LED Fish Tank Light White+RGB

[nein166]

So for almost a year now I've been collecting parts to make an LED fish tank light fixture. I saw the Solaris in a Fish Store and loved the effect of the colors dancing through the rippling surface onto everything below. But the price was way to high. I don't have saltwater tanks just fresh so the 10-13,000K Solaris wasn't even applicable. Now theres cheaper Galileo fixtures that are more suited to freshwater but still pricey.

So I gathered up some Kennan Drivers from Kaidomain... two and a half months waiting.
Scrounged up some discarded heatsinks from computers thrown out at work.
Scored Q5 XR-E emitters and Red, Green and Blue Cree 7090 Stars from DX.
Put together a frame from an old aluminum CFL Fish Tank light, and epoxied my heatsinks to it.
Got a IBM thinkpad power supply thats 16v at 3amps more than enough for 3 drivers

Modified a 1amp Kennan board to ~700ma so as not to fry the 7090 Crees
Soldering on a .5ohm resistor in parrallel with the .2ohm SMD was a major pain.
And I still need to do another SMD piggyback solder job as I plan to have a set of RGBs on each side of 3 Cree Q5s in the center.

Still a work in progress and the triple optic may need a diffuser film but heres a shot of it all powered up.
There is a fan that isn't connected.
Running for an hour like this the heatsink got to 100F but thats with IR Thermometer on shiny Aluminum.
My eyes hurt from looking into that while getting temp. readings, with sunglasses on.
The fish should be protected some by the water's diffraction (or is it diffusion)
I'll know its too much if they all hide, the Riccia and Duck weed will help shade them in one half of the tank which is a 15gallon High(10"W x 20"L x 18"H)

I had to get close with the flash on to get a shot.
The RGB blends well but throws a multilayered shadow edge.
Any recommendations of diffusing films or ideas???

 

[brokemypalm]

could you try using some shims to tilt the RGB lights inward so they overlap better?

maybe i forgot physics class, but doesn't RGB combine to make white? Why don't you just use a white LED instead?

are you looking for a diffuser like this? you could probably rip the diffusing lens off and mount it on your lights.

 

[Illum]

maybe i forgot physics class, but doesn't RGB combine to make white? Why don't you just use a white LED instead?

Keep in mind that the principle behind LEDs allows it to emit only one frequency of light, whereas white light say an incandescent filament burning at 3300K outputs all frequencies of light all rolled up into what we consider as "white."

A white LED does not emit the array of frequencies real white emit. White LEDs actually produce blue light that gets converted to white light through the phosphor coating. An RGB LED assembly, if tweaked correctly will yield "white" light that doubles or even triples the color rendition of standard white LEDs. EDITED UNTIL INFO CITED

 

[brokemypalm]

Keep in mind that the principle behind LEDs allows it to emit only one frequency of light, whereas white light say an incandescent filament burning at 3300K outputs all frequencies of light all rolled up into what we consider as "white."

A white LED does not emit the array of frequencies real white emit. White LEDs actually produce UV rays that gets converted to white light through the phosphor coating. An RGB LED assembly, if tweaked correctly will yield "white" light that doubles or even triples the color rendition of standard white LEDs.

(Re)Learn something new everyday. Thanks for the lesson! The "tweaking correctly that you're talking about sounds like it would take more effort, or need more lights than this setup, right? you're referring more to one of those LED wall washes that they have in theatres, correct? the ones that can cost $1000 per panel?

what would be a good way to do it on the cheap? it seems like this way doesn't work as well as it could....

 

[2xTrinity]

[qutoe] could you try using some shims to tilt the RGB lights inward so they overlap better?

maybe i forgot physics class, but doesn't RGB combine to make white? Why don't you just use a white LED instead? [/quote]
The combination of red green and blue appears white to humans because we only have three color detectors in our eyes. so that means even if your RGB light looks the same as a "blackbody" (eg like the sun emits energy at all wavelengths) white light source, it may not be emitter energy at the correct wavelengths to produce photosynthesis in the fish tank.

A white LED does not emit the array of frequencies real white emit. White LEDs actually produce UV rays that gets converted to white light through the phosphor coating.

Most white LEDs these days are blue LEDs not UV, with a phosphor layer producing longer wavelengths. Some are better than others in terms of CRI, color temperature etc.

An RGB LED assembly, if tweaked correctly will yield "white" light that doubles or even triples the color rendition of standard white LEDs.

Not true. A good phosphor white light will almost always have higher color rendition than an RGB. Adding a fourth color (amber) to RGB is usually needed to produce good CRI.

Under RGB light for example, most of the wood in my house looks bright orange. This is because it reflects a lot of red, and a little bit of green. A broad spectrum light source, such as a warm white LED on the other hand will have red, yellow, and green wavelengths, so when reflected off of wood the color will appear more accurately.

However, Color rendition (related to human color vision) does not indicate how effective a light is for illuminating a fish tank -- where light energy needs to be produecs at particular wavelengths for photosynthesis.

 

[Illum]

ouch....
yeah, thats relearning on my part

 

[kuprith]

I was thinking that White LEDs are not really that suited for plants because plants need more RED light for photosynthesis. Warm White LEDs would be much suited.

 

[Illum]

if your dealing with photosynthesis and not just for accent lighting, I'd recommend giving this thread a read
LED grow lights