Another bit of work completed, not without hiccups & second thoughts. But I did mention earlier that I'm building on the fly without extensive planning on paper...
Still awaiting the arrival of the 10,000K LEDs, but have wired up 3 each of the Cool White & Royal Blues to the first rail for some testing. Sourcing small screws/bolts to fasten the 10watt LEDs to the heatsinks was an issue, but the other day it dawned on me to check the local hobby shops & scored some M2 nylon bolts plus tap to thread the heatsinks for LED mounting! Worked like a charm until I snapped the tap on or about the 5th heatsink, so I need to get another. Two of the heatsinks I had already tapped for #4 (American std) screws, so I still need to get my hands on some of those.
I decided to snip off the little connectors on the heatsink fans & solder them to the + - terminals of the the LEDs along with the hookup wire. Trying to keep the number of connections to a minimum, but it does have drawbacks, since now the fans are destined to run at whatever voltage is delivered to each individual LED array, vice running at their full 12 VDC rating. I lose the ability to independently control the fans on the heatsinks. Hoping that won't be a big issue, since they may not need to run at full power if the LEDs are not being driven at max current either. Was originally going to use 18 guage wire for LED hookup, but decided on 20 guage single strand instead. This made it easier to solder both the LED hookup wire & the very tiny fan wires to the LED terminals. #18 would have been a very tight fit in the terminal hole. Also added a small section of heatshrink tubing over each connection for protection from the elements... salt water.
Photo is not great, but you should be able to see the relevant details here. The center LED is placed between the two mounted ones for reference, showing the fan connector still on it, whereas the mounted ones have been cut off & wires soldered to LED terminals. Heatshrink tubing on the RH cool white LED has been given the shrink treatment, while the RB LED on the left has the tubing pulled back to show the solder joints. Note also that the cool white LED on the right has no mounting screws yet, this is where I need the #4 screws. The RBs are fastened with the nylon M2 screws.
A full length shot of the rail. May still modify the hookup wiring to shorten all leads & use terminals to connect the 20 guage wire to larger guage for the run to the power supply.
After soldering the 6 LEDs yesterday evening, I tested each one for current draw with the power supply adjusted to the lowest possible setting of 10.7VDC. This is slightly higher than the rated voltage for the Royal Blues but within the acceptable range for the Cool Whites. Found that the RBs were running at over the 900mA rating, in fact a good bit over 1 amp, so didn't leave them on very long. Fans worked well on all the LEDs. I did hook them all up shortly after lights out on the aquarium to see how it looked & was quite impressed. Great fluorescence on my LPS & amazing shimmer.
I know I'm going to need some sort of additional regulation to limit the current to the RBs in particular, so today I dug up an old 2 ohm variable resistor I've had laying around for decades. Did a lot of reading on various regulation scenarios, voltage, current, pwm, simple resistor & even found out about another possibility, something called a PTC resettable fuse. This device acts a little like a resistor, but the main purpose is to regulate current. If the current rises above the PTCs rating, the PTC will heat up & cut the current, thereby protecting the circuit or LED in this case from frying due to overcurrent. However, since my power supply is relatively stable at the set voltage, it seems that a 2 to 3 ohm (or variable resistor in that range) in series with each LED will be the simplest, most cost effective solution.
Testing of each LED today with the variable resistor set @ 2.8 ohms & power supply @ 10.7 VDC showed a variance from 700 to 740mA for the 3 Cool White LEDs. The 3 Royal Blues ranged from 880 to 910mA with the same voltage/resistance values. This testing also showed the value of proper heatsinking & having the LEDs firmly mounted with heatsink compound. The Cool White LED which I have no screws for at the moment had lifted from the heatsink without me noticing & when I hooked it up the current was rising steadily as time passed. I had been tilting the rail away from me to avoid getting blinded, but noticing the rising current, I snuck a peek & noticed the problem immediately. Once I pressed the LED back onto the heatsink with the compound more or less holding it in place, the current settled rock solid @ 700mA. I ran each LED for a good few minutes to ensure the reading was stable. The fans & heatsinks appear to be doing their job very well. I could even feel some of the heat being transmitted to the mounting rail. Will likely add some heatsink compound to that interface as well to aid further in cooling.
So far the results are very encouraging. The rail is ultra light. I think I will probably end up going with 10 LED arrays per rail. This will provide plenty of options as far as colour mixing goes. Downside is, I still need to figure out a dimming solution. Will certainly not be sophisticated but my current set up has nothing, so chances are my livestock will not care a whole lot. I reckon simply putting the RBs & some blues on first & last using timers will provide enough of a dawn dusk effect & keep things simple. It's kind of what I do now with my T5 & halides, so business as usual, probably a tad better.