My cob light just fell over and then died, please help :/

nfhiggs

nfhiggs

Well-Known Member
DreadCthulhu said:
That thing runs 0-15A what amperage would I run that at?
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Amperage is determined by the voltage applied. You trim the voltage all the way down, connect the wires to the cob, then slowly adjust it upward until the cob starts to glow. it will only be pulling a few mA. The higher you push the voltage the more current flows through the cob. Even if you were to max it out, it will only go to 31 volts or so, not nearly enough voltage to drive the 36 v cobs more than a couple hundred mA.

The constant current Meanwell supplies just automatically adjust the voltage to maintain the current setting.
 
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DreadCthulhu

Member
nfhiggs said:
Amperage is determined by the voltage applied. You trim the voltage all the way down, connect the wires to the cob, then slowly adjust it upward until the cob starts to glow. it will only be pulling a few mA. The higher you push the voltage the more current flows through the cob. Even if you were to max it out, it will only go to 31 volts or so, not nearly enough voltage to drive the 36 v cobs more than a couple hundred mA.

The constant current Meanwell supplies just automatically adjust the voltage to maintain the current setting.
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Ahh, that makes sense. So with that power supply I'll just need to buy a power cord for it right, then just hook it up using the wire I already have to the ideal holders and I'll see which works.
 
nfhiggs

nfhiggs

Well-Known Member
DreadCthulhu said:
Ahh, that makes sense. So with that power supply I'll just need to buy a power cord for it right, then just hook it up using the wire I already have to the ideal holders and I'll see which works.
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Personally, I would disassemble it all and test each cob individually without any holder. Just hold the wires against the terminals. You won't have to worry about them getting hot, you'll only put a few mA into them, just long enough to see if they light up.
 
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DreadCthulhu

Member
nfhiggs said:
Personally, I would disassemble it all and test each cob individually without any holder. Just hold the wires against the terminals. You won't have to worry about them getting hot, you'll only put a few mA into them, just long enough to see if they light up.
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So happy right now. I had almost given up on something having knocked loose but I just found the loose wire and now my light works again. I really appreciate all the time you've taken to help me out tonight. I was so worried I fucked up my just built light. Thank you all so much.
 
M

Manfromthenorth

Well-Known Member
I have found that it takes some finangling to get the contacts on the holders to line up with the chips when it fell may have moved the chip just far enough to loose contact
 
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dstroy

dstroy

Well-Known Member
nfhiggs said:
Won't do any good. A cob does not read like a diode with a multimeter. It takes .7 volts to forward bias a single junction and Cobs have 10-25 junctions in series. That's 7 to 18 volts just to see a front to back ratio on it. A multimeter uses a little over .7 volts in its diode setting. Cobs will show open, good or bad with a meter - unless its shorted.

They will need to be removed and tested individually with an appropriate power source.

This is one reason I don't do series.
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Hey, so you can use a diode check function on a multimeter if your multimeter does that. I don't have my cheapo multimeter upstairs but I'm sure it has it. Checking forward and reverse bias resistance works as well.

Not sure why it wasn't working for you because it seems to be working fine on these brand new cree cxb 3590 which are large diode arrays.
 

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iHearAll

iHearAll

Well-Known Member
i use a variable dc supply to check cob and everything else on my benchtop. i use a 30v 10a supply which is enough to at least illuminate most devices if current is applied correctly. i have cracked cobs from too much heat exposure, this was a result of a diy-ist take on heat sinking without any math. it wasnt obvious because i would run a series of four cob and one would crack and break the circuit to the others. very much like a fuse.

if you want to be cheap, you can use 2ct 9v batteries in series to illuminate a chip at 18v. add another battery for 27v etc etc.

or if you have a transformer/bridge rectifier or 12vdc PSU you may be able to illuminate them partially
 
nfhiggs

nfhiggs

Well-Known Member
dstroy said:
Hey, so you can use a diode check function on a multimeter if your multimeter does that. I don't have my cheapo multimeter upstairs but I'm sure it has it. Checking forward and reverse bias resistance works as well.

Not sure why it wasn't working for you because it seems to be working fine on these brand new cree cxb 3590 which are large diode arrays.
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Might just be the particular meter. If you're using a good Fluke it may show a front to back ratio, but the little cheapie meters usually won't
 
I

ImAgrAsian

Active Member
For future use you can $5 rig up the chinese led driver(20v-39v, 300ma, 10w) and your AC power cord add a Switch if you wanna get fancy. Sorry Idk how to upload pics
 
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