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[APD] Re: LED lighting update

Message: 5 Date: Mon, 05 Jan 2004 16:01:46 +0000 From: "Andy Lavery"
<wagoneer78 at hotmail_com>

Well I figured I'd let everyone know how my weekend of electronic
debauchery went!

Some folks get high on the damndest substances! :-) [BTDTBTWW!]

LED lighting is now the only lighting on my 2g tank; Hemianthus Callitrichoides and Hydrocotyle verticillata (pennywort I think) are
pearling like crazy roughly 1 hr after lights on.

Here's the basics - I'm using an old computer AT powersupply to feed
12v (thanks for the idea listers- a few of you mentioned it). I built
3 LED arrays, 2 arrays to a board - the boards are 3/4" wide and
roughly 8" long to sit nicely on the rim of the 2g. Positive power is
fed on the right, negative to the left - LEDs and resistors sit in

The boards themselves were a Radio shack special - the local store
had a clearout on the IC board etching kits. Once etched, cut drilled
and assembled, the boards were sealed with 3m 5 minute epoxy, roughly
1/8" on top and bottom - totally waterproof.

After redneck testing the first board - it was way too blue, so on my
 mission to radio shack, I picked up 4 red LEDs too, and a
potentiometer. I built an X shaped array, with the potentiometer so I
can dial it up for a lot of red, or dim it down for aesthetics.

I ended up using 12 white LEDs to light the tank - largely due to the
small distance from light to substrate (8" or so). The red array
rests on the white. The tank is MUCH brighter with the LEDs than it
was with the 2 13w PC's that I was running over it.

OK, so our new rule of thumb is 16 LEDs per 2G or 8 LEDs/G? :^) [A 55G tank could get mighty expensive!]

The 10g is the next test subject - I'm trying to find some LEDs with a very wide beam for this one to handle the overall lighting; possibly these - http://www.ledsupply.com/l1-0-w5th70-1.html Then use some smaller arrays of more focused light to put light where its really needed.

FWIW - ebay seems to be the best/cheapest place to find LED lights;
they seem to go for half what they're sold for on retail sites. But
at the same time - I haven't found any wider angle white LEDs there.

Nothing says you can't immerse the ends of the plastic lenses in the tank water. That should give a big spread, and increase efficiency a bit in the process.

Alternatively, it should be easy to grind the ends off the lenses so they are flat instead of roughly parabolic. For efficiency, you might need to re-polish the flat surface, but that should be pretty easy to do. See any amateur telescope-making text for simple grinding and polishing techniques. For maximum output, you might want to grind down as close to the actual chip as possible, without hitting it.

Congrats, Andy, on actually doing it and giving us some real world results. [Please ignore my sarcasm as simple envy that I didn't do it. :-)]

One question: How much total power are you using, and what percentage of that is being dissipated in the resistors? The resistive heat and power could probably be saved with a simple switching, current-regulated supply. I have a hunch that one of the real benefits of LEDs is that the efficiency could eventually be higher than incandescent and that those of us with warm summers might like the "cooler" lamps. That will probably never happen with resistors as ballast (voltage-to-current converters), and voltage-regulated power sources.

[Almost as silly as buying 800psi CO2 when what we need is usually less than 1 psi!]


Wright Huntley -- 760 872-3995 -- Rt. 001 Box K36, Bishop CA 93514

    "...there are only a limited number of things that government
 can do more effectively than individuals or other organizations
 can do."
     -- T. Sowell

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