King Cob Led grow light

Discussion in 'LED and other Lighting' started by VegasWinner, Dec 1, 2017.


    ledgardener Well-Known Member

    The funny part about people being so against parallel wiring is (like somebody already mentioned) if you look at any strip or COB, the diodes are already wired in all sorts of series/parallel combinations anyway. If it was such a problem, you'd think that people would have issues with half their COBs not working.
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    nfhiggs Well-Known Member

    Yeah, funny how they always dismiss that little fact as being "irrelevant".
    Stephenj37826, Moflow and Randomblame like this.

    GrowLightResearch Well-Known Member

    You'd think so. The problem is you guys don't know what is happening and don't know that you don't know. And that's okay.

    And some of those combinations actually work well because they were well thought out by someone very knowledgeable on the topic. There are ways to minimize the risk. There are also many things that can be done wrong. More so than most anyone will ever know but a very few.

    Do you really think the CoB manufacturers are that ignorant?
    A CoB uses additional circuitry to balance the current through the parallel paths of the dice. If a CoB has a failure in any string of dice, the radiant and luminous flux remains the same.

    A case in point. The below are two Luxeon L2C5-RM001211E1900 CoBs. One is severely damaged. Their luminous flux remain nearly identical.


    This is a very minor issue. What bugs me is how some of you guys justify continuing to wire CoBs and strips in parallel. It's the rationalization using mythical excuses that makes it so irritating. I hear so many things said on this site that defy the laws of physics it goes beyond humorous. I do not mind someone does not know about the stuff I have studied every day for the past 40 years. But when they try to baffle me with their bullshit on the one topic I am an expert, it's irritating. I am not that fuckin' high I'm not going to see the bullshit. I have done the research, I have found the problems, I am now finding solutions, that is what I do 18 hours a day, 7 days a week.

    This issue on its own is nothing, it's inconsequential. Many say "Don't sweat the small stuff". I have found that to be a bad thing to say. That's because the little things add up. It's like web page load times. Years ago I studied web page load time issues for two years. The solution was paying attention to all the little stuff.
    There are more things that can go wrong with LED grow lights, just like there are many things a website developer can do wrong. I know, it's me. I care about shit more than anyone else.

    But what the fuck, I'm old and I'm high. I try to do the right thing. I think grow lighting is very important. It is possible LED lighting may significantly impact World hunger. In a good way.

    LEDs are not yet ready to take on World hunger. LEDs are certainly way past HPS. But you have to pay attention to the small stuff.

    Depends on how a strip is manufactured and specifically how the LEDs were sourced.
    For example when Samsung makes a strip as the manufacturer of the LEDs they can specify a very tight tolerance on the forward voltage. When the manager of strip manufacturing sources his LEDs from the manager of LED manufacturing, he just requests them to put a very tight tolerance on the forward voltage. They bin every LED that comes off the production line so it's no big deal to do so in-house. It would be a big deal to have to do that for the general public. The tightest Vf tolerance Samsung offers to the public is 300mV. The more LEDs used in each strip the lower the statistical probability there will be a big balance issue. But this applies only to an individual board. While the LEDs on on individual PCB are fairly balanced by Vf binning that does not mean two of their boards will be balanced but they will not be as bad as if they did not control the source binning tolerance. 21.9 to 24.2V (23.0 typ) and 43.7 - 48.3 (46.0 typ) on the 1200mm. Additionally these strips use mid-power LEDs with 0.18W at test current which minimizes the problem.When it comes to strips of high power LEDs and CoBs there are going to be noticeable issue with balance. That does not mean the difference will be noticeable to the human eye, it will not. If you have not measured the current in the parallel CoBs or strips you don't have Jack Shit to say that matters. The only reason I measure is because I have seen tow strips go into thermal runaway. Thermal runaway is rare whereas unbalanced loads are very common.

    Since apparently you guys that buy these strips do not give a shit, why should anyone else care? Blind leading the blind.
    Last edited: Dec 5, 2017

    GrowLightResearch Well-Known Member

    Funny? I don't think so. What I do think, is what you do say, is not even true.

    It's almost as you just have to say something negative. Nothing else matters, you just have this compelling urge to say anything as long as it's negative. That anything you say turns out to be some stupid stupid shit to those of us that know the truth. Is the Earth flat? Is GMO a bad thing? Did vaccinations cause autism? Is organic superior to traditional foods? Did Oswald shoot JFK? Is it wrong to wire CoBs and strips in parallel?
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    nfhiggs Well-Known Member

    LOL - You sure are funny when you're angry.

    No, no, no, sometimes, most likely, and no.
    SSGrower likes this.

    GrowLightResearch Well-Known Member

    Thank you. Except I'm not angry. I'm old. At this point in my life my biggest concern is making the world a better place. After the shit I have been through in this life, there is nothing anyone can say to me over the Internet that is going to make me angry. I am smiling with every character I type. I know I'm doing the right thing. I actually fuckin' care about shit8)

    Am I delusional or are you delusional. Does it matter?
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    Delta-9Pyromaniac Well-Known Member


    VegasWinner Well-Known Member

    I love this attitude. You can not change the world without changing you first.

    Folks think they can say things to anger folks but it is a waste of time and energy. I decide how I feel not someone on the internet.

    Interesting how the thread started about a light and is now about something else altogether. RIU style. I agree with GLR it is the loittle stuff you need to concern with regarding leds.
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    Randomblame Well-Known Member

    Even an old dog can learn new tricks and and I'll convince you that it works!
    At fisrt, there is no secondary circuit in COB's for balancing. Each diode has it's own ESD protetion device in parallel and thats it.
    If one or more strings failed the current is divided by the number of strings left. More current flows thru these strings and they therefor lit up brighter. But effiency goes down and total light output also. Slightly more heat is produced by less diodes, because they need a bit more voltage. At the end a damaged but still working COB would still use the same amount of power -within a few percent- but produce less light and more heat.

    You have given the answer yourself. The stripes and COB's are produced with narrow differences so that the differences in parallel operation remain calculable. Remember, we use only a few of them in parallel not hundred. Yes, little things adds up quickly but whether one strip with 10w and the other with 12w run is really not important for the plants underneath. As long as you not run into thermal runaways there is not really a disturbing problem. Also these Meanwell CV/CC driver have a voltage limiter which allows us to limit tha max. voltage and this helps a lot to avoid thermal runaways.
    I do not want to say that it is right to operate COB's/strips in parallel. But if you plan the circuit neatly, it will work within some fluctuations.

    Growcob5 Active Member

    Same thing happened to me I purchase some citizenship and they had a strip out on them I had to get on brand new chips and back to me because of that only reason I once in a blue moon do parallel myself is because my driver may not have enough forward both edge to do it so I do a chipper to and parallel to use that driver and not have to buy another one that's the only time I've ever use parallel that light right there is actually in parallel because it requires a hunter and for volts for to chips and series but I don't have that so I use parallel because I had a not voltage to do it in parallel

    Growcob5 Active Member


    ledgardener Well-Known Member

    Tell me more about this additional circuitry in the COBs. If you're going to accuse everyone of junk science, you can't be vague with your explanation.

    Sure, there are going to be minor differences in current among like strips or COBs or whatever in parallel, but does it really truly matter? Yes, I have 2 multimeters, and yes, I've compared current between lights on a parallel circuit, and yes, there might be 50mA difference between them. So what? I've done thermal runaway testing on COBs, Quantum Boards, and Samsung strips, and I've only seen it happen a couple times at max rated current or more where the cooling wasn't adequate.

    How tight do you think the tolerances are on all of the LM561C boards with 10+ parallel strings that are out there now? Do you think Chinese manufacturers are adamant that all the strings match precisely? How many of these boards have you heard of failing?

    If we're making lights that'll be used to grow weed on the ISS, sure, drive 'em constant current. If we're throwing a few lights in parallel in our basements, who cares if there's a literal 1-2% difference in current between them?

    GrowLightResearch Well-Known Member

    While searching for info on the CoB balancing circuit, I found this patent which is about some "additional circuitry" and a lot more interesting than a pair of transistors. Filed April 2016 and granted days ago.

    Philips was granted a Patent 9,832,830 on Nov 28.,832,830.PN.&OS=PN/9,832,830&RS=PN/9,832,830

    Philips wants a constant voltage powered CoB. They will supply the Driver on Board. The problem is setting the current. Constant current drivers typically use a resistor value to set the current. The patent is for a programmable resistor to set the current for the on board driver.

    How's that for additional circuitry?

    I was wrong, please forgive me. You are correct on both counts. I don't think they all use the schottly ESD diode, but it is common.

    I am going to recant what I said about the on board pair of transistors for balancing each string within the CoB. I saw them in the past, don't remember where, and now cannot find it. I had an electron microscope image of the circuitry. LED manufacturing has come a long way in the past few years. It is now a very fast paced industry. One thing they are getting better at is forward voltage. For good reason, Vf is one of the top concerns in LED R&D. By lowering Vf the lm/w efficacy increases significantly.

    Also regarding the balancing of parallel strips, I am still looking into it. I purchased a pair of Samsung F-Series and one pair of Bridgelux EB Series strips when the topic came up a few days ago. They arrived today. So far the forward voltages are matched extremely well. Running them at 700mA the forward voltages are 22.42, 22.44, 22.46, and 22.43. I have not yet measured the currents, but I suspect they will be well balanced.

    I do some small volume manufacturing. I make strips with strings of 16 Cree XP and OSRAM SSL and OSRAM SQUARE. I wanted to power them in parallel. I knew at that time closer Vf would minimize the balance issues. The problem stems from each module having a different Vf. When powered in parallel you are forcing all the modules to operate at the same Vf. And there are consequences. And they can be minimized.

    I may have been very bad luck but the first strips I tried about a year ago went into thermal runaway. I set the strips up to test one night and in the morning one was very bright and the other was almost dead, its LEDs were flickering very dimly. I tried matching strips by Vf and even 0.5V difference created an imbalance of 60/40. I have since run a number of experiments and concluded I will use a driver for each string. But I wanted to have a current (i.e. adjustable PPFD) setting for each string anyway. Which brings me back to the patent.


    Fig. 1 and 2 are CoBs with an external power supply shown. The driver is on board with the LEDs inside the CoB.

    Fig 1 is has a third pin to set the resistor value associated with a specific current.

    Fig 2 adds another pin to provide communications with the power supply.

    The plan is to put an antenna in the CoB holder so you can set the current remotely. Kinda cool dimmer circuit.

    There is also an on board thermal monitoring circuit.


    FIG. 1 shows a known example of LED module and driver using a current setting resistor in the LED module;

    FIG. 2 shows a first example of LED module and driver together with an external interface device;

    Down lighting and accent lighting solutions are typically based on LED modules, where each module combines a LED light engine and an LED driver. The light engine may for example be based on Chip on Board (CoB) LEDs. Holders are used to mount the CoB LEDs and a cable passes from the holder to the driver. The total system thus consists of a driver, cable and light engine.

    As explained above, driver flexibility means that there is a large range of drivers that can drive the same light engine. For instance there are fixed output current drivers, dimming drivers and programmable drivers. There are also different housing types.

    It has been proposed to incorporate a small PCB as part of the holder, and the PCB can then include passive current setting components.

    Different light engine may require different operation current. The PCB may for example provide a circuit that allows the driver to sense the temperature of the module as well as having a setting resistor used by the driver to know and set the correct current.

    A simple schematic of this function is shown in FIG. 1. The LED module 10 comprises the light engine 12 (i.e. the LED string), a current setting resistor 14 and a thermal protection circuit 16. The module 10 connects to a driver 18 using only three terminals. Terminals LED+ and LED- connect to the ends of the LED string 12, and a third terminal LEDset enables the driver 18 to measure the resistance of the current setting resistor 14 by injecting a measurement current Iset. With a certain resistance of the current setting resistor in the LED module, a certain voltage occurs across the setting resistor and is detected by the driver 18, and in turn the driver 18 is aware of how much current/power the LED module requires.

    This arrangement does not allow the end user to change the current (and therefore light output flux) of the light module 10. If a different current is needed, the setting resistor 14 needs to be modified.


    Last edited: Dec 7, 2017
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    GrowLightResearch Well-Known Member

    I recently tested some CoBs and the results were very bad. I tested two Luxeon 40W CoBs.

    Currents and Vf powered individually at ≈600mA and in parallel with ≈1200mA.

    Amp, Vf
    0.613 33.4
    0.613 34.2

    0.764 34.9
    0.463 34.9

    Based on this morning's testing of the Samsung and Bridgelux boards:
    Strips with the mid powered LEDs (e.g. LM301B) when the strip is manufactured by the manufacturer of the LED like Samsung, very likely can be powered in parallel. I would still measure the currents. I'm going to add a series shunt resistor (0.01Ω 1%) to every string so it's easy to measure the current in each string during QC and test. I don't use mid-powered LEDs so for now I will still use a driver for each string.
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    Randomblame Well-Known Member

    A difference of 0.8v would be also too much for me. My COB's(Cree, Blux, Citi) were, with only one exception, all within 0.1v deviation(tested with the same driver / heatsink combo ) and the one who drew significantly more had three broken strings.
    Are you sure both COB's are fully working? One or more defective strings would increase voltage and current for the rest of the strings by a certain margin.

    Randomblame Well-Known Member

    For this post I would like to give you 3 likes. Yeah, it's almost impossible to create a blue and a red string with matching voltage. Also if they match the differe es will increase when they warmed up. Meanwell LDD's can be used here but they are only dimmable via pwm.
    I remember a user called @NoFucks2Give who tries nearly the same like you, maybe he could be helpful for you ... ;-) or you can try do it together...;-)
    But I have not read anything from him for a long time. No idea if he is still with.
    GrowLightResearch likes this.

    nc208 Well-Known Member

    I'm sorry but this is priceless. lol. Ledgardner asked you for examples and you give one that was created like 5 days ago and for Phillips? I'm not sure anyone here uses cobs made by phillips. Do you have examples of any for cree, bridgelux, citizen?

    GrowLightResearch Well-Known Member

    They were purchased months apart. I use them for heat sources when running thermal experiments. So they could have been damaged. I will be setting up a test bench for this issue and will test more CoBs in the near future. I do not use CoBs, I prefer strips but the topic is interesting so I will try test them.

    I'm trying 16 white, or blue in each string compared with strings of 21 red, yellow, amber, or orange. I am now convinced Samsung and Bridgelux bin the LEDs used on their strips with a very tight tolerance on Vf. The Vf on my strips are all over the place.

    NoFucksToGive was banned. He liked to drink:blsmoke:

    I like the LDDs. At $3.50 it's difficult for me to make a less expensive driver . Parts for my driver design run about $2.50 but I also have a thermal watch dog too. Also I can tweak the switching speeds and inductor to maximize efficiency for various currents. I want to see if I can run some LEDs at maximum power using the thermal circuit to regulate the maximum current. I will not monitor the current only the temperature. I will increase the current as long as they are at a safe temperature. The actual purpose is if the water cooling fails the driver will turn off when the LEDs get hot.
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    GrowLightResearch Well-Known Member

    I also recanted and apologized.

    The patent was filed April 2016.

    Phillips is probably the biggest player in horticulture lighting worldwide. They make more than HPS bulbs.

    Lumiled is Phillips as in Luxeon. The guys with the Crisp White CoB that has the violet peak at 405nm that make white shirts sitting on retail shelves look brilliant by activating the florescent FWAs. And some plants like that near UV wavelength that sits on the very edge of the photosynthesis bandwidth. . I like their Fresh Focus line too. The Red Meat has great red spectrum. Similar to Bridgelux's Decor.

    I'm seeing more like 40% at test current.

    Funny you should ask, I just bought a couple pairs of Samsung and Bridgelux strips to answer that almost same question. I would not buy any LED from China. I now believe the Koreans do. The tolerances of the strips I received today were incredibly close. About 10mV difference between strips. The measurements were post here:
    Last edited: Dec 7, 2017
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    GrowLightResearch Well-Known Member

    Sincerely, I am impressed anyone someone here has actually measured. I am shocked someone here knows thermal runaways is a real thing. @CobKits and many other self proclaimed "experts" says thermal runaway is not real. I just received some of the mid-powered strips today. First time I have had an LED under 1 watt.

    I am very interested in the forward voltages of the Quantum Boards. My hypothesis is that Samsung binned the LEDs they use very tightly. Much tighter than anything they sell to the public. After measuring what I received today, I believe it to be true now. I just cannot fathom buying a QB to test. I abhor the small rectangle form factor. Everyone seems to think LEDs are like light bulbs and should be packed into a small area. The rectangle form factor is a waste of PCB real estate. Cut the boards into strips and save the cost of the wasted PCB. Oh, yeah, I guessing the QB's forward voltages waver more than Samsung's.

    I have wondered for some time now, why would anyone buy a Quantum Board?

    Am I missing something? I just looked at their HLG 550. 1,152 LEDs for $1,049

    Compare with qty four Samsung SI-B8UZ91B20W. 1,152 LEDs for ≈$160

    Or I can buy 28 strips (288 LED/strip) for the same $1,049. 8,064 LEDs vs 1,152 LEDs.

    Strips do not have the uniformity issues of a Quantum Board. QB has a 3X PPFD difference from center to corner in a 4'x4' area.
    The Samsung strips come in up to 4 foot lengths and will easily cover a 4' x 4' area with near perfect uniformity.
    The Quantum Boards recommend hanging 18" to 28" above the canopy. I would think you could run the Samsung with half as much electricity as the QB closer to the canopy and come out way ahead.

    Samsung vs Quantum Board: 700% less up front cost for same number of LEDs. Better uniformity allowing a significant savings in electricity.

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