SENSORS/ACTUATORS

INTERNET OF THING (IoT)

ESP32 S3 UNO - Motion Sensor - Servo Motor

This ESP32 S3 Uno motion sensor servo motor tutorial shows you how to wire an HC-SR501 PIR sensor and a servo motor to the ESP32 S3 Uno form board and control them with Arduino code. When the PIR motion sensor sees a person, the servo turns to 90 degrees, and when the movement ends, it goes back to 0 degrees. You can use the same idea to open a small gate, aim a camera, or move a robot arm.

In this tutorial, you will:

Wire an HC-SR501 motion sensor and a servo motor to the ESP32 S3 Uno
Set the time delay, detection range and trigger mode of the PIR sensor
Detect when motion starts and stops with digitalRead()
Rotate a servo motor with the ESP32Servo library

Hardware Preparation

1	×	ESP32 S3 Uno-form Board
1	×	USB Cable Type-A to Type-C (for USB-A PC)
1	×	USB Cable Type-C to Type-C (for USB-C PC)
1	×	HC-SR501 Motion Sensor
1	×	Alternatively, AM312 Mini Motion Sensor
1	×	Servo Motor
1	×	Jumper Wires

Or you can buy the following kits:

DIYables Sensor Kit (18 sensors/displays)

Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you.
Additionally, some of these links are for products from our own brand, DIYables .

Buy Note: For controlling multiple servo motors, use the PCA9685 16 Channel PWM Servo Driver Module to save MCU pins and simplify wiring.

Overview of Servo Motor and Motion Sensor

This project links one input and one output. The motion sensor tells the board when someone moves, and the servo motor turns to show it. If one of these parts is new to you, read its own tutorial first. Each one explains the pinout, how the part works, and how to program it.

Servo motor

A servo turns its arm to an exact angle between 0 and 180 degrees. The board sets the angle with a PWM signal on one wire. See the ESP32 S3 Uno - Servo Motor tutorial.

Motion sensor

The HC-SR501 is a PIR (passive infrared) sensor. It feels the body heat of people and animals. Its OUT pin goes HIGH when it detects movement and goes back to LOW when the movement is over. See the ESP32 S3 Uno - Motion Sensor tutorial.

ESP32 S3 Uno Pinout

The image below shows the pinout diagram of the ESP32 S3 Uno form board. Use it to find the Uno header pins (D2, D9, 5V…) and their GPIO numbers when you connect the sensor and the servo.

Wiring Diagram

Connect the motion sensor output to D2 and the servo signal wire to D9, as shown below. Both parts take power from the 5V pin and share the board GND.

This image is created using Fritzing. Click to enlarge image

Component Pin	ESP32 S3 Uno Pin
Motion Sensor VCC	5V
Motion Sensor OUT	D2 (GPIO18)
Motion Sensor GND	GND
Servo VCC (red)	5V
Servo GND (brown or black)	GND
Servo Signal (orange or yellow)	D9 (GPIO46)

D9 is GPIO46, a boot strapping pin on the ESP32 S3 Uno. The board checks this pin at power-up to choose its boot mode. A servo signal wire is usually safe here. But if the board does not boot or cannot upload code, unplug the servo signal wire from D9, upload the code, and then plug it back in.

※ NOTE THAT:

The HC-SR501 runs on 5V, but its OUT pin gives a 3.3V signal, so it is safe for the ESP32 S3 Uno input. ESP32 S3 Uno pins are NOT 5V tolerant, so never connect a 5V signal to them. The servo also runs on 5V, but its signal wire only receives a 3.3V signal from the board. Most hobby servos work fine with this.

Initial Setting

The HC-SR501 has two small screws and one jumper on its back. Set them as below before you run the code. This makes the sensor react quickly and gives it the longest range, so the servo moves as soon as you walk by.


Time Delay Adjuster	Turn it fully anti-clockwise.
Detection Range Adjuster	Turn it fully clockwise.
Repeat Trigger Selector	Place the jumper as shown in the image.

ESP32 S3 Uno motion sensor initial setting

ESP32 S3 Uno Code - Motion Sensor Controls Servo Motor

The sketch reads the motion sensor on D2 (GPIO18) in every loop and compares the new state with the last one. When the state changes, it prints a message to the Serial Monitor and moves the servo on D9 (GPIO46) to 90 degrees or back to 0 degrees.

/* * This ESP32 S3 Uno code was developed by newbiely.com * * This ESP32 S3 Uno code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/esp32-s3-uno/esp32-s3-uno-motion-sensor-servo-motor */ #include <ESP32Servo.h> #define MOTION_SENSOR_PIN 18 // The ESP32 S3 Uno pin GPIO18 (D2) connected to motion sensor's pin #define SERVO_PIN 46 // The ESP32 S3 Uno pin GPIO46 (D9) connected to servo motor's pin Servo servo; // create servo object to control a servo // variables will change: int angle = 0; // the current angle of servo motor int prev_motion_state; // the previous state of motion sensor int motion_state; // the current state of motion sensor void setup() { Serial.begin(9600); // initialize serial pinMode(MOTION_SENSOR_PIN, INPUT); // set ESP32 S3 Uno pin to input mode servo.attach(SERVO_PIN); // attaches the servo on GPIO46 (D9) to the servo object servo.write(angle); motion_state = digitalRead(MOTION_SENSOR_PIN); } void loop() { prev_motion_state = motion_state; // save the last state motion_state = digitalRead(MOTION_SENSOR_PIN); // read new state if (motion_state == LOW && prev_motion_state == HIGH) { // pin state change: LOW -> HIGH Serial.println("Motion detected!"); servo.write(90); } else if (motion_state == HIGH && prev_motion_state == LOW) { // pin state change: HIGH -> LOW Serial.println("Motion stopped!"); servo.write(0); } }

The standard Servo.h library does not work on the ESP32 S3 Uno, so the code uses ESP32Servo.h. It has the same attach() and write() functions, so the rest of the logic does not change.

Detailed Instructions

New to the ESP32 S3 Uno? Follow ESP32 S3 Uno - Getting Started first.
Wire it up as shown in the diagram.
Connect the board to your computer with a USB Type-C cable.
Open Arduino IDE, choose the ESP32S3 Dev Module board and the correct COM port.
Install the ESP32Servo library. Open the Library Manager, search for ESP32Servo, and install the one by Kevin Harrington.
Copy the code above and paste it into Arduino IDE.
Upload the code by clicking the Upload button.
Wave your hand in front of the motion sensor.
Watch the servo turn, then open the Serial Monitor at 9600 baud to see the messages.
Tip: The PIR sensor needs about 30 to 60 seconds to settle after power-up. Wait a little before you test it, or you may see false triggers.

Newbiely | Arduino IDE 2.3.8

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Newbiely.ino

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8 Serial.println("Hello World!");

Output

Serial Monitor

Message (Enter to send message to 'ESP32S3 Dev Module' on 'COM15')

New Line

9600 baud

Motion detected! Motion stopped! Motion detected! Motion stopped!

Ln 11, Col 1

ESP32S3 Dev Module on COM15

ESP32 S3 Uno with HC-SR501 Motion Sensor - Video Tutorial

Watch the video below to see this ESP32 S3 Uno project step by step. At the end of the video, you will see an automatic door: a servo opens the door and a buzzer beeps when someone comes near. The code for that door project is below.

In this door version, the motion sensor stays on D2 (GPIO18), the servo uses D5 (GPIO20), and a buzzer is added on D6 (GPIO3). When motion starts, the servo turns to 180 degrees and the buzzer beeps twice. When motion stops, the servo goes back to 0 degrees and beeps again.

#include <ESP32Servo.h> #define SENSOR_PIN 18 // The ESP32 S3 Uno pin GPIO18 (D2) connected to the output pin of the motion sensor #define SERVO_PIN 20 // The ESP32 S3 Uno pin GPIO20 (D5) connected to the servo motor #define BUZZER_PIN 3 // The ESP32 S3 Uno pin GPIO3 (D6) connected to the buzzer Servo servo; int motion_state = LOW; // Initialize current pin state to LOW int prev_motion_state = LOW; // Initialize previous pin state to LOW void setup() { Serial.begin(9600); // Start serial communication at 9600 baud rate pinMode(SENSOR_PIN, INPUT); // Configure GPIO18 (D2) as an input for the sensor pinMode(BUZZER_PIN, OUTPUT); // Configure the buzzer pin as output servo.attach(SERVO_PIN); servo.write(0); noTone(BUZZER_PIN); } void beep() { for (int i = 0; i < 2; i++) { tone(BUZZER_PIN, 5000); delay(100); noTone(BUZZER_PIN); delay(100); } } void loop() { prev_motion_state = motion_state; // Assign the current pin state to the previous pin state for comparison motion_state = digitalRead(SENSOR_PIN); // Read the current state from the sensor output // Check for transition from LOW to HIGH which indicates motion detected if (prev_motion_state == LOW && motion_state == HIGH) { Serial.println("Motion detected!"); // Print message when motion is detected servo.write(180); beep(); // Optional: Additional actions when motion is detected } // Check for transition from HIGH to LOW which indicates motion has stopped else if (prev_motion_state == HIGH && motion_state == LOW) { Serial.println("Motion stopped!"); // Print message when motion has stopped servo.write(0); beep(); // Optional: Additional actions when motion stops } }

D6 is GPIO3, a boot strapping pin on the ESP32 S3 Uno. A buzzer on this pin is normally fine. If the board does not boot or upload with the buzzer connected, unplug the buzzer wire from D6 during upload, then connect it again.

FAQ

Can I power the HC-SR501 motion sensor from the ESP32 S3 Uno?

Yes. Connect the sensor VCC to the 5V pin of the board. The sensor works from about 4.5V to 20V, and its OUT pin gives a 3.3V signal. This signal is safe for the ESP32 S3 Uno input pins, so you do not need a level shifter.

Why does the code use ESP32Servo.h instead of Servo.h?

The standard Servo library supports AVR and some other Arduino boards, but not the ESP32 S3 Uno. The ESP32Servo library by Kevin Harrington uses the PWM hardware of the board and keeps the same functions. Your old UNO R4 servo code works after you change the include line and the pin numbers.

Why does the servo move again after I stop moving?

The HC-SR501 keeps its OUT pin HIGH for a while after the last movement. The time delay screw sets this time, from a few seconds up to a few minutes. Turn the screw fully anti-clockwise to make it as short as possible.

Can I use a different pin for the servo instead of D9?

The wiring uses D9 (GPIO46), which is a boot strapping pin. It works in most cases. If you have boot or upload problems, move the signal wire to another PWM pin such as D5 (GPIO20) and change SERVO_PIN in the code to 20.

What if my project needs more sensors or servos than the Uno headers give?

The ESP32 S3 Uno has two extra rows of holes with more GPIOs: GPIO15 and GPIO16 (I/O, PWM, analog), GPIO45 and GPIO35 to GPIO42 (I/O, PWM), and GPIO47/GPIO48 (output only, PWM). Solder pin headers to use them and write the GPIO number in code. For a second motion sensor, use GPIO35 to GPIO42, not GPIO47/GPIO48, because those two are output only. For more servos, GPIO15, GPIO16 or GPIO35 to GPIO42 work well. Be careful with two things. First, GPIO47/GPIO48 may run at 1.8V instead of 3.3V on some modules (especially ones with "V" in the name, like R8V or R16V), so 3.3V devices can be damaged or act strangely. Second, GPIO0, GPIO3 (D6), GPIO45 and GPIO46 (D9) are boot strapping pins, and a wrong connection can stop the board from booting or uploading code. Use the other extra pins first.

Troubleshooting

Problem	Possible Cause	Solution
No COM port shows up in Arduino IDE	USB driver missing or board not in upload mode	Install the CP210x or CH340 driver. Or hold BOOT, press RESET, then release BOOT and upload again
Upload fails or board does not boot	The servo signal on D9 (GPIO46) affects the boot strapping pin	Unplug the servo signal wire from D9 during upload, then plug it back in
Compile error "Servo.h - No such file"	The code uses the AVR Servo library	Install the ESP32Servo library and use #include
Servo does not move at all	Wrong wiring or no power to the servo	Check that red goes to 5V, brown to GND and the signal wire to D9 (GPIO46)
Sensor never detects motion	OUT pin on the wrong pin or sensor not powered	Wire OUT to D2 (GPIO18) and VCC to 5V, then wait 60 seconds after power-up
Sensor triggers by itself	Sensor still settling, or heat sources nearby	Wait one minute after power-up and keep the sensor away from heaters, fans and direct sunlight
Servo jitters or the board resets	The servo draws too much current from USB	Power the servo from an external 5V supply and join the GNDs

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