what Vdrop do u get across a Good or bad LED ? - diyAudio
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Old 8th April 2003, 10:48 PM   #1
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Default what Vdrop do u get across a Good or bad LED ?

eg 12v ,1k resistor in series,

thanks
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Old 8th April 2003, 11:06 PM   #2
Jeff R is offline Jeff R  United States
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About a volt in the forward (on) direction if good. If you see 12 volts, the device is obviously bad if hooked up correctly. But if you have voltage and a resistor, the LED will turn on if it is good and you hook it up in the right direction, so you can measure the voltage directly.
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Old 16th April 2003, 12:39 AM   #3
EC8010 is offline EC8010  United Kingdom
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1.7V for a red LED. More for other colours (up to about 3.6V for blue).
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Old 10th August 2016, 02:11 PM   #4
jfetter is offline jfetter  United States
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i get around 2.1 for red
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Old 10th August 2016, 02:31 PM   #5
AndrewT is offline AndrewT  Scotland
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IR Leds from ~1.2Vf to 1.3Vf
red LEDs from ~1.6Vf to 1.9Vf
yellow and orange and green LEDs from ~1.8Vf to 2.0Vf
white and blue LEDs from ~2.9Vf to 3.3Vf

each manufacturer is usually different.
I don't have any manufacturer codings on any of my LEDs, that means a random LED pulled from the drawer could be anywhere in the range for that type !
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Old 10th August 2016, 02:48 PM   #6
TheGimp is offline TheGimp  United States
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Voltage will depend on the current. As long as you are between 1 and 10mA, what AndrewT stated is pretty good. However I've operated LEDs at 0.5mA and the voltage is lower because you are down in the knee of the curve for the I/V relationship.

Some of the newer low current LEDs will turn on at very low currents, but they are almost exclusively in SMT packages so you probably won't encounter them.

Nothing like guessing which the clear plastic LED is, white or IR?
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