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Subject: Re: controlling leds

Date: 11/26/02 at 5:13 PM
Posted by: Russ Kincaid
E-mail: russlk@netzero.com
Message Posted:

In Reply to: Re: controlling leds posted by Richard Astley on 11/26/02 at 4:30 PM:

390 ohms was designed to supply 20 mA to a 2 volt LED. The red LED is probably 1.6 volts, the green & blue LEDs are probably higher than 2 volts.

In the equation below, the symbols mean:
Vs=Source voltage
0.5v=transistor Vbe
Vled="on" voltage of LED
R=current limiting resistor
I=rated current for the LED

R=(Vs-0.5-Vled)/I


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