# Led ceiling light project



## imagine (Dec 17, 2014)

Hi there, this is my first post on the forums  I see there are A LOT of knowledge here, so I figured that there is no way no one of you can help me out. hehe.

I'm working on a project at home, trying to make a ceiling light with LED and plexiglass. The idea is based on the stock LED panel fixtures you can buy.
This is a pretty poor sketch of the idea. Im mounting the plexiglass to close of the box. Idea was to have led in the roof shine down on the led plate, makeing a much smoother light.
The only thing I need is the ability to dim the leds.

Now, I dont have much experience with LED except from led strips so I have no idea on what LEDs would be the best alternative. Also if anyone has any suggestions to better positioning or solutions feel free to enlighten me. I have looked at both plexiglass made specific for the use of LED and diffuser films, what would be best solution? Would a simple milkywhite plexiglass with low transmission be a better solution?

The plexiglass is going to be 192cmx72cmI really do appreciate any help


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## Ken_McE (Dec 19, 2014)

_I'm working on a project at home, trying to make a ceiling light with LED and plexiglass. _

How bright? runs off line voltage?


_This is a pretty poor sketch of the idea.
_
I'm not seeing the sketch

_
The only thing I need is the ability to dim the leds._

Leds dim well. A dimmable power supply would do that nicely.

_
I have no idea on what LEDs would be the best alternative. _

What do you want the lighting to look like? Are you familiar with warm/cool white distinction? Do you have a way to dump waste heat?


_Also if anyone has any suggestions to better positioning or solutions feel free to enlighten me. _

I need the sketch. Don't understand the description.

_
The plexiglass is going to be 192cmx72cmI really do appreciate any help _

Two foot by six foot? You could get a lot of light out of that.


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## imagine (Dec 20, 2014)

_I'm working on a project at home, trying to make a ceiling light with LED and plexiglass. 

How bright? runs off line voltage?

_*Something like this: Led panel lights . It's Going to act as an immitation of the sort of lighting. Not going to be super bright, but it got to shine light on the floor 2,4m below.*_

This is a pretty poor sketch of the idea.

I'm not seeing the sketch
_*Sorry about that, HERE it is. It's a cross section of the box. *
_

I have no idea on what LEDs would be the best alternative. 

What do you want the lighting to look like? Are you familiar with warm/cool white distinction? Do you have a way to dump waste heat?
__*I'm actually an electrican, just not very familiar with LED, hehe... I want a warm light, or the ability to change color like RGB LEDs as theese give the opportunity to give both warm and cold? **I wont be able to get the heat out of the box, but the box is pretty big and holds a lot of air. Could high power led strips be good enough, would they emit enough light? I guess you could describe the light as more of a daylight glow.*
__
Also if anyone has any suggestions to better positioning or solutions feel free to enlighten me. 

I need the sketch. Don't understand the description.


The plexiglass is going to be 192cmx72cmI really do appreciate any help 

Two foot by six foot? You could get a lot of light out of that.
*Sounds about right. I imagine I can get tons of light from it, just got to find the right amount.

*_Thank you very much for your help, I really do appreciate the initiative.


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## imagine (Dec 20, 2014)

Forgot to answer and can't find out how to edit post.

But yes, it will be running on line voltage which is 230 volts.


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## DIWdiver (Dec 20, 2014)

You might need 3 posts before you can edit one.

To get an idea of what's right for you, can you estimate how many watts of incandescent or fluorescent lights you would need to get what you want? We can estimate from that the number of lumens you need, which will tell us what LEDs you want. LED strips are often rated in lumens/foot or lumens/meter, while individual high power LEDs are usually rated in lumens. You'll probably be limited by the amount of heat you can get out of the fixture. LEDs generate a lot less heat than other lights, but they also can't stand heat like other lights.

Then you want an LED Lighting Transformer, or perhaps several. In the DIY world we call them drivers, and most of them are designed to run one or several LEDs from a battery. In the lighting industry, they are commonly called transformers, and normally run off line voltage, but they may also be called power supplies or drivers. 

Strip lights normally run on a fixed voltage, usually 12 or 24V. The fixed voltage is applied all the way down the string. Every group of (usually) 3 LEDs is across the 12V. Most of what are called power supplies are used for strip lights. The current drawn from the supply is dependent on the number of groups of LEDs you have in the string (i.e. length of the string).

Most other applications use fixed current sources, and the same current is fed through every LED. In this case the voltage required from the power supply is around 3-3.6V times the number of LEDs in the string. The current is determined by the transformer/driver. Common values are multiples of 350 mA (0.35 amps). The rating of the driver must be less than the rating of every LED in the string.


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## imagine (Dec 21, 2014)

DIWdiver said:


> You might need 3 posts before you can edit one.
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> To get an idea of what's right for you, can you estimate how many watts of incandescent or fluorescent lights you would need to get what you want? We can estimate from that the number of lumens you need, which will tell us what LEDs you want. LED strips are often rated in lumens/foot or lumens/meter, while individual high power LEDs are usually rated in lumens. You'll probably be limited by the amount of heat you can get out of the fixture. LEDs generate a lot less heat than other lights, but they also can't stand heat like other lights.



I'm pretty sure 100W of fluorescent tubes would be enough. Maybe I should over do it a bit, It's going to be dimmable anyways.
Would you know if I need a diffuser layer or if the sheet itself is enough?


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## Ken_McE (Dec 21, 2014)

imagine said:


> I'm pretty sure 100W of fluorescent tubes would be enough.



I'm going to assume 3,000 lumens for a four foot (1.2 meter) 32 watt T-8 linear tube. So for three tubes (96 watts) that is 9,000 lumens. Too get that much light output from the area available I believe you will have to go with high powered LEDs. "High" in this sense meaning that the individual LED draws over one watt. 

The high power LEDs need cooling or they will bake themselves to death. It can be passive cooling, you don't need all muffin fans in there whirring. You need to look at your design and see how to make all the edges of the fixture into radiators. Any sheet of copper or aluminum with air moving past it will do as a radiator.





> But yes, it will be running on line voltage which is 230 volts.




OK, so you have all the power you could possibly need. Did you follow what DIWdiver said about using 240 volt drivers to generate low voltage DC to run the light? The actual diodes want DC, if you feed them AC they flicker annoyingly. You also need to be sure never to overdrive them - they are very current sensitive.




> _*I'm actually an electrican, just not very familiar with LED, *_



You learn a few basic facts about what they want, what they hate, how to power them and then they're easy to work with.



> _*I want a warm light, or the ability to change color like RGB LEDs as theese give the opportunity to give both warm and cold? *_



If you have some strings of cool LEDs and some strings of warm, you could dim them separately to change your color temperature. If you want to be able to do colors you will need colored LEDs in there. Red, Green, Blue and Amber can be mixed to give any primary color, however they probably won't imitate daylight as well as the warm and cool whites. You can have some of each kind in your fixture and just dim them separately.



> _*I wont be able to get the heat out of the box, but the box is pretty big and holds a lot of air. *_



If you absolutely positively cannot dump the waste heat then you need to stick with low powered LEDS. Otherwise one day all that volume of air will over heat and the unit will commit Hari Kari. This will offend your professional pride. Your other appliances will sulk. I myself have a fixture that is a circle about 1/3rd of a meter across. The entire thing is faced with low power LEDs on strips. Working together they produce about as much light as a 75 watt incan.




> _*Could high power led strips be good enough, would they emit enough light? *_



I think so, you'll have to pick candidate components and do the math.




> _*I guess you could describe the light as more of a daylight glow.*_



LED light is normally slightly off from sunlight. You may or may not notice.





> Maybe I should over do it a bit, It's going to be dimmable anyways.



I would suggest you aim for 10,000 lumens. You will lose light as it passes through the various bits of the fixture.


I'd like to suggest some things for you to work out:

How many lumens per centimeter will the unit need to produce? 

How many LEDs will it take to produce that much light?

How many/how big a driver will the LEDs require?

This information will allow you to set the basics of the job, how much material, how much space, rough costs. You could simplify things by dumping the ability to produce various colors, unless that is important to you.

Once you know how much light/centimeter you need, I would like to suggest you consider building a little unit, say 1/3rd of a meter across, just so as to try everything out, see how you like it.


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## imagine (Dec 21, 2014)

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The high power LEDs need cooling or they will bake themselves to death. It can be passive cooling, you don't need all muffin fans in there whirring. You need to look at your design and see how to make all the edges of the fixture into radiators. Any sheet of copper or aluminum with air moving past it will do as a radiator.

Yea, I see your point. At 10.000 lumen I will need 72 lumen pr squarecentimeters and 5050 led strips will only emit 28 lumen pr squarecentimeters. So I guess I need some high power LED's. As it seems like high power LED's are the way to go I would need to make a cooling system for the box. The best I can do is probably a computer fan 60x60 or 120x120 through one of the walls. How much heat would something like this generate and will it be hard to cool it down?



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I will use a transformer and get the voltage down and convert it to DC, I can make som space to fit more of the components away from the LED's




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Yea, I might have exaggerated a bit. I do know the basics, but planning something like this is above my level.


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I think I should just stick with 6000K LED's, this should be the closest to natural light.


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I was thinking about filling the whole surface with 5050 led strips, but it seems I won't reach anywhere near the 10k lumen wish. I did take a closer look at the assembly of the led panels that I wish to imitate and to my suprise the LEDs are actually put along the side of the fixture. LED panel light assembly <--- click here to see the same video. Maybe the same would work for me? But then again, maybe I would need a clear sheet and a diffuser instead. Maybe the 72cm are too far to get the light to spread evenly.




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If my calcualtions are correct, then a 5050 led strips covering the whole surface will only emit about 4k lumen.




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Absolutely, and the strips seem to be nowhere near that.



> I'd like to suggest some things for you to work out:
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> How many lumens per centimeter will the unit need to produce?
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Lumens per squarecentimeter should be 72 lumens. LED strips will only produce 28 per SQCM.

Regular 5050 SMD LEDs are only 19 lumen per and strips will only let me fit 2 of theese pr SQCM, and I cant solder 4x4 5050 SMD leds to cover the whole thing. That will take years.
I have no clue at all how to even find LEDs that are not mounted on strips, so if anyone can provide me with some sort of website or name of LEDs I can look up, that would be awesome.

I have some 3528 LED strips laying around, I'm going to try and put that togheter and see how that looks. Should give me an idea if 5050 would even work.
But atleast I have gotten further down the road and I have some more knowledge. 
Thanks for an extra awesome reply, it was very helpful and educating.


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## SemiMan (Dec 21, 2014)

Its less than 1 lumen/sq. Cm and the proper way to do this is with quality strips made with 5630/3030 or similar mid power LEDs. Look at Philips/Osram etc.

Then match with a good constant current driver .. Likely 100w to get your 10000 lumens.

Yes you will need your front cover to have diffuse properties.

Semiman

Sent from my SM-T320 using Tapatalk 4


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## imagine (Dec 21, 2014)

SemiMan said:


> Its less than 1 lumen/sq. Cm and the proper way to do this is with quality strips made with 5630/3030 or similar mid power LEDs. Look at Philips/Osram etc.
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> Then match with a good constant current driver .. Likely 100w to get your 10000 lumens.
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Mmm, yes. Math+multitasking(no such thing)+nightime is not a good combination.
1 lumen/sq.cm is absolutely correct, and that means that even one 3030 smd led pr. sq.cm is an overkill?
So I will need to calculate how to place it to spread everything equally.

Where do you get led strips of this quality? Can't really seem to find them, only some chinese sellers claiming its both samsung, osram and philips led used. Dosen't really seem legit.


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## DIWdiver (Dec 21, 2014)

To get 10,000 lm you need 80-100 W of good modern LEDs. That's going to generate something like 40-70 watts of heat. In a fixture that size, you should not have trouble dissipating that without fans, provided there's some air flow to an open area. You will have to pay attention to heat dissipation, but it should not be difficult. AFAIK, strip lights are substantially less efficient and therefore would require better heat dissipation to maintain a good temperature, as well as higher power input.

Diffusing requirements depend on your light source. With strip lights you have many small lights over a big area, and you probably only need enough diffusion to hide the strips, very minimal. If you were use high power LEDs like the XM-L2 or XP-L, you'd need only 10 or so. These would be very bright and very small lights, so diffusion is very important. If you want to know why, take the lampshade off a lamp in your house and see how annoying it is. High power LEDs are much, much worse.

It is very possible to build your own power source for the LEDs. However, it's important to understand whether you need a current source or a voltage source, and provide the correct one. No matter which way you go, make sure it is well regulated to ensure consistent lighting and long life.


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## SemiMan (Dec 22, 2014)

From Future, Mouser, Farnell etc. Real distributors


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## SemiMan (Dec 22, 2014)

Given ops knowledge just buy one.

You will not have much issues with heat as long as the back surface is metal and is not completely insulated. Uninsulated ceiling is fine.

Look at the 570mm strips from Philips, Osram, etc. They also make them half that size. These must be driven with a constant current driver.

Unlike DIWs post, these strips will be very efficient, 125 lumens/watt+ but expect to lose 15% at the diffuser so about 105-110 lumens/watt at the LEDs then you will lose another 12-14% at the driver likely.

Don't expect this to be real cheap to build.


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## imagine (Dec 24, 2014)

Real cheap? Seems that only the strips sells for 500-600 USD, are they really that much better? You could buy almost 100 5m strips from china at the same price.

Are there any alternatives except for low quality? 800 dollars seems to be a bit out of budget.


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## SemiMan (Dec 24, 2014)

I am looking at 1580 lumen strips for $15 at Mouser. Not sure where you are coming up with 500-600 USD.


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## imagine (Dec 25, 2014)

The one I found were Osram from a different place.

Would you mind giving me a link or a prodt number to the one you are looking at on mouser?
I've been looking at mouser but can't find any with 1580 lumens to 15 dollars.


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## SemiMan (Dec 25, 2014)

Will do after Christmas


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## imagine (Jan 11, 2015)

SemiMan said:


> Will do after Christmas



Did you forget about me?


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