2024-03-25

How to choose the current limiting resistance of LED

The main part of the LED is also a PN junction, but after the LED is connected, its pressure drop is generally about 2V, and some leds can reach 3V. Common diodes have a voltage drop of about 0.5V, such as Schottky diodes.

Light-emitting diodes are often used as indicators. For example, when sending or receiving data, if the power indicator or communication indicator blinks, it means that data is being sent or received.

In the circuit design, a current limiting resistor should be connected in series. How to determine the value of current limiting resistance? First, we need to know the forward voltage and current of the LED. The forward voltage of the LED is 2.5V and the forward current is 5mA. This forward current has a range of values. If the current is too high, the diode may burn out. If the current is too small, the brightness of the LED is not enough.

These parameters can be found in the LED data book.

Assume that the DC voltage is 5V. Subtract the 2.5V voltage drop of the diode from 5V. The remaining 2.5V divided by 5mA of current. The resistance is equal to 500 ohms.

Therefore, a 500 ohm resistor is required in series in the circuit.