DIY COB reflectors

[Doer]

Alright, so I found a cad file, picket up a rivit gun, tin snips, now I just need to find some aluminum sheet. It's been surprisingly difficult to find. I think if I scale the design to 1/2 size (based on the 14" lumenarc III mini) it would be a good match with an arctic alpine 11GT cpu cooler.

I miss drilled the SS dish I found. That's what I get for trying to do it free hand while burning midnight oil, have to go pick up another one. I didn't want to tap the heatsink again so I tried to center it around the LES and using the mounting screws for the LED to also hold the reflector.

I wonder if galvanized sheet metal would be decently reflective if painted with white paint? I need to go through this thread again.

Nah.
36 inches x 48 inches - $46.44

https://www.onlinemetals.com/merchant.cfm?pid=10564&step=4&showunits=inches&id=858&top_cat=60

 

[tightpockt]

How about just rolling cones out of aluminum sheets?

A cone laid flat is a pair concentric 1/2 circles (plus a little extra for overlap and pop rivet)
View attachment 3386560

I can get 2 of them for every 1 square foot of .032 aluminum sheet. I can get 12 square feet for a little over $40. And that gives me the 24 cones I need for under $2.00 apiece.

I will cut it into 12x6 inch blanks, and stack them. I'll drill the pop rivet holes one one side only. That way I can do final alignment and drill thru, attach pop-rivet.

Now all the holes are the same. tape the blanks together, attach paper pattern and cut all of them at once on a band saw.

I just used some left over thermal epoxy to glue the reflectors..I don't think you'd need pop rivets. Also, if cost were an issue...I got 6 from a disposable cookie sheet from the dollar store. Thicker than the aluminium from a can but thin enough to still cut with scissors.

 

[Doer]

The aluminum sheet I quoted is pebbled not smooth.

 

[UKpeanuts]

Couldn't you just buy some 0.7 or 1mm sheet and dent it lightly with a ball pien hammer. its cheap and it doesnt take long.

 

[Doer]

Couldn't you just buy some 0.7 or 1mm sheet and dent it lightly with a ball pien hammer. its cheap and it doesnt take long.

Sure. But, I can buy this.

 

[bicit]

I'm thinking this might be a bit better. I could make two reflectors from a 24x48 with little waste.

link

 

[Doer]

Yeah. I love DIY! I was also thinking of going with smooth aluminum and painted white.

We can chose what size we need. I'm making 100mm cone wide and tall. 50mm bases.

 

[bicit]

Shipping doubles the price. Need to check out some local vendors.

So I was thinking 4 of these reflectors, each equipped with a CXB3590, 4000k 70cri chips, driven at 700ma to cover a 3x3 space. ~12 Parw/square foot. A bit on the low side, but maybe similar or superior to a 315w CMH over the same space. With an aim to quality over quantity.

 

[Doer]

Origami-ness praised.

 

[UKpeanuts]

Yea Doer, I suppose you are right, I was thinking small scale.

@bicit - I have built 2 shades using those drawings, I scaled them up (cad or paint, I can't remember know) and got them printed at 1:1 scale by a printing shop in town.
I found them originally on a tropical reef forum a few years ago; strangely I looked for them a few months back and couldn't find them. Where did you find that version ?
Looking at it know, it would seem feasible to stretch out the 6.05" dimension

 

[Doer]

Well, UK, I was just checking my pebbled hood, and it does look more like it was gone over with a ball peen. All the dimples are different sizes and depths. For a large hood it make sense.

I really am thinking it might be better for a small cone reflector to be smooth white,

 

[bicit]

Yea Doer, I suppose you are right, I was thinking small scale.

I have built 2 shades using those drawings, I scaled them up (cad or paint, I can't remember know) and got them printed at 1:1 scale by a printing shop in town.
I found them originally on a tropical reef forum a few years ago; strangely I looked for them a few months back and couldn't find them. Where did you find that version ?
Looking at it know, it would seem feasible to stretch out the 6.05" dimension

I found it over in the DIY section on this forum. The lumenarc III mini, is what the production version would be called. If you notice, it also looks about the same as the sunsystem LEC reflector. I'm thinking about scaling it by 50% for use with smaller emitters. Got to tack down some aluminum first though....

 

[UKpeanuts]

Yea, I had a hard time when i was trying. Old 400W bay fittings used it, maybe a few of those on ebay? spares or repairs?

 

[UKpeanuts]

What size room are you using doer?

 

[bicit]

Apparently I'm not the only one to this of this.

 

[Doer]

What size room are you using doer?

I'll be in bedroom sized space. This light should cover 24 sq feet. Maybe 6 x 4 feet.
15wPAR a square foot.

Sunshine is more like 44wPAR, mid-afternoon max, at sea level. (100w of all radiation typical, 1300w at the equator, sun directly over head.)

But, if you were to average out the sunlight that hit the earth it is only about 15w per square foot.

http://solar.smps.us/solar-energy.html

 

[SupraSPL]

Also, I was catching up on your math earlier and I couldn't help but notice how lenses and reflectors are ultimately prone to losing light, regardless of the gain of concentrating photons. Do you see this as a reason to NOT use reflectors and lenses or do you believe, with your experience, that there is a legitimate and productive reason behind doing so?

For designs like Churchhaze, many lower powered COB close to the canopy, there is less advantage to using reflectors and even less for lenses, but maybe short reflectors could increase intensity. The opposite setup, a high powered emitter a long distance from the canopy may benefit from the sharp cutoff a lens provides versus the reflector's softer cutoff. I think you can improve the cutoff of a reflector, but it requires a larger reflector and ultimately more bounces whereas the lens gets it done in one swoop.

It makes sense that if you do not have reflective walls you may benefit most from reflectors/lenses. Even if you do have reflective walls on all sides, you still may benefit because the wall will scatter photons in all directions including upward and laterally. I am not sure how much difference adding reflectors/lenses will make to gpw, but judging by the lux meter numbers I am expecting a lot.

Church, greengenes and others have pointed out the "diffuse light" effect which should somewhat improve the spread of photons in the canopy. Going without lenses/reflectors and relying more on the walls should create more diffusion. But overall I believe lens/reflector will be even more beneficial. I have gone without lens/reflector for many runs and as I start adding a few in, the luxmeter is happier. My lights are not strictly overhead. I try to position the modules to fit the canopy and shape the canopy to the lights, so the photons are getting into the canopy from multiple angles.

 

[AquariusPanta]

For designs like Churchhaze, many lower powered COB close to the canopy, there is less advantage to using reflectors and even less for lenses, but maybe short reflectors could increase intensity. The opposite setup, a high powered emitter a long distance from the canopy may benefit from the sharp cutoff a lens provides versus the reflector's softer cutoff. I think you can improve the cutoff of a reflector, but it requires a larger reflector and ultimately more bounces whereas the lens gets it done in one swoop.

It makes sense that if you do not have reflective walls you may benefit most from reflectors/lenses. Even if you do have reflective walls on all sides, you still may benefit because the wall will scatter photons in all directions including upward and laterally. I am not sure how much difference adding reflectors/lenses will make to gpw, but judging by the lux meter numbers I am expecting a lot.

Church, greengenes and others have pointed out the "diffuse light" effect which should somewhat improve the spread of photons in the canopy. Going without lenses/reflectors and relying more on the walls should create more diffusion. But overall I believe lens/reflector will be even more beneficial. I have gone without lens/reflector for many runs and as I start adding a few in, the luxmeter is happier. My lights are not strictly overhead. I try to position the modules to fit the canopy and shape the canopy to the lights, so the photons are getting into the canopy from multiple angles.

A few photos come to mind of one of your grow operations where you had an array of CPU coolers scattered above a few plants, all angled differently.

One thing I would like to point out that stems from my experience with grow tents is that the walls of the tent aren't always flat and eventually become wrinkled. I'm not sure if this would be desirable, and whether or not this is just something that happens to the cheapo tents. I've wondered a many a times if ironing the tent would straighten the walls out, without ruining anything, including the fabric.

I've seen many results where individuals have reported the dramatic swing in photon density when equipping COBS with lenses and reflectors, and I think you were one of the first to document such numbers. By the way, how are the homemade bottle-reflectors holding up?

I don't know the average prices for reflectors and lenses off the top of my head, because I haven't looked into it yet as the market appears relatively new, but I'd like to know if the extra cost of such equipment (lenses, reflectors) justifies the desired benefits of such addons? Or are we better off just buying additional COBS in order to satisfy a general standard photon/PAR range?

 

[SupraSPL]

Yep that is the general idea and good point about the walls. Mine are panda plastic and only on 1 side of the canopy. Minimally reflective and gathers dust over time.

I am still using the bottle reflectors in the veg room with 5K CXA3590s. Walked in there today and was surprised by the growth. Best looking plants I have ever had in veg and using less power (80W), good stuff.

The 44mm 60 degree lenses can be had for $3-$5 with the lens ring, maybe $2 for just the lens. These fir Vero18 and CXA3070. The 50mm 90 degree lenses are about $5 ea and are a good fit for Vero29 and CXA3590

CXA3070 3K Z4, driven at 2.55A, 44mm 60 degree lens, messing around trying to focus the image of the COB.

 

[AquariusPanta]

Yep that is the general idea and good point about the walls. Mine are panda plastic and only on 1 side of the canopy. Minimally reflective and gathers dust over time.

I am still using the bottle reflectors in the veg room with 5K CXA3590s. Walked in there today and was surprised by the growth. Best looking plants I have ever had in veg and using less power (80W), good stuff.

The 44mm 60 degree lenses can be had for $3-$5 with the lens ring, maybe $2 for just the lens. These fir Vero18 and CXA3070. The 50mm 90 degree lenses are about $5 ea and are a good fit for Vero29 and CXA3590

CXA3070 3K Z4, driven at 2.55A, 44mm 60 degree lens, messing around trying to focus the image of the COB.
View attachment 3400536

I know where you live... neighbor...



I would be interested in trying out lenses or reflectors for my Vero 18's. 60 degrees sounds a little too intense but 90 would probably be best. I wonder how soon before the 90 degrees becomes available for the 18/3070 models..