DIY COB reflectors

[nomofatum]

How are you testing these? Individually or in a grid?

I would think the best way would be one grid without reflectors vs one identical grid with reflectors, measure from same distance at multiple points, average out.

I have my LED setup as a grid of lights for even distribution. I would think these would just focus them onto a smaller area, with a little loss from hitting the reflector. With the walls being a reflector also no light will escape reaching the plants anyway and average intensity should be the same or slightly higher (due to less reflector loss.)

That is my assumption/theory. I would be curious to see the actual results.

 

[churchhaze]

Supra, do you think you'd be able to silver those plastic reflectors like this? I'm not sure how well it would take.

 

[stardustsailor]

....
Supra ...
Try to find "hammertone reflective aluminium sheet".
http://www.hellotrade.com/tailv-aluminium/hammertone-reflective-aluminium-sheet.html

(The one I've is very-very thin .Easily torned/ripped by hand! Salvaged it from an old HID weather-proof lampo fixture ...You know the ungly ,bulky black ones with the ballast on board ....)

Resin/oil based paints will be outgassing VOCs for pretty long time..
(BAD for COB arrays .
Forget any silicone sealants too ...
Siloxane fumes are BAD-BAD for COB arrays ..
Specifically ,for the silicone encapsulant .. )

A good solution would be water-based paints...
Only that they do not adhere to polymers that easy ...
Wrap the 2-liter soda piece with some of that sheet ...
Leave some 'ears' so to be attached at 2 or 4 of Vero29 screws.

If I'll ever go the " reflector - way " ,I will probably prefer the good ol' stuff ..





(it seems that is doing a pretty fine job ,confining/ restricting the light into a rectangle shaped emission pattern ,while via dispersion ,the light seems to be much more evenly distributed,power-wise . )

Cheers.

 

[salmonetin]

...bro SDS i think i saw lamines (reflective aluminium very similars) in leroy merlin on the kitchen zone or extractors of airs zone...

saludos

 

[stardustsailor]

...bro SDS i think i saw lamines (reflective aluminium very similars) in leroy merlin on the kitchen zone or extractors of airs zone...

saludos

Seriously ?
I've to check upon that ...
Hmm...If so ,then DIY reflectors for COBs ,are not going to be so tricky,as I 've previously thought so ..
Thanx ,brother Salmo...

Cheers.

 

[stardustsailor]

Some useful info regarding Supra's fine project ..

Led optics :
http://rl.omslighting.com/data/images/ledacademy/pdf/lesson2.pdf

Light measuring and more ... :
http://www.dfisica.ubi.pt/~hgil/Fotometria/HandBook/Light-Measurement.2.pdf

 

[SupraSPL]

A silver mirror finish is also white, and it reflects more than a flat white paint. If it wasn't white, mirrors would filter certain wavelengths more than others. Why don't they make mirrors out of polished white paint? Flat white might reflect "better" if better to you means dispersing the light more evenly. (and what's so bad about aluminum? looks the best at blocking UV-B!)

Yesterday I asked my mom what she wanted for Christmas. She had skin cancer years ago and showed me a sunscreen her dermatologist had recommended. I looked it up and it is made with 6% titanium dioxide. What a coincidence, it does block UVA and UVB physically rather than chemically.

Why are some metals "shiny"? It goes a bit beyond my understanding. Apparently they absorb and re-emit light. In the case of copper and gold, when thet re-emit the light it is preferentially in the yellow/red spectrum. Whereas silvery metal re-emit the light almost equally in all spectra.

So polished surfaces reflect about the same amount of light as flat white except a clear image is not formed from the flat white surface because of the diffusion. Another problem with mirrors is the the light has to pass through the layer of glass twice, which gives the advantage to polished aluminum or flat white. What polished surfaces are great for is focusing light to project a long distance.

 

[Tazbud]

Thanks Supra, another great theme. Iv'e been thinking about reflectors for my low current cobs, afterall the angle and 'wasted light' patterns are similar, regardless of current draw?

I like SDS's idea, does it really matter about cobs inner reflection.. towards the centre of the grow.. in a larger fixture with multiple cobs if the side (ie 'wasted' light at the edge of a fixture on to the walls of a cabinet) lighting is reflected then all light is used? (Iv'e probably managed to sound confused )

 

[stardustsailor]

. What polished surfaces are great for is focusing light to project a long distance.

Depends ...
Not these ones :
https://www.google.gr/search?q=hammertone aluminium sheet&source=lnms&tbm=isch&sa=X&ei=XlyTVJnsEMPgOL-0gfAG&ved=0CAgQ_AUoAQ&biw=1280&bih=929

Some notes:
Silver is a bad idea ...Prone to sulfurization...Eventually it will become "smokey" or go very dark .. ...
Specially at urban environments ....Or near volcanos ... ....

Metals are shinny because they reflect light as 'image' ..
(Specular reflection ) ...
' Pentelikon ' marble (The Parthenon at Athen's Acropole is made of that ) does reflect light at >95% .
Thery say that it evens glows slightly at night ... ( a fade bluish-greenish light )
Still it does not reflect the light angular ,but with >95% diffusion also ....

Which is best for plants ?
Proven to be the diffusion way ...
So ...
Ideally ,a reflector for horticultural use will have those characteristics :
Light diffused reflection: 100%
Light absorption/absorptance : 0%


Cheers.

 

[stardustsailor]

Thanks Supra, another great theme. Iv'e been thinking about reflectors for my low current cobs, afterall the angle and 'wasted light' patterns are similar, regardless of current draw?

I like SDS's idea, does it really matter about cobs inner reflection.. towards the centre of the grow.. in a larger fixture with multiple cobs if the side (ie 'wasted' light at the edge of a fixture on to the walls of a cabinet) lighting is reflected then all light is used? (Iv'e probably managed to sound confused )

And confusing ,at the same time ...
Yeap ...

 

[Tazbud]

Lol. OK. I'll watch, I'm thinking of hood style over multiple lights V single reflectors on individual cobs... but it's me > wasted.

 

[stardustsailor]

Lol. OK. I'll watch, I'm thinking of hood style over multiple lights V single reflectors on individual cobs... but it's me > wasted.

Let us not to forget some basic things ...
1)
COB arrays are made for a) replacing HIDS (i.e high or low bays )
b ) Replacing high power halogen (i.e automobiles , high-bays ,and rail spot lights ...)

2) Most available conical shaped COB/array / array holder reflectors are designed & made with "high power rail spot lights ' in mind ...
Even the standard density arrays like the cxa3070 series or the Vero29 series ,still emit lots of light from a relatively small
surface ..

The obvious way is going multiple ( 6-12 units / m^2 ) arrays ,low driven ,each one with it's own reflector ...
way expensive ....
If you want a good job done ,a project like that requires plenty of those colourful, shitty ,dirty & smelly ,cotton -reinforced
bank notes ...
Otherwise ,you will have to cut down cost ,from other parts ,by selecting lower quality parts or leave some things out of the built ...
Nope ..
Not a good plan ,from my POV .

L.E.D cob tech offers more than 50.000 H of service life ,still above of 90% of LM (Lumen Maintenance ),if
fixtures are designed correctly , & COBs are driven and cooled as best as possible ..
(If Tc never exceeds 55°C ,for example ...Search a tad at the web,and you might find a Cree report about that ... )
But forget that " made to operate with Case temperature :70-80 or even 105 C ...."

Cobs are ment to last for at least 7-15 years ,3x grow cycles per year ,1400h average per grow cycle ) ..

So .Good ,but way expensive (for the time being , at least ..)

Cheers,bro.

 

[Tazbud]

Thanks man and I always learn a lot (relatively) from your posts (after a couple of reads.. lol, my banknotes are plastic..)
And i'm not sure how relevant to Supras thread other than to my personal benefits , a square and long grow space.

Sorry you are right, very basic i suspect, $ V efficiency on the cobs but reflectors, in short (and swayed more towards your design SDS), using what I was considering for my 4 cob light bar (and square DIY reflectors) as an example is this.

Is one design really much more efficient than another regardless of current drawn:


It's not really intuitive to think that there would be any difference except light further into the centre of a large reflector has further to travel (before being reflected). Individual reflectors concentrate intensity = more from each cob? a more even light spread towards the centre.

 

[churchhaze]

Wall mirrors silver the back of a piece of glass and cover the other side with cardboard or something. Mirror backing material.

I'm pretty sure that mirrors used in precision optics applications generally use the silver side out, so light never passes through glass.

But like SDS was saying, it's probably a bad idea. just touching it with your fingers will cause it to turn gray over a relatively short period (months)...

But I have a dirty trick to clean silver... Use a pencil eraser. You'd be surprised how well that gets the tarnish off.

Another problem with mirrors is the the light has to pass through the layer of glass twice, which gives the advantage to polished aluminum or flat white. What polished surfaces are great for is focusing light to project a long distance.

 

[stardustsailor]

But I have a dirty trick to clean silver... Use a pencil eraser. You'd be surprised how well that gets the tarnish off.

....
Well ,some might have objections to that practice ...


......As a general matter we find it hard to be really at home with things that shine and glitter. The
Westerner uses silver and steel and nickel tableware, and polishes it to a fine brilliance, but we
object to the practice. While we do sometimes indeed use silver for teakettles, decanters, or sake
cups, we prefer not to polish it. On the contrary, we begin to enjoy it only when the luster has
worn off, when it has begun to take on a dark, smoky patina. Almost every householder has
had to scold an insensitive maid who has polished away the tarnish so patiently waited for.....

" In Praise of Shadows "
Junichiro Tanizaki.
http://dcrit.sva.edu/wp-content/uploads/2010/10/In-Praise-of-Shadows-Junichiro-Tanizaki.pdf
http://dcrit.sva.edu/wp-content/uploads/2010/10/In-Praise-of-Shadows-Junichiro-Tanizaki.pdf

Cheers.

 

[SupraSPL]

It does not take long if you use a lot of garlic and onion. I like them polished + patina. You can polish them in about 15 seconds with a bit of baking soda.

 

[SupraSPL]

So I found a can of the 20 titanium dioxide at Walmart (Rustoleum 2X satin blossom white). Unfortunately it has the same chunky texture as the other flat white with 15% TiO2. You can see other complaints about that on Amazon, the satin is not satin at all LOL. Anyway, the 20% TiO2 white did slightly outperform the 15% TiO2. But the 10% TiO2 "high heat" white outperformed them significantly.

That does not the 20% TiO2 is useless though. Great for reflection, just not for reflectors of this type. I sprayed it inside my cloning box, which is powered by only 1W, so the flat white helps spread the light around much better.

Ironically, the very first paint I tried works the best so far. I do have one more I can try, the Rustoleum satin white "smooth protective enamel" (7791) with 10% TiO2 and 5% calcined aluminum silicate. Maybe it will be slightly whiter than the heat paint because the heat paint does have a very slight warmth to it. You can even see it on the wall when I add the reflector, the light becomes very slightly warmer.

 

[SupraSPL]

Regarding VOCs, there is some good news. I have noticed that the flatter whites dry much faster and give off much less aromatic fumes than the semi gloss and gloss paints. Before installing near the COBs, I will shine a 250W heat lamp at the reflector for awhile to drive off as much of the volatiles as possible before bringing it inside. Any other gasses that make their way out will soon end up on the carbon filter. So I have no worries about the reflector paint damaging the COBs.

As far as the silicon goes, I don't have to use it because the kapton works excellently. But if I were to use the silicon I would dry it thoroughly under a fan and then with heat to get rid of the majority of the fumes. I don't want to be breathing any of that stuff anyway. When I was a kid I made a vaporizer out of a piece of glass and a plastic bottle top, siliconed to the glass. I warmed it up on my halogen lamp and took the first hit before the silicon was even dried You should have seen my face, that was the worst silicon chemical horror you can imagine I will never forget that!

 

[FranJan]

......took the first hit before the silicon was even dried You should have seen my face, that was the worst silicon chemical horror you can imagine I will never forget that!

Brilliant "Stoopra" , but maybe that gave you your mutant super smarts? Pardon me while I go lick some caulk and write an opera LOL.

 

[stardustsailor]

Well..
All I wanted was some peanuts and almonds to make some company in the bourbon ,
inside my stomach ...
General Blanton's spirit felt quite lonely ,in there ..
Anyway ..
I needed a bowl for my peanuts & almonds ..
From those the small inox ones ...
That kind ...
https://www.google.gr/search?q=inox nuts bowl&biw=1280&bih=929&source=lnms&tbm=isch&sa=X&ei=4nWUVJTlFcWtPJC4gcgG&ved=0CAYQ_AUoAQ

( or these .. for the reflector-job ...

https://www.google.gr/search?q=small aluminium bowls cups&tbm=isch&tbo=u&source=univ&sa=X&ei=1HSUVJDkE4KsOoPOgcgB&ved=0CC0QsAQ&biw=1280&bih=929#tbm=isch&q=aluminium cake forms )


You can find them made of Alum ,too ..
Probably there going to be Teflon-coated inside ,cause they serve as brownies cake cups ..
Make a hole in the midlle of the base ..
About 3-5 mm ..
Place a bolt screw 1.5 -2 cm long ...
Head inside the cap ..
Tighten with a nut ...
Place on a hand drill ...
Take sand-papers 300-500-1000-2500 grit ..
Some fine oil ...
Spin the cup ..
Low to average speed ..
Wear protective gloves and dust-mask / eye protection ...
Make a mirror -polish ...Inside ..
Then ...
Make an 30 mm opening for the LES ...
Holes for screw attachments ...

Ready ...
Shinny Inox or Aluminium D.I.Y reflectors ,for COB arrays ...