LED idea

[Greybeard]

Has anyone considered facing LED's UP, into a reflector?

IMHO, Halides are the absolute best light for a reef... except for two points: 1) The heat they generate, and 2) the power consumed by them. Ok, I suppose there are some lesser negatives... big heavy ballasts, having to replace bulbs... but honestly, if it weren't for the first two, many more reefers would still be using them. Am I wrong?

Ok, so a good Halide setup is only as good as it's reflector. Without one, the bulk of the light shines away from the tank. If you put a single halide in a light absorbing mount over a tank, it'd look much like the LED's of today... a single spot light, no diffusion.

Put that same bulb in a well designed reflector, and you get MUCH more light into the tank, and a far more diffuse output. Instead of the light coming from a pinpoint, intense halide bulb, it's coming from a large, mirrored reflector, scattered over the entire lit surface of the tank.

Wouldn't the same logic work on an LED? We've got more than enough raw power... many of today's LED aquarium lights have to be cranked down to keep from burning corals. Pack those LED's in a thin strip, say 1" wide, 8" long, facing UP, into a well designed (Pebbled?) 8" x 10" mirrored reflector. Wouldn't this diffuse the pinpoint source? Perhaps, if properly designed, even more effectivly blend the various color LED's?

Thoughts?

 

[Eagle_Steve]

Has anyone considered facing LED's UP, into a reflector?

IMHO, Halides are the absolute best light for a reef... except for two points: 1) The heat they generate, and 2) the power consumed by them. Ok, I suppose there are some lesser negatives... big heavy ballasts, having to replace bulbs... but honestly, if it weren't for the first two, many more reefers would still be using them. Am I wrong?

Ok, so a good Halide setup is only as good as it's reflector. Without one, the bulk of the light shines away from the tank. If you put a single halide in a light absorbing mount over a tank, it'd look much like the LED's of today... a single spot light, no diffusion.

Put that same bulb in a well designed reflector, and you get MUCH more light into the tank, and a far more diffuse output. Instead of the light coming from a pinpoint, intense halide bulb, it's coming from a large, mirrored reflector, scattered over the entire lit surface of the tank.

Wouldn't the same logic work on an LED? We've got more than enough raw power... many of today's LED aquarium lights have to be cranked down to keep from burning corals. Pack those LED's in a thin strip, say 1" wide, 8" long, facing UP, into a well designed (Pebbled?) 8" x 10" mirrored reflector. Wouldn't this diffuse the pinpoint source? Perhaps, if properly designed, even more effectivly blend the various color LED's?

Thoughts?

You just made me think about trying this. I have some old LED lights and a few of my old halides out in the garage.......might have a project this weekend.

 

[redfishbluefish]

Interesting idea! If anyone does this, please us a PAR meter or the poorman's PAR meter (a LUX meter) to get the numbers for comparison.

Initial thoughts....

1. A halide bulb is small and composed of clear glass 360 degrees all around, so light is emitted in all directions. That is the reason for the reflectors...to capture that light going in the "wrong" direction and direct it back to the tank. LED's only emit in the direction of the LED and don't need a reflector to redirect lost light.

2. LED fixtures tend to be large, requiring a fancy reflector to capture and redirect the light. I would thing that large portion of the fixture would now cause for a shadowed area in the center where the fixture sits.

3. I've got to believe reflection causes for some light lost??

That said, I'd still like to see someone try it! @saltyfilmfolks , any thoughts?

 

[WVNed]

All you would be doing is increasing the apparent distance from the emitter to the tank.

 

[Eagle_Steve]

All you would be doing is increasing the apparent distance from the emitter to the tank.

True to that and maybe a shadow. I have noticed that a lot of LED fixtures are not at 100%. With that being said, even if there is loss from going up and then down, one could turn the power up to the LEDs to compensate. I use Black Box LEDs on a lot of my tanks and have the lenses removed and only have them at 60-70% power on 24" tanks, still getting almost 200 par on the sand.

Another idea might be a polished heat-sink for the leds, and the heat-sink be rounded to allow light to reflect back off of it and either down, around or back up to go down.

There does come the issue with cooling. I think some small copper tubes routed down the heat-sink and back, then routed to the top of the fixture with a small fan, may suffice. Even a small fan, blowing across the LEDs and heat-sink may do it. Something to toy with there. Heck, one could even make a small liquid cooler similar to that of what would be used for a CPU, but again smaller.

 

[WVNed]

If you want to alter the spread you want a diffuser, not a reflector.

 

[Greybeard]

If you want to alter the spread you want a diffuser, not a reflector.

Unless it's a perfect mirror, a reflector will act as a diffuser. The polished aluminum ones that are common certainly don't qualify as perfect.

Add in a pebbled finish, and it'd diffuse even more.

 

[Lingwendil]

LEDs already have a relatively narrow native spread as it is- often 120-135 degrees, depending on the type chosen, with the vast majority of the light being given in about half of that... Adding a reflector can be beneficial in some instances (single-point arrays, like with larger COB array types) but but will actually make the color mixing worse, with more noticeable separation and spotlighting of individual colors. Unless you pack them really tightly into a single smaller cluster and share a common reflector you don't have to many options here. Look at what @theatrus is doing on his designs for an idea.

The main issue in using a reflector is that they really don't work well on a natively narrow output source like most LEDs. A lens will work much better in getting more spread, but so will simply using more emitters spread out further. Look at some of the prismatic lenses some manufacturers use.

 

[theatrus]

LEDs already have a relatively narrow native spread as it is- often 120-135 degrees, depending on the type chosen, with the vast majority of the light being given in about half of that... Adding a reflector can be beneficial in some instances (single-point arrays, like with larger COB array types) but but will actually make the color mixing worse, with more noticeable separation and spotlighting of individual colors. Unless you pack them really tightly into a single smaller cluster and share a common reflector you don't have to many options here. Look at what @theatrus is doing on his designs for an idea.

The main issue in using a reflector is that they really don't work well on a natively narrow output source like most LEDs. A lens will work much better in getting more spread, but so will simply using more emitters spread out further. Look at some of the prismatic lenses some manufacturers use.

There are a bunch of interesting side effects of a reflector, especially on narrowly spaced LEDs. The peaks of most LEDs is in a more narrow 60 degree cone, with spill over to the sides up to the 120 degree normally quoted numbers. Some LEDs have very different profiles. For example, compare the Luxeon CZ with the Luxeon C lineup, and note how the C has very different curves for some of the LEDs.

Also, annoyingly, the axis between the datasheets is not the same - the CZ is much more focused and features a flatter dome top (more of a surface emitter)

So, now reflectors. The bulk of reflectors that are wide are all the same shape, but the wider ones feature faceting and roughening to spread the light out more. What happens when you do something like take the Luxeon C and put it inside a Ledil Angela reflector, without any diffuser? The pin-source of the light hits certain facets and is lost by others, leading to on a whole a very knarly zebra stripe effect of colors in your tank. The overall light capture is absolutely increased, and peak PAR and edge PAR more than double (I can go from 260 to 940PAR).

So, enter the diffuser, since no one wants their aquarium to look like a multi-colored Zebra. There are two approaches - inside the reflector and outside.

I use an acrylic material which embedded with tiny lenses which turns the LED light source into a large flat emitter, using the reflector to re-capture the lost edge light, and using the flat properties of the acrylic to act as a limited direction light source (~ 60 peak beam width). This causes a drop in PAR (about half), but its dramatically flatter with less peaks, and no weird color zebra stripes

The second option is to embed a mixing lens inside the reflector. I'm still testing the Ledil Color Mixing lens inside the Angela reflector.

Now, all of these are "down" and cone reflectors. An up reflector will work, but due to the clustering of pin-point light sources suffers the same effect, _and_ is less efficient to boot as a lot of the light will strike the LED array again.

The capture reflectors used for round bulbs are simply an engineering optimization due to the constraints imposed on the physics of those light sources, not that anyone actually wants those reflectors.

 

[User1]

I use the reflectors noted above on those chips I can say without a doubt that the par does increase when using them. They also help to punch light through a 30" tall tank. I need to try the diffusers again through because I am getting a lot of shimmer although it isn't troubling at the moment. Will wait until I finish the canopy.

On flipping the LED - I wouldn't. I did, however, on my other LED builds use a thin piece of sheet metal, shiny, and made a ad-hoc reflector. That is before I switched to the LED chips from Blue Acro.

 

[Lingwendil]

Thanks @theatrus - thats exactly the sort of descriptive explanation I was hoping you would bring to the table

 

[Skydvr]

The reason reflectors make or break MH, flourescent, or any other type of bulb based lighting solution is due to the bulbs emitting in all directions.

With no reflector, you are using maybe 60° of the output. 16-17% of the light is shining down directly into your tank. The rest is being wasted if it isn’t efficiently reflected back into the tank. Properly designed reflectors can recover the majority of that light and put you closer to 95%, or better, usage.

As was stated above, LED emitters are typically in the 135° or narrower optics range with lenses that can focus the beam into just about any degree pattern you would need. Firing the LED backwards into a reflector would allow you to more finely tune the pattern of the light, but there are more cost effective ways to accomplish this that do not put the circutboard in the path of where you are trying to shine the light. You can build reflectors that would take the beam from the side and reflect it down, but you would need to focus the beam first, adding cost, complexity, and reducing the output.

It is far simpler and more cost effective to use narrower optics to control light spread, or the reflectors posted above that scatter and mix the majority of light that would have been lost to light spill.

 

[oreo54]

Just an addition:

The simple answer to your question is that above 45-50 degrees the efficiency of TIR optics drops off which is why we offer a range of 20mm reflectors to fill in the gap:
http://www.carclo-optics.com/optics-for-leds/reflector/diameter-20.0mm/

Beyond ~90 degrees bubble optics are more efficient than reflectors so our range switches to these:
http://www.carclo-optics.com/optics-for-leds/bubble/

I hope this helps.

Best regards
Bernie

Bernie Daniels • OEM Sales Manager

t: +44 (0)1753 575011
m: +44 (0)7976 268874
e: [email protected]

 

[oreo54]

Properly designed reflectors can recover the majority of that light and put you closer to 95%, or better, usage.

Marketing...at least that is my belief..

 

[Skydvr]

.....

Another idea might be a polished heat-sink for the leds, and the heat-sink be rounded to allow light to reflect back off of it and either down, around or back up to go down.

There does come the issue with cooling.....

You hit on a huge issue with polishing metal, you change the heat transfer coefficients and will affect the transfer of heat from the LED into the heatsink. Think of all those air cooled motorcycle engines who’s owners polished the rough castings of the case, jugs, and heads. They went from great running machines to engines that over heat at the mere mention of the possibility that it might be a little warm today.
LEDs do not last long without good thermal management.

Also, the LEDs have a narrow pattern that typically wouldn’t send light back towards the heatsink. Polishing the reflector would help send scattered light back to the tank, but if you have significant enough of an issue with scattering light, you have bigger issues to deal with that would result in much better gains than polishing the heat sink and possibly significantly reducing the life of your light.

 

[Njdevils1220]

I mean, reefbrites and GHL Mitras use reflectors but the LED's arent facing up.

 

[Lukas75]

I'm thinking off of the top of my head and may be off, but... Most LED fixtures dissipate heat through a heat sink on the top of the fixture and then heat rising or maybe some fans take care of the rest. If you turn the LEDs over and shine them up into a reflector the heat instead of being carried away from the chips goes into the chips and is trapped by the reflector. This would lower the life of the chip. That having been said I like your train of thought and where it is going. Maybe someone could solve the heat problem

 

[User1]

I'm thinking off of the top of my head and may be off, but... Most LED fixtures dissipate heat through a heat sink on the top of the fixture and then heat rising or maybe some fans take care of the rest. If you turn the LEDs over and shine them up into a reflector the heat instead of being carried away from the chips goes into the chips and is trapped by the reflector. This would lower the life of the chip. That having been said I like your train of thought and where it is going. Maybe someone could solve the heat problem

You can still use a heat sink to mount the LED on be it oval in design or a bar. I have a 2" wide by 54" heat sink that I mounted my 4 chips on. If I wanted to flip it over I could and it would bounce off the canopy then back down again to the tank with no loss of cooling. But as already noted it wouldn't really accomplish anything. Cooling LED's isn't really an issue I don't think although finding a DIY heat sink that is reasonable price, well, that is another story

 

[saltyfilmfolks]

If you have enough power to spare , it’s a fine idea. It’ll mainly change whatnot we in film call the “quality “
Of light. How it looks.

Mainly I think it’ll reduce hot spots. As the light will bounce around more.

It could be cool to do in a canopy if you don’t mind the extra power bill.

Fwiw , all my canopy’s are and have been lined with reflective materials.
Both with led and t5.
ROSCOE and Lee are manufacturer of these.
Order a swatch and you’ll also get a full set of gels you can use on your phone as a bonus. Selection varies from a Mylar to lightly and highly dimpled surfaces.
All are fire retardant BTW.

My though I’m doing this was, I wanT ALL the light back in the tank.

You can see the material I used in this picture attached to the top next to the light (that has diffusion)

 

[bblumberg]

I have 6 BlueAcro Mega4Z 20KBlue Pro pucks on my 150g reef (along with 4 x 80W T5s). Because I clumsily broke many of the diffusers (even after Theatrus kindly replaced a bunch of them), I have about 3 pucks with them and 3 without. I have to say that I do not see any sort of disco ball effect without the diffuser, but with them, the light is a bit softer (although I have not measured PAR). I like them a lot.