any traffic light with faulty LEDs ever, and almost all of them are LED powered around here. Puzzling...


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## Lynx_Arc (Nov 15, 2008)

even if they don't but last 5 times as long as an incan the cost of replacing 4 incan bulbs probably is more than the cost of aoother LED module perhaps.


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## ikendu (Nov 15, 2008)

csshih said:


> I see many, many, lights with broken patches of LEDs. :shrug:



Roughly how many is "many, many"?

2? 10? 20? More?

Just curious. I've never seen any in our city.


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## Superdave (Nov 15, 2008)

i know a certain CPF member that has a few pieces of a LED traffic light, we have yet to pull any of the emitters off the boards but damn they are bright!


we've had them for years around here and i haven't seen any fail.:thinking:


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## Jarl (Nov 15, 2008)

Lynx_Arc said:


> even if they don't but last 5 times as long as an incan the cost of replacing 4 incan bulbs probably is more than the cost of aoother LED module perhaps.



There's the cost of a new bulb ($0.10), then there's the labour cost of fitting the bulb. Including that, new bulbs are quite expensive, so it probably works out cheaper to replace them less often, even if the modules cost more.


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## JohnR66 (Nov 15, 2008)

What kind of LED do they use? 5mm? Superflux?

I have not noticed this in traffic lights, but in some semi trailers, I've noticed tail lights that have several LEDs out.

As stated, it is a quality issue, but more specifically a quality and design issue. If the designer used good LEDs, but tried to over drive them so he could get by with less, then you end up with failures.

Why is this in "LED flashlights" board. Should be moved.


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## applevision (Nov 15, 2008)

I was just in Belmont, MA visiting a friend and was amazed at how many LEDs were out. It did seem like mostly the red lights but even in the greens there were tons of LEDs that were out. The weird thing was that they tended to cluster, almost like a slice of pie. I was thinking about how this did seem odd and I was wondering how much it would cost to replace/repair them... Weird!
:thinking:


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## PhotonWrangler (Nov 15, 2008)

The clustering might be due to poor solder joints on the power rails of the circuit boards. I'm guessing these aren't made by one of the big name manufacturers like G-E.


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## Mr Happy (Nov 15, 2008)

I was wondering if cold winter weather might have some connection? Also the possible use of ROHS-compliant lead-free solder might have something to do with it. If you use lead free solder it is almost certain you will have unreliable solder joints.


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## csshih (Nov 15, 2008)

ikendu said:


> Roughly how many is "many, many"?
> 
> 2? 10? 20? More?
> 
> Just curious. I've never seen any in our city.



maybe around 10..

and yea, they are either cluster or in a diagonal.


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## Superdave (Nov 15, 2008)

JohnR66 said:


> What kind of LED do they use? 5mm? Superflux?
> 
> I have not noticed this in traffic lights, but in some semi trailers, I've noticed tail lights that have several LEDs out.
> 
> ...


 

I asked Socom, he said his are green 5mm.. when i get back to work after my vacation i'll see about posting a pic.


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## winston (Nov 16, 2008)

WadeF said:


> Could people be throwing bottles, rocks, or who knows what at the lights and damaging them?



Maybe one or two. Five, tops - and you gotta be impressed by my accuracy, given how drunk I was and how fast I was driving at the time. :nana:
-Winston


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## ak645 (Nov 16, 2008)

November 7th was my 20 year aniversary as a signal tech in Broward county,Fla. We maintain about 1200 signalized intersections.

Some years back we converted most signals to LED.We used all GE LEDs and about 60% of the greens were defective.GE ended up just sending us all new greens.All the defective ones have been replaced.We did not do the ambers at that time.Since they're only on 4 seconds at a time management did not consider it cost effective.After Wilma we started installing amber LEDs.

LEDs use about 1/10 the electricity of a 135wt bulb but the average cost is $150.00 each!They draw so little current that I've seen intersections operating just fine with an open neutral till the controller finally dies.At an intersection that's been totally converted (including ambers and peds) electrical consumption has dropped about 75% from 20 amps to 5.

In an average week we replace 20-30 bad LEDs but they are much more vulnerable to lightning,surges and other power related problems then are incandesents so that number can skyrocket after a serious storm.We replace all burn-outs within 24 hours after being made aware of them usually much quicker then that.I have never noticed any dimming.

Andy


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## unique (Nov 16, 2008)

Okay, came back home and looked and few LED traffic lights. One of them about 10 were out and were clustered together and on another a whole SET of red light was not working... Amber and green where but red was not at all..
Another one, a pedestrian light few LED's were not working either...
Could hot weather affect these? It does get really hot here sometimes..


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## ak645 (Nov 16, 2008)

unique said:


> Okay, came back home and looked and few LED traffic lights. One of them about 10 were out and were clustered together and on another a whole SET of red light was not working... Amber and green where but red was not at all..
> Another one, a pedestrian light few LED's were not working either...
> Could hot weather affect these? It does get really hot here sometimes..



Usually when all the reds (or any color) in any one direction (or all directions) at an intersection are out the problem is not in the LED but elsewhere.Of course that's here.Maybe in Australia the traffic engineering depts are just that lax.

Andy


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## unique (Nov 16, 2008)

ak645 said:


> In an average week we replace 20-30 bad LEDs but they are much more vulnerable to lightning,surges and other power related problems then are incandesents so that number can skyrocket after a serious storm.We replace all burn-outs within 24 hours after being made aware of them usually much quicker then that.I have never noticed any dimming.
> 
> Andy


Hmm, thats interesting. We had really bad lightning the other day. Lightning striked train power lines and brought whole train lines to a halt, even someones chimney got hit by lightning bringing all the bricks down...
Though that is like once or twice a year thing to happen here... I would just think these are faulty like LED flashlights. You always get people who come here to complain they have got a lemon. These ones are the ones I guess that somehow pass quality control...


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## unique (Nov 16, 2008)

ak645 said:


> Usually when all the reds (or any color) in any one direction (or all directions) at an intersection are out the problem is not in the LED but elsewhere.Of course that's here.Maybe in Australia the traffic engineering depts are just that lax.
> 
> Andy


Traffic lights here are getting converted in record numbers. Just yesterday I drove past an intersection and the lights had all been changed to LED. Just two days ago I drove past it was incandescent lights but now they are all brand new LED just two days later. They were all working perfectly and bright enough to see from miles away. So I'll be keeping an eye out on these see which ones start playing up first..


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## ak645 (Nov 16, 2008)

unique said:


> Hmm, thats interesting. We had really bad lightning the other day. Lightning striked train power lines and brought whole train lines to a halt, even someones chimney got hit by lightning bringing all the bricks down...
> Though that is like once or twice a year thing to happen here... I would just think these are faulty like LED flashlights. You always get people who come here to complain they have got a lemon. These ones are the ones I guess that somehow pass quality control...



Not faulty just the nature of the beast.LEDs have many electronic components contained within,incandescents have none.More potential failure points=more failures.

Usually when the LED retrofits take place they happen as rapidly as possible.The capital outlay is substantial and local gubmints need to recoup the investment ASAP.In many jurisdictions traffic signals are not metered so the power company does not cut the bill untill the entire billing area has been completed.We did all 1200 intersections in 90 days.Each tech was responsible for 3 intersections per day.

Andy


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## Zendude (Nov 16, 2008)

In San Francisco where I work, I see bad clusters everywhere(by cluster I mean a random section of the array). We don't have dramatic temp swings and we don't get any lightning. Some of the dead clusters are flashing like lightning though, which leads me to believe its not the LEDs but the boards. Solder joints seem most likely.


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## unique (Nov 16, 2008)

I haven't actually seen any flickering LED traffic lights.. All comes down to manufacturer and quality I guess.


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## CM (Nov 16, 2008)

Illum_the_nation said:


> I guess no one took heatsinking seriously while designing the LEDs to sit so close to each other:shrug:



I think you hit on the root of the problem. These LED's are exposed to a lot of heat from the sun (and I don't see any traffic lights painted white--they're all black). Since traffic lights are not originally designed for LED's, there's probably not a good way to put "drop in modules" into these things with proper heatsinking. Think of the Mag LED drop ins. At least they recognize that you can't get the heat off the LED's and put some thermal back off for protection. Unfortunately, you can't do this with traffic lights. They have to be on at full brightness.


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## Superdave (Nov 16, 2008)

Here are pics of the ones we have..

Green (5mm LED;s)







and Red (looks like Lux1's)






ak645, do these look like what you use?


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## NightFlyer (Nov 16, 2008)

All of the ones here in the Atlanta area appear to be 5mm and I imagine are drop-ins as the actual traffic light housings aren't being replaced in a lot of cases. Still, the worst I have seen is a single light with a partially failed cluster, so it looked like a big black "splotch" within the green light. It was working fine later that week. I have not seen any of them that have completely failed and rarely see any with more than a single LED out.

I'm not sure who is responsible for traffic lights here, whether it is Georgia DOT or the individual counties, but they seem to be on top of it when it comes to keeping these lights working.

We now have the new LED walk signals that count down in many intersections, too.


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## NightFlyer (Nov 16, 2008)

ak645 said:


> November 7th was my 20 year aniversary as a signal tech in Broward county,Fla. We maintain about 1200 signalized intersections.
> 
> Some years back we converted most signals to LED.We used all GE LEDs and about 60% of the greens were defective.GE ended up just sending us all new greens.All the defective ones have been replaced.We did not do the ambers at that time.Since they're only on 4 seconds at a time management did not consider it cost effective.After Wilma we started installing amber LEDs.
> 
> ...



All due respect, when I lived in Boynton Beach for 4 years, I lost more electronic gear and UPSs due to bad power than my 25+ here in Atlanta. APC and Tripp Lite both informed me that Florida had over double the claims than any other state in the US due to bad power. Storms are one thing, but I saw major fluctuations and spikes on clear, sunny days as well. I lived there from late '95 to mid '2000. Since moving back to Atlanta, even with some of the heavy storms we get in the summer, I've had only one incident where I had electrical damage and that was due to a direct lightning strike to the building I live in. I work in IT and have several servers and a full network + lab at home.

So I imagine the higher heat and humidity down there contribute to those power issues, as well as the daily summer thunderstorms that hit the area.

Going from 20A to 5A is a big drop! I'd imagine more than half of that is the controller itself.


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## PhotonWrangler (Nov 16, 2008)

ak645 said:


> November 7th was my 20 year aniversary as a signal tech in Broward county,Fla. We maintain about 1200 signalized intersections.
> 
> Some years back we converted most signals to LED.We used all GE LEDs and about 60% of the greens were defective.GE ended up just sending us all new greens.All the defective ones have been replaced.We did not do the ambers at that time.Since they're only on 4 seconds at a time management did not consider it cost effective.After Wilma we started installing amber LEDs.
> 
> ...



Andy, thanks for your great perspective here, and congratulations on 20 years in an illuminating job!

Are there any LED signals still running on old electromechanical controllers in your area? There's one intersection here where there's a flashing red LED stoplight, and every time it turns on it sort of strobes first, then goes solid. I can't tell whether this is a really dirty relay contact on an old cam-actuated system or if it's a deliberate feature in a solid state controller.
:thinking:


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## ak645 (Nov 16, 2008)

Superdave said:


> Here are pics of the ones we have..
> 
> Green (5mm LED;s)
> 
> ...



Hi SuperDave,

We only opened up one LED and that must've been 7-8 years ago when we first did the retrofit.It was a GE and similar to your first pic except the individual LEDs were spaced farther apart and all the electronics were mounted on the front.The LED modules are glued shut and are a MAJOR PITA to open.Not sure what second pic is?

Andy


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## ak645 (Nov 16, 2008)

PhotonWrangler said:


> Andy, thanks for your great perspective here, and congratulations on 20 years in an illuminating job!
> 
> Are there any LED signals still running on old electromechanical controllers in your area? There's one intersection here where there's a flashing red LED stoplight, and every time it turns on it sort of strobes first, then goes solid. I can't tell whether this is a really dirty relay contact on an old cam-actuated system or if it's a deliberate feature in a solid state controller.
> :thinking:



Hi PW,

Thank You!

Nope we got rid of all our mechanicals long before our first LED went in,Thank God.I really,really hated them.

I'm not aware of any controllers that have a setting for strobing a signal nor anywhere n the MUTCD (our bible) that'd permit that.So it's either A-a dirty contact if mechanical (like you said) B-a bad LED or C-a bad load switch.Load switch is a big relay where the 24vdc from the controller switches the 120vac to the signal.Some older ones expect to see a load on the output and the LED has virtually none vs a light bulb.We had to change a bunch,due to strobing,when we first installed LEDs.They cost a hundred bucks a pop. This fact also changed how we troubleshoot overhead shorts as we used to read the resistance of the filament to diagnose wiring problems.

Andy


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## TrainCop (Nov 16, 2008)

ak645 said:


> I'm not aware of any controllers that have a setting for strobing a signal nor anywhere n the MUTCD (our bible) that'd permit that.


I've seen some stop lights (steady red) with what appears to be a strobe tube horizontally in the center. I imagine the best way to have a steady red signal surrounding the strobe would be to use LEDs.

Around here (Maine), it seems they use them to make drivers aware of a stop at a greater distance, like where the intersection is just after a higher speed zone, or where drivers might be looking into the sun at certain times of the day. They are an attention-getter.

As railroad grade crossing signals get upgraded around here, they are going more and more to big, bold LED modules. So far, no gaps in any that I'm aware of, but they're still pretty new on our line.


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## Superdave (Nov 16, 2008)

ak645 said:


> Hi SuperDave,
> 
> We only opened up one LED and that must've been 7-8 years ago when we first did the retrofit.It was a GE and similar to your first pic except the individual LEDs were spaced farther apart and all the electronics were mounted on the front.The LED modules are glued shut and are a MAJOR PITA to open.Not sure what second pic is?
> 
> Andy


 

the 2nd one is from a red light, red Lux 1's


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## KD7EIR (Nov 16, 2008)

TrainCop said:


> I've seen some stop lights (steady red) with what appears to be a strobe tube horizontally in the center. I imagine the best way to have a steady red signal surrounding the strobe would be to use LEDs.
> 
> Around here (Maine), it seems they use them to make drivers aware of a stop at a greater distance, like where the intersection is just after a higher speed zone, or where drivers might be looking into the sun at certain times of the day. They are an attention-getter.
> 
> As railroad grade crossing signals get upgraded around here, they are going more and more to big, bold LED modules. So far, no gaps in any that I'm aware of, but they're still pretty new on our line.



They use strobes at some intersections here as well - mainly the intersections with a high incidence of red light running caused accidents.


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## SemiMan (Nov 17, 2008)

The second light, the one with a bunch of red lux-1s is likely Dialight. Much of the initial LED conversions for traffic lights were done with 5mm LEDs.... lots and lots of them with the ensuing heat and reliability issues. I believe it is more common today to use fewer higher powered and higher reliability LED such as Lux, Cree, Osram, etc. When you look at these, they do not have the "LED" look of 5mm. You likely will not know on first pass it is LED other than the color looks more saturated as it is just a light source behind a traditional lens.

Semiman


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## Foxx510 (Nov 17, 2008)

I think here in Aus, they were using Kingbright LEDS at one stage, pretty sure they were normal 5mm types.


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## Stillphoto (Nov 17, 2008)

AK - thanks for the info...I've gotta admit I loved the fact that amidst this conversation you popped up with actual been there done that knowledge. Now I know why a good number of the yellows haven't been replaced, that totally makes sense. Recently 

I've seen some going bad around here too (SoCal). It seems a little cluster will go out here and there, but they aren't completely out, they just flicker erratically.

I've even seen some signs that look to be city installed (as they were hanging from traffic lights) that had white led arrows. They appeared to only be 5mm's but wow could I see them from blocks away.


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## Canuke (Nov 19, 2008)

Stillphoto said:


> I've seen some going bad around here too (SoCal). It seems a little cluster will go out here and there, but they aren't completely out, they just flicker erratically.



It does seem to be a California thing; seeing red lights with jagged patterns of dead emitters is a fairly common occurrence for me in and around the San Fernando Valley.

It makes sense to me that California municipalities would be early adopters on these... and end up with a lot of units made before the suppliers gained the engineering experience to get them right.


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## Oznog (Nov 19, 2008)

Ha I wonder if they had people who knew nothing about LEDs and put the strings in parallel without ballast resistors in each string. Or did not regulate voltage/current tightly. One would hope not...

I heard a funny story that the first problem they noticed was that the LED traffic lights iced over far sooner than the incandescents, because no substantial heat was being generated inside. Or is that an urban legend?


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## AvPD (Nov 20, 2008)

There was a thread linking to an article about traffic lights a few months ago, they save a lot of money by using less electricity as traffic lights are on 24 hours a day, and the bulbs they use have less efficient filaments than regular household bulbs.


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## dbvanhorn (Nov 20, 2008)

Zendude said:


> In San Francisco where I work, I see bad clusters everywhere(by cluster I mean a random section of the array). We don't have dramatic temp swings and we don't get any lightning. Some of the dead clusters are flashing like lightning though, which leads me to believe its not the LEDs but the boards. Solder joints seem most likely.


 
I would also suspect thermal cycling, and maybe issues with converting to ROHS compliance, depending on when and where they were made.

Here in Pittsburgh, I see a few of the greens on my way to work with missing sections, and some blinking erratically.

All in all, I suspect they are WAY ahead on costs though, since even the failing ones are still very usable, and seeing replacement trucks on the street is now a rare thing.


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## surfinsmiley (Nov 23, 2008)

I live in Tokyo city, Japan. "All" the traffic lights here are LED and I`ve never seen a single failure, believe me I really look for them to.
Before they changed them over outside my shop there seemed to be people fixing a light on a weekly basis and since the LEDs went in I`ve not seen the repair guys at all... I bet the repair guys don`t share the love of LEDs we do.


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## Oznog (Nov 23, 2008)

I've never seen a bad LED traffic light.

LEDs DO flicker madly when bad, I've seen it when I hooked up a bunch all wrong without ballast resistance.


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## LEDAdd1ct (Nov 23, 2008)

I have not seen any dim or out since I started paying attention to those lights that were retrofit in my area. However, my guess would be a poor choice of suppliers for those that go out in "chunks" or "slices."


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## Illum (Nov 23, 2008)

LEDAdd1ct said:


> I have not seen any dim or out since I started paying attention to those lights that were retrofit in my area. However, my guess would be a poor choice of suppliers for those that go out in "chunks" or "slices."



regardless of suppliers...if a reputable supplier designed one chunk to be wired in series and it just so happened that the first LED in line was the one faulty LED in a 100K batch of LEDs the result is the same *blip* 

Some suppliers wire the chains in parallel to give each LED its chance to succeed or fail, others...inevitably, goes with the slightly cheaper option


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## Drivers100 (Nov 24, 2008)

One of the main reasons for converting to LED was to power intersections with UPS.

Most of the failures you see out there are from cities and counties that jumped the gun to retro before DOTs could right the specs. In CA the specs call for a minimum # of LEDs per module, temp. compensation and a minimum # of series/parallel strings.


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## Lightingguy321 (Nov 26, 2008)

Cold weather effects the driver circuit, in the extreme cold (like in upstate new york during the winters) modules have certain sections of LEDs that don't work or the entire module does not work until it warms up. I have seen this on multiple occasions where in the morning commute half a Green LED or Red LED module looks dead (off) but on the way home, the entire module works again.


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## Lightingguy321 (Nov 26, 2008)

AK645- your picture of the Red module is indeed of Low dome Luxeon I emitters (which city do you work for?) 

I too have a few modules at home (partially dead so I got them from a friend of mine who works for the DOT, I pretty much just salvage the good emitters off of the module for my own use) there are something like 192 LEDs in a 12" (or is it 8") GELcore (GEs LED module) board and they are wired in strings of 4 LEDs per string. The module consists of a plastic enclosure case around the module which includes the LED board and a converter board (AC to DC). This is the issue with heat sinking (no where for heat to go since the front side of the LED board is covered with a multi-lens module for focusing each of the LEDs.


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## mikey99 (Dec 20, 2008)

Has any one experienced the problem of flashing / flickering LEDs (one fails)
when connecting standard 10mm leds, 4 in series with a proper resistor for the circuit?

I tested the current and voltage going through each LED and its fine for their requirements. 

what does flashing / flickering of an LED mean?:thinking:


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## RODALCO (Jan 1, 2009)

Flickering LED's are more likely to be a poor soldering connection somewhere in the circuit or a faulty powersupply board.

LED units I have seen boards off are wired up series parrallel with strings of 4 LED's in parrallel. Running current at 80 mA which is 20 mA per LED.
In New Zealand we initially (±2002) had a lot of the amber LED lights failing in strings of 4 or 8 LED's.
Now (2004 - 2008) most Auckland traffic lights have been converted to LED and I have seen a few faillures in red and green LED modules as well.
Even with some failed LED's or not these lights are still amazingly bright and can be seen from a lot further distance than the incandescent lamps.
The changeover between colours happens a lot faster too, which gives milliseconds earlier warning of a colour change.


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## greenlight (Jan 1, 2009)

Every millisecond counts.


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## Fallingwater (Jan 2, 2009)

They probably went with the cheapest they could find.
Here in backwater Italy most lights are still incandescents (though we're starting to ssssllllooowwwwllly switch to LEDs), but I live in a city whose main square has been fitted with several blue lights, each made of 20 or so LEDs, and no LEDs have failed in the, what, three or four years since they've been put in place. Whole light assemblies have failed, presumably because of bad connections or something, but no single LEDs and no clusters.


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## leeleefocus (Jan 2, 2009)

I have not read all the posts as i do not have time but i work for a rail company and have had some dealings with the people that design LED signals. They were having problems with the units loosing brightness and changing colour which was taking them out of spec. After speaking with them for a while they have no clue about how an LED should be treated for it to perform properly. All they were doing was putting about 80 LED's into a sealed unit with no cooling whatsoever and driving them at their maximum rated current (they were Nichia LED's they were using). They were probably being paid about three times as much as me but i could have probably done three times better at designing the unit that they did. They didn't even know about high power LED's and when i mentioned Cree they just looked at me funny. What happened to research.


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## foxtrot29 (Jan 2, 2009)

Sounds like your city bought it's traffic lights from dealextreme.


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