Bars vs Boards

An admitted layman's understanding:

The more diodes in play - provided they are appropriately spread - the greater potential penetration. Point-source intensity does not equal greater penetration (that's an HID hangover that can't die soon enough). This makes strips/bars the most practical choice, as you can generally get that spread at a lower cost; however, if you do lay out the cash for wall-to-wall boards, that really should provide the greatest penetration.

Basically, I agree with both Wietefras and Prawn, despite the fact that they disagree with each other. Always entertaining when they start it up though!

My main issue with him is that he is never honest in his debates.

For example, here is what a High Light board looks like to scale in his 24" x 24" room. The High Light measures 16.3" x 8"



Here is what two High Light boards look like to scale
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And here is the light output of the strips


There is no perfect light spread with strips. The red circles represent hotspots where the light is reflected very close to the source. The blue lines equate to roughly the elliptical light output from a strip. It is this way due to not only its shape, but the fact strip LEDs are placed very close together.

Here is a 2" F-Series strip. Note how closely the LEDs are placed. This forms a strong, thin light source that emits in the shape above.


I know all this for two reasons. Firstly, I have measured strips with IES files using Dialux. Secondly, I have grown with both boards and strips.

Here is my old strip build.


Here are the frames. I did not use double-row F-Series for this build because I got better light spread using two 24V single strips wired in series to run off a 48V driver. Also, these strips have their LEDs space further apart than the ones above. Note the spacing – it is similar to the spacing of the LEDs on a High Light board.


I've built loads of strips. Now I build boards.

I'm not so sure about the subject of penetration. Maybe examples using dialux may present a clearer picture. If we were to produce a par map with a product using 4 boards mounted ~36"/90cm above. And then raised that 4 board product another 12"/30cm, and measured out another map. What fall or drop off in average readings would we see?

Now what if we took the same driver/wattage and used double the boards. How high would we have to mount it, to reach similar mapped average as in the first case above that was at 36"/90cm?
And if we then raised this product up 12"/30cm, what would the average result be from mapping?

So is penetration an important consideration? I get all the examples showing uniformity of spread using boards, bars and lots of boards or bars.
What about light intensity fall off? I'm averse to use or mention the term, "inverse square law" for fear of triggering anyone.

There must be greater fall off in intensity with the second product that has more even spread of light. It might produce a more even spread than the 4 board example. But by virtue of design has to be hung lower to match the intial averages of the 4 board light. Am I wrong? Average values?

Think about it. Is penetration important? Do you grow trees, shrubs, or scrog. Or little lollipop clones. "Ass-uming" intensity drop off will be greater under the extra board example running same wattage. Or does it not count because both fixtures might both be producing the same quantity of photons per second? Photon rain. Cognitive dissonance.

Humple said:

if you do lay out the cash for wall-to-wall boards, that really should provide the greatest penetration.

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But how would that be different from spending half and going for wall-to-wall strips? You get the same number of diodes and they would still be spread better with strips. Even though at this level we are arguing such small benefits they would be immeasurable.

Humple said:

An admitted layman's understanding:

The more diodes in play - provided they are appropriately spread - the greater potential penetration. Point-source intensity does not equal greater penetration (that's an HID hangover that can't die soon enough). This makes strips/bars the most practical choice, as you can generally get that spread at a lower cost; however, if you do lay out the cash for wall-to-wall boards, that really should provide the greatest penetration.

Basically, I agree with both Wietefras and Prawn, despite the fact that they disagree with each other. Always entertaining when they start it up though!

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I used to love the colourful HID intensity charts that you'd find in older grow books. Cone of light.

end_of_the_tunnel said:

Maybe examples using dialux may present a clearer picture

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Dialux shows nothing about penetration. In fact the charts are so poor I wonder what use they are at all for this use case.


The point is though that 8 strips would provide a better spread than 4 boards and would produce adequate uniformity at half the height the boards would need..

So is penetration an important consideration? I get all the examples showing uniformity of spread using boards, bars and lots of boards or bars.
What about light intensity fall off? I'm averse to use or mention the term, "inverse square law" for fear of triggering anyone.

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Indeed inverse square law does not apply here. You need to look at Leaf Area Index (LAI). The leafs will take away the light quite rapidly if the canopy is full. Although light coming from all angles will slip under the leaves easier of course.

If no plant canopy was there then ïnverse square law" woul dstill not aply. After you have raised the light high enough to get uniformity, then from that height upwards you only have wall losses to deal with.

Think about it. Is penetration important? Do you grow trees, shrubs, or scrog. Or little lollipop clones. "Ass-uming" intensity drop off will be greater under the extra board example running same wattage. Or does it not count because both fixtures might both be producing the same quantity of photons per second? Photon rain. Cognitive dissonance.

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Penetration is not really the issue no. Wall losses are. When you hang the light higher you will lose more photons on the walls. So the light might produce the same amount of photons, in a small tent a fixture hanging at 20" will put say 20% less of those on the plants than one at 10" would.

That's the main reason why spreading the light sources is important. In the smaller grow spaces like we are talking about here though. If you grow in a football stadium then you can hang the light meters in the air and it wouldn't get near a wall.

Prawn Connery said:

My main issue with him is that he is never honest in his debates.

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I am. You have difficulty understanding what I write, but ok

For example, here is what a High Light board looks like to scale in his 24" x 24" room. The High Light measures 16.3" x 8"

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I looked at more respectable products. Indeed I did not incorporate all kinds of boards from less reputable cloners and other hobby stuff.

Even so, from your drawing it's still abundantly clear that splitting that board in two strips would provide much better spread.

There is no perfect light spread with strips. The red circles represent hotspots where the light is reflected very close to the source.

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That's just nonsense. You don't get hotspots from gaps

And your light distribution as an ellipse is nonsense too. Each led spreads it's light in a circle. A row of circles does not create an ellipse. You are accounting for reflection losses, but that's not the point

end_of_the_tunnel said:

What about light intensity fall off? I'm averse to use or mention the term, "inverse square law" for fear of triggering anyone.

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Inverse square is for a single point of light. Place many points of light close to each other and they overlap, forming a singular density of photons that does not drop off until the photons hit something. If photons are not being absorbed, they continue their path. So the more photons you have at different angles, the more photons will penetrate a mottled canopy. The trick is, getting those photons to penetrate without supplying too many to the top of the canopy and burning it.

At risk of turning this into another tedious back-and-forth . . .

wietefras said:

Dialux shows nothing about penetration. In fact the charts are so poor I wonder what use they are at all for this use case.

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You don't know anything about Dialux.

If you know the angle of light emission (120 degrees) and you know the source of light, you can triangulate between height and width to know how high the source needs to be before it starts to hit a wall. If light doesn't hit a wall, it hits a plant. If it does hit a wall, it gets reflected back at the same angle with some losses depending on reflectivity. Tents and white-painted walls are typically 70-80% reflective.

All of these variables can be factored into Dialux.

wietefras said:

I am. You have difficulty understanding what I write, but ok

I looked at more respectable products. Indeed I did not incorporate all kinds of boards from less reputable cloners and other hobby stuff

That's just nonsense. You don't get hotspots from gaps

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You get hotspots when light from the main source – the strip – overlaps with light that is reflected off the wall. The strip is elongated, so light all along the line is shining back towards the reflected wall, where light that is further up the line is being reflected. This overlap creates a hotspot – which is something else you can see in Dialux.

Please, don't be ignorant – go and learn Dialux.

It is science: https://www.dialux.com/en-GB/

There is one in German if you prefer: https://www.dialux.com/de-DE/

wietefras said:

But how would that be different from spending half and going for wall-to-wall strips? You get the same number of diodes and they would still be spread better with strips. Even though at this level we are arguing such small benefits they would be immeasurable.

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I don't disagree, but the wiring and sinking would be a pain in the ass. Whatever floats your boat, really.

wietefras said:

I looked at more respectable products. Indeed I did not incorporate all kinds of boards from less reputable cloners and other hobby stuff.

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Yes, and for my last post to you, while I know ^ this is intended to be an insult to the board I designed, even a HLG Quantum board is much bigger than your depiction.

A Quantum Board is 2/3 the size of a High Light board and measures 11.25" x 6.8". It is the red square and to scale.

Prawn Connery said:

You don't know anything about Dialux.

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I saw the horrible charts you produced with it. It's not even symmetric for a simple single light in a square area.

If you know the angle of light emission (120 degrees) and you know the source of light, you can triangulate between height ...

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Yes I wrote my own simulation software with much better visualisation and it can account for reflectivity of the walls and even measuring angles of a proposed sensor.

You get hotspots when light from the main source – the strip – overlaps with light that is reflected off the wall.

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No you do not. if Dialux shows you that then throw that garbage out for sure. There is a bug.

Again, this should be really easy to understand. Put one led 1 cm away from a 70% reflective wall. Now compare this to two leds hanging 2 cm away from each other.

These are in essence the same thing, since the wall simply reflects the led 1cm deep into the "mirror". However the "mirror" only reflects back 70% of that light, so there would be .... LESS light in the case of a reflective wall in between.

That's why you see LESS light next to the walls all over the tent.

Just try to understand things before you come with these tedious arguments of yours. It's like when you joined this forum stating Ï don;t know anything about LED so be gentle" and one week later you were telling people what to do. You lack a filter to understand that you first need to learn to understand things before you yell things out.

Prawn Connery said:

View attachment 4609921

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They are large. Saw mention on vendor site that they can be run sinkless up to 70W per board, in tropical summer zones? Lot of Nichia diodes and thick copper layer. Seems quality.

can we get a Teknik in here? oh wait...

ive got no idea who's right but feel a 3rd nerd will settle it pahaha

lukio said:

can we get a Teknik in here? oh wait...

ive got no idea who's right but feel a 3rd nerd will settle it pahaha

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I appreciate all poster input here. Just wish feelings did not get in way of discussion or explaining. Think everyone can better explain when its not personal or snipey. Just not as much fun, haha.

end_of_the_tunnel said:

I appreciate all poster input here. Just wish feelings did not get in way of discussion or explaining. Think everyone can better explain when its not personal or snipey. Just not as much fun, haha.

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im wayyyyyyyy too guilty to weigh in on that

end_of_the_tunnel said:

Think everyone can better explain when its not personal or snipey. Just not as much fun, haha.

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It also helps not to have a vested interested one way or the other.

Humple said:

I don't disagree, but the wiring and sinking would be a pain in the ass. Whatever floats your boat, really.

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Maybe that opens up an potential avenue for some enterprising individual to come up with a cheap sheetmetal heatsink and busbar combination? Thing is, choice of strip is pretty wide, but people could come up with barebone configurations for use. A person with a cnc router could drill screw holes to customer/strip spec, and supply low resistance busbar to suit.

lukio said:

im wayyyyyyyy too guilty to weigh in on that

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Miss all the pics your buddy used to post. Enjoyed his threads and grows. I missed out on early history here so don't have strong feelings.