PROJECT 3 · PWM OUTPUT

PWM (Analog Output) — Fading an LED

Produce an analog‑looking output from a digital pin to smoothly fade an LED.

⬇ Download the sketch Save Project_3_ESP32_PWM.ino, then open it in the Arduino IDE (setup: Project 0b).

An LED shown at increasing brightness levels — Same LED, different duty cycles → different brightness.

1 · What is PWM?

A digital pin is only ever fully ON (3.3 V) or OFF (0 V). But switch it on/off very fast and the LED's average brightness follows the fraction of time it's ON — the duty cycle:

0% · off

25% · dim

50% · medium

75% · bright

100% · full

The switching here is 5000 Hz — far faster than the eye — so you see steady brightness, not flicker. That's Pulse Width Modulation.

PWM also dims lights, sets motor speed, and (Project 6) mixes colors on an RGB LED.

2 · The ESP32 LED PWM controller

The ESP32 has a 16‑channel LED PWM controller. Configure a channel, attach it to a pin, then write a brightness:

ledcSetup(channel, freq, resolution);  // define a PWM channel
ledcAttachPin(gpio, channel);          // route the channel to a pin
ledcWrite(channel, dutyCycle);         // set brightness (0..255 at 8-bit)

ledcWrite() takes the channel, not the GPIO. (Newer cores also offer analogWrite(), but these calls work everywhere.)

3 · Parts & wiring

Qty	Part	Notes
1	ESP32 · breadboard · jumper wires	—
1	LED	Has polarity
1	220 Ω resistor	Current limit

LED on GPIO 4 through a 220 ohm resistor to GND — GPIO 4 → 220 Ω → LED → GND.

GPIO 4 → 220 Ω → LED anode (long leg)
LED cathode (short leg) → GND

4 · Code & expected serial output

The sketch ramps 0→255 then 255→0 in a loop, printing one line per direction change (printing all 256 steps would be noise). Open Serial Monitor at 115200:

==============================================
 Project 3: ESP32 PWM (Analog Output)
==============================================
LED (PWM) -> GPIO 4
PWM: 5000 Hz, channel 0, 8-bit (duty 0..255)
The LED should fade up and down continuously.
----------------------------------------------
Fading UP   (0 -> 255)
Fading DOWN (255 -> 0)
Fading UP   (0 -> 255)
...

5 · Demonstration

LED fading on a breadboard — The LED breathes smoothly brighter and dimmer.

6 · Troubleshooting

Symptom	Likely cause	Fix
LED off	Reversed LED or mis‑wired pin	Long leg toward the 220 Ω / GPIO 4 side
Full‑on, no fade	Didn't upload / wrong pin	Re‑upload; confirm LED on GPIO 4
Fades but flickers	Frequency too low	Keep `freq` at 5000 Hz
Monitor blank	Wrong baud	Set it to 115200