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Author Topic: LEDs: What resistor do I need?  (Read 896 times)

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Sasquatch!

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LEDs: What resistor do I need?
« on: January 31, 2004, 09:54:37 pm »
I'm wanting to place on order from Mouser to do OSCAR's very cool LED driver board, but I'm stuck on the resistors that I need

The equasion is (supply voltage minus forward voltage) divided by LED current.  I get that - I'll be using 5V from the power supply, and the LEDs that I have (blue and white) are both 3.5V.  But what I'm stuck on is the LED current.  My LEDs are 2500 mcd (for the white) and 1500 mcd (for the blue), but is that the "LED current", or just how bright they'll be?  If it's not the LED current, then I have no idea how to find this out.

Help?

Edit: Doh, fixed the URL code.
« Last Edit: January 31, 2004, 10:02:01 pm by Sasquatch! »
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OSCAR

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Re:LEDs: What resistor do I need?
« Reply #1 on: January 31, 2004, 10:04:16 pm »
Correct, the mcd value is the brightness.  Most all super bright LED's will illuminate correctly with .020 amps, so use that number in your equation.  I always figure on 20 mA for a super bright and haven't blown one yet.
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Sasquatch!

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Re:LEDs: What resistor do I need?
« Reply #2 on: January 31, 2004, 10:30:45 pm »
Cool.  Thanks (AGAIN!) for the info, OSCAR.
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OSCAR

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Re:LEDs: What resistor do I need?
« Reply #3 on: January 31, 2004, 10:36:12 pm »
Quote from: Sasquatch! on January 31, 2004, 10:30:45 pm
Cool.  Thanks (AGAIN!) for the info, OSCAR.


No problem, bud, let us know how it works out!   :)


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