Strip Light Fixtures and Distance/Light Burn

[Digger Leveler]

Hello,
Am I wrong to assume that the standard LED strips are less intense than COB's? My sense is that the photons diffuse more quickly with these, with distance.

If so then one can place these closer to the canopy?
In addition it would mean that COB's benefit from a higher degree of penetration vs. strips?
Strips seem to offer better coverage, if laid out well.

Is this all true or just my fancy?


Part of why I ask is because I constructed a 3-COB fixture using Vero29-C's (69V/1.5amps). I then retrofitted this with four 2' Bridgelux EB strips, two on either side of the COBs. Strips and COB's are on separate drivers and are dimmable.

If in spacing the fixture higher above the canopy due to the COB's, am I wasting energy on the supplemental strip lighting?

Thanks.

[Freeeg0]

discrepancy in intensity could be an issue....I would add another COB then dim that channel to comply with the strips...
also an option to change reflector to a wider angle in order to coordinate intensities.

[LivingLight]

I think you are right. Cobs and strips should not be setup at the same distance of the canopy, unless the strip is really overpowered. But it's not supposed to be a big problem
Also, your 3 cobs are really close from each other and the geometry of your fixture doesn't seems to be optimal to me. you are creating a hot point with the cobs, you should better make a sort of triangle with it.

[unkle_psycho]

Currently I'musingstrips as side lighting, feeding them 12.5w per foot. The strips have been about 1-2cm from leaves for close to two 12h periods, and I cant see any damage. Plants are mature.

[Digger Leveler]

Thanks all.

Regarding COBs, what is a better distance on spacing?

I would assume that that would also be affected by their Voltage rating as well as the driven amperage. I used Vero C's at 1.05amps.


At this point I wish I had only used EB strips. But the fixture started out as a finished COB project- the retrofit came as a fun afterthought. The strips come out way cheaper (1" x 24" heatsink = $4+shipping) and seem to be as good or better. I do like having an experience with COBs though.

Is there a thorough article on this site regarding COBs vs. Strips? I'd like to see one.

[unkle_psycho]

You can do some exercises on spacing by checking your cobs spec sheet to see the lens angle on your cobs. Then you can draw your imagined spacing on a large sheet or cardboard, and draw the beams coming from your cobs. You can then calculate what distance the cob beams intersect at.

Last summer I was reading about leds, and didn't bump into strips yet. Lucky I moved the project to this spring, and the strips were already popular. I guess next year there will be lots of aluminium pcbs, and a whole new range of products filling the gaps from these 0.3w mid power leds to more powerful cobs. 1w, 3w, white diodes and a whole range of new horticulture products. This stuff is going to move fast for some time now.

Probably drivers will be the part that ages slowest. I got 10 75w drivers, so in the coming years I'll be in a position to dabble around and try a few strips of this or that.

Certainly the most important development already happened in the cob era - you can now grow good dank with leds.

[Digger Leveler]

In response to Unkle Psycho:

You mentioned researching the lens angle on the COBs I'm using. Then you mentioned to:

"do some exercises on spacing by checking your cobs spec sheet to see the lens angle on your cobs. Then you can draw your imagined spacing on a large sheet or cardboard, and draw the beams coming from your cobs. You can then calculate what distance the cob beams intersect at."

Really good idea. And helpful.


The Bridgelux Vero 29's are at 120degrees as far as the beam is concerned.

My initial internet trigonometry for cheaters, came out to a spread of over 62" at a distance of 18". A COB spacing of 31"?

That seemed weird so I took a better look at the Bridgelux data sheet. Seems to show a Light Intensity loss after 60degrees. Therefore an Isosceles triangle is no good. Need to go with an Equilateral one?

Looks more complicated than that, but assuming that, one needs apx. 10" spacing at 18" from canopy and 14" COB spacing at 24" distance. These would leave little overlap. I would think some overlap is better than none. Also the greater the distance the less intense the photons.

10-12" spacing seems good to me. Makes me think re-purposing the fixture into two separate ones, might be something to do down the road.

[unkle_psycho]

I was trying to imagine the perfect light for salads and microgreens, and it seemed to me no one really had a fact based approach on how high they placed their light.
This is where I got the idea for drawing out the beams. I was looking at getting the lights perhaps 2cm away, and what kind of spacing I should aim for. After that I talked with engineers from some light companies and they were all asking me to send them my documentation, and the alibaba manufacturers seemed to want to start building products from that base before I even test the idea.... So I started thinking I might be on to something...

Later when I was building from strips, I used the same logic to think about strip placement and distance to canopy