Reverse-biasing an LED?

[Michael A. Covington]

Would an ordinary red LED be damaged by reverse-biasing it with 12 volts
delivered through a 1k resistor?

I'm adding reverse-polarity protection to a circuit, and one LED will be
left unprotected unless I add a component.

I know the data sheets say not to reverse-bias LEDs, but I don't know how
much damage actually occurs, or how much resistance would prevent it.

Thanks!


--

Michael A. Covington - Artificial Intelligence Ctr - University of Georgia

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variable, a 'dangling' pointer, or an expression that indexes an array
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[Watson A.Name - Watt Sun, Dark Remover]

Would an ordinary red LED be damaged by reverse-biasing it with 12 volts
delivered through a 1k resistor?

The specs say the maximum reverse voltage is usually 5VDC, so anything
over that would exceed the maximum. But someone pointed out a
document that showed tests done in conditions simulating the
automobile environment, and tests showed that LEDs could hold up under
much higher reverse voltages without damage.

I'm adding reverse-polarity protection to a circuit, and one LED will be
left unprotected unless I add a component.

So, add the component. Like a 1N4148 or whatever.

I know the data sheets say not to reverse-bias LEDs, but I don't know how
much damage actually occurs, or how much resistance would prevent it.

If damage occurs it will probably be catastrophic.

Thanks!

--
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[Chaos Master]

Michael A. Covington[[email protected]] said this in
sci.electronics.components, at Sat, 3 Jan 2004 21:54:25 -0500, in article

Would an ordinary red LED be damaged by reverse-biasing it with 12 volts
delivered through a 1k resistor?

In theory, yes. But it's tested that in automotive environments LED's may not
suffer from exposure to higher voltage.

I'm adding reverse-polarity protection to a circuit, and one LED will be
left unprotected unless I add a component.

Add an 1N4148 diode as protection.

IIRC, it would be something like this:
(If I am wrong, someone correct me, please. It's 03:45 AM here (Brazil)).


1N4148 (I think 1N400x series also works too)

.-|<-.
| |
1k_ | |
----|___|--.->|-.--.
| L.E.D |
Your 12V --- |
- |
| |
'-------------------'

created by Andy?s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

 

[Michael A. Covington]

Thanks. Even better, I'll put in a two-color LED: green for normal
operation, red for reverse polarity.