Has anyone on this forum used LED desk lamp?

[Ken_McE]

Hotbeam, the light looks awesome. No idea what you mean by "switching power supply". I hope you'll make a 120 volt, 60 cycle model available?

 

[2xTrinity]

Yes, I know about this-they are usually concerned about the UV since it does the most damage by far. I also know that both incandescent and fluorescent sources produce UV. Interestingly, since they're a quantum source white LEDs produce no UV at all. I also know that some but not all so-called full spectrum fluorescents purposely emit extra UV for some hocus pocus marketing reasons. I personally DO NOT recommend such lights as added UV has no additional seeing or health benefits but does in fact do things like discolor furniture and damage eyes long term.

Absolutely agreed. Releasing extra UV is a pure waste, it would be better off to throw it away completely, or even better, actually convert it to visible light using phosphors! Also, using a blue light that is longer wavelength, say 470nm, is going to be a LOT less damaging than near-UV light at say, 400nm. Not only is photon energy is inversely proportional to the wavelength, perceived intensity is a lot lower the deeper you go. The fact that LEDs have ZERO UV component, LEDs should actually be a better way to go in the long run, especially if they have a "warmer" phosphor mixture.

My 4900K was indeed a conclusion based on a continuum, not on binary thinking as you seem to think. The hypothesis of the researchers was that light with higher proportions of blue may cause macular degeneration. I'm assuming then based on their recommendation (i.e. to avoid light sources with CCT over 5000K if you're in a risk group for macular degeneration) is also based on a continuum. For example, 10000K would be considered very dangerous, 8000K dangerous, 7000K somewhat dangerous, 6000K possibly dangerous, 5000K just barely safe. Of course, those are my words but usually when studies of this sort offer recommendations for safety it's based on this type of thinking. As a result, the recommendations if anything are overly conservative. And note that the recommendations only apply to those in risk groups for macular degeneration, NOT to the entire population. For most people there is no risk at all being under even 6500K, provided the UV is filtered out and it's not ridiculously intense like staring into the business end of a flashlight.

Here's one criticism I have of the whole color temp thing, certianly the relevant factor for this, and also the circadian rhythm thing must be the overall quantity of light. Consider the following scenarios:

A) being outside, at noon, under direct sunlight with a color temp overall of around 5500K.
B) being outside, right after the sun has set, where the only light source is "blue sky" with a color temp of 10000k

Even taking into account pupil dialation to compensate for the lower intensity in case "B", I would wager that the eye would be intercepting a lot more (perhaps even orders of magnitude more) total blue and soft UV photons in broad daylight, as opposed to at night, when the only light source is just a sliver of blue sky that is just bright enough to see by. Of course, case "A" is a good time to have UV-filtering sunglasses, especailly if at risk for macular degeneration. Wearing polarized sunglasses is another good idea -- as those selectively remove the direct glare and scattered light as well (scattered light is almost all short wavelength), without interfering with color perception at all.

I also realize that not all lights with the same CCT are created equal. Sure, it's better to avoid a light with copious spikes in the far blue portion of the spectrum and instead opt for one with either a broader but less intense blue emission, or with a blue spike centered on a higher wavelength. And the beauty of that approach is that LEDs can be tailored to give such broad blue emissions as well as having different center wavelengths. In fact, some earlier blue LEDs based on SiC had exactly such emissions. You can also use several InGaN blue emitters in tandem which have their center wavelengths 10 nm apart in order to get a combined effect which is similar. In fact, this latter approach is quite easy since emitters are binned by wavelength.

Again this is a good point. Looking at even a warm white fluorescent lamp with a CD (diffraction grating), or even a halogen incandescent, reveals a non-zero amount of violet/deep blue -- wavelengths that don't even exist from my LEDs, yet that real shortwave component (the most dangerous stuff isn't even visible at all) isn't contributing much to the apparent color temp, since the eye's sensitivity there is so low.

Actually to the contrary, people hate cool white lights. It creates more eye strain when viewing on hours at a time in an office environment. As far as 'yellow incandescent', maybe you've been hanging around CPF too long talking about flashlights Incandescent is in the mid/late 2000ks and it is indeed 'yukky'. You will find mid 3000ks much better. Efficiency is not an issue when the unit is being powered from the mains. FYI, the lamp with use Nichia's NS6L083T-E. If people really want a cool white version, it is a matter of switching to NS6W083T.

This depends on the definition of cool white. Some conisder 4000k cool, others call it neutral. I like lights that are within the 3500-5000k range, with good color rendering. 4000k would be ideal, but unfortunately, most light sources at that color temp have bad CRI (70 or under). To cite one example, we replaced the lights in our garage -- flickery magnetic 3000k T12s, CRI 65, with flicker-free electronic 5000k T8s, CRI 89. In a different room, we replaced a halogen tracklight system with a similar fluoro fixture. Made the rooms a lot nicer to work. People who genreally dislike cool white, especialy fluorescent, don't mind these fixtures at all -- suggesting it has more to do with CRI and flicker than color temp. The sun for example doesn't flicker at all, and has CRI 100, and is most certainly a cool white source.

Howevre, I would consider 5000k the limit of what I consider pleasant color temp to work under for artifical lighting. 4000k, if it had the same high CRI, would be better. Artificial lighting of 6500k, even with great CRI, looks atrocious in my opinion. 2700k or even lower incan lighting is bad too, but more tolerable than 6500k+.

Another place to compare the difference is with car HID lights (ideally driving behind a car equipped with them, NOT staring into the headlights). I find the lighst in the 4200K variety offer the best actual visibility of the road. 6500K headlights on the other hand make everything look terrible, and are significantly harder to see under than the 3000K halogens.

 

[hank]

Anybody know this one? I don't read the language:

http://www.oxxio.nl/Oxxio/Thuis/Producten/Lamp/LampInfo

 

[Melchior]

http://store.sylvania.com/show_item.cfm?i=72112

Personally I find, it OK. 3 LEDs have burned out. Also a crappy non-switching linear type transformer...

Decent colour temperature, abit high on the green spectrum. It beats most other crappy 5000K lights out there.

 

[hank]

Has anyone found a red-green-blue desk lamp?

A friend just contacted me asking for a "dimmable low-blue spotlight LED light" saying he's been looking and can't find anything.

I recall someone (Luxeon?) makes dimmable LED modules including amber.

Doesn't appear anyone's making a commercial product. I can try to build him one if anyone has suggestions for what to put together.

I realize most LEDs get destroyed if put on ordinary dimmers.

 

[2xTrinity]

Has anyone found a red-green-blue desk lamp?

A friend just contacted me asking for a "dimmable low-blue spotlight LED light" saying he's been looking and can't find anything.

I recall someone (Luxeon?) makes dimmable LED modules including amber.

Doesn't appear anyone's making a commercial product. I can try to build him one if anyone has suggestions for what to put together.

I realize most LEDs get destroyed if put on ordinary dimmers.

The only problem with RGB desk lamps that I can think of today is that I have yet to find any efficient green LEDs. Cree has a blue LED coming out at 40 lumens per watt, and Luxeon III Red is already about 40 lm/W as well. That suggests over 40% efficiency. The only greens I've been able to find are stuck at around ~30 lumens per watt, considering the eye has eight times more sensitivity to green light than the blue or red I mentioned, that suggests green LEDs are only about 5% efficient. If the Green could be made as efficient as existing blue and red LEDs, they would produce over 300 lumens per watt, and 200+ lm/W warm-white light would be no problem.

Your best bet for efficiency as of right now would probably be to get some Cree XR-E WH bin (around 5000K with a greenish cast), along with a Luxeon III Red emitter, then put a blue-blocking filter over the Crees (a filter that would only block ~570nm and under would be best, you don't want to lose any of the phosphor emission) and blend it all together with a diffuser of some sort.

 

[jtr1962]

Your best bet for efficiency as of right now would probably be to get some Cree XR-E WH bin (around 5000K with a greenish cast), along with a Luxeon III Red emitter, then put a blue-blocking filter over the Crees (a filter that would only block ~570nm and under would be best, you don't want to lose any of the phosphor emission) and blend it all together with a diffuser of some sort.

Looking at the spectra of these, the cooler bin XR-Es already don't have as pronounced a blue spike as most whites. The blue spike of the WH bins should be even less pronounced. In other words, really no need for a blue filter at all since the spectrum isn't that far off a broadband spectrum, especially with the addition of the red. It's only the really cheap, really blue 5mm LEDs which seem to have that pronounced blue spike which some find worrisome. Filtering the blue light from the combination you mentioned would result in some really awful looking light with virtually no ability to render anything from violets through cyans. Don't forget that the CCT of the WH XR-E and LIII red combination will probably be 4000K to 4500K, well under the 5000K where one would even start to be concerned about macular degeneration.

 

[2xTrinity]

Looking at the spectra of these, the cooler bin XR-Es already don't have as pronounced a blue spike as most whites. The blue spike of the WH bins should be even less pronounced. In other words, really no need for a blue filter at all since the spectrum isn't that far off a broadband spectrum, especially with the addition of the red. It's only the really cheap, really blue 5mm LEDs which seem to have that pronounced blue spike which some find worrisome. Filtering the blue light from the combination you mentioned would result in some really awful looking light with virtually no ability to render anything from violets through cyans. Don't forget that the CCT of the WH XR-E and LIII red combination will probably be 4000K to 4500K, well under the 5000K where one would even start to be concerned about macular degeneration.

I believe that's actually close to what Hank is using in this case -- he has mentioned using using incandescent "bug lights" in the past, which are filtered in order to produce zero blue output, due to concerns with blue light resetting the sleep cycle. (this also rules out use of computers, which are backlit much brighter than a sheet of paper under a typical lamp) I suppose using an external removable filter (maybe something like a 5000 -> 3000 "warmifying" filter) may be a better approach, to give a choice between white or amber light as desired.

 

[hank]

Look at the spectra of LEDs at ledmuseum.org. Craig also has the spectra there for the 'bug light' lamps we've used (compact fluorescent, not incandescent).

Any LED producing little or no light shorter than about 500nm will work.
Question was if anyone makes those in a dimmable reading light.

This isn't a question about 'color temperature' (which is human perception of overall result of the combined light).

I'm suggesting the fellow who asked me just gets a low wattage incandescent and a dimmer for it, it's probably all he needs.

 

[hank]

Look at the spectra of LEDs at ledmuseum.org. Craig also has the spectra there for the 'bug light' lamps we've used (compact fluorescent, not incandescent).

Any LED producing little or no light shorter than about 500nm will work.
Question was if anyone makes those in a dimmable reading light.

This isn't a question about 'color temperature' (which is human perception of overall result of the combined light).

I'm suggesting the fellow who asked me just gets a low wattage incandescent and a dimmer for it, it's probably all he needs. LEDs and fluorescents both put so much energy into the range below 500nm that filtering them wastes a lot of the light.

For covering the computer screen, a Rosco #312 "Canary" yellow filter gel works fine to block the range that suppresses sleep. http://www.rosco.com/us/filters/roscolux.asp#colors (scroll down; spectra are clickable links)

Personally, I just use the amber LED spotlights -- these are NOT dimmable:
https://store.lsgc.com/R20-AMBER-FLOODLIGHT-MEDIUM-EDISON-BASE-P50C11.aspx
https://store.lsgc.com/R30-AMBER-BUG-LIGHT-LONG-CONE-P38C0.aspx
in a luxo-type lamp --- I just push it farther away to "dim" it. For reading text without interrupting sleep (or for protecting baby turtles when they hatch) they're great.

If those were dimmable, they'd be what my friend's looking for.

Sea turtle safe lights: http://myfwc.com/seaturtle/WildlifeLighting/index.htm

 

[jtr1962]

Any LED producing little or no light shorter than about 500nm will work.

Question was if anyone makes those in a dimmable reading light.

Given that the nature of a reading light is to help one see well I highly doubt anyone would make such a light as it would be like trying to read under a sodium vapor streetlight. I suggest you find a dimmable LED reading light, and then replace the stock LEDs with amber ones. That shouldn't produce any light less than 500 nm. Even a dimmed incandescent will produce some light under 500 nm, and it will be horribly inefficient to boot. An amber Luxeon on the other hand can give 35 to 45 lm/W.

Exactly what are this person's reasons for wanting this? Just curious.

As a starting point if you want to build one yourself, and are versed in electronics, the HV9910 driver IC might be a good starting point. It has inputs for both PWM and linear dimming, and runs directly off line voltage. I bought five of these recently to play with but it might be a while before I have time to do anything with them. Mouser sells these. They also sell a demo board but it's a bit pricey at $90.

 

[jtr1962]

I forget to add that it's probably much easier to design a desklamp to operate from a 12VDC wall wart. I have some step-down switching regulator boards of my own design which can drive 1 to 3 LEDs off 12VDC at up to 1 amp. I can easily make them dimmable via a few additional parts. Actually, the boards can work on input voltages up to 24VDC, so I could probably drive a string of 6 or 7 LEDs if you needed that many. PM me if you're interested.

 

[easyschnucki]

Hi,

Did you ever got these desk lamps fabricated?

THX
-Sven-

I'm about to get a bunch of these table lamps produced.

Specs (to be finalised) will be:

Light output: 350 Lumens
Light colour: ~3300k warm white
Size: 370mm tall (right angle) x 400mm deep
Switching power supply
Dimmable for lighting output (0~100% lighting output)
ON/OFF switch with touch button
Built-in the high temperature protection function

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Light output: 650 Lumens
Light colour: ~3300k warm white
Size: 470mm tall (right angle) x 490mm deep
Switching power supply
Dimmable for lighting output (0~100% lighting output)
ON/OFF switch with touch button
Built-in the high temperature protection function

What do you think?

 

[abvidledUK]

4sevens lightbar ?

https://www.fenix-store.com/product...d=345&osCsid=4ee03f78aee6c8cd42059a99416782ee

 

[hotbeam]

Hi Sven
I've been a bit busy to continue with this project personally. I've passed this to someone else to complete.
HB

Hi,

Did you ever got these desk lamps fabricated?

THX
-Sven-

 

[easyschnucki]

HB

Sorry to hear that. They are indeed very nice and I would like to get one or two.
So any chance you could hook me up somehow ?

Cheers
-Sven-

Hi Sven
I've been a bit busy to continue with this project personally. I've passed this to someone else to complete.
HB

 

[BVH]

5000K are the only fluorescent tubes I allow in my office!

For my home desk lamps, 3000K spiral Sylvania full spectrums. I actually get a feeling of warmth when I turn them on. It's almost like being outside in summer at noon.

 

[Ted Edwards]

I think that's more a factor of the crappy low-CRI old halophosphor cool whites and flickering magnetic ballasts still used in a lot of workplaces rather than the light being cool.

This reminds me of an experience I had in ~1960. I designed and built a battery (5 of 4Ah NiCd cells) operated flourescent lamp for hiking/camping. It used a current source inverter operating at 30KHz and could vary output to trade off battery life vs. light output. The tube was a 6 inch, 4 watt cool white.

My wife had always hated reading by flourescent lights but was quite happy to read by the above lamp. My theory is that although the magnetic ballasted tube flourescents of the day did not visibly flicker, there would be some 120Hz flicker not completely damped by the persistence of the phosphor. Any 60Khz flicker of my lamp would be completely damped out.

Thus it is probably the flicker that gives rise to eye strain rather than the colour temperature.

 

[Erasmus]

Due to a lack of good LED desk lamps I'm making my own. Currently I get around 750 lumen from 12W warm white LEDs. LEDs will be mounted on a big copper heatsink and be installed in a desk lamp of which the 60W bulb is blown away by this 12W LED lamp.

 

[Illum]

I've recently tried to read on a cluttered desk using the fenix lightbar mounted to the side

it was HORRIBLE! absolutely horrible as every object on the desk now has 30 shadows. this isn't the light bars fault, in fact any lighting fixture with multiple light sources will come up like this.

I made remedies by mounting it directly on top....ahh, much better:twothumbs