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LED Resistor Formula:
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The LED current limiting resistor formula calculates the appropriate resistor value to limit current through an LED to a safe level. This prevents the LED from burning out due to excessive current.
The calculator uses the LED resistor formula:
Where:
Explanation: The formula calculates the voltage drop across the resistor and divides it by the desired current to determine the required resistance.
Details: LEDs are current-driven devices that require precise current control. Without proper current limiting, LEDs can be damaged or destroyed by excessive current. The resistor ensures the LED operates within its specified current range.
Tips: Enter the supply voltage in volts, LED forward voltage in volts, and desired forward current in amperes. All values must be positive, and the supply voltage must be greater than the LED forward voltage for the calculation to work properly.
Q1: What happens if I don't use a current limiting resistor?
A: Without a current limiting resistor, the LED will draw excessive current, potentially causing it to overheat and fail prematurely or instantly.
Q2: Can I use this calculator for multiple LEDs?
A: For multiple LEDs in series, add their forward voltages. For parallel configurations, calculate resistors for each LED separately.
Q3: What if my calculated resistor value isn't a standard value?
A: Use the next higher standard resistor value to ensure the current doesn't exceed the LED's rating.
Q4: How do I determine the LED's forward voltage?
A: Check the LED's datasheet. Typical values are 1.8-3.3V for red/yellow/green LEDs and 3.0-3.6V for blue/white LEDs.
Q5: What wattage resistor should I use?
A: Calculate power using P = I²R and choose a resistor with at least twice the calculated wattage for safety.