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Hi,

I've got an Aqua One AR380. Its a 10Gal aquarium which is 18 inches tall. Currently lit by one fluorescent 11w of some sort. This isn't enough light to grow the plants I want.

So I'm going LED. I've got some electronics understanding, so I don't see wiring to be that big an issue.

I'm having some problems selecting parts though.

So far, I've got 8 x Cree XR-E Q5 LEDs for lighting.

I need help with:

1. LED Drivers (What do I use? I want to drive the Q5s at at least 700mA)

2. Power supply from wall -> LED Drivers?
700mA * 8 = 5.6A
(Driving Amps * Amount of LEDs = total current).

So,
5.6A * 12V = 67.2W
(Driving Amps * Driving Input Voltage = Power supply total wattage needed.)

Does this mean I can get an old 200w computer power supply and rig up the LED drivers to the 12V rail on the power supply?

Basically I need to make sure my maths is correct and I'm on the right track. Secondly, Where can I source the LED Drivers from? I've already got a supplier for the LEDs (dealextreme.com/details.dx/sku.2394).

Now I need a place to get 10 of the LED drivers (8 for production, 2 for testing in case I blow some or something :p)

If someone knows a place that sell these online, It'd be great if the store ship overseas as I'm in New Zealand.
 

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When I get home I can find the link to the DIY driver for LEDs. Using a power FET, controller, and a few resistors is all, you can make the driver for a few bucks compared to what they want for retail drivers.

For a power supply I just ordered a 200W adjustable laptop power supply, mostly because with those Cree LEDs you end up with a lot of wasted power driving them with 12V just because of how they multiply out. Also, the spare PSUs I have are all of questionable quality and life remaining.
For instance, with your 8 lights you would have to have 2 sets of 3 and 1 set of 2. Which would mean the driver for the 3 LEDs would have to drop about 1-2Vs, and the driver for the 2 LEDs would have to drop closer to 5-6Vs, which will require larger parts on your driver and less overall efficiency.

As an aside, I've got those exact same LEDs ordered from dealextreme.com. Its been about 2 months now and they still haven't been shipped. The flashlights I ordered at the same time are here though. I ordered 14ish of them and they have been listed as pending supply for a long time now, so I think they have some and thats why its not listed as out of stock, but not that many.
 

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My 2 cents worth: It is a mistake to assume that you should drive each LED separately with one driver. Much better is to put some in series, enough to get close to the power supply voltage output. Then put the groups that are in series, in a parallel circuit, increasing the current needed, until it is close to the power supply optimum output current. That keeps both the voltage and the current to minimum total values.

If they are all in series, the voltage can be high enough to making isolating them from the heat sink a problem. If they are all in parallel the total current can be high enough to require attention to the size wire being used and can be too much for the power supply. And, of course, using a driver for each individual LED greatly adds to the cost of the light fixture.

Today there are many options for driving LEDs. Look through the Ebay listings and you will soon decide that there are too many.
 

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Find a calculator like this http://led.linear1.org/led.wiz if you want to use a voltage regulated psu. Using a huge psu will be wasteful. There's some secondary reason you want a resistor in line with one of this type power supply and I don't remember it. Voltage spikes? I don't remember. On the plus side, you can easily alter the drive current.

Places like meanwell and xitanium make constant current drivers.

I think your math is messed up. Example, 3.5vf*.7a = 2.45w 2.45w*8= 19.6w

I cancelled my order for emitters from DX. It was more than a month and a half. Now there's something newer and better. Q5's are so last year.
 

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I cancelled my order for emitters from DX. It was more than a month and a half. Now there's something newer and better. Q5's are so last year.
Ah, but "last year" stuff, be it cars or LEDs, are much cheaper as a rule. If the cost isn't a problem, I agree that going with the latest and best is a better idea. What is the latest and best?
 

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Here is the constant current source I'm going to be using


As for the Q5s... yeah they are a bit older but they are also a fair amount cheaper. They had the R2 bins available, but you are spending about 20-40% more for maybe 5-10% more light. Its not a big deal if you are building a small lighting system, but if you consider that you need probably 24-36ish for a decent sized tank they really start to add up.
 

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http://www.instructables.com/id/Cir...-LED_s/step11/an-even-simpler-current-source/ is the constant current source I'm using. I found it the easiest to make, and easiest to design modifications to. Mine has been working since last Summer, with no problems. The only problem with this circuit is finding the voltage regulators, which are really "last year's" big thing, so most hobby supply places don't have them any more. RadioShack has the original LM317 regulators, but I wasn't able to find the improved models anywhere.
 

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I just ordered all the parts I needed from Digikey and Newark. I had looked at that design a fair amount too, I just decided not to use it because the higher drop out was very potentially going to cause me problems with the voltage supply I'm planning on using. I think it also ended up being a little bit more expensive.
 

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The only problem with this circuit is finding the voltage regulators, which are really "last year's" big thing, so most hobby supply places don't have them any more. RadioShack has the original LM317 regulators, but I wasn't able to find the improved models anywhere.
My favorite supplier: http://www.digikey.com I got all the parts for my AutoWC Controller there. Good search function and interactive online catalog, and small orders are no problem. Shipping is from Minnesota so it's reasonably quick to most of the country.

http://www.mouser.com is also a good source.
 
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