Choosing the perfect resistance for LED

How to choose the perfect resistance for your LED circuit.

Introduction-

Choosing the correct resistance value is an important thing to ensure that your LED receives the proper voltage and current. Choosing the wrong valued resistor will shorten the life of your LED or may kill it.

To calculate the correct value for the resistance, you should know these 3 things- 

1. Vf - forward voltage for your LED

2. If - forward current of your LED

3. Vcc - Supply voltage 

With these, you can calculate the resistance value using a simple equation - 

R= (Vcc - Vf) / If 

Now we have to calculate the power dissipation by the resistor, P= V x I,

Power dissipation by resistor = (Vcc- Vf) x If 

Example - 

For a LED with Vf = 3v , If = 20mA and Vcc = 9v

R= (9-3)/0.02 = 300 ohms 

P = (9-3)x 0.02 = 0.12W

So we can go for a 330 ohm 1/4W resistor. 

Buy your resistor kit here- 

Amazon.in