Luxeon Rebel 145 lumens output

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Your calculations are correct as far as resistors are concerned. They will have to be fairly big resistors, .5 W will do but barely, you'd be better off with 1 W.

I hope your aquarium is huge because this is going to be bright, about equivalent to a 150 W incandescent bulb.

I don't understand why you insist on using Rebels. They will be extremely hard to work with because of their size and SMD caracteristics. Cree would be easier to use or Lux lll if you don't mind a little less light. Your design will have to take into account the heat generated by your 16 LEDs.

It will certainly keep your fishes warm.
 
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Calina said:
Your calculations are correct as far as resistors are concerned. They will have to be fairly big resistors, .5 W will do but barely, you'd be better off with 1 W.

I hope your aquarium is huge because this is going to be bright, about equivalent to a 150 W incandescent bulb.

I don't understand why you insist on using Rebels. They will be extremely hard to work with because of their size and SMD caracteristics. Cree would be easier to use or Lux lll if you don't mind a little less light. Your design will have to take into account the heat generated by your 16 LEDs.

It will certainly keep your fishes warm.
Click to expand...
I hope your aquarium is huge because this is going to be bright, about equivalent to a 150 W incandescent bulb.
Click to expand...

A huge reef aquarium will require a lot than 500 watts. 150W is a for a small desk reef.
 
Outdoors Fanatic said:
I didn't say that that quantity of lumens would kill them (that don't even comes close of the output of a proper reef tank illumination ). The problem is,
LEDs lack the proper light spectrum necessary to support the marine life, that's why HQI's are used in this type of aquarium. Your are not rasing a pet iguana, marine tanks are a whole lot more serious.
Click to expand...

First, in marine aquariums, fish and some corals will do fine in color temperatures of 65000k-10000k+ and certainly the color temperature of these LEDs range from 6500k-10000k. That means it is good enough for a salt water tank. These LEDs may not produce up to 20000k, but a healthy marine life does not need 20000k color temperature.

The light spectrum from these LEDs are capable of producing 6500k-10000k but that does not mean that they lack the proper light spectrum necessary to support the marine life in a salt water tank. Marine fish and corals will do fine with these color temperature. They only need around 10000k which is about right for fish and maybe some corals that doesn't require too much of a different color temperature than 10000k.
 
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Outdoors Fanatic said:
A huge reef aquarium will require a lot than 500 watts. 150W is a for a small desk reef.
Click to expand...

Exactly, 150W is for a small desk reef and a small reef is exactly what I have. I have a 3 gallon salt water tank, currently with nothing but sand sitting on the bottom. This 16 LEDs should be good enough illumination for a small salt water reef tank.
 
Some thoughts:

- 15V adapters (from Radio Shack) generally are not 15V unless they are regulated and even then it is questionable.

- The LEDS could be from 3 - 3.8V, meaning they could be dim or burnt out quickly.

You must go with a regulated solution to make this work.

Semiman
 
You can use a LM317 voltage regulator and a 1.8 ohm 2 watt resistor set up as a current regulator instead of a voltage regulator.

If you do this, I would use a single lm317 current regulator in each string to keep the device power dissapation down.

That would require at least a supply voltage that is about 1.25 volts more than your required voltage. The input voltage could then be anywhere between 1.25 volts more than you need up to about 35 volts and the output would remain constant at 700ma.
Keep the input voltage as low as practical to keep the LM317 power dissapation down.
 
Just a tip: use a laptop adapter they can be anywhere from 15 to 19V and are current limited at anything between 1.7 and 7.5 A. In your case 4 rows of 4 leds in series paraleled ( 4S4P ) the best choice would be a TOSHIBA 15V/2.7A adapter ( this is a standard value, i am holding one in my hand) so you would end up driving leds at 675mA .
You can find them on e-bay or used at a laptop service for anywhere north of 20 $.
Hope this helps.
 
SemiMan said:
Some thoughts:

- 15V adapters (from Radio Shack) generally are not 15V unless they are regulated and even then it is questionable.

- The LEDS could be from 3 - 3.8V, meaning they could be dim or burnt out quickly.

You must go with a regulated solution to make this work.

Semiman
Click to expand...
+1.

Even if it's a switchmode supply there'll be some variation in the supply voltage when you hit it with 4 x 700mA. You really don't have much margin for error when you're dealing with only dropping 0.6V. I wouldn't cut it that fine myself.

A better (cheap) solution would be to have 5 strings of 3 LEDs each, which will mean using a 5.6 or 6.8 ohm 3 watt resistor with each string (depending on what your actual supply voltage is under load). In this part of the world I'd use 5 watt resistors because that's what's available. (They ship internationally.) Yes, it means more energy wasted as heat but it's much safer for the LEDs.

For something a little more upmarket, read http://en.wikipedia.org/wiki/Current_source

I'm working on a constant current supply for a headlamp at the moment, based on this. It's more useful in my situation because I'm going to be using it with batteries, not a mains-driven power supply, so my supply voltage is going to be changing constantly, not be constant.

Incidently, that's a project where I had the circuit first, and now I'm looking around for suitable off the shelf components I can use in it.
 
AZ Sky said:
You can use a LM317 voltage regulator and a 1.8 ohm 2 watt resistor set up as a current regulator instead of a voltage regulator.

If you do this, I would use a single lm317 current regulator in each string to keep the device power dissapation down.

That would require at least a supply voltage that is about 1.25 volts more than your required voltage. The input voltage could then be anywhere between 1.25 volts more than you need up to about 35 volts and the output would remain constant at 700ma.
Keep the input voltage as low as practical to keep the LM317 power dissapation down.
Click to expand...
Some instructions for setting up an LM317 can be found here and the high power LM317 in question is this one. Don't forget to put a heatsink on each LM317, and because of the voltage drop across the LM317 and its resistor you will have to go with strings of 3 LEDs for a 15V supply.
 
I wonder if any one has read my post ??????????
Leme clarify : NO resistors, NO voltage regulators, NO current regulators, NO messy wireing.................. Just a power suply and his leds as he wished them, and it has built in CURRENT AND VOLTAGE regulators, they take anything from 100 or 110V to 270V and they are WERY reliable.
 
Something like this would be ideal for a k2 luxeon light setup.

Here are some pics I found in a forum:

6 one watt Luxeon LEDs
circuit-luxeon.jpg

test-luxeon.jpg


This is his full 12 k2 Luxeon LEDs light fixture
pc107396.jpg


His tank with the light fixture
bac-spot.jpg


Pretty nice k2 luxeon setup if you ask me :)

Does anyone know if those are resistors and current regulators? I'm assuming those would be resistors and current regulators but in a different form, since this setup was made in France.

Kind regards,


Chingy
 
Are you linking to someone else's photos (frowned upon at CPF) or hosting them yourself? Is there a write-up that came with the photos, even in French?
 
PS - Here's a table of standard resistor values - 27 is there, but not 2.7.
http://www.rfcafe.com/references/el...stor_values.htm
Click to expand...
Your table is suspect, since it has no values under 10 ohms. Digikey's catalog implies that 2, 2.4, 2.7, and 3 are all standard values for 1/2W resistors (ie they're $0.26 for 5, and significantly cheaper if you buy 200.)

I would think the problem with LEDs and aquarium lighting is that LEDs are not "full spectrum" lights; while their overall color temperature may be appropriate, they'll have power peaks in the blue and yellow and be missing power in red, orange, green areas of the spectrum. I don't know much about aquatic organism requirements, but it seems to me that green plants are likely to want frequencies that aren't present.
(Hmm. http://generalhorticulture.tamu.edu/lectsupl/Physiol/P24f1.gif )

(so if "they" sell 200+ LED flashlights, how come no one has a "full spectrum" LED lamp that throws in some red/uv/green/etc LEDs to balance things out.)

(IMHO, doing some experiements on how plants grow with various light sources, including LEDs, would make a very nice science fair project for the middle to highschool age group... (later you can use your experience to grow illicit plants in hydroponic warehouses!))
 
Thanks for all your replies. Anyhow, moving along towards my setup. This is how the setup would look like.


Supply Voltage
18V (Originally 15V, but due to the Voltage Regulator LM317T, I need an additional 1.2+ V)

Voltage Drop Across LED
3.6V

Desired LED Current
700 mA

LEDs Connected
16

16ledsno7.png



From the resistance calculator, I need (4) 5.6 Ohm with power rating of 4.2 watts. Does anyone know where I can find these resistors?

Once I get these resistors, I will connect them to the LM317T. The resistors will help by reducing the current flow to 700mA and the LM317T will help by regulating the amperage to 700mA. Is this correct?

Will the amperage that is coming from my power supply become constant at 700mA due to the help of my resistors and LM317T?

I am new to electronics and never taken a class from electronics, just been reading, so I don't know if my thinking is correct. Appreciate it if someone would read and make sure my setup is correct before I make a mistake and blow up any Luxeon Rebels.
 
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