Are LED lights harmful?

[agent00f]

Your perception that LEDs are extremely bright or harmful are probably due to a few reasons.

1. Color Temperature - Most LEDs in recent history are 5000K+, which is very harsh to your eyes due to the scattering nature of higher frequency light. Switch to ~2700K and that issue goes away.

2. Optical Control - Many early LED lamps and fixtures did not put much emphasis on optical control or visual comfort. Optical control hurts efficiency, so many LED lamps and fixtures avoid it and just use bare LEDs, which result in high candela concentrations into your eye. The most visually comforting fixtures/lamps have a very diffuse optics or prismatic structure to break up the light source. Most LED office lighting now uses indirect optics, meaning, the LEDs are pointed up into the fixture (white painted surface) and then the diffuse light bounces down into the environment. This is very visually pleasing because the light is spread over the entire fixture instead of a smaller area like a lamp envelope. Visual comfort is all about candela per square meter (nit). 1000lm out of a lamp (9 sq inches) is much more harsh than 1000lm out of a 2x2' (576 sq inches) troffer fixture. This is why most traditional lamps have lamp shades.

3. Electrical Control - Some LED lamps/fixtures use very simple (cheap) electrical circuits that will produce high frequency flicker. Depending on the type of circuit, this flicker can be bad and/or be influenced by your local power source. Some cheap direct AC fixtures have a bad perceptive flicker which is similar to the old days of fluorescent flicker, and can make you feel nauseated.

It's technically lower freq "flicker" which causes motion problems, and has little to do cheapness per se since it doesn't cost any more to pulse at higher freq w/ typical led drivers. Led flicker is generally worse since the pulses are closer to a square waveform.

"Begs the question" doesn't mean what you think it does.

It's been used wrong long enough that it's the standard accepted definition outside the context of making an argument, and technically correct usage is more of a treat.

 

[Imp]

I had to pull out the sun glasses on my last road trip during a nighttime drive through Utah on a 2-lane highway. They were a bit too dark but without them I could not see much because of constantly being blinded by oncoming cars. I now try to get behind an 18 wheeler if I'm in the same situation.

I wonder if yellow lens sunglasses semi-work for night driving. I thought about picking up a pair for night/winter use a while back but never went through with it -- sometimes I don't carry a bag and have nowhere safe to put my $200+ sunglasses at night.

 

[Red Squirrel]

Those are electronic insect lanterns. The tubes are black light (not black light blue) lamps to attract insects to their killing grids (4500VAC 9mA typical). They often employ pheromone attractant strips for flies and other biting pests.

Interestingly enough, the Automatic Radio Corporation's "Flowtron" division back in the 70s tried using a combination of black light and blacklight blue lamps in their higher end killers. These proved quite effective however the blacklight blue lamps don't have as long of a life and cost more. This mix of electromagnetic spectrum also seems to attract more larger winged moths which cannot reach the killing grid through the openings of the outer protective screen. (And for good reason!)

Later models used multiple black light blue lamps.

LEDs (such as dental blue) are starting to show up as well.

Is that what those blue U bulb fixtures in grocery store meat dept are for? I always wondered what those were. So basically they're just bug zappers?

 

[John Connor]

"Begs the question" doesn't mean what you think it does.

What is this? Jeopardy?

 

[Rubycon]

Is that what those blue U bulb fixtures in grocery store meat dept are for? I always wondered what those were. So basically they're just bug zappers?

Yes. Even though flies and other disease carrying six legged pests don't eat and poop very much, most (sane) folks would rather NOT see them landing on a piece of meat they intend on purchasing for their own consumption.

 

[edro]

It's technically lower freq "flicker" which causes motion problems,

Yeah, I guess you're right.

and has litle to do cheapness per se since it doesn't cost any more to pulse at higher freq w/ typical led drivers. Led flicker is generally worse since the pulses are closer to a square waveform.

That depends on how they do it. True, PWM can be done at high or low frequency, but many non-PWM AC driven LEDs are stuck at 60/120Hz, and the ramp up/ramp down time causes perceptible flicker.

 

[agent00f]

That depends on how they do it. True, PWM can be done at high or low frequency, but many non-PWM AC driven LEDs are stuck at 60/120Hz, and the ramp up/ramp down time causes perceptible flicker.

I would think such applications are quite uncommon given the specific voltage requirement of LEDs.

 

[IronWing]

On UV in hospitals, yes the ones you see near entrances are probably bug zappers. However, hospitals also use intense UV-C to sterilize operating rooms and other sensitive areas. These disinfecting lamps pack a wallop and people can't be in the room while they are running. Some hospitals also install UV-C lights in the duct work to prevent the spread of germs (straight out of the Andromeda Strain!).

 

[Rubycon]

On UV in hospitals, yes the ones you see near entrances are probably bug zappers. However, hospitals also use intense UV-C to sterilize operating rooms and other sensitive areas. These disinfecting lamps pack a wallop and people can't be in the room while they are running. Some hospitals also install UV-C lights in the duct work to prevent the spread of germs (straight out of the Andromeda Strain!).

Yes germicidal lamps have a much shorter wavelength and they can do real damage. They are also decent at producing ozone just from irradiating the ambient air!
Back in the early 90s we tested an axial flow reactor irradiating seawater that was part of a state of the art captive marine life system. The drive power of the lamps as well as dwell time could be varied to dial in the exposure precisely. What we did not expect to see was the increase in oxidation-reduction potential (delta of effluent vs. input in excess of 200 millivolts!)

 

[Red Squirrel]

Wow that's some serious UV gear. Wonder if that affects plastics in the room like the sun would, as most plastics don't do well with UV unless specifically treated. I guess the exposure time is too short for it to be a concern.

 

[Raizinman]

If they are too bright for you or you have concern, very simple solution: Wear Sunglasses.

 

[FelixDeCat]

Chinese LED's.

 

[IronWing]

Yes germicidal lamps have a much shorter wavelength and they can do real damage. They are also decent at producing ozone just from irradiating the ambient air!
Back in the early 90s we tested an axial flow reactor irradiating seawater that was part of a state of the art captive marine life system. The drive power of the lamps as well as dwell time could be varied to dial in the exposure precisely. What we did not expect to see was the increase in oxidation-reduction potential (delta of effluent vs. input in excess of 200 millivolts!)

Yep, I have to open the windows in the room to let the ozone out when I run my fluorescent mineral display for more than a minute or two. The light source is transilluminator running 60W of UV-C (254nm) and 30W UV-A (365nm). The transilluminator is designed for DNA separations under UV-B. Eventually, the UV-C will destroy the glass filter.

Wow that's some serious UV gear. Wonder if that affects plastics in the room like the sun would, as most plastics don't do well with UV unless specifically treated. I guess the exposure time is too short for it to be a concern.

Between the UV and the ozone, plastic deteriorates very rapidly. For portable fluorescent mineral displays, clear marine vinyl is often used to shield observers from the UV light. One mineral dealer has 400W of UV-C in his display and the vinyl degrades so fast he has to scrub the vinyl every day to remove the layer of discolored vinyl that builds up.