DiY LEDs - How to Power Them

[BobCajun]

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

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.

 

[PicklesRus]

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.

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]

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.

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]

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.

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]

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)

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

 

[BobCajun]

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]

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.

I'll double check the data sheets.

 

[BobCajun]

I'll double check the data sheets.

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]

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.

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]

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.

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

 

[HalfBee]

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

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

 

[welight]

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
Cheers
Mark

 

[PicklesRus]

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
Cheers
Mark

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

 

[sunny747]

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.

https://cobkits.com/product/clu058-1825-light-engine-single/

http://www.mouser.com/ProductDetail/Mean-Well/HBG-160P-36B/?qs=sGAEpiMZZMvV8Y9YugmIgnF6KVaZUxTyNNg1uvWUM3MESk3FhLloSA==

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]

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

 

[BobCajun]

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.

https://cobkits.com/product/clu058-1825-light-engine-single/

http://www.mouser.com/ProductDetail/Mean-Well/HBG-160P-36B/?qs=sGAEpiMZZMvV8Y9YugmIgnF6KVaZUxTyNNg1uvWUM3MESk3FhLloSA==

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?

It says it requires 50v though.

 

[sunny747]

It says it requires 50v though.

Yea, I thought of that after I posted.. I made the assumption that it was a 36v, but it's not.

For the sake of argument lets say it was a 50v driver running at 3 amps. What's wrong with running these cobs at higher wattage's? I believe you lose efficiency,.

If that's the case, then will there be a day when we have single cobs that can run at higher wattages and still be efficient?

I only ask because it's nice to have a powerful single COB light source. It cuts down on cost and complexity of build etc.. think of a 600w HID. You just buy it for $150 bucks and in 10 minutes your lights are rigged and on. Then you spend the rest of the summer worrying about heat and your AC bill etc

 

[BobCajun]

Yeah you just lose efficiency. At 25 C and 3000 ma it runs at 55v though so you'd need even higher driver voltage. Most of them only go up to 54v which may not be enough. Most don't go up to 3 amps either. Probably better off to use more COBs at lower power, just from a driver availability standpoint.

 

[sunny747]

Yeah you just lose efficiency. At 25 C and 3000 ma it runs at 55v though so you'd need even higher driver voltage. Most of them only go up to 54v which may not be enough. Most don't go up to 3 amps either. Probably better off to use more COBs at lower power, just from a driver availability standpoint.

Thank you..

Here s a 60v at 2.6 amps.
http://www.mouser.com/ProductDetail/Mean-Well/HBG-160P-60A/?qs=sGAEpiMZZMt5PRBMPTWcaTdz0ax3t15k5ED5DVE8TEzmVYkWsCYhDA==

I'm just stuck on this thought because there is a producer putting together nice 55w units using 1812's I believe... I just like the single light design. I'd just like more watts. I guess there is no free lunch

 

[BobCajun]

Thank you..

Here s a 60v at 2.6 amps.
http://www.mouser.com/ProductDetail/Mean-Well/HBG-160P-60A/?qs=sGAEpiMZZMt5PRBMPTWcaTdz0ax3t15k5ED5DVE8TEzmVYkWsCYhDA==

I'm just stuck on this thought because there is a producer putting together nice 55w units using 1812's I believe... I just like the single light design. I'd just like more watts. I guess there is no free lunch

View attachment 3870980

There's a problem with that driver too, because it's constant voltage and constant current, which means it puts out exactly 60v all the time, which is too high. The voltage of COBs changes from when they're first turned on to when they get to the highest temperature. That's why I don't think constant voltage is appropriate for COBs. I don't know the exact details of what happens when you try to drive a COB with CV but it looks problematic to me. Maybe there's enough safety factor in the COB voltage requirements that it would work, but maybe there's not. I recommend finding a CC only driver with a voltage range considerably beyond the COB's requirements in both directions. I wouldn't try to max out the driver's voltage range, I'd leave a safety factor of probably at least 5v.