DIY LED Light Questions

[Beanz]

Y would I have to run then without optics if I only have 24-36 LEDs?

Thanks, Ian

[StirCrazy]

Originally Posted by Beanz

Y would I have to run then without optics if I only have 24-36 LEDs?

Thanks, Ian

because you will need the full 120 degree spread of the LED to cover the area. if you put 80 degree optics on on with that few LEDs you wont get good coverage and you can get spotlighting and it will look bad.

Steve

[Beanz]

Ok so i thought about the set up (lol woke up this morning and couldn't go back to sleep b/c i was thinking about it ). Anyways i was thinking that i could just get constant current drivers i was thinking Mean Well LPC-35-700W for the blues and then i could still get the same amount of cool whites with dimmable drivers and use them at 700w or higher if it still looks good. Then i will probably b able to get a total of 48 LEDs, anyways just a thought. What do you guys think?

Thanks, Ian

[Beanz]

Originally Posted by StirCrazy

because you will need the full 120 degree spread of the LED to cover the area. if you put 80 degree optics on on with that few LEDs you wont get good coverage and you can get spotlighting and it will look bad.

Steve

Ok, do you think that if i just get the 36 LEDs and raise the fixture up, 4 inches like Cal said (maybe higher if spotlightinf still occurs, or would this reduce PAR too much?), this would eliminate the spotlighting and work for keeping SPS closer to the light and LPS and maybe some softies near the bottom of the tank?

Thanks, Ian

[StirCrazy]

Originally Posted by Beanz

Ok, do you think that if i just get the 36 LEDs and raise the fixture up, 4 inches like Cal said (maybe higher if spotlightinf still occurs, or would this reduce PAR too much?), this would eliminate the spotlighting and work for keeping SPS closer to the light and LPS and maybe some softies near the bottom of the tank?

Thanks, Ian

I tent to agree with Ron, that at 36LEDs your not going to get the coverage. I was looking at 48 LEDs on a tank that was 30 long x 12 wide. with 40 degree optics. you have a tank that is the same width but over 1.5 times longer so with 40 degree optics that would put you at 72 LEDs with 40 degree, you can go a little bit less each time you increase the angle of your optics so 60 degree you could get away with fewer and at 80 degree even less but I would think that if you did 3 stagered rows at a spacing of 2.5" you chould be good with 80 degree optics, so that works out to 3 rows of 18 which is 54 LEDs. the problem is you don't want to build your system and find out you don't have enough as then the only option is to remove your optics and decrease the PAR or lift them and decrease the PAR, so this is a case where it is better to have to many than to little. you might be able to get away with a 3" spacing with 80 degree optics.

I think the best way to determin what you like is to get 6 blue and 6 white LEDs and 1 mean well driver. get a scrap chunk of heat sink about 36" long and 2" wide (1/4" hunk of aluminum will do as this is a test only heat sink) drill holes at a 3" spacing and wire them up. put it over your tank at night with the rest of the room dark and look at the effect. try 60 degree optics, 80 degree and no optics and try to determin where you get spot lighting. you will be able to reuse everything except the optics you don't like and the temp heat sink so you will be out maybe 20 bucks for testing.

if you get an even blending of color at 3" spacing then you are good to go. if you get spotlighting then re drill at 2.5" spacing and try it all again and see how it looks. this will tell you exactly how many you need with out trying to guess.

once I get my shop finnished, I am going to do this and conduct some testing including looks and PAR out puts at different spacing with different optics, only problem is it will probably be next year befor I can even think of doing ti because I have to save up another 5K to finnish the inside of the shop and heat it.

as for your ballasts, I personaly would put dimable ones on all the LEDs. not a lot more money (under a 100 bucks for the whole setup) and give you a lot more ability to do different things. you could later ass a andruno based controler which would gradualy fade all your lights in and out for sunrise/sunset, ect. with blues stuck at 100% all the time then you would have a bang of blue light and the white would gradualy fade in. also for new corals it would be nice to be able to dim the lights to 50% for a day or two then increade them in bits over a week to prevent bleaching of new corals.

Steve

[Ron99]

Originally Posted by Beanz

Ok, do you think that if i just get the 36 LEDs and raise the fixture up, 4 inches like Cal said (maybe higher if spotlightinf still occurs, or would this reduce PAR too much?), this would eliminate the spotlighting and work for keeping SPS closer to the light and LPS and maybe some softies near the bottom of the tank?

Thanks, Ian

I would say no. The reason for more LEDs is not only for even coverage and colour blending but because the overlapping output of the multiple emitters adds up to the amount of PAR you want. I did a quick experiment measuring PAR output of single emitters driven at 350mA at a distance of about 3 inches from the LED and no optics. A cool white Cree XRE put out about 176 PAR, a SemiLed cool white (about a middle of the road bin, not the highest brightness bin) put out about 100 PAR and a cheap generic chinese white LED put out about 50 PAR.

So even with say a 60 degree optic you will probably have no more then 350 PAR at 3 inches from a single emitter. You need the light from the LEDs to overlap to add up to the PAR you want if you want to get up to 500 PAR for SPS.

For further comparison, a 12" AI module uses 24 Cree XPG and XPE emitters to give the high PAR numbers it produces. You would need 3 to 4 modules to cover a 48" tank so that would be 72 to 96 LEDs.

Unfortunately, if you want a high output LED fixture there are no shortcuts and the up front costs are relatively high. But you will save in the long term by not having to change bulbs for 6 to 8 years, using less electricity, and putting less heat into your tank so you may not have to run a chiller or fans etc. (my tank stays between 78.5 and 80 degrees depending on the ambient temperature. During the heatwave it went as high as 81.5).

[Ron99]

Forgot to address the drivers. You could go with the non dimming drivers as you suggest but as Steve says you won't be able to do nice sunrise and sunset effects or adjust colour temperature or change things for acclimation purposes. If you don't care about that and just want to have the blues come on at a set time and then the whites come on at a set time you could save a bit by using non dimming drivers for both. But the cost difference for dimming drivers isn't that much more and gives you more flexibility for the future.