Arduino Code for RGB LED: Driver Sizing, Flicker Fixes, and Circuit Math

The Core Circuit: Arduino Code for RGB LED PWM Control

Standard AVR-based Arduino boards (like the Uno) output PWM at roughly 490 Hz by default. When you point a smartphone camera at a 490 Hz light source, the rolling shutter creates a beat frequency, resulting in severe visual banding. To fix this, we use the ESP32 DevKit v1 programmed via the Arduino IDE. The ESP32's LED Control (LEDC) peripheral allows us to push the PWM frequency to 20 kHz, which is entirely imperceptible to both the human eye and high-speed camera sensors Espressif LEDC API Documentation.

Because the ESP32 GPIO pins output 3.3V logic and can only source about 40mA, you cannot drive the LED strip directly. You must use N-channel logic-level MOSFETs (like the IRLZ44N) to switch the 24V load. The gate threshold voltage (Vgs) of the IRLZ44N is fully saturated at 3.3V, making it ideal for direct ESP32 drive without a gate driver IC.

// ESP32 Arduino IDE Code for 20kHz Flicker-Free RGB PWM
const int freq = 20000; // 20 kHz to eliminate camera flicker
const int resolution = 12; // 12-bit resolution (0-4095)
const int redPin = 16;
const int greenPin = 17;
const int bluePin = 18;

void setup() {
  // Configure LEDC channels
  ledcSetup(0, freq, resolution);
  ledcSetup(1, freq, resolution);
  ledcSetup(2, freq, resolution);
  
  // Attach channels to GPIO pins
  ledcAttachPin(redPin, 0);
  ledcAttachPin(greenPin, 1);
  ledcAttachPin(bluePin, 2);
}

void loop() {
  // Example: Smooth crossfade to warm white (RGB: 255, 180, 50 equivalent in 12-bit)
  ledcWrite(0, 4095); // Red 100%
  ledcWrite(1, 2890); // Green ~70%
  ledcWrite(2, 800);  // Blue ~20%
  delay(5000);
  
  // Fade out
  for(int duty = 4095; duty >= 0; duty -= 10) {
    ledcWrite(0, duty);
    ledcWrite(1, duty * 0.7);
    ledcWrite(2, duty * 0.2);
    delay(5);
  }
  delay(2000);
}

Sizing the Power Supply (Lumens, Watts, and Inrush Math)

When sizing a constant-voltage (CV) power supply for an RGB strip, you must calculate the maximum simultaneous draw (all channels at 100% duty cycle, yielding white light) and add a 20% derating margin for thermal longevity. Below is a lumens and watts equivalence table for standard 24V architectural strips, including efficacy context to help you judge light output per watt DOE Solid-State Lighting Basics.

Circuit Impact Math: Let's size for the 120 LEDs/m strip (144W total). Adding the 20% safety margin brings our required continuous capacity to 172W. A standard 200W 24V supply is required. However, the hidden killer in LED circuit design is inrush current. When a switching power supply like the Mean Well LRS-200-24 is first energized, the bulk input capacitors act as a dead short. The datasheet specifies a cold-start inrush of 60A for 0.5ms at 230VAC. If you put this on a standard 10A Type B residential breaker, the magnetic trip will instantly fire. You must use a Type C or Type D MCB (Miniature Circuit Breaker) which tolerates 5x to 10x instantaneous inrush spikes without tripping.

Additionally, consider the Power Factor (PF). A 200W driver with active PFC will show a PF of 0.95 at full load. But if your Arduino code spends most of its time dimming the strip to 20% brightness, the PF can drop to 0.75, increasing the apparent power (VA) and causing slight inefficiencies on the AC mains side.

Dimmer Compatibility and Wall-Switch Integration

If your project requires integration with a physical wall switch, you cannot place a standard AC dimmer on the DC output of the power supply, nor can you use a leading-edge (TRIAC) dimmer on the AC input of a switching power supply. Leading-edge dimmers chop the front of the AC sine wave, which causes the power supply's EMI filter capacitors to draw massive current spikes, resulting in audible buzzing, destroyed TRIACs, and premature driver failure Lutron LED Dimming Guide.

Which dimmer/driver for this fixture count? For a single 5-meter run of 120 LED/m RGB strip (144W), pair the Mean Well PWM-120-24 (a dedicated CV dimmable driver) with the Lutron Diva DVELV-300P trailing-edge dimmer. The PWM-120-24 translates the AC phase-cut signal into a clean 24V PWM signal for your strip, bypassing the need for the ESP32 MOSFET circuit entirely if you only want wall-dimming. If you want ESP32 smart control *and* wall dimming, wire the Lutron to a smart relay, and let the ESP32 handle the DC-side MOSFET dimming.

Solving PWM Flicker and Thermal Enclosure Constraints

Why flicker happens and the fix: As mentioned, 490 Hz PWM causes rolling-shutter banding. But there is a second type of flicker: low-frequency strobing caused by the power supply's internal protection circuits. If your ESP32 code demands more current than the power supply's rated limit (e.g., asking for 150W from a 120W driver), the driver enters 'hiccup mode'—shutting down and restarting every 2 seconds. The fix is strict adherence to the 80% continuous load rule outlined in the sizing table above.

Heat and enclosure constraints: High-density RGB strips generate significant heat at the PCB trace level. While the IRLZ44N MOSFETs on your breadboard will only dissipate about 0.088W each (Calculated via $P = I^2R$, where $I = 2A$ and $R_{ds(on)} = 0.022\Omega$), the LED strip itself will degrade rapidly if trapped in a sealed enclosure. A 28.8 W/m strip running at 100% white in a sealed polycarbonate diffuser will push the LED junction temperature past 85°C, causing a 30% drop in lumen output within 6 months. You must mount high-density strips inside an aluminum extrusion channel with a thermal pad to act as a heatsink, and ensure the MOSFET driver board has at least 15mm of clearance for convective airflow inside your project enclosure.

Decision Tree: Finalizing Your Component Pick

Use this decision path to lock in your exact Bill of Materials (BOM) based on your strip length and control requirements. Do not mix and match incompatible topologies.

Final Default Recommendation: For the most common architectural use case—a 5-meter run of 24V COB RGB strip (120W total) requiring both smooth color mixing and zero camera flicker—purchase the Mean Well PWM-120-24 power supply, an ESP32 DevKit v1, and three IRLZ44N MOSFETs. Wire the ESP32 to the DC side using the 20kHz code provided above, and leave the AC side on a dedicated 10A Type C breaker. This exact configuration eliminates flicker, survives inrush spikes, and provides 1:1 color resolution without thermal throttling.