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

"In the core C# language it is simply not possible to have an uninitialized
variable, a 'dangling' pointer, or an expression that indexes an array
beyond its bounds. Whole categories of bugs that routinely plague C and C++
programs are thus eliminated." - A. Hejlsberg, The C# Programming Language

 

[Watson A.Name - "Watt Sun]

In article <4Kmdnd8SMM_4HWqiRVn-hA@speedfactory.net>,
look@www.covingtoninnovations.com.for.address mentioned...

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!

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[Chaos Master]

Michael A. Covington[look@www.covingtoninnovations.com.for.address] said this in
sci.electronics.components, at Sat, 3 Jan 2004 21:54:25 -0500, in article
<4Kmdnd8SMM_4HWqiRVn-hA@speedfactory.net>. I can prove it. And thus I reply:

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


--
ChaosŽ - posting from Brazil
Please ask for e-mail address.

 

[Michael A. Covington]

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