N00B Going to build a SAD lamp and need advice

[yanomeacuerdo]

Hi guys, I'm totally new here, I have no idea about flashlights but I'm an architect and designer so I know a but about lighting.

After struggling with SAD this winter I decided to make my own SAD lamp...

I searched here but all I could find where old threads so they don't talk about new technologies

I've made my research and I think I have the idea

for the lamp I want to build a +12,000 Lm (aiming at 10,000 lux at 1ft)
I want a small footprint and thinking of using

1 300-SMD 5630 LED 6000k strip http://www.dx.com/p/85w-12000lm-300-smd-5630-led-white-car-decoration-light-strip-12v-5m-308576
2 a opaque diffuser (what do you recommend here I know I need to make up in lm what I will loose with it)

I saw an interesting video on how to make an array of these leds but not sure how efficient is it.

I know about ohm's law but never applied it to lights

any help, pointers or advice welcomed

thanks!

 

[yanomeacuerdo]

I think I will need some kind of heat sink for it, will it be enough to glue the strips into an aluminum panel? I want to be able to plug it directly to the 110 outlet

 

[nein166]

I can tell you that 6000K DX LEDs tend to look more like 10,000K more Purple-Blue than the slight blue of Daylight white
I bought a strip to make a light box and was dissappointed to find it was far beyond neutral white
I'd mix 2 bright whites with a warm strip unless SAD lights don't need warm light

I have taken apart old LCD computer monitors and found great diffuser panels inside maybe you have one lying around

 

[yanomeacuerdo]

I can tell you that 6000K DX LEDs tend to look more like 10,000K more Purple-Blue than the slight blue of Daylight white
I bought a strip to make a light box and was dissappointed to find it was far beyond neutral white
I'd mix 2 bright whites with a warm strip unless SAD lights don't need warm light

I have taken apart old LCD computer monitors and found great diffuser panels inside maybe you have one lying around

... I gave one bad screen 1 week ago!!

what are the pros/cons of using a parallel configuration rather than a series one?

 

[DIWdiver]

Running LED strips in series is different from running LEDs in series. With the strips theoretically it shouldn't matter whether you run the whole strip as one or cut it in pieces and run the pieces in parallel. This is because in the strips, the power and ground lines go all the way down the strip, so ideally you should have 12V at every point on the strip.

In practice, however, the power and ground lines are not zero resistance. That means that there will be voltage drop along the lines due to the current through them, and the LEDs at the far end of the strip get less voltage than the ones close to the supply. I'd bet that if you just powered the entire 5m strip right off the reel, there would be a significant brightness difference between the two ends.

But say you cut the strip in half, and power both halves from the same power supply. Now you have half as much current in each strip, so the voltage loss per meter is reduced, and you have less length, so the brightness difference should be considerably less. I don't know how short you have to cut the strips to make the brightness difference unnoticeable. I'm sure it varies from one brand to another.

As far as the heatsink, it depends on how big the panel is. You have 85W going in, and probably 25-35% of that coming out as light, the rest is heat. That's not a huge amount of heat, but if you pack the strips tightly on the smallest panel possible, that might not be adequate without a fan or other means of improving the cooling.

 

[yanomeacuerdo]

I need your help with some funky info...

I'm building a prototype with some semi-locally sourced leds but they are giving me some conclicting info.

these are the leds http://articulo.mercadolibre.com.mx...-5630-60lm-5m-ip33-blanco-100w-la-potente-_JM

specs
100 W

12VDC

luminous flux 13000 lm

angle 120 º

Temp 6000 K

No of leds SMD5630 - 300pcs

Adhesive 3M

Protection IP 33

these are supposed to be 40lm per led and say they have a 100w output but then they tell me that the real wattage consumption is more less 36w so I just need a 12v 5amp power source, these can't be right, right??

and they tell me that as these have more phosphor they are brighter with less wattage

 

[gofastman]

I'll be following this thread with great interest!

 

[DIWdiver]

100W vs 36W? That's a big enough difference that I wouldn't trust much of anything they say. They also claim IP33, which means they are protected from downward spraying water, but not splashing water.

If you must buy this strip, be prepared to be disappointed.

Where did you see that 12V, 5A supply (60W) would be enough? Or that it's really 36W?

 

[nein166]

Looking into a Luxeon 5630 LED they are 1/2 watt emitters, pretty sure the strip has resistors in line to voltage drop the 12v supply not sure what the LED current will be but 100W seems like it is the actual power input for the strip
I don't think a 12v 5A supply could be enough, but it will probably still light up dimmer just doesn't have the power to go 100%

 

[yanomeacuerdo]

well a little update, I ordered 2 of those strips "supposedly 12,000 lm" each got a 5amp power source but I'm a bit skeptic about it, I have a 8 amp one here just to see if there is a difference on brightness.

I will be mounting them on a 1/8 sheet of aluminum so the heat dissipates (would that be enough?)

I'll receive them in 2 more days so I'll build it over the weekend then try to figure out what to use as a screen, I want to get as much uniformity of light while keeping the most lux possible out of it, I wouldn't like to have 300 bare leds pointed at me at 50cm any ideas on what material?

I have a usb led strip http://www.fasttech.com/products/15...-usb-powered-8-5152-180lm-5800k-neutral-white so I tried in a Makrolon (Polycarbonate) screen and it diffuses it perfectly but I do loose about half the brightness so that's not the best option as I'd have to double the amount of leds I need

 

[Anders Hoveland]

If you are planning to build a seasonal affective disorder lamp with a multi-emitter array (where the LEDs are not all the same color), I would suggest adding longer wavelength blue emitters (>470nm). Because otherwise if you have too much shorter wavelength blue light it can lead to "LED eye" or just some glare and a little eye strain. This is just my opinion, based on personal observations and experimentation with different wavelength LEDs. High CRI white LEDs tend to have a better ratio of this longer wavelength blue in their spectrum than standard white LEDs.

 

[AnAppleSnail]

Doctor! Not "LED eye?" Oh no!

The study you're referring to blasted tissues with stupidly intense light - More intense than sunlight - And, unsurprisingly, found damage. I can do the same to a picnic table with a magnifying glass.



Yanomeacuerdo, it sounds like you're on the right track. If you want less direct light, you may point them 'up' into a white ceiling to diffuse the light. I use 1/8" aluminum sheet on my LED strip lights.

 

[DIWdiver]

I'll receive them in 2 more days so I'll build it over the weekend then try to figure out what to use as a screen, I want to get as much uniformity of light while keeping the most lux possible out of it, I wouldn't like to have 300 bare leds pointed at me at 50cm any ideas on what material?

Search CPF for 'diffuser'. There are numerous threads discussing various ideas.

 

[SemiMan]

SAD is all about getting sun into the eyes. It is photoreceptors in the eye that regulate circadian rhythm. A bright diffuse surface to look at works, but no need to light up everything.

Semiman