RGB LED Mixer

The tool calculates the required PWM duty cycles (0–100%) for each red, green, and blue channel to achieve a target RGB color on common-anode or common-cathode LED configurations. It also computes current-limiting resistor values based on your supply voltage and LED forward voltages (assumed typical: 2.0V R, 3.2V G, 3.2V B), ensuring safe and accurate color mixing.

For common-cathode LEDs, invert the calculated PWM duty cycles (i.e., use 100% – duty_cycle) since high signal turns the LED on. The tool assumes common-anode by default; no input change is needed—just reinterpret the output PWM values accordingly. Resistor calculations remain valid as they depend only on voltage drop and desired current.

The calculator uses standard nominal forward voltages: 2.0 V for red, 3.2 V for green, and 3.2 V for blue LEDs. These values reflect typical high-brightness InGaN (G/B) and AlInGaP (R) diodes. For precision applications, replace these with datasheet values and adjust manually if higher accuracy is required.

This input sets the supply rail voltage (e.g., 5 V, 12 V) used to compute voltage drops across current-limiting resistors. Since forward voltages are fixed internally, only the system V_CC is needed to determine resistor values per channel. It simplifies entry while maintaining practical design relevance for most constant-voltage driver setups.

No—this tool is designed for discrete, analog-controlled RGB LEDs driven via PWM and resistors. Addressable LEDs (e.g., WS2812B) use digital protocols and internal constant-current drivers; their color control maps directly to 0–255 RGB values without external resistor or PWM duty-cycle conversion.

Use ≥400 Hz to avoid visible flicker; 1–2 kHz is ideal for most applications. Higher frequencies reduce audible noise from ceramic capacitors or inductors but may increase switching losses. Ensure your MCU timer or driver IC supports the chosen frequency and maintains sufficient resolution (e.g., 8-bit = 256 steps) for perceptible color gradation.

Verify that your current-limiting resistors are sized for the *lowest* forward voltage channel (typically red), as it draws the most current at the same duty cycle. Also confirm LED brightness binning consistency—mismatched luminous intensities between R/G/B chips require gamma correction or calibrated PWM scaling, which this tool does not apply.

The tool maps linear 0–255 RGB inputs directly to 0–100% PWM duty cycles—e.g., R=128 → 50% duty cycle. Note that human vision perceives brightness logarithmically, so for photometric accuracy, apply gamma correction (typically γ ≈ 2.2) before converting RGB to PWM in production firmware.

20 mA per channel is standard for continuous operation in through-hole or basic surface-mount RGB LEDs. The calculator assumes this default current; if using high-power or SMD variants (e.g., 2020, 3535), consult the datasheet and adjust resistor calculations manually to match rated I_F and thermal limits.

No—it performs linear RGB-to-PWM conversion without chromaticity or luminosity compensation. Red LEDs typically emit more lumens per mA than blue, so equal PWM values often yield oversaturated reds. For balanced white or pastel tones, use measured luminance ratios or pre-weighted RGB inputs before entering values.