pg16
--Those are good prices on either the Xitanium or the GE. It wouldn't surprise me if they were made at the same place with different labels. Either one is a good bet and the prices are very good... jump on them. I use a 25 watt Xitanium as one of my test supplies.

While you can physically layout the leds in a single string, they will actually have to be electrically connected in 2 parallel strings of 6 to 8 LEDs depending on desired wattage. I would have a positive feed point in the middle of the layout and the negative on each end.

You can put the 2 resistors on either end or both in the middle.
5 watts is the max rating and gives you no margin of error on your voltage control plus you must have superb thermal management, plus you really shouldn't let your grow area temp get over 75 degrees. In order to run at 5 watts you will need a $180 digital bench power supply in order to get the 2 line resistors set up right on the money. You will then have to burn in each LED string over a period of 3 to 4 days while monitoring voltage changes at a constant current and also monitoring temperature. After the string has stabilized and you take measurements, you will probably have to make a custom resistor combo in order to get the precise value needed.

If you decide to run in the 3 to 4 watt range it will be much simpler to set up without the danger of wiping out $120 worth of LEDS. In reality you are probably only going to get about 10% more light at 5 watts then you would at 4 watts and will avoid the need for the expensive test equipment and testing.

Your first step is to get your hands on a heat sink. What is the desired and maximum length you want your array? I will send over the heat sink link from Ebay after I get back from dinner.

tetra info
The best configuration for the Tetra is 3 parallel strings of 8 LEDs.
Giving you about 72 watts to the array (3 watt per light).

If you want to run the lights at a higher rating of 4 watts you would be limited to 2 strings of 7 lamps. Giving you approx. 56 watts total for the assembly

Here's some pics of a 25 watter I just knocked out using K2s. I will be using different nm combos in seperate areas of the grow to try and find out what wavelengths are most effective.

------ I am starting on a 660nm array. If you want I can post pics and details of construction of progress, if you think that will be of help to you.

Both supplies are 120 ac in and 24vdc out. The big one is 180 watt.

The link for the heat sink is HEATSINK ALUMINUM EXTRUSION 8 1/2 WIDE PROFILE - eBay (item 170209048370 end time Apr-15-08 11:05:34 PDT)

So many theories floating around on color combos. I have even read one paper, that says plants will readily adapt to the wavelengths that are available to them. I have no personal opinion on what is going to work the best, so I am going to start experimenting, trying this and that.. It will probably take about a year or two before we start getting it really dialed in.

-----, I will start on the 660 nm strip array this weekend and post pictures of progress.

I got some 660s and am starting on some lamps this weekend.
I am able to set up 4 different grow sections to try different light combos.

Anyone know where to get high power 435s. I am currently running cool whites in order to pick up some light in that area.

Don't worry about replacing individual LEDs. By the time they burn out they will be obsolete. 2 or 3 years from now we will be getting our hands on the good stuff. No more HPS.