Self-made LED panel general discussion

English is good and I'm on board with the topic. For those that know me, I'm a keen bean on building my own panels. Just ordered some multichip pcbs looking at making a grouped version for side lighting.

Thank you

I've been looking for info on white LEDs and I've come up with some conclusions. Some people say that it's better to use whites instead of reds or blues because whites have better efficiency. This does not appear to be true. There is something very confusing when comparing LED chips, especially when doing it in the perspective to build the best grow light: white LEDs have more lumens per watt than reds and blues. The problem is that the lumen is not a good unit to compare lights when the colors are different because it is a unit measuring the intensity of light as the human eye can see it.
So I think that looking at the radiant flux is much more relevant as it is closer to the actual amount of photons that are emitted by the LEDs. And guess what I found out... When comparing radiant flux of different LED colors, the white LEDs are not more efficient than the blue ones or the red ones. Most manufacturers don't provide the radiant flux of their white LEDs, so I had to do a bit of math to figure it out when only having the luminous flux (lumens) available. For the Osram Oslon SSL Pure white LED, for a luminous flux of 119 lumens, I found a radiant flux of about 433mW (at 350mA). The LED has a forward voltage of 3.2v which means that the radiant efficacy is around 387mW/W. The Oslon SSL Hyper Red (660nm, obviously from the same manufacturer) is rated for 386mW/W and the Oslon SSL Deep Blue (450nm) is rated for 460mW/W.
This has led me to believe that white LEDs are not more efficient than red or blue LEDs. In fact the most efficient LEDs are the blue ones which is no big surprise as the chemical used in most modern LEDs seem to emit blue light (I am no expert in that domain though). Unfortunately, the plants do not have use for large amounts of blue lights so efficiency alone doesn't mean much.

In conclusion to this short post, I would say that in my opinion, nothing really justifies the use of white LEDs instead of blue or reds; aside from covering a larger spectrum (which no one really has really proven that it is useful) they seem to have some of the drawbacks of HID lights (emitting light that cannot be used by plants) and not take full profit of the capability of LEDs to emit in very specific wavelengths.

As I am expert in none of the above subjects and only used basic logic to come to these conclusions, I'd be happy to be criticized by better advised individuals

Haha your findings I would agree with. It's not about lumens but par. Par is what plants eat to live on. The rest is just for us to take a better look

I think that PAR is watts per square meter of irradiance within the 400nm-700nm range so comparing radiant flux (watts) and comparing PAR is basically the same thing. In both cases, it is definitely very different from lumens.

Good info patrik...........+rep......I see many growers/manufacturers adding cool/warm white leds now, even full white, who knows what's the right spectrum anymore. It's gonna take some experimental grows(that are being done here/other forums) to show us what truly works IMO....

Experimenting surely is the best way to compare; there might always be a gap between theory and practice. But so far the best results I've seen - pure efficiency wise - have been made by "red & blue" lights. Well, anyway I do not consider that as a solid proof because most of the LED grow lights out there are "red & blue" and thus, with more people using them it is more likely to find the best results. This is why I still keep an eye on grows made with white LEDs, it is not unlikely that a good surprise could happen.

Well i'm doing I test with a panel you may know, it will be started as soon as my friend drops off his "freebies" from Attitude that he doesn't want......031.jpg034.jpg037.jpg036.jpg035.jpg026.jpg ha .......i'm quite fond of this little panel.......the show will start soon

FROM KNNA THREAD, SOMETHING IMPORTANT ABOUT THE PHOTONS

Photosynthesis is tightly linked with total amount of photons absorbed. This concept is the base of all, and it should be clear for any grower. So im going to analyze it deeper:

-Amount of photons. Not of watts, or lm. Plants use photons, so the number of photons is the essential figure to consider. The more the photons which reach the plant, the better (up to a limit).

Its important to note that same energy (for example 1 watt) of blue (450nm) have 33% less photons than of red ones (670nm) (450/670=0.67 : as noted before, energy carried by a photon is inversely proportional to its wl) if we take the amount of red photons as base. If we take the amount of blue photons as reference, then 1 watt of red ones carries 49%, near half, more photons (670/450=149). So very often, producing as more red photons possible is the most effective way of using artificial light for growing plants (if the efficiency of producing 1 watt of each are similar).