Correct resistor for LED – In real life, LEDs cannot be separated from electronic devices. almost all electronic devices use LEDs such as TVs, radios, cars, home decor, aircraft, drones and so on, both in Axial and SMD types. But how do we connect this LED to the voltage source safely?
The most important thing is that we have to know the specifications of the LEDs we will use, both maximum current and voltage of the LED . In this article we will learn general LED specifications that are used by most projects. For more details, you can see the datasheet of the LED manufacturer you are using.
Generally LEDs have a maximum specification of forward current of 20mA and minimum forward voltage is 1.8 Volt and the maximum is 2.2 Volt. If the source voltage we use is 5 volts and we connect it to the LED without a resistor, the LED will burn so that we cannot be used again. Why? because the current flowing through the LED terminal or semiconductor exceeds the limit of the specification permitted by the LED itself. The solution is we have to use a resistor to limit the current flowing into the LED.
To get the right value or correct resistor for LED to be used, we will use the following formula:
We get the result of the calculation that the minimum resistor used is 139.99 ~ 140 Ohm. But in the market “as far as I know” there is no resistor with 140 Ohm resistance, which is near to that value is 150 Ohm. If we use a resistor with 150 Ohm resistance, the LED is still relatively safe but the light produced is very bright and will shorten the life of the LED. Generally, the resistance used by most people in limiting the LED’s electric current is in the range of 220 or 330 Ohms. The greater the resistance value used, the more dim the LED light will be.
In the picture above this is one example of using a resistor on an LED. Where the LED is connected to one of the Arduino Uno Digital pins that give HIGH logic or 5 Volt voltage. By using a resistor as a limiting current flowing the LED, the LED will be safe from burning and will extend the life of the LED itself.
If you need a calculator for calculating resistors for LEDs, you can use the LED calculator made by digikey.com. Please click here.