If you plan to build a LED light you should first learn what mAmps (miliamps) are, and what PAR (photosynthetically active radiation) is.
I used data from the LED lights I have made to develop an equation that relates how much light you get in PAR units (micromols of photons per square meter per second) to number of LEDs, how far apart they are spaced, what their lumen output is vs LED current, what the lens cone angle for them is, how far from the light you want to know the PAR is, etc. That equation, combined with data from Cree for the LEDs gave me those numbers.
This is what I'm trying to figure out. I want to build something that is relevant to what my tank needs. Im so lost when PAR and mAmps gets involved. Then when you start throwing in the height that it hangs from the tank, dimmers, drivers etc...im just completely lost
ledgroupbuy has XML's for like $7 each, two of those over a 20 would be enough. The real problem with XML series is finding a power supply that will drive them at higher currents, that isn't fantastically expensive. "powergate llc" (google them or try the obvious) has the whole line of meanwell drivers at very good prices, and you can get a suitable unit there for sure. With fewer LEDs you also buy fewer optics and need make fewer connections, can save you a good bit of time.
I have some Citizen 18w 5000k 85 CRI emitters that I am really liking over my planted tank with a peacock cichlid in it. He glows orange under this one, and I really like the single light source, the ripple isn't so overwhelming. I had(still have actually) an array of 8 XPG 5500k (WH bin code) over the tank, it had a greenish tinge reminiscent of cheap cool white fluoros. The citizen emitters cost me $9.53 each, not at all bad for what they are, and you can drive them at 30w (datasheet max for this model). They're around 75 lumens/watt, which is not great until you compare to other high CRI emitters.
Idk like to spend no more than $150. This is going to be my first LED build and I just want to make sure I know what I'm doing before throwing in more money. So you think two XML emitters are enough for a 20gal? That seems like its too little? I wouldn't know though lol
Seriously- 12 XP-G's will provide more light than you'll ever need on a 20 gallon tank. Don't get me wrong- The XM-L's are great leds,but for your application they would be "beyond overkill". Save some money upfront by purchasing the cheaper XP-G's and roll the money into a dimming controller or some other neat gadget for the tank.
how many XP-G's would I need and what kind of driver?
Look into Cree XM-Ls i've been thinking about using those, can get them imported from hong kong for around $9-10 each. comparable to XP-Gs at 3 amps, 20% more efficient at 1.3 amps.
I agree with hoppy. Your phasers are set on "fryalate."
I use 29 Crees to light my 36x18x22 high 57 gal (see the signature), and I can easily get it to pearl on full blast. The fixture is about 8" from water surface. I run it well below full intensity most of the time.
If cost is an issue, I'd do a single string of 14 LEDs on a 20g--maybe 3 Royal blues, 7 cool whites, and 4 warm whites. If cost were no object, I'd go with two strings of 8 each. One with 4 Royal Blues and 4 Cool whites. The other with 4 cool whites and 4 warm whites. Put them both on Meanwell 48D variable drivers, and fiddle to get the color balance you want.
14 emitters sounds more reasonable to me. If i do a strip of 14, I would have to space them out at 1.5 inches, correct? would that be sufficient for heat dissipation?
I know there are a lot of thread on DIY led builds and I have been researching them for weeks now and I alway end up more confused. I guess my real question is how do I calculate PAR, mAmps, what dimmer, what driver, and what optic lens?
Sorry for the redundancy. Just trying to learn as much as I can. Thanks again for all your input and replies!