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Discussion of the pragmatic application of LED's

alkalien

Member
I use both, the anodized heatsink and kapton, i just cut away the kapton for the glueing point under the LED. Doing that I do have the kapton underneath the soldering point, just in case. If xou look carefully, you can see the tape between the LEDs.

The glue is a two component arctic silver heat conductive glue. It is a electric isolator. We built three panels and did not have any problems with short circuits till now.

Kapton tape is pretty cheap, the heatsink was only available with the anodized finish so I didn't really think about it. It's working great!
 

ion

Active member
not to interrupt the tek hissy you guys got going on(because i'll be chewing on it later for info...) but id like to propose one of the best reasons to get the LED out;

hearken yer mind's eye to yonder catastrophe in the pacific. the suck on this hasnt even begun to register yet.....just recently TEPCO has admitted witnessing neutron rays emitting from reactors 1 and 2.......but one of the nastier dilemmas the japanese are facing now is LOSS OF ELECTRICITY!!!!!

blackouts, brownouts.......rest assured radies and yentlemen this term will be coming to a democratic/first world nation in your neighborhood sooner>later. that is just my opinion, of course, but i live in a region that is prone to power-outtages due to a rural locale. what do YOU do when the lites blink and go bye-bye?

im haff-assed prepared with a 350watt inverter(2 actually) and a car battery. now, i run cfls in a micro setup--350watt would keep one of three grows going, so the idea of extended power outtages really hits my sphincter.

LEDS would of course give me the option to run all three grows as long as i can keep charging batteries with my fossil-fuel auto.....HAR! not very 'green' eh? or am i extra green?

one option for like-minded peeps who are thinking about the possibility that society could actually wake up soon and realize that there is no such thing as "safe" nuclear power at this stage of human/technological development and therebye realize that the meter may stop running.......or the X-class CME that occurred before the 9.1 erthqk could come more frequently and stronger(which'll fry the grid.....prob yer grow too) and are worried about keeping their genetics from dying out, might want to look into generators that DO NOT depend on fossil fuels. micro-hydro/solar/wind are within grasp, on an individual scale, of every farmer on here that has built a median-complex grow-op. my project is looking into pedal power. get a bike trainer, a bike, batteries, some electrical supply and for a coupla hours of riding you can keep your girls going sans grid.....unless you forgot to enclose your grow in a faraday cage and the EMP from the CME fried all yer lights/circuits/electronics on yer gear.


apart from the doom/gloom, the possibility of an extended blackout for you is something to consider. never mind if you think it'll happen or not, you cannot disregard that it is a factor that you must deal with.....plus, if the grid does go down, and yer prepped, think of the market corner youd have! 99% of growers would be outdo only! see, there just could be a plus side to a collapse of western civilization....
 

Fin

New member
Led-spesific problems

Led-spesific problems

I've been lately doing some troubleshooting about too much light. It seems that all the talk about "too much light" is always mixed with talk about "too high heat", as traditionally they go together.

How does cannabis behave under too much light without too much heat? I think I have solved my problems, this qustion is more for general interest.
 
G

guest456mpy

At first you will notice that the plants will slow growth at the closest point to the light. As light increases beyond the threshold it will begin to bleach the parts of the plant closest to the light creating "albino" growth as light is too intense to support photosynthesis.


Necrosis of plant tissue is not evident at these locations.
 

LetsSeeYa

Member
Hi alkalien,

Wow 1st Hydro and 1st LED at once, you are brave indeed!
I did the very same thing when I switched, btw. that's how I know.
Ran into the same Mg def in veg, K in veg and flowering. I now have separate Cal and MG solutions so I can balance the nutrients without adding extra N that's in CalMag. I'm hoping a more detailed discussion of nutrients will follow our treatment of lighting per se. I think we are wrapping up light quantities and strengths and ready to move on to qualities, but who knows what direction this thread may take.

Thanks for your input!
H.G.


Me too, Mg and K i think is my issue. I started out with Bio Tone as it was gifted from my hydro guy. Im in soil with 2 150w LED bars in a tent. I am loosing my lower leaves and with the BT in the soil mix, i was told id be good till 2nd week of flower. Well i flipped on the 1st of this month and had to give a dose of N to get me through flower. I have the E & J line, well most of it, got ripped on ebay, but have grow veg and meta K, I USE THE META K once a month. Its the 1st run with them in my tent and the canopy is messed up, so maybe i have the LED's to close, one plants leaves are crispy. The other plants are fine, but yellowing of leaves, but the interesting thing is that if one starts to get yellow, the leaf across will do the same. Its like a symmetrical yellowing thing as one goes yellow, i can count on the leaf across to become yellow. Dont have a clue as of why?

Anyone:thank you:

LSY
 

budlover123

Member
...Necrosis of plant tissue is not evident at these locations.

that is good info, I've seen what people thought was light burn turned out to be deficiency that was brought on by more intense light, which is not light burn

alkalien, how do you have that wired? are 2 types of reds on the same circuit? where'd you find those LEDs?
 
S

sm0k4

Any experience here with LED flowering lag?

Not really. They might take a few extra days to start the stretch, but after the stretch it seems normal. I also notice with 1W emitters the stretch is bad for lower growth. The lower branches grew quick but its all stem. It could be the genetics also, so more experience on my end is needed.
 

alkalien

Member
@OGmolton: sorry, didn't see your question....

Its powered by one meanwell CEN-75-54 driver which puts out up to 54V maintaining an exact current you can set it up to. I run on full power 1,4A. I use the red and blue LEDs inline in two strings and then combine those two strings to power the white Cree XM-Ls. The combined dropvoltage is a little bit under 54V which gives me a little room for calculating errors.

Finding those Osram Golden Dragons is a little bit hard. knna on the forum here used to ship them but I haven't heard from him for some months. You better check prices too, they are very different...


As for the flowering discussion, I for the first time did flower using three different panels for one plant. She turned into flower at once and hardly stretched at all. I can't tell whether this is normal but I like it!
 

budlover123

Member
Thank you for the info, but it actually raises more questions for me. It was my understanding that only blue and white LED's could be on the same circuit together because they had the same forward voltage. I thought that if a 1.15 v red led was in series with a 1.5 v blue led only the reds would light, I guess that is incorrect?

Do you know what is the voltage of the different leds used?

Do you know if 1.15 v and 1.5 v leds are in series, do they all run at 1.15 v or 1.5 v?

If you look at my LED light I built in my signature you'll notice I got 3 different power supplies for 32 1-watt LEDs, so this design of yours is very interesting to me. When you say the 2 red, blue strings are powering the white one, do you mean like this?

attachment.php


If that works, that totally changes my idea of LED circuits

Thanks again
 

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alkalien

Member
Hey OGmolton,

thats exactly how I wired them.

The voltages are not important, they just add up when wired in series. Just make sure they are lower than the output of your driver. When you want to drive more than one string parallel they must be identical, otherwise the current would be different for the strings. If they are identical, the current will split up equally. Make sure the current is not too high for any LEDs you got on your strings. I run my red and blue ones with about 650mA and the white ones up to 3A. In every string the current is constant, so don't put LEDs not ready for this current in the string, the weakest LED will determin the current for the string.
I put fuses in front of any row to make sure I don't overpower them.
 
S

sm0k4

Thank you for the info, but it actually raises more questions for me. It was my understanding that only blue and white LED's could be on the same circuit together because they had the same forward voltage. I thought that if a 1.15 v red led was in series with a 1.5 v blue led only the reds would light, I guess that is incorrect?

The reason most put blue/white on the same string is to have control of dimming just that color, or trying to match up voltages for driving them. In my case I use two DC power supplies that power my 10 driver boards. So I separated my drivers into red and blue/white to keep my string voltages as close as possible. I have equal amounts of each in every string so each set of that color can run off the same voltage. I also will incorporate PWM dimming so I can tune my colors when/if I need to. Having separate red and blue control might be handy. If you want to run 75V worth of red, blue, and white off of one driver you surely can. You just don't have any control over certain color brightness.

Do you know what is the voltage of the different leds used?
I have used Cree and Osram GD+ so far and at 600mA I get:

Red is typically 2.2-2.3V
Blue is typically 3.3-3.5V
White is typically 3.3-3.5V

The data sheets are accurate, and they are available on the Cree web site.

Do you know if 1.15 v and 1.5 v leds are in series, do they all run at 1.15 v or 1.5 v?
LEDs drop your string voltage as you add more. Meaning if you have a 12V driver you can run eight 1.5V LEDs. Add up the voltage of the LEDs Vf until you reach your driver voltage. You can then run parallel strings of the same size until you use up all the power of the driver. Running in parallel splits the total current though. So running two parallel strings off of a 1A driver will give 500mA roughly on each string.


 

budlover123

Member
...LEDs drop your string voltage as you add more. Meaning if you have a 12V driver you can run eight 1.5V LEDs. Add up the voltage of the LEDs Vf until you reach your driver voltage. You can then run parallel strings of the same size until you use up all the power of the driver. Running in parallel splits the total current though. So running two parallel strings off of a 1A driver will give 500mA roughly on each string.

Thanks for the quick, and great response. So it won't run the blues at a lower voltage or the reds at a higher voltage if they are in a series like that? They will all work at the same amp rating but different volts?

If I knew that my LED light would have totally had some green too.
 
S

sm0k4

Yes, current is constant, the voltage of the supply drops as you add more. It is always best to use up almost all of the driver voltage for a more efficient running driver.
 

alkalien

Member
@OGmolton: forget about green. If you got white you are fine!

@sm0k4: Actually your drawing wouldn't work, his was right!
 

budlover123

Member
Hey OGmolton,

thats exactly how I wired them.

The voltages are not important, they just add up when wired in series. Just make sure they are lower than the output of your driver. When you want to drive more than one string parallel they must be identical, otherwise the current would be different for the strings. If they are identical, the current will split up equally. Make sure the current is not too high for any LEDs you got on your strings. I run my red and blue ones with about 650mA and the white ones up to 3A. In every string the current is constant, so don't put LEDs not ready for this current in the string, the weakest LED will determin the current for the string.
I put fuses in front of any row to make sure I don't overpower them.
great idea about the fuses, I missed your answer, I got 2 answers so fast about this.

I'm going to have to buy a big power supply and some leds of all different colors I wanted to use, like those luxeon rerbel cyan leds, and build something cool. Just for the hell of it. I did get neutral white for maximum green-ness so that probably is good enough, but everything I made up until now has been one color per power supply, and I always wanted to do more with the colors.

Is there anything to wanting to keep the forward voltage of each LED the same? Do you know if a blue in a series with red leds will run at a lower voltage to match the reds, or will the reds be at a higher voltage to match the blues, or will they run at different volts with the same current (Amps)?
 

alkalien

Member
They run at the voltage they are rated for, no problem at all. The current is fixed though. Try to find LEDs that are rated for currents close to each other, you'll have to used the lowest current one LED is rated for. Voltage is not important with LEDs, just suplly enough, the closer to the driver the better, just let a little room for changing LED voltages, they do change with different temperatures and stuff. I calculate with about 2V room.
 
Interesting thread!

I've been sneaking into cree and rebel led datasheets for some time now so i'm obviously intrigued with this led thing.

What's the actual consensus on watage compared to HIDs and on light spectrum of led fixtures if any??
 

budlover123

Member
Thanks to both you guys for clarifying and then I guess confirming that info about different LED voltages.

I think the consensus is that comparing led wattage to HID wattage is apples to oranges.

Me personally, I say anywhere you see a comparison of LED to HID, I wouldn't just disregard it, I would be suspicious of what they are selling all together.
 

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