Sol-Skin, let the journey begin...
- Thread starter welight
- Start date
lukio
Well-Known Member
youve got me worried, the bigger tent is 4ft wide so this might be a lil much for them at the mo - hmmmm...i'll probably dim them, cheers!
captainmorgan
Well-Known Member
Just keep a eye on it, my current run at 270 watts and 800 umoles was too much so I dimmed it down closer to 200 watts and 600 umoles to finish and the plant recovered nicely.
KonopCh
Well-Known Member
How do you know when is too much light? Can you upload pic please?
Moflow
Well-Known Member
coreywebster
Well-Known Member
OLD MOTHER SATIVA
Well-Known Member
i am seeing that in many ways ...less is more
you have too much light when you notice yellowing , leaf burning/colouration changes..
then it mean raise the lights or use less wattage
NoFucks2Give
Well-Known Member
How does a resistor balance current on strings of LEDs?
With a constant current source resistors are a complete waste.
With a constant voltage source the current in one string is independent of other strings.
540 pieces is quite a balancing act.
welight
Well-Known Member
Resistors balance voltage not current, ie 2 leds one 2 volt one 3volt, in series they are 5v, in parallel they remain 2 and 3 v, a resistor between makes them both 2.5v, the current operates on the basis of forward voltage and is balanced by the forward voltage relationship, balanced strings vs limited strings are two different things
Cheers
Mark
StonerCol
Well-Known Member
NoFucks2Give
Well-Known Member
That kind of defies Ohms law. There is a direct relationship between voltage current and resistance. You cannot change one without one of the others not changing.
But that is not the point
I used current because that is what you stated. But I still would have been confused if you had said voltage balancing. So moot point.
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More confused:
First off the voltage across the resistor is dependent solely on the current flow through it.
Secondly the voltages of the LEDs are still and will always remain 2v and 3v when forward biased.
Thirdly if they were connected in parallel the 2v would remain lit and the 3v would either be very dim or not lit up at all. The voltage across the 3v LED would be 2v.
But this just clouds the original question.
What I did not understand about your phrase "resistor loaded for current balancing" is the reason for this solution.
- What problem is being solved by these resistors?
- How are the resistors solving that problem?
Got any more of what you're smokin'?
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I'm with you here on the ohms law comment. But I also understand how adding a resistor can balance a load. If you had a 3v power supply the 3v led wouldn't be dim at all. The 2v led could be parallel connected to the 3v led in the 3v circuit with the addition of a resistor right? I'm not sure if this is what Mark was trying to describe, I was a little confused myself. Both with what Mark said, and what you said. It's entirely possible that I'm an idiot too.
Mullumbimby
Well-Known Member
You don't sound like an idiot to me.
Haha, thanks!
I won't pretend to know as much as a builder or manufacturer. But I know in a parallel connected circuit the voltage at each resistor, diode, load, or whatever will be equal to the supply voltage. It doesn't really matter what you put in the circuit. It's entirely possible to use resistors to help something with a lower voltage rating exist in a circuit beyond its rating. But there's definitely not any adding of voltages in a parallel circuit. Voltage at any point in the circuit is equal to the voltage applied to the circuit.
Sometimes all the super techy lingo gets in the way of basic electrical theory. Both of those guys know a little something, I think the delivery was just off a bit.
Mullumbimby
Well-Known Member
You're making a lot of sense but I suspect that there's something about 'forward voltage' of a diode that puts a bit of a spanner in the works. I'd love to be enlightened further...
welight
Well-Known Member
perhaps too abstract, your correct the relationship between voltage and current is defined you raise current on a led and the voltage raises, back to basics
LEDs are used individually and when more light is required, LEDs are stacked in series with the same current passing through each one. The voltage across the string increases with each LED added. After a number of LEDs are added in series, the power supply may not be able to handle the higher output voltage required. Also, a change of output voltage could be a problem for the power supply if the range of LEDs required is high enough to increase the range of the output voltage and auxiliary circuits. The Sol-Skin circuit structure is to balance the current in parallel strings of series loads where the individual loads vary in ie led forward voltage, because LEDs have been shortened or opened. Without a balance circuit, the variation of the parallel loads could cause most, or all of the current to pass through the path of the load with the lowest voltage and a small amount of current through the path of the load with the highest voltage. The result would be a variation in light output and could cause LED failure from excessive current. The objective is to achieve the same current to pass through each parallel string of series loads even though the voltage across each load is not the same.
Hope that answers the question
Cheer
Mark
Ya, me too!
If I'm not mistaken, forward voltage wouldn't change how a parallel circuit works at all. But It is one of the main reasons such a resistor would be used. Any difference in voltage would in effect cause a change in current. Using a resistor to "current balance" is nothing new. In a parallel circuit, the supply voltage doesn't care what the diode voltage is or will change to when it gets hot. The voltage applied is going to the diode, the current would typically react in this case hence the term "current balance" as a way to keep this from being an issue. Where we came up with 2+3 and adding a resistor to make it 2.5+2.5 as far as voltage goes is beyond me. So I was hoping to learn something too.
There will be some diffences in say using a constant voltage vs constant current driver. But I don't suspect anyone in this conversation was getting that far, not yet anyway.
NoFucks2Give
Well-Known Member
You may not understand my perspective. I have been an accomplished electrical engineer for over 40 years and have been designing LED grow fixtures for the University of Florida Horticulture Research Department.for the past couple of years.
I understand your problem. I like that you are not using lethal voltages. I also prefer working in the 48V range. I like your white and red. I am using Olson SSL hyper red rather than XQE photo red.
A resistor is not the solution. A resistor will not help. A resistor will work when each and every LED has its own resistor. Incredibly inefficient as well. I struggle with the decision between inductors with DCR's of 110 mOhm, 120 mOhm, and 186 mOhm which represent efficiencies of 98%, 97%, and 96% respectively. I could NEVER add a resistor in the current path.
An LDD-H (or custom buck driver) on each board is a good solution. An LDD-H for every 45V (16 x 2.8v) string is better.
A combination of individual CV powered CC buck drivers, CC drivers (e.g HLD), and load balancer chips is my idea of a solution.
This is a really cool circuit. The values or the resistors sets the ratio of current for each string. No limit to the number of strings. Just one chip, a resistor and cap is all the is needed to add another string. You can adjust the current on all strings using the dimmer on the current source.
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I am working on explaining it to you guys. I will let you know when (and where ) it's ready. I will post in a new thread rather than hijack this thread. LEDs are so much more complex than they appear at first glance.
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Randomblame
Well-Known Member
This means that the resistors only take effect when the voltage is not identical in all strings. If all voltages are identical, the resistors do nothing. Basically, the voltage differences in modern LED's are very small, but in long strings the differences can already be a few millivolts. The resistors compensates that, right? Is not the same technic used in COB's?
NoFucks2Give
Well-Known Member
They are never identical.
I use strings of 16 for white, green, and blue and strings of 21 for red, amber, and yellow. The strings of the same white LEDs (2.8v typ.), their Vf differed by volts, e.g. 42v-46v. They all came off the same reel and likely were manufactured on the same wafer. The closest two strings to have matching Vf I have seen, differed by 200mV. I ran them in parallel with an HLG-40-54 and the next day one string was dimly flickering and the other was very bright. Thermal runaway.
See the highlighted paragraph on page one of the attached PDF.
CoBs use parallel stings but they also use current balancing circuits.
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