# LED Voltage

Discussion in 'The Projects Forum' started by torpedochief, Apr 22, 2010.

1. ### torpedochief Thread Starter Senior Member

Mar 30, 2008
126
6
I have a sorted number of LEDs. How do I determine required voltage? Also are the voltages different for RED, GREEN, WHITE?

Thanks friends you guys are of enormous help!

Don

2. ### ELECTRONERD AAC Fanatic!

May 26, 2009
1,146
16
Each of your LEDs will have a foreward voltage drop (1.8V ~ 3.2V, aroud there). The LEDs have internal resistance, which forms that voltage drop across each individual LED. Being the case, I would suggest that you connect a 5V source in series with a 250Ω resistor and LED. Then, take a voltmeter and measure the voltage drop across each of your LEDs. Once you know that, you can calculate the full brilliance of light:

$\frac{V_I_N - V_F}{I_F} = R$

Where Vin = 5V
Vf = Foreward voltage you previously found out with a voltmeter.
R = Resistance you end up needing in that series circuit I mentioned.

Austin

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3. ### torpedochief Thread Starter Senior Member

Mar 30, 2008
126
6
Just the info I needed! Thanks Austin!

Don