Need little advice making my own DIY led light....

joonatan11 · Feb 2, 2015

Hi,

So i came here to get some advice and guidance, i hope you guys can help me sort some things out...

So i would like to make a plexiglas lamp hanging from the ceiling . I'll add a picture of the drawing i have.

So the question is how many and what leds to use ? room it self is 18m2 or 193 square feet. I have heard that 500 lux for 1m2 is enough...?

And i think the most important question is cooling of the leds or choosing leds that can be in closed place...Or just running them lower mA..?

And driver should be as small as possible to hide it in the cover part in the ceiling .

So any ideas are most welcome...

Joonatan11

joonatan11 · Feb 4, 2015

It seems to me that i posted this thread to wrong section... So mods if you see this can you move it to more appropriate section.

Norm · Feb 4, 2015

joonatan11 said:
It seems to me that i posted this thread to wrong section... So mods if you see this can you move it to more appropriate section.

It has already been moved to the correct section - Norm

joonatan11 · Feb 4, 2015

Alright, thank you!

So i have looked at the options and seems like high power leds are out of the question because of the heat issue... (correct me if i'm wrong)
I've seen some led stripes that are very bright and might work... So the question is how many lumens per 1m will i need and do they have that powerfu
And for color temp. i'd go with close neutral white 3500K-4500k

DIWdiver · Feb 4, 2015

500 lux is 500 lm/m^2.

I work at a company that assembles circuit boards. There is an industry standard that covers this, and they recommend 1000 lm/m^2, which is 1000 lux. If you light a room like this, it's really bright. Our assemblers prefer about 1/3 this from overhead, with local task lighting to 2/3 this level.

When my office area (room for 7 people) was built in the room next to the PCB assembly area the lighting came out around 500 lux. This was so bright that we ended up turning off the lights most of the time because it caused eye strain while working at the computer (which we do most of the time in this area). One day I took half the bulbs out of the fixtures. Ever since then we keep the lights on and nobody has complained about the light levels.

So I would say in an office environment 250 lux or so is a good target if you have local task lighting. Maybe up to 500 lux if no local lighting. In a home environment, much less than that is probably appropriate for most areas. Kitchens and bathrooms typically want more light, living rooms less, and video rooms much less.

Once you decide how many lumens you want, we can discuss LEDs and drivers.

joonatan11 · Feb 5, 2015

So if you say that 250lux is enough for office i'd say that i need something like 175lux to 200lux... So lets go for 200lux and dimmable

AnAppleSnail · Feb 5, 2015

joonatan11 said:
So if you say that 250lux is enough for office i'd say that i need something like 175lux to 200lux... So lets go for 200lux and dimmable

200 lux is a reasonable figure. But be careful about your light 'control.' If you just say "OK, 200 lux over 12 square meters means 2400 lumens" you'll miss some details. Here is a lux schematic for a 4x5m room lit by a point source to an average of 200 lux:

The center is brightly lit, and the corners are pretty dim. However, this might not be a BAD room light. Still, we can do better. Let's say that we have a light over a bit more of the room - Tiny LED units in two places.

More of the room is brightly lit - None is under 100 lux. LED has a great advantage over filaments - It's possible to shape the light beam in a thin appliance. The "minimalist" approach is to shine an LED at the ceiling, creating a large light source of light reflected from the ceiling. This gets dusty but works nicely. I have some neat ones: 4 Cree XM-Ls on a Pentium computer heatsink, with a 12v computer fan, all running on 12V power. I get about 2000 lumens of clean light from that.

The less-dusty way to build is with an enclosure, as you've drawn. If you're working on keeping weight down, consider an aluminum 'chassis' for your light. A fan-cooled heatsink can be much lighter than a fanless heatsink, but all fans make noise. Your sketch could be implemented in either way. The 'heat with LEDs' problem is solveable. With a good thermal connection to the outside of the device, they are pretty rugged.

So how large an area are you trying to light, and what tools do you have?

joonatan11 · Feb 5, 2015

AnAppleSnail said:
So how large an area are you trying to light, and what tools do you have?

So the room is 18m2 and the light doesn't need to be very bright... Matt plexiglass will make the light smooth enough so i dont need do reflect it from the ceiling .. And using a fan is out of the question, the light should look thin as possible and minimalistic...
And by tool what do you mean..? To cut plexiglass i will use CNC...

joonatan11 · Feb 5, 2015

I found ta picture of similar light, So what kind of leds are used in this case?

Steve K · Feb 5, 2015

neat concept, but the scale must be wrong... or is the ceiling really 7 meters high??

Do people sketch this sort of thing out and get the LEDs right the first time? Or does it take a few iterations to get the details worked out?

joonatan11 · Feb 6, 2015

Steve K said:
neat concept, but the scale must be wrong... or is the ceiling really 7 meters high??

Do people sketch this sort of thing out and get the LEDs right the first time? Or does it take a few iterations to get the details worked out?

Actually this light is 670mm in diameter the bigger circle and 470mm the smaller so yeah the scale is wrong...
And i hope to sketch it and get it right with the first time..

Steve K · Feb 6, 2015

joonatan11 said:
Actually this light is 670mm in diameter the bigger circle and 470mm the smaller so yeah the scale is wrong...
And i hope to sketch it and get it right with the first time..

my personal experience is that not many projects get all of the details right in the first try. It sounds like the plexiglas portion of the light is pretty well fixed in size/dimension/etc. At this point, it appears to be a question of what LEDs to use, how many, etc.

Well, there's also the question of getting the heat out. If a fan is ruled out, then it's a question of how much surface area you can provide. On the plus side, you could use the aluminum as part of the aesthetics. If you are limited to just using the flat upper surface of the light, then things get tougher. It all depends on how much light you want and how long of a lifetime you want.

Once you decide how much light you need, you can try out various ideas in small prototypes. i.e. build a 100mm strip and try out ideas with it. See how hot the heatsink and LEDs get, so how diffused it looks, see how hard it is to build, etc. You'll probably learn a few things, and it's easier to modify a 100mm strip than the whole light.

joonatan11 · Feb 6, 2015

Steve K said:
my personal experience is that not many projects get all of the details right in the first try. It sounds like the plexiglas portion of the light is pretty well fixed in size/dimension/etc. At this point, it appears to be a question of what LEDs to use, how many, etc.

Well, there's also the question of getting the heat out. If a fan is ruled out, then it's a question of how much surface area you can provide. On the plus side, you could use the aluminum as part of the aesthetics. If you are limited to just using the flat upper surface of the light, then things get tougher. It all depends on how much light you want and how long of a lifetime you want.

Once you decide how much light you need, you can try out various ideas in small prototypes. i.e. build a 100mm strip and try out ideas with it. See how hot the heatsink and LEDs get, so how diffused it looks, see how hard it is to build, etc. You'll probably learn a few things, and it's easier to modify a 100mm strip than the whole light.

Yeah i would like to have flat surface on top of the light, so was thinking that maybe i can make the top part from aluminium so it would work as a heatsink.... so the aluminium top part will be flushed with the edge of the bottom part plexiglass, but i have to check how much would it cost to make 3-4mm thick aluminium circle with 790mm diameter...
And i have question about the led stripes sold in rolls... Is it possible to flat bend them in to a circle ..? And how much light can a 1m long led stripe produce.
If you guys have any info. that would be great...

Microa · Feb 6, 2015

I have seen a similar product the top of the light using a reversed circular aluminium U channel and the LED strips mounted at the side of the U channel.

joonatan11 · Feb 9, 2015

Does anyone have some suggestions..?

AnAppleSnail · Feb 10, 2015

I agree that you'll get the best answers possible with a few bucks of aluminum U-channel and some different LEDs. Make a few dozen centimeters of fixture to simulate the real thing.

I would suggest getting a U-channel, lining the 'sides' inside with LED strips - One at 3500K and one at 4500K (Or 3000 and 5000). Hook it up to 12v and see how you like it shining away from you. Next, add a diffuser. Ten hours of this mockup-and-test strategy will answer more questions than any hundred hours researching and planning. "Spending a month in the library to save an hour in the lab" is most applicable to design-build-test with well-known components.

Need little advice making my own DIY led light....

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