Help on DIY LED brightness issue
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Old 02-20-2015, 07:09 AM   #1
dadodadolontong
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Help on DIY LED brightness issue


Hi all,

I need advise to troubleshoot my DIY LED; The installation is as follow:

Series of 15x1W White 350ma, with forward voltage around 3.0-3.8V
Driver's spec: 350ma, max Voltage 85VDC minimum operating voltage 60VDC

When I switched it on, the circuit is flashing, then stabilize but the light is very dimmed.

I have check all the cabling and soldering, everything seems ok.

Any clue?
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Old 02-20-2015, 09:29 AM   #2
sushant
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Quote:
Originally Posted by dadodadolontong View Post

Driver's spec: 350ma, max Voltage 85VDC minimum operating voltage 60VDC
what's the minimum output voltage and wattage of the driver??
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Old 02-20-2015, 01:07 PM   #3
jeffkrol
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Quote:
Originally Posted by dadodadolontong View Post
Hi all,

I need advise to troubleshoot my DIY LED; The installation is as follow:

Series of 15x1W White 350ma, with forward voltage around 3.0-3.8V
Driver's spec: 350ma, max Voltage 85VDC minimum operating voltage 60VDC

When I switched it on, the circuit is flashing, then stabilize but the light is very dimmed.

I have check all the cabling and soldering, everything seems ok.

Any clue?
Minimum operating voltage.. 60 volts

@ 3.8 you are barely there and at 350mA you are most likely not close to 3.8 V(f)
Using 20 diodes should get you to the operating range..
Your definitely a diode or 2 short.
Adding diodes is your first trouble shoot..

Checking for any bridging to the heat sink is next..
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Old 02-21-2015, 03:13 AM   #4
dadodadolontong
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Hi, I've found the culprit, one led has decided to become resistor. Replacing the led solved this issue.. Thanks all
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Old 02-21-2015, 05:52 AM   #5
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Originally Posted by dadodadolontong View Post
Hi, I've found the culprit, one led has decided to become resistor. Replacing the led solved this issue.. Thanks all
Huh, odd they usually fail "open"...
I still think you should increase the diode count..
If you are so inclined, measure the output voltage.. I'm curious.
Even the Chinese don't usually just make up specs like the 60V thing..
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Old 02-21-2015, 06:17 AM   #6
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Yes, very odd.. I added to 20 leds but it was still dimmed until I replace the faulty led.. Never thought it can become resistor-like
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Old 02-21-2015, 06:21 AM   #7
dadodadolontong
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I took measurement using multimeter on each led to check voltage drop.. , it shows 60volt on first led, 50 on input but 2 volt output on the faulty led..
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