EEVblog #361 - LED Ceiling Panel Lighting 101 - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: September 27, 2012, 04:44:54 am
content: Dave.

author: T4P
author_rank: Super Contributor
timestamp: September 27, 2012, 05:53:20 am
content: Great doug-gy!It was interesting, who would have known he was working for the lighting industryFrom last week's teardown i wouldn't have expected that

author: JoannaK
author_rank: Frequent Contributor
timestamp: September 27, 2012, 06:24:23 am
content: Nice material there. Was expecting you two (three) to blow up something.. but perhaps on next video

author: nitro2k01
author_rank: Frequent Contributor
timestamp: September 27, 2012, 07:17:35 am
content: Come on, open it up and scope the PWM signal! (Or if you have a light sensor like an LDR handy, scope it without opening it up.)

author: IanB
author_rank: Super Contributor
timestamp: September 27, 2012, 07:24:02 am
content: About the closing remarks in the video: if you installed a panel like that as a lighting fixture in new construction, and after a few years it has faded and needs replacing, what would you do? Supposing an equivalent panel in the same form factor with the same mounting arrangements might not be available any more...The big necessity with new lighting systems like that is going to be standardization. We have standard bayonet fittings (or Edison screw) for light bulbs and standard sizes for fluorescent tubes, ensuring universal drop-in replacements. LED technology will surely have to go the same way before it can become a mainstream lighting solution.

author: Psi
author_rank: Super Contributor
timestamp: September 27, 2012, 10:55:00 am
content: Proper led lighting should last 10+ years, maybe even 30Long enough that changing some mounting wont be an issue.The week point will be the drivers failing due to dead capacitors etc..But with a proper driver they should last pretty much forever with just the light output falling off as they age.If LED development leads to cheap output power then it wouldn't be hard to have the lighting unit start at 60/70% of its rated power and monitors it's light output then increase current over it's lifespan to keep the output constant and prolong the usable life.We're seeing massive power output led units coming out. An average 100W incandescent is only 1600 Lumens, which means one of those panels is ~twice the light output you need for a typical room.

author: T4P
author_rank: Super Contributor
timestamp: September 27, 2012, 12:24:53 pm
content: A typical fluoro tube might give 70lm/W but put on a diffuser and that drops very quickly, i might have 2800 coming out of my ceiling lamp but that drops what seems like 2/3 once i put on the glass diffuser

author: IanB
author_rank: Super Contributor
timestamp: September 27, 2012, 02:33:59 pm
content: Quote from: Psi on September 27, 2012, 10:55:00 amI'm not certain of this. LEDs use similar phosphor technology to fluorescent tubes, and the light output of tubes falls off rapidly enough that they need replacing once every year or two in office situations where they are on all the time. LED manufacturers quote an expected life time to 50% output, but there is reason to believe that these claims are optimistic, especially outside big name brands like Cree. If LED lighting becomes more popular, then factories making cheap LEDs are going to spring up all over and there is no saying what kind of lifetime those Wun Hung Lo brands will have.

author: T4P
author_rank: Super Contributor
timestamp: September 27, 2012, 04:51:00 pm
content: It's always not the phosphor that goes first, flouros lose emission within a year or two

author: lewis
author_rank: Frequent Contributor
timestamp: September 27, 2012, 05:27:07 pm
content: Dave, are those LED panels constant voltage or constant current?Most of the edge-lit panels we've come across are CV at 12V or 24V. If they are, I'll send you one of our RF dimmers to try with them if you're up for it.

author: SeanB
author_rank: Super Contributor
timestamp: September 27, 2012, 06:50:58 pm
content: The remote phosphor technologies will help with lumen maintenance, as the dies do run hot, and degrade the coating on them with time. There is a place for them, and a place for incandescent as well. Incandescent is well suited for high temperature applications where they are able to run up to the softening point of the glass. LED and fluorescent is suited for areas that do not exceed 50C at the lamp surface at peak, and are a poor choice for enclosed fixtures.The major killer of linear fluorescent is the green label, as the tubes are dosed with a critical amount of mercury, and as they age the mercury is adsorbed into the phosphor and the glass. You need more than 2mg of mercury in the tube, and cutting the amount down is the killer. Full mercury tubes ( 6-8mg inside) are made on the same plant and with the same technique and material as the eco tubes, which are pretty much going to fail within 2 years, while the full mercury units will run for nearly a decade before failing due to rising electrode drop as the cathodes are stripped and ion burnt. The low mercury will fail and glow pink due to starvation long before the cathodes are worn out. I buy the full mercury tubes, as they last longer with better lumen maintenance. Much better to have a single 6mg tube than replace 5 poor tubes in the same period. Mercury is not an innocent metal, but then again neither is LED manufacture, using toxic metals like Gallium ( similar in properties to mercury) and Arsenic in the construction.

author: robbak
author_rank: Contributor
timestamp: September 28, 2012, 02:26:28 am
content: Quote from: IanB on September 27, 2012, 07:24:02 amThose panels are already standardized. They look to be a drop-in replacements for the 'trophers' - twin flouro tubes in a metal box - that are currently used in suspended ceilings everywhere. Take out the tropher and drop in the panel. Those trophers just plug into standard 10A GPOs mounted in the ceiling space, so plug in your power pack.That is more than enough standardization. The short lives of light bulbs have got us used to the idea of cheap replaceable bulbs in expensive permanent fittings. These lights are going to outlive their fittings by a fair margin, and we will be replacing perfectly good LEDs because the fitting has become tatty long before the LED becomes an issue.

author: EEVblog
author_rank: Unknown
timestamp: September 28, 2012, 06:40:10 am
content: Quote from: robbak on September 28, 2012, 02:26:28 amI do exactly this in an upcoming video.Dave.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 29, 2012, 01:24:55 am
content: If the diffusing panel absorbs about half the light, why not diffuse the LEDs by reflecting them off a matte white sheet that absorbs less than 10%?Quote from: SeanB on September 27, 2012, 06:50:58 pmGallium is nowhere as bad as mercury or lead. Also, most modern white LEDs are made of InGaN.

author: G7PSK
author_rank: Super Contributor
timestamp: September 30, 2012, 08:48:59 am
content: If the green portion of the equation is taken into account including all the driver electronics how do the led's stack up then against a standard discharge tube.I purchased a couple of LED MR16 replacements about 5 years ago for use in a display cabinet and was so disappointed with the light out put that I removed them straight away. They have been sitting in a draw of my desk ever since, but after seeing Dave's video I went out and purchased a E14 light bulb replacement to play with, I tried it in a picture lighting fitting and although it is labeled warm white the output is far to harsh for the purpose but the light would be good for a work light. The LED industry needs to progress a lot further before it is mature enough for general household lighting.The power consumption of the LED's compared with other light sources would certainly pay for themselves, the bulb I purchased would take years to use one unit of power if the specification on the side is to be believed.

author: Mikey
author_rank: Regular Contributor
timestamp: September 30, 2012, 09:32:52 am
content: Quote from: G7PSK on September 30, 2012, 08:48:59 amDon't believe all of thoseSome of them are so optimistic that they almost feed power back into the outlet instead

author: SeanB
author_rank: Super Contributor
timestamp: September 30, 2012, 09:50:08 am
content: Most electronic ballasts lass less than the lights they drive. I have magnetic ballasts that are 40 years old, and still work, though the lighting they drive has had multiple lamp changes since they were new. Contrast this to the electronic ballast, where it is more common to replace the ballast and carry on with the tubes it had in it, with them being nowhere near worn out. Often I replace the electronic with magnetic gear, as it is often cheaper and always more reliable. The only time I replace magnetic units is from them getting physically damaged and falling apart or from them overheating and going open circuit.

author: robbak
author_rank: Contributor
timestamp: October 01, 2012, 04:20:12 am
content: Quote from: NiHaoMike on September 29, 2012, 01:24:55 amMost of the losses seem to be getting the light into the panel. If so, then the fix is just waiting on enough volume to be worthwhile. Instead of using packaged LEDs, mould the LED dies directly into the acrylic. Chamfer and silver the edges to prevent edge losses, and you should get darn near 100%. But the volume needed to set up a production line to do this will take a few years to build, but it will happen. Look up next time you are in a commercial building and you'll see the market for these type of panels.

author: ptricks
author_rank: Frequent Contributor
timestamp: October 01, 2012, 12:14:04 pm
content: Quote from: SeanB on September 27, 2012, 06:50:58 pmThis is my main issue with LED lighting, the 'it is green' crowd. Yes it is green in that you get a cheaper utility bill and possibly the power plant outputs less CO2, but it is far from a green technology as a whole. LED plants produce tons of industrial waste that will be dumped in landfills in barrels with the hope it never leaks out. LED are not recyclable . LED lighting requires a serious increase in other components like resistors, capacitors, and other components to power the LED, adding more waste to the environment. Those productions plants and vehicles transports for the extra materials and the increased resources they need are never talked about. CFL has the same issue, it is not environmentally friendly because of the circuit boards used and all the plastics that will be dumped into landfills. 10 small circuit boards dumped is not better than 1 old tv dumped that the green crowd thinks is such a threat. The return on trying to recycle electronics from led and CFL isn't worth it.The real green technology is incandescent lights, their only non-green problem was power plants, the rest of a light bulb is 98% recyclable , they are just metal and glass. What people fell for is the marketing of power producers to get people to switch based on it saves the user money. Power producers are doing this for one reason, it cost them too much to control emissions from their plants and if they can get their load reduced and can still use old plants and not have to build new ones they profit. I would rather try to solve the problem of power plant emissions , that is one target, than I would want to solve the problem of disposing all the waste generated because of the increased LED/CFL usage by hundreds of different sources. Before the danger was consolidated in one area, now it has been spread to lots of others and people sold out because their utility bill went down.

author: T4P
author_rank: Super Contributor
timestamp: October 01, 2012, 12:51:22 pm
content: But i prefer white to orangeLEDs are just making it even whiter but i like that. I guess it's personal preference

author: EEMarc
author_rank: Regular Contributor
timestamp: October 01, 2012, 01:09:55 pm
content: I much prefer 5K LED lighting over any florescence lighting available. The second best is the warmest white florescence available with a quality ballast. If you want to really annoy me, use daylight florescence lighting or use a cheap ballast. That is my kryptonite.

author: G7PSK
author_rank: Super Contributor
timestamp: October 01, 2012, 08:46:08 pm
content: At one time NASA developed some form of surface discharge material that glowed green all over and you could have over as big a surface as wanted, what happened to that all I have seen it used for is night lights and its still in green only. But with such a material the entire walls and ceiling could be covered in light producing surface.

author: ivan747
author_rank: Super Contributor
timestamp: October 01, 2012, 11:25:53 pm
content: Quote from: Psi on September 27, 2012, 10:55:00 amThat's the problem. We used to have some huge bayonet-mount Panasonic fluorescent lamps that lasted over 8 years at least (they became increasingly dim). Now most of the cheap fluorescent lamps we can get fail after less than 2 years, sometimes regardless of how much they were used. Most of the time they just won't turn on because the power supply failed.I am convinced that the same thing is going to happen with LEDs. You can already see $50 Philips MR16 lights and $7 MR16 LED lights.We bought the $7 ones and some other $15 LED retrofits. We installed both the same day on 2 identical elevators that kept them on constantly. Guess which ones failed first?

author: Pentium100
author_rank: Frequent Contributor
timestamp: October 02, 2012, 04:41:08 am
content: Incancdescent light bulbs are the only ones that can provide point lighting (clear shadows, I like that) with sufficient power and angle (individual LEDs are also point sources, but they tend to light only in one direction and are rather small).Dead CFLs are going to end up in landfills because people won't bother taking them to the store or whatever is needed to do to dispose of them properly. At least you can get paid for dead lead-acid batteries (not a lot, but still), which is an incentive to not throw them in the dumpster. Also, since peole usually buy the cheapest item available and the cheap CFLs fail quickly, there is going to be a lot of them in the landfill.

author: SeanB
author_rank: Super Contributor
timestamp: October 02, 2012, 03:56:16 pm
content: G7psk, you are talking of Electroluminous displays. Great for backlighting, but need a high power driver at 400Hz 115VAC sine wave to drive them. Basically a capacitor, and common on aircraft as exit lighting and panel illumination, as they have no moving parts and can run direct off the AC bus via a resistor. Problems are poor efficiency, and the materials are hygroscopic and degrade with time as well.They need to be sealed in a plastic or glass envelope, and are pretty good. I have a 35x30mm one in front of me from an old electronic thermostat. Elite 13467en Made In USA 12/30/1997. Thin as a business card plastic envelope and makes a nice green white light.

author: SteveyG
author_rank: Unknown
timestamp: October 03, 2012, 09:39:17 am
content: Quote from: EEMarc on October 01, 2012, 01:09:55 pmA high quality T5 5000K tube with a high CRI is IMO superior in terms of cost and light output (and quality) to any LED fixture unless you're after the novelty value.

author: T4P
author_rank: Super Contributor
timestamp: October 03, 2012, 08:42:05 pm
content: Unless you want to keep on changing the tubes ...

author: SeanB
author_rank: Super Contributor
timestamp: October 04, 2012, 04:59:46 am
content: You will never change those tubes if they are made by a reputable manufacturer. Ballasts on the other hand will be a regular replacement item.

author: SteveyG
author_rank: Unknown
timestamp: October 04, 2012, 09:02:18 am
content: Quote from: SeanB on October 04, 2012, 04:59:46 amI've had good luck (so far) with Osram Quicktronic ballasts.

author: G7PSK
author_rank: Super Contributor
timestamp: October 04, 2012, 01:20:46 pm
content: Quote from: SeanB on October 02, 2012, 03:56:16 pmThe ones that I have got run on 50/60HZ no electronics of any form in them just a flat panel that glows green, If the whole room was covered in something similar that was white it would be good.

author: T4P
author_rank: Super Contributor
timestamp: October 04, 2012, 03:22:27 pm
content: Quote from: SeanB on October 04, 2012, 04:59:46 amI use inductor ballasts. No matter which manufacturer i use it dims out within a year

author: SeanB
author_rank: Super Contributor
timestamp: October 04, 2012, 03:35:50 pm
content: G7PSK, They work on 50Hz, but are brightest at between 400-1kHz, as they are basically a capacitor. Need a pure well filtered sine wave drive, as they are basically a lossy capacitor. Sine wave to reduce the radiated EMI, as they are very effective radiators of harmonics.T4P, T5 tubes are really bad for loss of emission, and they unfortunately can only be run within a very narrow current band, as this is the only point where they are going to last. Too high and they overheat and dim, too low and they strip cathode fast. Only thing going for them is they use less material to make. T8 tubes I use last up to 10 years on magnetic ballasts, on 5 days a week for 9 hours. Cheap OHJ has a life of between 6 hours to 6 years, all depending on how it was made.

author: T4P
author_rank: Super Contributor
timestamp: October 04, 2012, 05:04:08 pm
content: Yeah ... Having to keep changing them every year it's really annoying then, but wait! i don't use T5 tubes! Although i do know they are the most efficientI use 40W T9 circular fluoro's

author: SgtRock
author_rank: Unknown
timestamp: October 04, 2012, 05:24:58 pm
content: Greetings EEVBees:--Doug Ford is simply the perfect guest for Dave's videos. Another charming loquatious Aussie bloke, this one a baritone. I really appreciate the little bits of math and physics that Doug throws in along the way, very helpful. I have been trying to learn about lumens, watts, color temperature, LEDs etc. I have watched Dave's videos and I have listened to the Amp Hour with Cree's John Edmond, multiple times. These lates videos just help cement what I have learned. Well done Dave!!"I wear suspenders and a belt. I am a security man all the way"Justin Wilson (The Cajun Cook) 1914 - 2001Best RegardsClear Ether

author: ptricks
author_rank: Frequent Contributor
timestamp: October 04, 2012, 06:33:21 pm
content: Quote from: SeanB on October 02, 2012, 03:56:16 pmI got a bulk lot of LCD displays that use EL backlights, the downside is that in addition to having a driver for the lighting, they also required -12V and 5V supplies. It seems EL output changes as the parts age. Out of 10 displays, only 3 are really bright. All were NOS.

author: SeanB
author_rank: Super Contributor
timestamp: October 04, 2012, 07:09:05 pm
content: Old TN displays then. Only LCD that really needed a negative bias, or rather a 15VAC drive to change from fully on to fully off. EL degrades from moisture ingress through the plastic housing, a sad fact. They would work well if they were made like LCD displays, using a glass front with an ITO inner layer and a sputtered back glass slip, with a side gap filler to separate them. That would be expensive, but is workable for aircraft display backlights where price is less of a concern than reliability.

author: tom66
author_rank: Super Contributor
timestamp: October 07, 2012, 01:20:08 am
content: Newer LCDs still use multiple drive voltages. One LCD monitor I repaired used +28V, +15V and -9V.

author: naimis
author_rank: Contributor
timestamp: October 09, 2012, 02:48:17 am
content: I may be the only one here who really cares at all about underwater lighting (I've built two dive lights, a 10W UV light and a 36W white light, both LED-based), but I found a paper I had used for reference when I was doing my design:Ronan Gray, "Underwater Illumination"(PDF)It has a fairly nice graph of the absorption coefficient of water over the visible spectrum, among other things.