Red LED Resistor Calculator

Resistor Formula:

\[ R = \frac{V_{supply} - 1.8}{I_{led}} \]

Resistor Value (ohms):

Definition: This calculator determines the appropriate resistor value needed to safely operate a red LED in an electronic circuit.

Purpose: It helps electronics hobbyists and engineers select the correct current-limiting resistor to prevent LED damage.

The calculator uses Ohm's Law formula:

\[ R = \frac{V_{supply} - V_{led}}{I_{led}} \]

Where:

Explanation: The resistor drops the excess voltage (supply minus LED voltage) at the desired current.

Details: Correct resistor selection ensures LED longevity, proper brightness, and prevents overheating or failure.

Tips: Enter your power supply voltage and desired LED current (typically 10-20mA). All values must be > 0.

Q1: Why 1.8V for red LED?
A: Most standard red LEDs have a forward voltage drop of approximately 1.8V.

Q2: What's a typical LED current?
A: Common values are 10-20mA (0.01-0.02A), but check your LED's datasheet.

Q3: What if my supply voltage is less than 1.8V?
A: The LED won't light properly - you'll need a higher voltage supply.

Q4: How do I choose the resistor power rating?
A: Calculate power with P = I²R and select a resistor with higher wattage.

Q5: Can I use this for other color LEDs?
A: No, use different forward voltages (e.g., 2.1V for yellow, 3.3V for blue).