I was wondering what the correlation between PAR and Lux. I assume the more lux, the more par, but I'm not sure.
YES and NO. The NO part:- Lumens are based on eyes but our eyes are not linear reacting to the light energy in different color(spectrum) even though the light energy may be the same. To better indicate what human beings feel visually, we use a formula in the Lux meter to express them what we human beings think the brightness is. Now that goes for PAR too, but this time they are formulated to be used for plants' photosynthesis. So the reading is designed to reflect better what the plants reaction is. The YES part:- Unless the light is very tight in the spectrum like LED, most commercial lighting technologies are a mix of spectrum and thus both the human eyes react to some of them while the chlorophyll of the plant react to some of them too, even though not necessarily the same. So in real frequently we find that higher Lumens bulb also yield higher PAR. Problem becomes even more complex-the meter you use. A lot of PAR meters also register green significantly in their readings but as scientists will tell you they are not of much use by chlorophyll in plants(hence the Zoa in coral), so the PAR value for coral growth is also an rough collectively assumption(not really exact) but yet yielding close results to what we expect them to be.
Also, have there been any reports of those aluminum U-channel's used in place of heatsinks causing heat problems? I have access to a bunch of scrap sheets of aluminum, and was wondering if I could just cut strips and bend them to make my own U channels. If I do, what thickness is ideal, and how long should the fins be? To calculate the proper surface area you need to know the total power of your LEDs, the heat co-efficient of the heat sink material and ...... I would just try to over do it than doing the math. If it's an passive heat sink design, you should not have the fins too tall as it will create channeling. The thickness of the aluminum base is to help the initial heat sinking when the diode fires up. There is a lot of heat energy when the LED is fired up, so you want thicker base over thinner base to quickly transfer all the heat energy away from a focal point and then let the fins to re-transfer than to the air. I myself would not trust an U channel thing from Home Depot as a heat sink unless you are using a fan to make it an active heat sink.
One more, I plan on using the ELN-60-48D and running 13 XM-L's in a series, and plan to dim with my Apex. Do I still use the 10v AC to DC power adapter to dial in my driver, or does the Apex take care of it?
Thanks!