Advanced LED Development Thread.

TO ALL NEWBS, PLEASE READ THE WHOLE THREAD BEFORE POSTING YOUR QUESTIONS THAT MAY HAVE ALREADY BEEN ANSWERED. thank you.


Hey folks. I have created this thread for those who are participating with experiements and development LED technology. As many of you know, I have a few threads already and have participated in many more threads about growth using LED's.

I myself am not a marijuana grower. I plan to do my experiments while growing tomatoes and eventually other vegitables that require direct sun or
intense lighting so my tests will still be viable towards this growing community.


Currently I am researching different things and planning my setup. My setup will include a total of 400 - 600 watts of LED's controlled with digital dimming and Pulse Width Modulation (PWM) which will allow for plenty of room to overdrive the led's to be able to get more light out of less LED's and making a more penetrating light.

Below is information for the newbies to LED's. I have compiled a basic list of information for people.

LED's have the potential to have a better efficency than other lighting methods like HPS. LED's can achieve the specific wavelengths in nanometers (nm) that are the plants peak absorption wavelengths for chlorophyl A + B and other plant processes. About %75 of the energy used by HID lights like HPS go directly towards heat and infared light, which is a bad guy for us growers. Wavelengths are the color of the light that is being emitted. HPS also produce lots of yellow and green light, about half of all visible light, which is what our eyes see the most of but that the plants do not absorb very much of so they are inefficient to provide for plant growth.

This link should give you a better understanding about the inefficentcy of HID lighing. Commercial Growing Analysis

There is a lot of technicality behind this and arguements on old OG threads, but for general purposes LED's dont emit radient heat, or too little for it to count, as opposed to HPS which emits lots of radient heat which can burn your plants if too close.

This is a list of peak wavelengths quoted form an old OG thread cached through google. This thread was made by Compgeek and can be found here: http://216.239.51.104/search?q=cache:IWwK_7_nqmkJ:www.overgrow.com/edge/showthread/t-721125.html

Beta-carotene 450nm 480-485nm dual peak
chlorophyll a 430nm 662nm dual peak
chlorophyll b 453nm 642nm dual peak
phycoerythrin 590nm single peak
phycocyanin 625nm single peak

670nm and 700nm for Emerson effect.
http://www.biologie.uni-hamburg.de/b-online/e24/12.htm

690nm from nasa
http://earth.esa.int/symposia/chris_proba_04/papers/19_merton.pdf

730nm
http://www.newton.dep.anl.gov/askasci/bot00/bot00582.htm

Click to expand...

Although not all of these wavelengths are neccessary for growth, they all play a role in improving growth within the plant. This is where experiments need to be done on effeciency and importance of wavelengths for how they contribute to rate of growth.

PWM controls a "blink rate" for LED's. Most LED's are to have "Instant on" with a turn on time of less than 100 nanosecond (ns), which allows for LED's to have a very high blink rate or frequency. This is very usefull because not only does it save even more energy then what will already be saved with using LED's, but it also will not take away from the plants growth. The way this works the way it does is when one of the "receptors" on the plants leaf catches a photon, the receptor take a little time to transfer that photon to the rest of the plant. So while this receptor is temporarly busy light is not needed. Though, much research will need to be done to find the right frequency rate for cannabis and all other plants, there is much research that will give a general area of what frequency to use, the rest is fine tuning.

Overdriving LED's is another great benefit. Also overdriving should go together with PWM unless you strongly know what your doing. Reason being is because LED's have their specs that tell you max voltage and max current. If you were to go over these specs you could cause the LED to overheat and eventually burn out. But when you use PWM, the LED becomes turned off for a period of time, so in that moment the LED is not creating heat. This is where the overdriving comes in. You could overdrive the LED's and still maintain decent temperatures. Overdriving allow the LED's to put out more light which means that the light will penetrate further into the canopy and you want need as many LED's as you would if you did not overdrive.

The still save money when you overdrive and use PWM as opposed to if you didn't use those at all. Study has shown that using a duty cycle of %0.5 percent is all thats needed for growing plants. The reason being that the number is so low is because there only needes to be enough light let off so one photon can reach each receptor. So that means that there only needs to be a tiny blink because each receptor can only catch one photon.

To explain more about duty cycle for all the newbs. A duty cycle is the percetage of time that it is turned on in a period. A period is the whole amount of time for the pwm to complete that blink cycle.
I.E.: If you define your period as being one second, and your duty cycle is %75 then your LED will turn on for 3/4 of a second and turn off for 1/4 of a second and then do that cycle over and over again.

There are many types of LED's out there. There are differences in color, shape, power usage, and angle at which it output the light. There are links below to different LED companies with all the different types. Some of the types are built for thermal management in mind, others for production costs in mind. But you can easily find everything you could need.

Luxeon LED's
Lumileds, the cheaper place to buy Luxeons
SunLED
Dotlight
LED Lighting Supply

These are some links to different information including resistor calculators and array wizards to help you design what you want.

Calculators:
http://www.quickar.com/bestledcalc.php
http://www.superbrightleds.com/led_info.htm
http://metku.net/index.html?sect=view&n=1&path=mods/ledcalc/index_eng
LED Array Wizard

Info:

Circuit Tutorial
Wiring LED's
http://216.239.51.104/search?q=cach...ml+site:overgrow.com&hl=en&gl=us&ct=clnk&cd=1

And now some links to other products including LED's light to replace you household incandecents.

http://www.superbrightleds.com/led_prods.htm
Kits and PWM Kits

Here are some commercial LED grow lights that you can buy and avoid the PITA of making your own.

LED Grow Lights.com
LED Grow-Master



OK, I'm done for now. I'll add more when I'm not so drunk. Have a good night folks and happy growing

Holy shit i was looking for a repost or s/t of that thread...Totaly forgot that it was in googles cache. Thanks a million DF!

DeadlyFoez said:

...
with digital dimming and Pulse Width Modulation (PWM) which will allow for plenty of room to overdrive the led's to be able to get more light out of less LED's and making a more penetrating light.
...
PWM controls a "blink rate" for LED's. Most LED's are to have "Instant on" with a turn on time of less than 100 nanosecond (ns), which allows for LED's to have a very high blink rate or frequency. This is very usefull because not only does it save even more energy then what will already be saved with using LED's, but it also will not take away from the plants growth. The way this works the way it does is when one of the "receptors" on the plants leaf catches a photon, the receptor take a little time to transfer that photon to the rest of the plant. So while this receptor is temporarly busy light is not needed. Though, much research will need to be done to find the right frequency rate for cannabis and all other plants, there is much research that will give a general area of what frequency to use, the rest is fine tuning.

Click to expand...

Can you please explain, why PWM, dimming and overdriving are so important?

If the average power used while using PWM equals linear driving power then so should the power of the emitted light be equal, right?

It's ALL fine and dandy...but I'm from the SHOW ME STATE...show me an ACOMPLISHED grower...like Hotcargo...MTF..or others that have done a LED grow and are HAPPY AND committed...and I'll be good to go...HOWEVER I've seen posts like this one...FOR YEARS...AND YEARS....AND YEARS...all I want is for someone to "PUT UP"!!!
tutt

What I'm saying is ANYONE cap post WHATEVER they want...do I know ANY of those people that say it rocks...NOPE....dont know em...AINT goin there...HOWEVER if someone with even a MODERATE amount of respect comes forward...I'll check it out...untill then....it's "ignore" mode..
tutt

Not interested in building a LED array but thanks a lot for sharing the info, that's some good stuff

http://www.uk420.com/boards/index.php?showtopic=69950
http://www.uk420.com/boards/index.php?showtopic=62193&st=0

Theres the proof for you. ALthough I think that Davids grow could have been even better if he used more wavelengths, but thats good enough to show proof. I am going to edit my first post later when I have more time to add more good info. I'm trying to make my first post the answer to almost all questions.

when they become mainstream i bieleve theyll be the new lights of the future!

The links show someone STARTING a grow...AS DO ALL THE LINKS...NO way...NO how...untill SOMEONE...hotcargo..JPL...MTF...etc does one...aint gettin ONE RED cent of my $$$$$...
tutt

The second link shows Davids first LED grow all the way to the finish. Go to the last page. His results weren't all that much to greatly boast about, but it certainly show the potential. He used a rather low wattage, but even so, he still got a good amount for what he did use. It proves the facts about it. And obviously using a higher wattage is even better.

The first link is showing his current grow and he is using more watts for this one. I'm sure results will be pleasing.

Very interesting links. I was looking into them to supplement some lighting on the side, but still keep a lower wattage MH/HPS on top for the summer months. But don't need them at the moment since my grows are tiny for the moment. But I do want to experiment with them for fun, just to see.

minimum said:

Can you please explain, why PWM, dimming and overdriving are so important?

If the average power used while using PWM equals linear driving power then so should the power of the emitted light be equal, right?

Click to expand...

It's important for a variety of reasons, not the least of which is photosynthetic efficiency. If you've read some of the threads (cached or otherwise) from Overgrow, you know that this has been an ongoing pet project of mine, although I don't currently have anything to show for it because I'm neither growing nor actively smoking. This should however establish the level of my own expertise.

The topic at hand is PWM (Pulse-width modulation) dimming/driving. Photosynthesis is not as constant a process as one might think. Each reaction center has hundreds (if not thousands) of antennae which can each receive a photon, but the reaction center can only process one photon at a time and the reactions that take place do take time to occur. Therefore, during the time that the reaction center is unable to process photons, all photons that its antennae intercept are completely wasted. Enter PWM, a way to only have the lights on when the reaction centers can accept photons, and have the lights off the rest of the time. The duty cycle (the percentage of time the LEDs are on for a given period, usually one second) is optimally less than 1%, which means you'll use less than 1% of the energy you would if you drove them at rated specifications 100% of the time.

But that isn't a really good idea, for reasons I'm going to explain. See, LEDs aren't yet as intense as HID lighting. They might produce a comparable number of photons when present in a decent quantity, but they don't have the same intensity.

Intensity is itself a tricky concept that I frequently have difficulty explaining, but I will try to explain it anyhow using a new method I have just come up with.

Consider the difference between a light rain and a pounding, pouring rain. The light rain is a analogous to an LED setup while the heavier rain is analogous to a HID system, with the raindrops being analogous to photons. If you take a picture of either rainstorm with a high-speed still camera, you will see that you have raindrops at different distances from the ground and different distances relative to one-another at any given instant. Suppose you put a grid over the photograph, a grid such that each square is the size of exactly one raindrop (just assume that all raindrops are the same size). When you examine a given row for the light rain, you will see that you won't have many raindrops on the same level as one another, with some being above or below. When you examine the heavy rain though, you will see that on many rows there are multiple raindrops at the same level. It makes sense statistically, if you have more raindrops then you should have more raindrops at each level (or each region in three-dimensional space).

So if you're still following me, I'm going to draw a little picture (in your head, though, because I don't feel like drawing right now). Imagine that in each of these hypothetical rainstorms you have a swimming pool, but each swimming pool is covered with a giant sheet of styrofoam. Inserted into the sheet of styrofoam are a bunch of funnels, packed as densely together as physically possible. But wait, each of these funnels is itself covered with a piece of styrofoam and inserted into it are even smaller funnels, each about three raindrops across in size. So in order for a raindrop to reach the pool, it needs to fall into one of the smaller funnels and then drip into a larger funnel, and then drip into the pool. There are gaps between the funnels and there is the possibility that some drops will just be wasted. But there is something else, something I didn't tell you yet: the little funnels have this peculiar behavior that will only allow one funnel in each group to pass a raindrop on to the larger funnel simultaneously, with any extra raindrops getting diverted to trickle down the outside of the funnel system and not be used. So in truth, a raindrop must be first to drop into a given group of small funnels so that it can be passed on to a larger funnel, which will then drop it into the pool. Each step in this sequence requires a finite period of time; raindrops don't roll down the sides of solid surfaces instantaneously, it can take up to a few seconds.

Now picture this Rube-Goldbergian contraption in either of our hytpothetical rainstorms. It becomes obvious that the heavier rain will fill up the pool faster just on the merit that there are more raindrops. Granted, more raindrops will get wasted than compared to the light rain, but the pool will fill faster overall.

Now suppose you've got the ability to turn the rain on and off, so that while raindrops are trickling down the small funnels and falling into the larger funnels, we aren't wasting any water. Doing this with the light rain doesn't make much sense, because the rain is so sparse that the chance that you'll get two raindrops in the same group of small funnels is negligible. Doing this with the heavy rain though makes a lot of sense, because the chances are much greater that you will get multiple raindrops falling in the same general vicinity, especially over short periods of time.

The small funnels are analagous to the antennae on each photosynthetic reaction center, and the larger funnels are analagous to the reaction centers themselves, the place where photonic energy is converted into chemical energy before being passed onto the plant's nervous system (represented by the swimming pool).

So you can see from this analogy that pulsing lower power LEDs doesn't make much sense, because they lack the raw number of photons (ie, "photon density" aka "light intensity") for it to make sense. But, if we had some way to make the LEDs produce more photons, maybe even enough photons so as to be comparable to an HID lamp for a very brief period of time (say a few millionths of a second) then it would make sense to pulse them.

Well, it turns out, there is a way to have the LED's output match the HID on a very short timescale, and that is by overdriving them in a manner far exceeding their specifications. First we need to establish the fact that an LED's drive voltage determines how much current it will consume--the higher the voltage, the more current consumed. The relationship between current consumed and light produced is different for LEDs of different chemical makeup. With that fact established, understand that we can feed the LED a higher voltage so that we can dump a huge amount of current into it, maybe 10 to 100 times its rated current, but only for a fraction of a second, and during this small period of time the LED will produce light of intensity comparable to an HID lamp.

This only violates the specifications in a sense. If an LED is rated with a power dissipation of 40 milliwatts, then you need to keep its energy consumption below 40 millijoules per second (1 watt = 1 joule per second; 1 milliwatt = 1 millijoule per second). If you drive it for only 1 millisecond at a power of 40 watts, you use (40 joules per second * 0.001 seconds) = 0.040 watts or 40 milliwatts of power, staying within the power dissipation requirements for the device but producing as much as 100 times more light for that one millisecond. Like I said before, different chemical makeups have different relationships between current in and light out. For some of them, the relationship is nearly linear, such that 1.0x the rated current gets you 1.0x the rated light and 100x the rated current gets you 99x the rated light. Others are nonlinear, perhaps 100x the rated current might get you 40x or 60x the rated light.

We do enter into a realm of physical limitations with these high-current pulses however, as the wire bond that connects to the LED chip's top side can only withstand a certain amount of current before it will either snap or vaporize due to heat stress (as you heat it up, it will expand; if it expands too quickly it will break away from the chip, or snap in two, or whatever). Determining this limitation could be done very easily by running an LED for a time pulsed at a certain level and then examining the structure of the device under a microscope in order to verify whether or not damage has occurred. If damage has not occurred, then we could increase the pulse power by 10% for the same amount of time and perform the same verification later on, and repeat until we determine the unsafe amount of current which will break the LED. In order to get a representative sample, it may be required to do this with 10-20 individual LEDs of a certain model number in order to rule out the effects of manufacturing on the data. You will most likely end up with a range of values, deviating maybe 20% from one another. Doing this would of course require sacrificing some LEDs in the name of science (I mean, you have to drive them all to the point of destruction to generate the data), but that's part of the fun IMO. Hey, I said it'd be easy, not cheap--you rarely get 'em both...

The short answer would be: You use PWM to prevent light from being wasted, and you use overdriving to match the intensity of LEDs to that of HID. I've never liked short answers, though. (those of you who remember me from overgrow should already know that. )

Good job explaining man. You went perfectly into detail where I just didn't know how to put my thoughts into words.

But yes, this is the goal with LED's. People have been rediculing me because I want to do both pwm and overdriving. Do you mind if I quote this into a thread on uk420?

My current project consists of me growing hydroponic catnip under led's and kinda doing a little experimenting as I go. I have recieved a rather decent amount of LED's recently and I am about to expand what I have going on.

Thank you for bringing this thread back up. I would like more people to participate in growing with LED's.

DeadlyFoez said:

Good job explaining man. You went perfectly into detail where I just didn't know how to put my thoughts into words.

But yes, this is the goal with LED's. People have been rediculing me because I want to do both pwm and overdriving. Do you mind if I quote this into a thread on uk420?

My current project consists of me growing hydroponic catnip under led's and kinda doing a little experimenting as I go. I have recieved a rather decent amount of LED's recently and I am about to expand what I have going on.

Thank you for bringing this thread back up. I would like more people to participate in growing with LED's.

Click to expand...

Yeah, I made some edits, go ahead and quote me. Give me a link to the thread too so I can come yell at the naysayers.

Hey Deadly Foez

Hey Deadly Foez

I went through all 96 agonizing pages of the link on 420 that was supposed to be the proof...... Well it wasn't ..... nadda..... zip...... zilch.......

I am not an electrician or anything like that... and if I started talking the Latin type language we use I could sound really smart but the point is.... a bunch of talking and one plant that is uuuhhhhh not impressive is not going to get the attention you want. "calculating the vector of " ssssshhhhheessssshhhh

the point is these produce light totally different, using hardly any energy compared to the big heaters we use..... but the technology and the prices just totally make it impracticle...... Peace

PWM has been done. The results are that it doesn't save energy. A lot of LED lights discussions unfortunately are an oversimplification and misrepresentation of science.

show me something to make me believe, otherwise seeing that a duty cycle of %0.5 of not being energy saving would be rediculous

Bree said:

I went through all 96 agonizing pages of the link on 420 that was supposed to be the proof...... Well it wasn't ..... nadda..... zip...... zilch.......

I am not an electrician or anything like that... and if I started talking the Latin type language we use I could sound really smart but the point is.... a bunch of talking and one plant that is uuuhhhhh not impressive is not going to get the attention you want. "calculating the vector of " ssssshhhhheessssshhhh

the point is these produce light totally different, using hardly any energy compared to the big heaters we use..... but the technology and the prices just totally make it impracticle...... Peace

Click to expand...

Well, there is more proof. and another grow link of davids that I haven't updated my 1st post to link to it is showing more proof. But the fact that a plant can grow under LED's is proof enough, although the watts that david use was a little on the slim side, a little more would show awesome growth.

And I'm not even done my system yet, when I am you'll see all the proof you need because I am doing it right. So dont be a skeptic yet because I have done enough research to show proof of it. I know that it will work better than any other artificial lighting in terms of electrical efficiency.

sy9942 said:

It's important for a variety of reasons, not the least of which is photosynthetic efficiency. If you've read some of the threads (cached or otherwise) from Overgrow, you know that this has been an ongoing pet project of mine, although I don't currently have anything to show for it because I'm neither growing nor actively smoking. This should however establish the level of my own expertise.

Click to expand...

Well, I have read one or two cached threads, to which some people have linked here (and other forums). So first of all I'd like to apologize if all (or most) my questions have already been answered.

The topic at hand is PWM (Pulse-width modulation) dimming/driving. Photosynthesis is not as constant a process as one might think. Each reaction center has hundreds (if not thousands) of antennae which can each receive a photon, but the reaction center can only process one photon at a time and the reactions that take place do take time to occur. Therefore, during the time that the reaction center is unable to process photons, all photons that its antennae intercept are completely wasted.

Click to expand...

Sorry, but for me, all this is so far hypothesis. How do you know that each receptor is able to process only one photon at a certain time? Does this receptor needs to be dis-energized (sorry, english is not my native language and it's already late) to convert photons into a chemical energy? (Or can it do so constantly, recieving steady stream of photons?)

Intensity is itself a tricky concept that I frequently have difficulty explaining, but I will try to explain it anyhow using a new method I have just come up with.

Click to expand...

X photons in a Y period of time ? (It's been long since I took any physics lectures and I have really bad memory so please dont laugh)

This only violates the specifications in a sense. If an LED is rated with a power dissipation of 40 milliwatts, then you need to keep its energy consumption below 40 millijoules per second (1 watt = 1 joule per second; 1 milliwatt = 1 millijoule per second). If you drive it for only 1 millisecond at a power of 40 watts, you use (40 joules per second * 0.001 seconds) = 0.040 watts or 40 milliwatts of power, staying within the power dissipation requirements for the device but producing as much as 100 times more light for that one millisecond.
Like I said before, different chemical makeups have different relationships between current in and light out. For some of them, the relationship is nearly linear, such that 1.0x the rated current gets you 1.0x the rated light and 100x the rated current gets you 99x the rated light.

Click to expand...

Please, show me such LED
LED's efficenty drops drastically when overdriving. It's not linear progression comparing input and output power of LED, it's more like geometrical - output power is "infinitely" (well, actually until it breaks ) closing up to a certain limit when you increase input power in linear.

I've never liked short answers, though. (those of you who remember me from overgrow should already know that. )

Click to expand...

Thank you for taking time, I'm looking forward for some more answers

DeadlyFoez said:

My setup will include a total of 400 - 600 watts of LED's

Click to expand...

Do you mean the equivalent of a 400 or 600 watt lamp in LEDs? Or are you using 400 or 600 watts of LEDs?

Because a watt is a watt, regardless of whether it's being expended by HID or LEDs. So 400 watts of LEDs, while generating much less heat and being more efficient, is still using 400 watts. So where is the power savings, besides the PWM thing, which I cannot intelligently discuss?

Let me rephrase: If I plug in a 400w HPS, it's going to use 400watts. If I plug in 400w of LEDs, it's going to use 400w.

So, are we talking equivalent wattage or actual wattage here? Or is the only power saving feature the PWM?