Calculation of the current limiting resistor for LEDs
Each LED has a maximum allowable current with which it can operate normally. Even a short-term excess of this maximum current will damage the LED. Thus, it is necessary to limit the current flowing through the LED, one of the ways is to connect a current-limiting resistor in series. It is important to note that this method is not recommended for high-power LEDs that need a full-fledged current regulator.
This calculator allows you to calculate the value of the current limiting resistor, which must be connected in series to the LEDs to limit the current. To do this, enter the specified values. The calculator will also calculate the power dissipated by the resistor, which will help you select the necessary power resistor.
Calculation formula
Where:
– The voltage of the power supply.
– Direct voltage. Voltage drop at the p-n junction of the LED.
– Forward current. The current at which the LED will work normally will not overheat and the p-n junction will not be broken. For LEDs with a diameter of 3 mm and 5 mm, it is usually 10-30 mA.
– The number of LEDs connected in series.
The table below shows the approximate values of the voltage drop on LEDs of different colors:
| LED Color | Voltage Drop (V) |
|---|---|
| Infrared | 1.9 |
| Red | 1.6 - 2.03 |
| Orange | 2.03 - 2.1 |
| Yellow | 2.1 - 2.18 |
| Green | 1.9 - 4 |
| Blue | 2.48 - 3.7 |
| Violet | 2.76 - 4 |
| Ultraviolet | 3.1 - 4.4 |