Some help with DIY Cobs, reflector and lenses

P

PepsCL

New Member
Greetings folks

I got this DIY Cob grow light from a guy who sells them pretty cheap. 200w, 4x50w COB, a big ass heat sink and 2 PC fans.
You can get the picture of its size based on the images. Quite powerfull for the price, but I think it need some improvement. After some research, I read that this naked chips have a beam angle of 180°, and are prone to environmental damage since they have no protection. The optimal solution would be good quality lenses, but I'm short on money and the chips are way too close to each other.

Then I came to think about building some kind of reflector using a casing covered in a mylar reflective film that I have. Manufacturer says it reflects around 90% of the beam. The goal here is to raise the PPDF (Photosynthetic Photon Flux Density) on a budget. I have access to a laser cutter and some basic knowledge in design software, so I can use MDF and PMMA acurrately enough. May be something like this:



You thing is worth the shot? Can I expect better performance?
 
Kretzlord

Kretzlord

Active Member
Those are the same cobs i vegged with, though with different heatsinks. For a 3x3 area it was nice and strong. But I will suggest directly venting them with some flex duct cause they get hot hot hot. As far as reflectors, you should be able to diy something with metal shears and metal flashing.
 
P

PepsCL

New Member
Kretzlord said:
Those are the same cobs i vegged with, though with different heatsinks. For a 3x3 area it was nice and strong. But I will suggest directly venting them with some flex duct cause they get hot hot hot. As far as reflectors, you should be able to diy something with metal shears and metal flashing.
Click to expand...
Thanks for the reply. It heats up to around 50°C at touch, but irradiates much less heat. That's how your average CPU heat sink works, or the one you find in a standard HPS light ballast. Sure it feels really hot at touch, but most materials have no issues with that temperature. Still, this dude used regular silicone and it melts a bit, so I'm gettin some heat resistant glue to fix that.

At what distance did you set your cobs? Dude told me he puts them as close as 10cm without lightburns, that's why I doubted its effectiveness since it has no lense nor reflector.
 
Kretzlord

Kretzlord

Active Member
I had mine fairly high up, but my current build is nearly touching the top of my ladies. The radiant heat isn't the issue so much as the convection heat in the air but as long as you have sufficient exhaust you're good. You can use red rtv/silicone from an auto parts store for high temp applications too.

You can find the cobs on wish to have a replacement ready on the cheap, that's where I got mine
 
wietefras

wietefras

Well-Known Member
All you get with optics is that you can (must) hang the light higher to obtain the same uniformity as without optics. In return you lose light on the optics and on some extra on the walls (more of the wall is lit up). Tests in 4'x4' tents have shown that you lose 12% of all the light with lenses and 15% with reflectors.

So unless you really want to hang your light higher than before, don't use optics.
 
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