EEVblog #361 - LED Ceiling Panel Lighting 101

[SteveyG]

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.

A 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.

[T4P]

Unless you want to keep on changing the tubes ... 

[SeanB]

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.

[SteveyG]

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.

I've had good luck (so far) with Osram Quicktronic ballasts.

[G7PSK]

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.

The 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.

[T4P]

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.

I use inductor ballasts. No matter which manufacturer i use it dims out within a year

[SeanB]

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.

[T4P]

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 efficient
I use 40W T9 circular fluoro's

[SgtRock]

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 - 2001
 
Best Regards
Clear Ether

[ptricks]

G7psk, you are talking of Electroluminous displays. Great for backlighting, but need a high power driver at 400Hz 115VAC sine wave to drive them.

I 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.

[SeanB]

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.

[tom66]

Newer LCDs still use multiple drive voltages. One LCD monitor I repaired used +28V, +15V and -9V.

[naimis]

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.