What you'll learn

How a hobby servo reads a pulse width
Making 50 Hz PWM with machine.PWM
Turning degrees into a duty value
Powering a servo from 5 V and sharing ground

Difficulty: Beginner
Time: About 15 minutes
Board: ESP32-DevKitC V4
Parts: 3

How it works

A hobby servo turns to an angle set by the width of a pulse it receives every 20 milliseconds, which is 50 Hz. A 0.5 ms pulse means 0 degrees and a 2.5 ms pulse means 180 degrees. GPIO 15 sends that signal, and the servo is powered from 5 V.

The loop moves the servo one degree at a time from 0 up to 180, waiting 15 milliseconds per degree. It prints at 180, then sweeps back down and prints at 0.

Parts list

3 parts, plus the jumper wires. They retail for about $12.50; on Mokxi they're free.

1 × ESP32-DevKitC V4
1 × Hobby servoIn Halloween Prop Kit, Christmas Lights Kit, Starter Projects Kit.
1 × Power, 5 V

Kits that can build it

These 3 starter kits have every part in the circuit. Each kit's page lists what else it can build.

Wiring table

Every connection, pin by pin, read from the circuit itself. Each row joins the pin on the left to the pin on the right, by a jumper wire or a breadboard strip.

Part and pin	Connects to
Hobby servo pin PWM	ESP32-DevKitC V4 pin 15
Hobby servo pin GND	Ground
Hobby servo pin VCC	5 V

The code

The MicroPython code exactly as the editor opens it. Change a line there and press Run: the board runs it on the official MicroPython firmware, with nothing to compile.

main.py · ESP32-DevKitC V4

# Servo sweep: the servo on GPIO 15 turns from 0 to 180 degrees and
# back, a degree every 15 ms, driven by 50 Hz PWM.
from machine import Pin, PWM
import time

servo = PWM(Pin(15), freq=50)

def angle(deg):
    # 50 Hz is 20 ms a period: 0.5 ms (duty 26) is 0 degrees and
    # 2.5 ms (duty 128) is 180 degrees
    servo.duty(26 + deg * 102 // 180)

while True:
    for deg in range(0, 181):
        angle(deg)
        time.sleep_ms(15)
    print("at 180")
    for deg in range(180, -1, -1):
        angle(deg)
        time.sleep_ms(15)
    print("at 0")

Code walkthrough

The key functions of the sketch, and what each one does.

`angle` main.py

Turns an angle in degrees into a PWM duty. At 50 Hz a period is 20 ms, so 0.5 ms is duty 26 and 2.5 ms is duty 128. The line servo.duty(26 + deg * 102 // 180) spreads the 102 steps between those over 180 degrees.

def angle(deg):
    # 50 Hz is 20 ms a period: 0.5 ms (duty 26) is 0 degrees and
    # 2.5 ms (duty 128) is 180 degrees
    servo.duty(26 + deg * 102 // 180)

Troubleshooting

The usual mistakes with this circuit, and the fix for each.

The servo jitters or does not move This project
Check that the servo's PWM wire goes to GPIO 15, it is powered from 5 V, and its ground connects to the board's ground.
The sweep is too fast or slow This project
Change the time.sleep_ms(15) pause. It sets how long the servo gets per degree.
The servo jitters, twitches or resets the board when it moves. Hobby servo
Power it from its own 5 V supply, not the Arduino 5 V pin, and join the grounds. A hobby servo can pull several hundred milliamps. Add a 100 uF to 470 uF capacitor across its supply.
The servo hums at the end of its travel or will not reach full angle. Hobby servo
Stay inside the pulse range, about 1000 to 2000 us for most hobby servos. Pushing past the end stop makes it strain. Calibrate the min and max pulse for your servo.
The board is not found, or upload fails with a connecting message. ESP32-DevKitC V4
Use a USB cable that carries data, not charge only. Pick the ESP32 Dev Module board. If it still fails, hold BOOT while uploading starts, then release.
Some pins never read right, or the board will not boot with a wire attached. ESP32-DevKitC V4
GPIO34 to 39 are input only and have no pull-ups. GPIO6 to 11 run the flash, so leave them alone. GPIO0, 2 and 12 are boot pins; avoid pulling them the wrong way at reset.