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Old 02-25-2004, 04:54 PM   #21
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Yaksplat,

Just wanted to comment on your mention of LED Brightness:

Quote:
The few moonlights that i have in my tank are rated at 2600 mcd. FWIW those are extremely bright. I can't imagine an array of 100, 12000 mcd, LEDs. The photon pressure alone should be enough to pin a fish against the substrate.
The problem here is that we have to remember that LED's produce reasonable intensity in a very focused beam - i.e. the Radiant Flux (measured in Steradians - three dimensional dispersion angles). How this relates to the Luminous Flux is of significant importance. For a single LED that has a power output of 2600 mcd (micro candela) it must be stated what the degrees of radiation is as well (the radiant flux). If you make that angle of dispersion wider (it is probably only about 15 degrees for these LEDs) to be closer to a standard bulb the mcd will drop drastically to just a paltry few. So inorder to cover a large area with similar lumonisty as a MH you will need, at the very least an LED at every exposed area above the subject you wand to illuminate. 100 LED's in a 10 x 10 array will only cover about a 3" square inches assuming a bit more than 1/4 square inch per LED. As an experiment, light up 10 LED's in a dark room and then light a 15 watt bulb and see which gives more light.

Also consider that 2600mcd is 2600 micro candela or .0026 candla at that narrow radiation yet "a typical 100 watt incandescent bulb puts out around 1700 lumen - if that light is radiated equally in all directions, it will have a brightness of around 135,000 mcd. Focused into a 20¬į beam, it will have a brightness of around 18,000,000 mcd." quote from Gizmo's. I'm afraid even 1000 LEDs aren't going to be pinning any fish down this century.

A basic premise here: You don't get anything for free, so considering that LED's consume about 20 milliamps or .1 watt at 5volts, 1000 of them would only consume 100 watts - your not going to get landing strip brightness from 100 watts of input energy.

Excellent point on missing the UV part of the spectrum - we certainly need those, However, there are UV emitting LED's as well. In fact it seems that LED's are manufactured in a wide variety of spectrum outputs. I would like to try a VLA of LED's of a white spectrum and see what it looks like and if we could difract the focused beams to make it seem a bit more natural.

BTW - LED's seem so bright to us because we look directly at their Photon beam - it's more like looking at a poorly focused laser beam then widely dispersed light of a room light or Flour. Tube.

Anyway - just some thoughts to consider.

Tom
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Old 02-25-2004, 08:43 PM   #22
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Now I was thinking that the 'm' was .001 and not micro. That changes a lot. If electricity was down around $.03/kWH I wouldn't even ponder this issue. I decided that i'm going to enclose a plant inside a box and just water it and light it with LED's. We'll see what happens


Jim
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Old 02-26-2004, 12:21 AM   #23
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Very Cool - I'm waiting with extreme curiosity on this one. If you are using the Blue LED's from lsdiode I think they're bandwidth is going to be too narrow - perhaps you should consider their Red/Green/Blue LEDs which together would give full spectrum.

This sounds like a pretty neat experiment. Good Luck Yak - let us know the scoop.
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Old 02-26-2004, 03:48 AM   #24
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lights

kell just scratches his head and looks confused, to much white man magic for him.
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