Purple street light tear down.

[zerodish]

The light was full of water. To be fair it has been through hurricanes. There is corrosion at the base of the LEDs and the phosphor is flaking off. Since every purple light I have seen is in Florida I'm going to assume it is the salt that is causing the phosphor to fail early. It should be possible to photograph this. There will be a purple background with spots of white light. The light is labeled TCP and the driver is SOSEN 320M 56BH

 

[BVH]

Thanks for posting this interesting topic. Nice to know what's inside them.

 

[ampdude]

They tried those here many years ago with the traffic lights. Then after they were all put in they didn't melt the snow off. No more LEDs.

 

[pnwoutdoors]

They tried those here many years ago with the traffic lights. Then after they were all put in they didn't melt the snow off. No more LEDs.

Though, LEDs of course make plenty of heat. (Our flashlights get plenty hot, if of sufficient output.) Seems like an engineering question, as to whether a light's components can be made intelligently enough that all of the issues can be addressed. One would think the snow-melting surfaces of any light ought to be capable of being heated by at least some of the heat generated by the LEDs themselves. Redirecting that heat to a framework supporting the lens. Can't imagine the heat of a street light's collection of LEDs couldn't be warm enough to keep snow off the lens surface. Then again, I'm no engineer. Perhaps it simply isn't possible; there's certainly been enough time for some engineer, somewhere, to have considered and solved the problem.

As for light housings leaking ...

 

[LEDphile]

The light was full of water. To be fair it has been through hurricanes. There is corrosion at the base of the LEDs and the phosphor is flaking off. Since every purple light I have seen is in Florida I'm going to assume it is the salt that is causing the phosphor to fail early. It should be possible to photograph this. There will be a purple background with spots of white light. The light is labeled TCP and the driver is SOSEN 320M 56BH

This failure type isn't limited to Florida, and the phosphor separating from the LED chip isn't caused by the salt environment.

The weird, worrisome mystery behind America's plague of purple streetlights

Streetlights in a bunch of major cities are turning purple. Is it just a fluke — or a warning of the chaos to come?The sky over the city of

www.businessinsider.nl

 

[PhotonWrangler]

The light was full of water. To be fair it has been through hurricanes. There is corrosion at the base of the LEDs and the phosphor is flaking off. Since every purple light I have seen is in Florida I'm going to assume it is the salt that is causing the phosphor to fail early. It should be possible to photograph this. There will be a purple background with spots of white light. The light is labeled TCP and the driver is SOSEN 320M 56BH

Thank you for this teardown pic! I've been wanting to see a photo of the phosphor delaminating for awhile. I can't quite make it out in this picture though - can you share a closeup of one of the bad LEDs?

 

[theory816]

I don't think its due to salt because where I'm from we also have purple LEDs. I believe its due to low quality, low cost LEDs that have been contracted by city council.

For the guy who said no more LEDs, what light source did your city start using?

 

[idleprocess]

Been a few such streetlights in the DFW area, where the seagull flocks are associated with landfills rather than the ocean some ~270 miles distant.

Though, LEDs of course make plenty of heat. (Our flashlights get plenty hot, if of sufficient output.) Seems like an engineering question, as to whether a light's components can be made intelligently enough that all of the issues can be addressed. One would think the snow-melting surfaces of any light ought to be capable of being heated by at least some of the heat generated by the LEDs themselves.

Definitely a problem that can be solved with some engineering. If not harnessing waste heat, thermostat-controlled heating elements can be incorporated into the design or the hoods can be designed to prevent snow accumulation in the first place.

 

[bshanahan14rulz]

Definitely a problem that can be solved with some engineering. If not harnessing waste heat, thermostat-controlled heating elements can be incorporated into the design or the hoods can be designed to prevent snow accumulation in the first place.

I wonder if the lack of thermal path from MCPCB to housing is the main problem, and if it's due to poor design, sloppy assembly, or both? Hard to tell from the pictures, but it looks like they're trying to thermally contact a flat mcpcb to a curved backplate using a thick glob of silicone adhesive to fill in the gap.

 

[idleprocess]

I wonder if the lack of thermal path from MCPCB to housing is the main problem, and if it's due to poor design, sloppy assembly, or both? Hard to tell from the pictures, but it looks like they're trying to thermally contact a flat mcpcb to a curved backplate using a thick glob of silicone adhesive to fill in the gap.

I was responding to the tangent on stoplights - a downward-firing streetlight should not experience snow and ice accumulation which is unlikely to be an issue in Florida.

Otherwise, looking at the zoomed-in photo the MCPCB interface looks flat. Thermal grease isn't ideal and the lens gasketing is moderately suspect.

 

[zerodish]

The LED shown had delaminated but was still attached. It popped off during transport. Here is what I think is happening. The board gets a bit of salt water in it. This causes a short, electroplating and chemical reactions. There is green between most of the pairs. The copper is exposed there and covered with plastic elsewhere. The aluminun turns into aluminum oxide which has 10 times the volume of aluminum. This pops off the phosphor like a watermelon seed squeezed between the fingers of a terminator wearing teflon gloves. Most of the failures were corner failures. The numbers on the board is AOL6QO VAL-7C5413 152073-1 7554D c backwards RU us EA73015.

 

[PhotonWrangler]

The LED shown had delaminated but was still attached. It popped off during transport. Here is what I think is happening. The board gets a bit of salt water in it. This causes a short, electroplating and chemical reactions. There is green between most of the pairs. The copper is exposed there and covered with plastic elsewhere. The aluminun turns into aluminum oxide which has 10 times the volume of aluminum. This pops off the phosphor like a watermelon seed squeezed between the fingers of a terminator wearing teflon gloves. Most of the failures were corner failures. The numbers on the board is AOL6QO VAL-7C5413 152073-1 7554D c backwards RU us EA73015.

Thanks for the closeup and the failure analysis, zerodish. This makes complete sense to me.