LED Lighting HELP NEEDED - The Planted Tank Forum
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post #1 of 17 (permalink) Old 12-30-2008, 01:18 PM Thread Starter
 
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LED Lighting HELP NEEDED

Hello there,

I've recently started a 10 gallon as such I want to change the lighting. I'm using an eclipse hood my options seem to be limited in what I can do, so I think leds are my best bet. The only problem is I don't have a clue how to go about it, where to get the leds and(or) resistors, power supply ect...

If anyone has knowledge they would like to share or links to articles on the subject I would greatly appreciate the help

_Green_
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post #2 of 17 (permalink) Old 12-30-2008, 05:57 PM
 
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You can get leds at any online part house or possibly frys electronics. I use digikey when i need parts, only problem is sometimes you cannot order 1 or two pieces but 10+. Also they charge a $5 i think for orders under $20.

In order to build the system you will need to find a led you need, check out the part sheet, find the V drop, find the max rated current and make sure not to exceed it, you are most likely going to want to run them in series so you can nail down a current on the line. Parallel will work as well but then you will have to make sure the power supply supplies the correct current. You can search for power bricks or build the supply yourself, it only takes a little know how to make a decent one.
Parts needed:
Step down transformer
Diodes to rectify the signal
large filter capacitors
few resistors to drop any excess voltage, make sure you check the power dissipation and DO NOT exceeded it or you will smell burnt resistor right quick.
voltage and current regulators to load and line regulate
wires to wire it up
blank circuit board to make it look nice.
a box to mount the stuff in.

multi-meter for measuring current(always in series) and voltage(across the part).

Couple of equations to solve:
V=IR
P=IV

Always orient the cap correctly or you'll blow it up (did that once )

Also for any reason if you are not 100% comfortable i would recommend you buy a power brick that supplies the specs you are looking for if you can. Since your tank is small you may luck out and find one.

For help i would goggle power supply design to get a better idea.

Download pspice student edition, its free and it will allow you to design the supply on the computer, test the specs and then build it. That way your not hunting in the dark. There are plenty of tutorials on how to use pspice and for simple dc caluclations its one button to see the results.

Im feeling nice today so if you want, pm me the details of what you want, i.e. what part so i can check specs, and ill see if i can build a quick one on spice and send you the pictures with the measurements.
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post #3 of 17 (permalink) Old 12-30-2008, 06:10 PM
 
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Led's are slightly different than your standard diode, but not by much. The voltage drop is closer to 2, and sometimes as high as 3-4V if it's a high brightness. If you Use .7V as a drop, you will underpower them.

Use this formula if you want the best results

Resistor impedance=(V(power supply)-V(diode))/Idiode

typically I will be between .02 and .04 amps


Instead of buying the parts to construct a massive power supply, I would recommend saving the time and buy a 12V or selectable voltage power AC/DC power supply...I know digikey as suggested above has many cheap ones to choose from

I just build a large system(well not for an aquarium), but the radio shack LED's I used were 28,000mcd's and they req'd [email protected] A 1 amp box ac/dc power supply could drive up to almost 50 led's like that.

Just one last word of advise, is that LED's don't have a very wide viewing angle, if you don't use many be prepared for shadows and dark areas.
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post #4 of 17 (permalink) Old 12-30-2008, 06:14 PM
 
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im confused aren't LED's (light emitting diodes)? Or are you saying that LEDs for fish tank lighting is different?

EDIT:: After doing some digging it looks like the LED for fish tank lighting is 3/4watt per light, i could not find a V or I spec to see what sort of drop we are talking but ill keep looking.
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post #5 of 17 (permalink) Old 12-30-2008, 06:18 PM
 
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You are right with the .7, but if you are calculating proper current go with the voltage recommended by the mfr of the diode. .7 is just enough to get the electrons flowing, not enough to light things up.

Thats assuming that we are referring to the T-1 3/4 plastic LED type.
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post #6 of 17 (permalink) Old 12-30-2008, 06:19 PM
 
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O i see, yes you are correct, .7 is the thresh hold, you have to go above that to get it working, thanks for catching my mistake.
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post #7 of 17 (permalink) Old 12-30-2008, 06:22 PM
 
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The diode you linked is 110V, you could just screw it into a regular lamp base. No fancy electronics required there..
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post #8 of 17 (permalink) Old 12-31-2008, 01:40 PM
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Check out the DIY and Lighting forums over at nano-reef.com there are lots of people building LED lighting systems there. There are several threads that give specific instructions on building, links to parts, etc.
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post #9 of 17 (permalink) Old 01-01-2009, 04:23 AM
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Quote:
Originally Posted by _Green_ View Post
Hello there,

I've recently started a 10 gallon as such I want to change the lighting. I'm using an eclipse hood my options seem to be limited in what I can do, so I think leds are my best bet. The only problem is I don't have a clue how to go about it, where to get the leds and(or) resistors, power supply ect...

If anyone has knowledge they would like to share or links to articles on the subject I would greatly appreciate the help

_Green_
i have a 5 watt terra-lux(120 lumen) led for a moon light on my 29 gal.

as far as i can tell, you would need like 10 - 15 of those things to get enough light into the tank to grow plants. not to mention - heat sinks, wiring, power supply, something to mount them on, (not to mention a ton of soldering) ect.

unless you really want a challenge, i would just go buy a light "pre-made".

edit - it would be much easier to retro a PC unit in there.
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post #10 of 17 (permalink) Old 01-01-2009, 04:54 AM Thread Starter
 
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something to put it in isn't a problem, I operate a water jet machine for a living. I can cut 100 holes in 10 minutes or so with it so that's the easy part for me lol. Actually I was going to cut the holes in a piece of mirror. I know, I know, leds point in one derection, but I figure some of that light has to be reflected up.

When I started this thread I didn't think it was going to be quite so complicated, I was wrong. I will probably still give this a try at some point, but I've got a lot to learn before that happens.

Happy New Year
Ross
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post #11 of 17 (permalink) Old 01-02-2009, 01:01 AM
 
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Green, it really doesn't need to be very complicated at all. If I were to build a LED lighting system for your 10 gal planted tank I would:

1. Buy 6 of these LEDs (Cree XR-E Q2 bin) http://www.dealextreme.com/details.dx/sku.2395
and run them between 700mA-1000mA. You should get 165 lumens out of each of these @ 700mA for a total of 990 lumens or 210 lumens from each @1000mA (total of 1260 lumens)
($3.53ea x 6=$21.18)


2.Go to ebay and buy a 12v power supply capable of at least 3 amps to give you room to add more LEDs in the future if required
(about $15-$20.)

3.Plan on hooking up 2 parallel circuits of 3 series wired LEDs in each circuit.
According to the datasheet ( http://www.cree.com/products/pdf/XLamp7090XR-E.pdf ) @ 700mA the LEDs forward voltage should be about 3.5v and @1000mA about 3.7v

Use this LED resistor calculator ( http://led.linear1.org/led.wiz .) I would get a few different valued resistors because the LED's actual forward voltage will be different then the datasheet says and will probably be higher. Get 1 ohm, 1.5 ohm, 1.8ohm, and maybe 2.2 ohm resistors and use a multimeter to determine which gives you the correct current (aim for between 700-1000 mA.)

4. Go to ebay and get 5 or 10 watt resistors of the aforementioned values (very cheap)

5. Now all you need is an aluminum heatsink to mount the LEDs and resistors to.

http://www.heatsinkusa.com/ -Good inexpensive heatsinks

or

Ebay has a lot of Aluminum plate stock that can be used.

7. Get a small 12v fan to circulate air across the back of the heatsink.

6. Hook it all up-You should now have a top of the line LED aquarium light capable of good plant growth for $80-$90 with no bulbs to ever change

Additional Notes-
*You may want to also buy some red, green, or blue LEDs to later add in to adjust the color renditioning of the LED fixture to your liking.

*You can always add more LEDs to the fixture in the future if your plants require more light

*Check out this thread where I roughly estimated that about 6,720 Lumens of white LED light w/40 degree optics = 250 watts of Metal Halide lighting.

http://www.aquaticplantcentral.com/f...t=57642&page=4

If this is correct then the amount of light produced by 6 LEDs on your 10gal tank should equivalent to around 2.5-3 watts/gal

*If you don't mind spending more, you can get higher binned Cree's from the same website that puts out more lumens/watt although for the extra money they cost you will be getting about 20 extra lumens per LED so you can decide for your self if it's worth it.
http://www.dealextreme.com/details.dx/sku.2394
http://www.dealextreme.com/details.dx/sku.15943

*You can use a constant current power supply like this one http://www.ledsupply.com/lt-901018700p.php to simplify things and cut out the 12v powersupply and resistor step. The disadvantage is that it may be more expensive and leave you less options for adding LEDs in the future unless you spend more and get one able of driving more LEDs.
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post #12 of 17 (permalink) Old 01-02-2009, 02:45 AM
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post #13 of 17 (permalink) Old 01-02-2009, 05:43 AM Thread Starter
 
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thanks for the advice and links, maybe it's not at complicated as I was starting to think.
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post #14 of 17 (permalink) Old 01-03-2009, 01:13 PM
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Yeah, it's really not that bad. It'll take a little while to build everything nice and neat but it's a fun project.

I built a LED unit last year with almost exactly what McJosh13 suggested except I used 5 white and one red LEDs. I had it over a 6 gallon custom tank, same height and depth as a 10g but shorter. I was growing HC and dwarf hairgrass in it fine- it took a little while for the plants to adjust to the light but they eventually took off.

Give it a shot, what the heck- it's winter!
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post #15 of 17 (permalink) Old 01-06-2009, 02:45 PM
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Originally Posted by youareafever View Post
Hey, thats me!

If you decide to go with high power LEDs, please, don't use resistors to limit current. They work fine for smaller LEDs, but once you start getting into the high power (and high price) LEDs, they start to become unreliable. There are drivers available that are designed to regulate the current for these LEDs, and they work very well. Keep in mind that a high power LED setup will push most small tanks into the high light range. A 10 LED array that I built (and I am selling replicas of) for a pico reef is capable of PAR numbers close to a 70W MH.

To keep light levels in a reasonable range, using 10mm or superflux LEDs would be a good alternative. Nice wide angle, and still pretty bright. Most cool white LEDs in that size are going to be in the 8000K range, and have tints of green or purple. Try and find something around 6000K. It will still be bluer than a 6500K PC bulb, but won't have the purple tint to it.
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