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Old 12-30-2013, 07:13 AM   #106
yashmack
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what power supply are you using for the LEDs?
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Old 12-30-2013, 03:18 PM   #107
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Quote:
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what power supply are you using for the LEDs?
I'm not using a power supply. I'm using a 30 watt LED driver for the 30 watt LED and a driver for 1 to 3 one watt LEDs for the 2 one watt LEDs. They are fed with standard 120 VAC power, and produce a constant current at the appropriate voltage for the LEDs. In both cases they drive the LEDs at a bit less than full rated current. I am thinking about installing a 1 ohm resistor in the wire to the LEDs to measure the current, but, since I can't easily change that current I may not bother.
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Old 01-10-2014, 10:16 PM   #108
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I bought a couple of LED drivers on Ebay for the 3 watt warm white LEDs I now have. Both have no markings to identify which wires on them are output, + and -, and which are input AC voltage. Is there an easy way to tell which is which?
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Old 01-10-2014, 10:47 PM   #109
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My guess is the white pair because they are closer to the transformer.
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Old 01-10-2014, 11:13 PM   #110
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the two whites will be ac....

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Old 01-10-2014, 11:27 PM   #111
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I think the two whites are AC, and I suspect the pink one is DC+. Does that seem reasonable? The other one has a yellow wire instead of a pink one.
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Old 01-11-2014, 12:53 AM   #112
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Yes, the two white ones will be AC as polarity does not really matter. You can check DC polarity via a multimeter or a DC fan. See the way it is spinning to determine polarity.
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Old 01-11-2014, 01:35 AM   #113
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This is the light, with 2 x 3 watt warm white LEDs, plus the 30 watt LED, at 36 inches above the PAR meter. Only 15 PAR! I'm disappointed I think. My plan was to get 20-25 PAR at that distance. More testing to follow.



25 PAR at 29 inches. This isn't any better than it was with the 2 x 1 watt red LEDs. I think this would work fine with a 40B tank, but it isn't likely to work at all well with my 65 gallon tank. The distances are from the LEDs not from the end of the can. That means the bottom of the can is only about 23 inches from the sensor in this photo. That would be about 1 inch above my 65 gallon tank if I used it there - 2 inches of substrate.

Last edited by Hoppy; 01-11-2014 at 01:59 AM.. Reason: Add another pic
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Old 01-11-2014, 02:47 AM   #114
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What about shortening the can and attaching some kind of optic.
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Old 01-11-2014, 03:26 AM   #115
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What about shortening the can and attaching some kind of optic.
Of course there are many ways to use LEDs. This project is about using them with a cylindrical "can" as the optical element that concentrates and evens out the PAR. The evening out part worked perfectly. For both of those tests shown above the PAR was very nearly the same over the entire diameter of the main circle of light. None of the optics we can easily buy for LEDs have that feature.

I think the next step is to try to greatly improve the polishing of the inside of the cylinder, to see if that gives me the needed gain in PAR. I haven't figured out a good, non power tool way to achieve that polish, but I'm sure there is a way.
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Old 01-11-2014, 12:57 PM   #116
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I'll be interested in seeing how you manage to polish inside that little can without resorting to a power tool.

I did see a Foam Buffing Ball attachment at AutoZone, if you should need take advantage of modern tool technology.
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Old 01-11-2014, 03:35 PM   #117
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I'll be interested in seeing how you manage to polish inside that little can without resorting to a power tool.

I did see a Foam Buffing Ball attachment at AutoZone, if you should need take advantage of modern tool technology.
While trying to go to sleep last night it occurred to me that I can just line the can with aluminum foil and find out if it is even worth the work polishing the inside of the can. That will be my next test. I am cautiously optimistic

EDIT: I just tested it with aluminum foil lining the "can", shiny side towards the light, and the foil is a little crinkled. I got 14-15 PAR at 36 1/2 inches. That is the same as without the foil, so I doubt that there is much to gain by polishing the inside of the can any more. Most of the reflectivity of aluminum is due to molecular issues, not extreme polishing - aluminum is inherently a very good reflector.

The somewhat crinkled surface did result in a less well defined circle of light. The effect isn't a big effect, but it is still there. And, the almost uniform brightness over the circle of light is still there.

DogFish, I was thinking of using a flapper wheel to start the polishing, by getting rid of the ridges and grooves. Then using finer and finer sand paper to finish it. I don't consider a hand drill to be a "power tool".
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Old 01-12-2014, 03:46 AM   #118
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I have one more idea for increasing the PAR from this. One thing the "cans" do is concentrate the light into a relative small circle. The longer the "can" the smaller the circle. So, tomorrow I plan to add a 3 inch long extension to the "can", made from aluminum foil, and measure the PAR with and without it. That should tell me what length of "can" is needed to get the PAR I want. If it is a reasonable length I can make new "cans" from cheaper material than the thick wall aluminum pipe - PVC, thin wall aluminum pipe, even cardboard, using aluminum foil for the reflective surface for the non-aluminum materials.
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Old 01-12-2014, 07:05 PM   #119
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I made an extension for the can from a big envelope - heavy paper - plus aluminum foil, and extended the can to 12.5 inches long, then 10.5 inches long.



Plotting the PAR vs the length of the can, with the LEDs always 36 inches from the PAR sensor gave me this:


Making the can longer definitely is a way to get higher PAR, over a smaller circle. It looks like I need to make the can about 10 inches long to get 20-25 PAR at 36 inches.
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Old 01-12-2014, 07:31 PM   #120
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Quote:
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Making the can longer definitely is a way to get higher PAR, over a smaller circle. It looks like I need to make the can about 10 inches long to get 20-25 PAR at 36 inches.
So.. You will end up with the pendent ending ~4 inches above the surface? That's unfortunate!

EDIT: Maybe if you lost the 3w LEDs you could use a second narrower can inside the primary one?
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