knna

CFL's efficiency is about 50-60% of large HPSs on average. So its probable that you can replace them with 25-35% of the LED watts without loss of yield.

For unreflectorized CFLs working intracanopy, about 40% of their watts should be required.

As with the 50-60% watts respect to HIDs, it refers to top bins LEDs running at their nominal power or just a little over it.

Talking about watts of LEDs may be very misleading. HIDs are very constant of their efficiency, so we can talk about watts of them, and it works pretty well. But LED's efficiency vaies a lot. It depend of the LED model, its bin and the current at you run them.

An example.

Say you are using a Cree XR-C LED. Currently, Cree is serving bins K, M and some N. K emits 35lm typical, M2 42lm, M3 48lm and N1 54lm. All of same spectrum, meaning a N1 bin emits 54% more light per watt burned than a K bin. More than half more light is a huge difference, so you can get same light burning 100Watts of bin K than 65watts of bin N1.

Or say you are using same LED, a bin M3 for example. But on one setup you use 50 LEDs running at 1A, and in other setup you use 120LEDs running at 350mA. You get same amount of light on both, but the first one burns 130W while the second only 90W (but the second one would cost initially 2.4X more than the first!).

So watts of LEDs dont say nothing without knowing the model and bin and the current used.

Im trying to caracterize emission of most used LEDs of quality brands, so any grower using a lamp with them may know how much light its actually emitting. But its a time consuming process, as I need to take a pic of each LED working with a spectroscope, process the image to obtain its SPD and later introduce it on a spreadsheet, nm by nm.

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choader

Ahhhhh. That example makes sense to me now.

I'm considering replacing the large CFLs in my small cab but won't hijack this thread to do it.

Choader

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19toker45

hello...
have been lurking about for a while now or as i like to call it...getting a free education.
if i start naming names...i will surely leave someone out so...
thanks to all, quite a read so far...

have decided to join your led party if i may, i love a project with a happy ending.

playing with ledeng 5 watt leds (from mouser so unknown bins).
660nm red, 465nm blue and warm white.
except for the soldering (really great heat sink, needs massive soldering iron)...
a very bright experience.

trying to grow inside 5 gallon buckets, leds mounted on lid,
1 plant inside each white bucket.
leds glued to computer cpu fan/heatsinks. (cheap and very reliable)
1 bucket with 4-5W reds and 1-5W blue, 15.4 volts @ 1Amp.
1 bucket with 4-5W reds and 4-5W warm whites, 24.4 volts @ 1Amp.

last night, the red/warm white combo toasted a plant like in an oven...didn't even have time to say goodbye....
it is time to pulse(pwm) them for brightness adjustments.

brain pick time..........
Q. am designing a fixed current source for pwm...
would i design the current regulator max to be the led pulsed maximum...2 amps?
( the pwm could then pulse about 2 amps for max uE....right?)

am not sure of what the voltage will do when the current is switched off by pwm.
cannot exceed led voltage specs by too much.

the voice of experience says.....
higher than max led voltage very very bad...will not love you long time.

i stole this pdf somewhere (if from one of you...oops...sorry) and as i read,
it mentions that plants can be pulsed. since it is so easy to pwm...i like their way,
but is it right? need some forum brain trust action.

"The light utilization efficiency and relative photon requirement of photosynthesis in pulsed and continuous light from
light emitting diodes (LEDs) has been measured. First, we chacterized the photon requirement of photosynthesis
from light of LEDs that differ in spectral quality. A photon requirement of 10.3 f 0.4 was measured using light
from a 658 nm peak wavelength (22 nm half band width) LED over the range of 0-50 pmol photons m-2 s-'
in 2 kPa 0 2 in leaves of tomato (Lycopersicon esculentum Mill., cv. VF36). Because the conversion of electrical
power to photons increased with wavelength, LED lamps with peak photon output of 668 nm were most efficient
for converting electricity to photosynthetically fixed carbon. The effect of pulsed irradiation on photosynthesis was
then measured. When all of the light to make the equivalent of 50 pmol photons mp2 s-' was provided during
1.5 ps pulses of 5000 pmol photons mP2 s-' followed by 148.5 ps dark periods, photosynthesis was the same
as in continuous 50 pmol photons mP2 s-'. When the pulse light and dark periods were lengthened to 200 ps
and 19.8 ms, respectively, photosynthesis was reduced, although the averaged photon flux density was unchanged.
Under these conditions, the light pulses delivered 1017 photons mP2, which we calculate to be equivalent to the
capacitance of PS I or PS 11. Data support the theory that photons in pulses of 100 ps or shorter are absorbed and
stored in the reaction centers to be used in electron transport during the dark period. When lightldark pulses were
lengthened to 2 ms light and 198 ms dark, net photosynthesis was reduced to half of that measured in continuous
light. Pigments of the xanthophyll cycle were not affected by any of these pulsed light treatments even though
zeaxanthin formation occurred when leaves were forced to dissipate an equal amount of continuous light."
thanks to: Daniel J. Tennessen Raymond J. Bulba Thomas D. Sharkey 1994 u of wisconsin
link to whole pdf-- https://mywebspace.wisc.edu/tsharkey...ght%201995.pdf
sorry kind of long....perhaps somebody can translate......

148.5uSec/1.5uSec = 99 that should save some energy...............
but will need 100 times the number of photons for that 1.5uSec.
would not be suprised if it evens out in the end.

Q. any ideas on what frequency i should run the pwm?
according to dan, ray and tom above, it appears to matter........
(150uSec = 6666Hz ??? not sure what 150ps is and what the heck is a pmol does p equal u ???)

Q. anyone have any way to convert from led output to uE's???

i have been mistreating electrons since vacuum tubes,
so if anyone needs any help in the designing
or the killing of electronic type thingys you but have to ask.

i do go on and on.....
but a toke or two helps the juices flow,
this is not so simple a subject!!!

thanks for all your help...
19toker45

Inside every older man is a younger man,
wondering what the hell happened!!!

knna

Well, I dont think it would be hijacking the thread at all. Maybe the process of selecting how much LEDs, what type and what current to use, although its necessary to build a DIY LED lamp. But for sure that talking how to distribute LEDs along the cab, thus, how to build a LED lamps for a given cab, is plenty into the scope of this thread.

I had opened some different threads about LED lighting so we can talk separatelly the color distribution and what LEDs to use and how to use them from the pure building of the lamp. But many people prefer to have it all joined on the same thread, so I dont have any problem to discuss it in this. It just will have the disadvantage of requiring people to dig the thread when looking just for building tips, but on the other hand, all the required info for doing DIY LED lamps would be on same thread.

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knna

19toker45, welcome to the Garden!

if you want a place where to talk and share without childish behaviors, you have choosen very well This a great commutity, with many experienced growers, very well moderated. I love this forum

What are the exact dimensions of those 5gal buckets?

5W Red LEDEngin are being served on 4 flux bins, ranging from 60 to 146lm at 1A, and 3 wavelenght bins very different (620 to 650nm dominant, corresponding to peak wavelenghts from 625 to 665nm). Its almost imposible to know how much light they emit without knowing the exact bins. Actual power of these LEDs are about 2.5-3W each.

Blue and WW draws about 3.5W each. Measure its one voltage drop, instead of the full string, so we can know how much power they are actually drawing. The three bins of the WW emits about 30lm/w (bin L), 37lm/W (bin M) and 46 lm/w (bin N) at 1A. In order to get better efficiencies, running them below 1A should be advisable. 700-800mA seems a better current level for them, aswell as for reds.

Without being narrow angle LEDs, they dont emit on a wide angle. 95% of the light is emited into a 90º beam (reds) or just 80º (blue). WW ones are slighty wider and emits more light to the sides.

So very high power LEDs and focused. It would be a good idea to mount them separately from each other to avoid hot spots.


Please, more details about it. How old was the plant? How concentrated the LEDs over it? At was distance were they from the plant?

PWM is of course a choice to dimming LEDs, but in general, direct dimming, meaning using a lower current level is way more efficient, at least from a energy efficiency standpoint.

Here we need to take a second, and think this question carefully.

First off, PMW refers to a way of dimming electronic devices by switching on/off very fast. The effect on the output of the circuit depends of its topology. It may produce a reduced continous current, or switching on/off LEDs aswell.

On many commercial drivers, dimming is achieved by a PWM signal, but the output to LEDs is continous, not switched.

A true PMW driver that gives the output to LEDs switched aswell, may be carefully designed to avoid transients. The highest the frecuency used, more problematic becomes the design. When using very high switching frecuencies, with individual pulses on the nanoseconds or still shorter durations (hundred of picoseconds), not all electronic components are able to handle it. Rise and fall time responses of components used must me considered.

In general the shorter PWM pulses used are in the range of microseconds. Response time of most LEDs are of a few nanoseconds. Going shorter is impossible with standard equipment.

As reference to those not used to the metric system, those prefix are diminutives:

mili: 1/1000. or 10^-3
micro: 1/1000000 or 10^-6
nano: 1/1000000000 or 10^-9
pico: 1/1000000000000 or 10^-12

Second consideretion, that refers to the nergy efficiency of the system. A LED is always less efficient as the current level goes up. So PWM is always less efficient electrically. Thus, any photosynthetic gain from the pulsed light might should compensate the lower efficiency emitting light.

The highest the peak current used, for the shorter pulses, the lower the efficiency.

Most experiments with pulsed light on plants are performed in the range of hundred of microseconds, up to a few miliseconds.


In this sense, what matter is the averaged voltage and current over a second period.

Say you are using a 50% PMW scheme: half time on, half time off. During that time you use half the current than if you were using continous. For example, 1A on continous mode equals to 2A peak current with a 50% PWM scheme (at least, it happen with relatively long pulses, as they go shorter, raise and fall time of the components may vary the average). From a current standpoint, both ways are the same. But not if you see at voltage, because voltage required to run LEDs at 2A is higher than to run them at 1A. Thus the average power burned is going to be slighty higher over a second period on the PWM scheme (how much? check datasheet for how much higher is Vf at 2A than at 1A).

Not only that, the LED not emits double light at 2A than at 1A, but way less. So the PWM scheme burns more power and emits less light. The highest the difference between the current used (thus, the higher the PWM frecuency used), the highest the efficiency loss.

Still when using relatively long pulses, a loss of 25% of energy efficiency is pretty common. Any photosynthetic gain from pulsing might be over 25% to worth doing it.

For sure. Always take in mind that voltage-current response curve of LEDs is exponential. Little increases on voltage leads to huge increments on current. What destroy LEDs is excess current. A peak current over specs result on the breakage of the very thin gold wires inside the LEDs, that act as a fuse. Often there is a wide margin for it, as many LEDs rated for 1A may support currents over 2A, and those rated to 2A often support 3A and more, but once you are over specs, you never know when its going to fail.

Notice that the study focused on the different ways of giving light to plants, for given amount of light. Its not interested on study how efficiently is that light delivered, that is an important part of the equation on actual applications.

And notice that when used 2ms pulses, photosynthesis for equal amount of light reduced to half. Why messing with pulsing then?

Aditionally, light densities used, 50 uE/m2 are very low in actual conditions. We use densities 10X of that on our grows (and same for tomato grows).

The study used a PWM scheme 150us long (148.5 off/1.5on), a 1% PWM (1%on/99%off). As a second has 1000000 us, 1000000/150=6666 cycles per second= 6666Hz= 6.67KHz was the frecuency used.




micro=μ. But for keiboard confort, u is often used instead of μ. So a microsecond is written us instead of μs, and a microEinstein, uE instead of μE (a Einstein is a mol of photons, 6.02 *10^23 photons).

pico is 1/1000 of micro.

I have linked a thread about it on my sign. But for doing it, lm emission (way better, mW emission) must be know accurately, aswell as the spectrum. With unkown bins, its impossible to know it.


Glad to find people who likes to experiement. Sure your experience is going to be usefull for all us.

knna

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choader

Could you give some dimensions of the heatsink you are using? Any shape considerations?

Thanks.

Choader

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slowthestone

With indoor gardening in mind...is there any practical purpose to the lens/dome/case over the diode?

Are they essential to the function of the LED?

scottcanada

KNNA - can you please provide a link to the spanish forum that is mentioned? thank you

knna

Hatsinks I use are 3.4cm wide, 2.6cm thick. Perimeter of 28.4cm. So each cm of heatsink bar is 28.4cm2. Im installing about 20W of LEDs on each meter, that averages 144cm2 for each watt installed. That is enough to keep it barely warm.

But there are lots of different HS's shapes, wider and bigger. As far as it has enough surface, its good for the task. When using high power LEDs, is almost a must to use finned HS. Not required a large density of fins, but some of them are needed to obtain enough dissipating surface.

There is, but little, just for using on some cases.

Generally speaking, on indoor gardening the best way to use LEDs is distributing them along all the growing volume and using wide angle LEDs for it, working relatively close to plants.

If you want to work with LEDs but you only want to work with an overhead lamp, then you will have limited penetration. In this scenario, using lenses to achieve narrow beams makes sense in order to get increased penetration. On the other hand, this scenario will obligue to install a high density of watts on the overhead lamp, demanding a way better cooling setup. I think that if you want to work just with an overhead lamp, the best is to use a HID. So I do not advice to use any lenses, but the opposite: wider beam angles.

Lenses arnt esential at all, while they block some percentage of the light emitted. 8-20%. Most lenses blocks about 10-15% of the light. On other application (for human) they are required, but not in ours.

Of course. This is the general forum: cannabiscafe - Powered by vBulletin

Growing with LEDs subforum: Cultivo con Leds - cannabiscafe

And LED's journals: Seguimientos con Leds - cannabiscafe

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knna

I forget to link too the tutorial for building LEDs lamps. Its larger than this, as I explained too methods of mounting Cree and there is questions about drivers, etc. It has too more pics than this.

Tutorial montaje LEDs - cannabiscafe

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