traffic lights meltring

MEXICOWANDERER wrote:
Street lighting is in it's infancy. The so called engineers who are designing what I see insist on using Fresnel lensing which is expensive, unneeded and just plain shows their lack of experience of using a flat platform COB device.

The following chip will blow a 70 watt high pressure sodium street lamp into the weeds. Pure floodlamp effect.



I made a tunnel-type shaded 100 watt streetlamp to cover the crosswalk across a federal highway the light was contained so it did not bother drivers. It was said the children never again had problems or close calls when using the crosswalk after the bus left them off 2nd shift.

Actually, it's the standard been the standard for a few years and available for significantly longer. Very few large agencies haven't switched to LED street lights (not all have completed the conversion). I suspect you aren't familiar with the considerations. Brighter is not necessarily what we are going after. Limiting variations in brightness is more important. Stare into a campfire some time and then look into the woods. At first it will be pitch black and gradually your eyes will adjust and you will start things. The problem driving down the road is you go in and out of bright areas every couple seconds so the eyes can't adjust. If you have a single light in an unlit area, that will work for a crosswalk but that's not typical streetlight layout.

The problem is LED lights are very directional in nature. That's why they need the lenses to spread the light out (still not nearly as even as incandescent). Otherwise, you will have a small pool of very bright light surrounded by dark areas.

The old incandescent bulbs distributed light pretty much in all directions evenly, so it was pretty simple to provide a spacing and call it good. Light would very gradually get weaker as you move further away but the next light in the row would overlap. Even with the lens, LED still have a much sharper drop off in coverage as you move further away, so area lighting is much more difficult.

My first project a few years back, the calculations were triple checked as we were new to them and while it technically meets the requirements, first time I drove it at night, I didn't like it. There were clear light and dark areas as you drive down the freeway. The dark areas met the minimum brightness requirements but the variation made it harder to see stuff in the darker areas.

That's why I have mixed feelings on them. Great for power savings and lifespan but simply not as good as incandescent.