EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: Raj on September 20, 2020, 05:35:03 am
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How come we never see leds lighting up at under 3v, outside of optocouplers? (sometimes even 1.5v)
How strong (optical power/ electrical watts) would they be, outside of optocoupler? compared to standard ir led
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What do you mean? The forward voltage drop of a typical red LED is between 1.7 to 2V.
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I believe voltage drop is mainly a function of color, something to do with individual energy of emitted photons and stuff like that. IR is the lowest, UV is the highest. White is a modified blue LED so also quite high.
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Optocouplers use IR-LEDs.
The >3 V you're quoting are for blue LED's (that can be converted to white with a fluorescent coating).
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I believe voltage drop is mainly a function of color, something to do with individual energy of emitted photons and stuff like that. IR is the lowest, UV is the highest. White is a modified blue LED so also quite high.
Only sort of. LEDs are made by using different technologies. Thus LEDs of the same color have different forward voltages.
(https://i.stack.imgur.com/9VdZX.png)
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I've been overvolting leds for such a long time* :-DD
*Except when the seller stated what voltage it should run at
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You should learn what is called constant current driven device.
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You should learn what is called constant current driven device.
Yes indeed. Used them with lasers since their forward voltage is all over the place depending on uncontrollable factors
With Led, I was like, eh, 3v is ok... if the current and supply voltage is high, like for flashlight, I just throw an LM317(easy to use constant current driver, but I'm looking to find better, more efficient drivers) in there set usually at 75% of max current.