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!@lukio I've noticed that with 4 QB's in a 3x3 anything over 700 umoles seems to be hard on the strains I run, maybe added CO2 would help but they seem stressed. The intensity is pretty consistent over the whole 3x3 so there's a lot of photons in a 3x3.
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.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!
How do you know when is too much light? Can you upload pic please?@lukio I've noticed that with 4 QB's in a 3x3 anything over 700 umoles seems to be hard on the strains I run, maybe added CO2 would help but they seem stressed. The intensity is pretty consistent over the whole 3x3 so there's a lot of photons in a 3x3.
Thanks Markyep my bad, got a lot of data on driver options just need to get it on site
Cheers
Mark
i am seeing that in many ways ...less is moreHow do you know when is too much light? Can you upload pic please?
Boards are resistor loaded for current balancing,
How does a resistor balance current on strings of LEDs?more uniformly, as one can not pull more current than the rest.
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 thingsHow 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.
Very clear explanation Mark, thanks dude!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
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.Resistors balance voltage not current,
___________________________________________________________________________Boards are resistor loaded for current balancing,
First off the voltage across the resistor is dependent solely on the current flow through it.a resistor between makes them both 2.5v,
Got any more of what you're smokin'?Very clear explanation Mark, thanks dude!
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.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'?
You don't sound like an idiot to me.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.
Haha, thanks!You don't sound like an idiot to me.
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...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.
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 basicsThat 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'?
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...
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.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.
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...
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.Sometimes all the super techy lingo gets in the way of basic electrical theory
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
They are never identical.t when the voltage is not identical in all strings.
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.but in long strings the differences can already be a few millivolts