Calculating the resistance and power capacity of the current limiting resistor is an important step in circuit design. The following is the specific calculation method:
Calculate the resistance value of the current limiting resistor
1. Basic formula:
According to Ohm's Law, the resistance of a current limiting resistor can be calculated using the following formula:
R = （V - Vf）/I
Among them:
-R is the resistance value of the current limiting resistor (unit: ohms Ω).
-V is the power supply voltage (unit: volts V).
-V_F is the forward voltage drop (in volts V) of components in a circuit, such as LEDs.
-I is the current to be controlled (unit: Ampere A).
2. For a single LED:
If the LED is used individually, the formula is:
Among them, V_supply is the power supply voltage, V_LED is the forward voltage of the LED, and I_LED is the current flowing through the LED.
3. For series connected LEDs:
If the LEDs are connected in series, the formula will consider the number of LEDs:
Among them, V_S is the source voltage, V_L is the voltage drop of a single LED, n is the number of LEDs in series, and I is the required current.
Calculate the power capacity of the current limiting resistor
1. Power calculation formula:
The power consumed by a resistor can be calculated using the following formula:
P = I²*R
Among them:
-P is power (unit: watt W).
-I is the current flowing through a resistor (unit: Ampere A).
-R is the resistance value of a resistor (in ohms Ω).
2. Practical application:
In practical applications, to ensure that the resistor is not damaged due to overheating, a higher power rating than the calculated power value is usually chosen. For example, if the calculated power is 0.06W, a resistor with a rated power of 1/10W (i.e. 0.1W) or higher may be selected.
By following the above steps, the resistance and power capacity of the current limiting resistor can be calculated to ensure the safe and stable operation of the circuit.