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DiY LEDs - How to Power Them

Discussion in 'LED and other Lighting' started by SupraSPL, Feb 22, 2014.


    PicklesRus Well-Known Member

    I think I understand constant current drivers pretty well: you run your leds in series and the voltage is used up by each LED and the leftover forward voltage is left unused.

    I'm not so clear on constant voltage though.
    If I put this cob on this driver what will happen to the leftover power? Will it blow the COB?

    VERO 13
    31.8 V @ 500ma

    Meanwell LPH-18-36
    36 V @ 500ma

    Tomula Active Member

    When you have constant voltage and you connect the COBs in parallel, the current is divided and the voltage stays.
    PicklesRus likes this.

    rocho Active Member

    HI! I'm studyng about the best light project cobering a 2.3x2.3 tent. (70x70x160cm) And my idea would be for a 200w(should be enought?) of total actual power lamp mounting 4 Vero29 D 3500k run at 1.4 A or at 1050mA ish 190W (5pcs)...I would prefer the second option because i know as vero 29 could run harder with good efficieny but it is also true that less ampere would be not only more lm/w(efficiency) but also less cob temperature (so more Volts/ Wats), and 5 COBs VS 4 COBs would give me a better light distribution cooler (so closer to the plants) but 190w of actuql light may be not enought....am I wrong? Any suggestion will be welcome also for other cob brands. Best regards and many thanx!
    HLG-320H-C1050A (up to 8 COBs)306W maybe too much for my space but maybe good if dimming at 700mA

    HLG-185H-C1050A (up to 5 vero at 1050mA internal pot) 191W maybe too low power

    HLG-320H-C1400A (up to 4 vero 29d at 1.4 internal pot 94% efficiency at full power but even good at 60% at 220V) may be my best choice but driver is more expansive(twice)

    HLG-185H-C1400A do not give enought VOLTS for 4 vero 29d run at 1.4A (37,2 volt each one at 25°c)wire in series(active CPU heatsink) but someone said me 100% would works fine and maybe a good cost/power ratio.

    Please help me!
    Last edited: Jan 2, 2017
    Rudi I&I Automan

    Rudi I&I Automan Well-Known Member

    HIGH All, well All HIGH i hope bongsmilie I have this led panel from a ufo light fitting, but have no idea how to power it up.
    It has 49 little leds (crees I believe?), anyone have any idea how to power it ?
    I have some 100w & a 50w drivers for led chips (?) forgot to take a pic of those, but heres the light panel.
    Theres an A+ & B+, B- & A- . ignore the cables, i just soldered them on to the A's & B's in prep for some power source.
    Anything I may have missed, just ask. thanx Rudi :weed:

    Attached Files:


    PicklesRus Well-Known Member

    So my question then is, what happens if you put too much voltage into a LED, is that overdriving? I presume that will break the LED?

    If I have a 36vf LED and I run it at 38v, I presume that would break the LED or at least reduce it's lifespan?

    What about providing less voltage to an LED? what if I have a 36v led and give it only 32v? will that also damage the LED?

    Tomula likes this.

    BobCajun Well-Known Member

    I don't think you can use that driver unless there's some way to reduce the output voltage. I don't know what you would need for that, more than just a resistor though. You need an output from 29.9 to 34.7v. However, at a higher current, like 1050 ma, it could take 36v. At that current it needs 32-37.9v. What would happen if you hooked up the 36v driver? I guess it would burn out, yeah.
    Last edited: Jan 2, 2017
    PicklesRus likes this.

    PicklesRus Well-Known Member

    I was thinking of adding a small LED to each Vero to bring the voltage just over 36v. That would mean the LEDs are getting a little less voltage than what they are advertised as, LEDs work in a range of voltage don't they? As long as I don't go over I'm good right? or am I misunderstanding it.

    BobCajun Well-Known Member

    Yeah maybe putting another LED or something on there would work. A resistor might work but when I searched how to reduce voltage it said you should never use a resistor for that. Doesn't mean it wouldn't work though. Maybe get a resistor and see how much it reduces voltage from a small adapter, like a PC fan power supply. You need something that would use up about 2-6v.

    PicklesRus Well-Known Member

    It would seem silly to use a resistor that generated heat when I could use a resister that generates light (LED) lol - cool though that combination might end up being cheap and modular (one cob per driver)

    BobCajun Well-Known Member

    Yeah I guess single LEDs are commonly 2-3v anyway, so just right.

    BobCajun Well-Known Member

    Since the data sheet says that it runs at 32-37.9v at 1050 ma then I guess it must be able to take at least 37.9v. So maybe you could just hook it up alone after all. If it doesn't burn out with 37.9v and 1050 ma then why would it burn out with 36v and 500 ma? I can't guarantee it won't burn out, but it seems unlikely.

    PicklesRus Well-Known Member

    I'll double check the data sheets.

    BobCajun Well-Known Member

    Actually I think you need one of these. You'd have to set the output to about 32.3v. If it's cheaper to buy the constant voltage driver AND the step down converter than to buy a constant current driver then it would make sense.
    PicklesRus likes this.

    PicklesRus Well-Known Member

    Im just kind of surprised though, are all cob builders using constant voltage drivers using step down converters? I just haven't heard of it yet so I'm surprised that's all.

    BobCajun Well-Known Member

    Nobody ever uses constant voltage drivers for COBs, because CC is recommended.

    HalfBee Well-Known Member

    Well those of us that do use constant voltage for our Cobs enjoy our Buck converters very much thank you...
    PicklesRus likes this.

    welight Well-Known Member Rollitup Advertiser

    the approach people use to power cobs is subjective, ie needs based, there is never one best approach, but there is a sliding scale of simplicity/risk, certainly CC is simple and the leds have less function issues with this approach, specifically for multiple leds in series strings, this is the the low hanging fruit on this forum. The CV with step down convertors, is the same system as CC but you can control individual leds and can dim to 0, CV by itself is doable as discussed above but has some challenges, my biggest concern with it is your whole system hangs on stable mapped voltage, so for example your subject to unstable mains or surges(lighting strike etc) your total system is under threat, bottom line, whats your investment and how prepared are your to protect it
    PilouPilou and PicklesRus like this.

    PicklesRus Well-Known Member

    If you dim a cob on a cv doesn't it spill the extra current unused to the other cobs?

    sunny747 Well-Known Member

    I feel a little dumb asking this, but here it goes..
    Something I am confused about. Why do we generally run cobs at around 50 watts? Is it purely for efficiency?

    Say I just wanted 1 cob to fill a 2x2 and cost was a factor.

    Could I attach this Citi 1825 active cooled light engine to the Meanwell HGB 160 36v and 4.4a. This would run the Cob at 158 watts or so.



    Would it just be too hot or lose too much of its efficiency?

    If it worked it'd be a pretty cool little light for around 150 bucks. Maybe take off the reflector or use a 120 degree to avoid a hot spot?
    Rudi I&I Automan

    Rudi I&I Automan Well-Known Member

    anyone got one of those 600w double chip £35-£49 on ebay? the lights seem a little close to the edge, can't see a name on it, just wanted to know if they were worth it as ive had no help in powering my viper/ufo round 49 cree light panel. it came as is, no power units. rudi
    sunny747 likes this.

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