I have have finished from building my ADA 120P like tank now it is the time to build its lights for a high tech system
well i am targeting about 75 PAR (micromols) at substrate for HC growth as main plant ( correct me if i dont need all that PAR
i did my home work and used https://www.plantedtank.net/forums/sh...3&postcount=14
I will use Cree XM-L2 ( http://www.fasttech.com/products/1277805
LED Spacing (inches) 5
PAR (micromols) 75
Number of LED rows 2
LED Height (inches) 28 from the substrate
Cone angle (degrees) 45
Lumens per LED 742
Cree XM-L Cool White LED Current (Amps)2.13
what i need your help with
1- what is the space between the rows is it the same as LED Spacing (inches) ??
That spacing should be about the same as LED spacing, but it doesn't have to be exact. One inch would be much too close, 10 inches would be much too far.
2- is using a 45 lenses will not spoil much light out of the tank or should i use 30 degree lenses ?
You should have very little spillover light using 45 degree optics, if the light is about 12 inches above the top of the tank.
3- and by using LED Spacing 5 inches that means i will need 10x leds in the row so that is total of 20 leds for the 2 rows ? ( correct me if i am wrong )
Yes, if you want the LEDs to run from about 2 1/2 inches from one end of the tank to about that same distance from the other end of the tank. You could probably do fine with just 9 per row, if the light is suspended about foot or so above the top of the tank.
4 -about the heatsink i will be using one big heatsink , and i can get what ever size i want ( specially made ) so what is the good size for ADA 120P that is a 48 inch , is it better to be a bit smaller than the tank ? how much then ?
It doesn't matter what the length of the heatsink is as long as it is long enough to fit the LED spacing you want. It will probably look best if it is only slightly shorter than the tank length.
My Greetings from Egypt
I didn't do the calculations, using that speadsheet, but I assume you used it right. You will have the fewest problems if you limit the maximum current to one amp (1000mAmps) or less, so the heatsink isn't so critical. And, be sure to use a LED driver that lets you dim the light. The spreadsheet isn't good enough to hit the exact PAR you design for, but if you only get 60 PAR you should still have plenty of light for HC.