You'll find that beam-spread is the problem with LED's. Not spectrum. It's an optical issue probably best solved by hundreds of smaller sources, with a diffuser.
You'll find that beam-spread is the problem with LED's. Not spectrum. It's an optical issue probably best solved by hundreds of smaller sources, with a diffuser.
Try some of that diamond diffuser?
Thanks for the clarification.
When you do pics I'd like to see a pulled-back shot that shows the lighting if you can manage.
Beam spread should not be an issue with this build.
The raw LED has a micro lens on it, with a "Lambertian" radiation pattern.
I am not adding any extra optics. With narrow beam optics, it would definitely be a problem.
You have to look in the datasheet for a detailed drawing, but basically, the radiation pattern is pretty spread out.
Relatively shallow curve between +/- 15 degrees.
Not steep really until +/-40 degrees.
So with 5 overlapping sources, coverage is fairly even.
Sources are about 2" apart, where target is 5" away. So a +/-45 degree angle is a lot of overlap.
Sure, not as diffuse/good as a big wide CFL bulb, but far better than a single metal halide.
But the concern is worth checking. I can move the light meter around the target area, and see what the difference is.
Nothing like real measurements.
That, and take some pictures. But I've been pretty busy lately.
Diffuser plate would certainly spread things out even more, but also absorb a lot of your light.
Even the thin plexiglass I used made a noticeable difference.
Ok, some more detailed measurements on spread / light distribution:
On original distance, lux range min/max over target distance = 5500 - 9800. (1.8X)
At 6 inches, lux range = 2,700 - 4,800. (1.7X)
Error in measurement is fairly large. Probably 20%+. Surprisingly hard to get a solid measurement.
That may seem like a problem, BUT:
Dual CFL setup at 6" = 5,500 - 10,000 (1.8X)
So yes, there are light distribution issues, but really not worse than dual CFL.
* However, I would expect a long tube CFL to be a lot better.
"Before" picture of tank.
Not bad, but plenty of short hair algae.
My LED / turf scrubber in action.
Nice comparison of lights.
15 Watt LED on the left.
2 x 26W = 54 Watt Normal dual CFL on the right.
LED is clearly pinker, but not quite as bright. Glare makes it a bit deceptive.
When I originally set it up, I was more excited, since LED seemed brighter.
But I made a mistake in not letting CFL bulbs warm up enough.
My ATS screen. Almost exactly two weeks.
I have cleaned it a small bit 3 times.
A lot better than before, where it was simply pale yellow, even after 3 weeks.
More on conclusions soon.
MY OVERALL CONCLUSIONS (OPINIONS) SO FAR:
Did the LED lighting improve my growth?
- Clearly Yes. Time will tell if it is truly good.
- BUT: I am quite certain I could have fixed it with repositioning/improving a normal CFL design as well.
- So do NOT do this project to "fix" your ATS. Do it for fun!
Does it use less power?
- Clearly yes.
- The light is slightly dimmer, but can be positioned closer easily.
- You can tune the spectrum.
- It is only 15 Watts, instead of 54.
Was it hard?
- Well, much harder than a simple CFL bulb in a home-depot socket.
- But on par with doing your own T5/Ballast setup. (Which I have also done on main tank)
Was it expensive?
- Well, yes. But only initial cost. Over time, should be cheaper , with no bulbs to replace, and power savings.
Other issues:
- Could be a beam spread problem. But after measuring, I think I must disagree with our resident expert on that.
- Spread is not constant. Far from perfect. But really no worse than a normal CFL setup. A T5 would be better though.
- It takes up less space. Produces less heat.
- Lower voltage near tank is MUCH safer. Did you know CFL starting voltages can be more than 400V!
- No mercury. And with changing bulbs that often, not and entirely trivial issue.
I am looking forward to the long term of seeing if the whole ATS concept will improve my tank.
Thanks for the pics! And the run down.
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