Author Topic: LED reverse voltage?  (Read 9111 times)

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Offline cooldogTopic starter

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LED reverse voltage?
« on: February 06, 2008, 05:09:24 AM »
this LED says that it's reverse volatge is 5v does that meen that i have to supply 5v

http://www.allelectronics.com/spec/LED-94.pdf
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Offline airman00

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Re: LED reverse voltage?
« Reply #1 on: February 06, 2008, 05:36:29 AM »
that LED runs off 2- 2.5 Volts according to datasheet
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Offline cooldogTopic starter

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Re: LED reverse voltage?
« Reply #2 on: February 06, 2008, 06:26:03 AM »
thanks can i run it a 3v

also i can't find the voltage for this one or the specs

http://www.allelectronics.com/cgi-bin/category.cgi?item=LED-2&category=search&type=
« Last Edit: February 06, 2008, 06:28:28 AM by cooldog »
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Offline gmatkins

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Re: LED reverse voltage?
« Reply #3 on: February 06, 2008, 09:27:54 AM »
Reverse voltage is the maximum "wrong way" voltage that this LED can tolerate. Anything over that and you start getting "wrong way" current.

With your first LED (the red one) 2.5 is listed as the maximum voltage you want to sustain across it. You can still use a 3 volt source  though as long as you use a resistor to turn some of them volts into heat, but it's not necessarily the most efficient way to do things.

Finally I think this is the spec sheet for you second LED (the green one)...
http://www.allelectronics.com/spec/LED-57.pdf

Offline airman00

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Re: LED reverse voltage?
« Reply #4 on: February 06, 2008, 10:16:54 AM »
Yea , you should always use a resistor with your LED

Search online for how to calculate that resistor value
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Offline benji

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Re: LED reverse voltage?
« Reply #5 on: February 06, 2008, 10:41:14 AM »
DONT USE A LED WITHOUT A RESISTOR, ITLL BURNNN
read the maxium current it can tolerate and choose your resistor according to that,
(consider leds resistance is approximatley 0)
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Offline HDL_CinC_Dragon

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Re: LED reverse voltage?
« Reply #7 on: February 06, 2008, 02:07:11 PM »
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Offline krich

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Re: LED reverse voltage?
« Reply #8 on: February 07, 2008, 10:17:16 PM »
You can still use a 3 volt source  though as long as you use a resistor to turn some of them volts into heat, but it's not necessarily the most efficient way to do things.

Dang it, just when I think I've got the basics learned, you have to go and say something like that.   ;)

My understanding is that you use a resistor to control the amount of Current flowing through the LED.  Are you saying that you can cause a drop in Voltage with a resistor too?

Offline Commanderbob

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Re: LED reverse voltage?
« Reply #9 on: February 07, 2008, 10:23:20 PM »
Quote
My understanding is that you use a resistor to control the amount of Current flowing through the LED.  Are you saying that you can cause a drop in Voltage with a resistor too?

You are correct. A resistor does control the amount of current flowing, but when the LED draws more current then the resistor allows the voltage drops.

Offline krich

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Re: LED reverse voltage?
« Reply #10 on: February 08, 2008, 01:27:49 AM »
Man oh man.  I've been doing my LED calculations wrong.  Probably not a huge deal, but... 

I just reread the LED tutorial.  I get it now.  Don't know why I didn't remember that part of the LED tutorial.

Thanks.


 


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