Connecting an LED light to 12V DC supply is possible only with a resistor or buck converter. If you planning for buck converter based projects, it makes more cost. In this article learn how to connect a 3V LED to a 12v supply directly using a single resistor and it is a less cost method also.
12V to LED Resistor Connection Diagram
Calculating the Resistor Value
To find out the correct resistor value for connecting LED with a 12V supply is using the formula of,
R = (Vs-Vf) / I
- R = Resistance value in ohms.
- Vs = source voltage it is 12VDC
- Vf = Forward voltage of LED
- I= Current of the LED in Amps.
The forward voltage and current is depending on the type of LED like color and size of the LED. To know the exact forward voltage and current you needs to check the official Datasheet of the LED. For white LED Vf is 3.4V and LED current I = 10mA or 0.01A
R = (12V- 3.4v) / 0.01A = 860ohms
Calculating the Power Rating of the Resistor
The resistors are comes with 1/4watt, 1/2watt and more high wattages, to ensure the resistor is not heating up select the right wattage for the LED. To find out the wattage of the resistor we follows the formula of,
P = (Vs-Vf) x I
So based on the above resistor calculations we got the resistance value of 860ohms. The wattage of the resistor is calculated as,
R = (12V- 3.4v) x 0.01A = 0.086W
1/4 watt resistor = 0.25W, the watt we needs in the 860ohms resistor is 0.086. So we can use this 1/4watt resistor and the resistor wont heat up.
For a White LED needs 820ohms resistor with wattage of 1/4 to work perfectly without fails.
