Calulate a resistor value uising Ohms Law
Submitted by Phil on Tue, 06/15/2010 - 16:50
We can then apply Ohms law to calculate the value of resistori needed.
Step 1 We first need to work out the difference in the voltage between the source and the component this is 12V - 3.4V = 8.6V
I thought users would find this easy to understand
First of all we need to collect the following information:
- The voltage of the supply
- The forward voltage of the component eg L.E.Di<
- The current the component uses
For calculating resistance we use the formula R= V ÷ I lets take the following as an example: Blue LED = 3.4V Forward voltage and 30mA maximum current, The supply voltage is 12V DC.
Step 2 We convert the current rating from mA into A we simply divide by 1000.
We now have R = 8.6 ÷ 0.03 Therefore R = 286 Ohms
The nearest resistori values would be 330 Ohms for carbon film resistors and 300 Ohms for Metal Film Resistors
I hope this helps.