SENSORS/ACTUATORS

Raspberry Pi - Touch Sensor - Servo Motor

This tutorial instructs you how to use Raspberry Pi and touch sensor to control servo motor. In detail:

How to use Raspberry Pi to make the servo motor rotate to 90 degree when the touch sensor is touched
How to use Raspberry Pi to make the servo motor rotate back to 0 degree when the touch sensor is touched again.

The same steps are done again.

Hardware Preparation

1	×	Raspberry Pi 4 Model B
1	×	Touch Sensor
1	×	Servo Motor
1	×	Jumper Wires
1	×	(Optional) Screw Terminal Adapter for Raspberry Pi

Or you can buy the following sensor kits:

1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

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Overview of Servo Motor and Touch Sensor

If you are unfamiliar with servo motors and touch sensors (including pinouts, functionality, and programming), the following tutorials can help:

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

Please note that the wiring diagram shown above is only suitable for a servo motor with low torque. In case the motor vibrates instead of rotating, an external power source must be utilized to provide more power for the servo motor. The below demonstrates the wiring diagram with an external power source for servo motor.

TO BE ADD IMAGE

Please do not forget to connect GND of the external power to GND of Arduino Raspberry Pi.

Raspberry Pi Code - Touch Sensor Controls Servo Motor

Detailed Instructions

Make sure you have Raspbian or any other Raspberry Pi compatible operating system installed on your Pi.
Make sure your Raspberry Pi is connected to the same local network as your PC.
Make sure your Raspberry Pi is connected to the internet if you need to install some libraries.
If this is the first time you use Raspberry Pi, See how to set up the Raspberry Pi
Connect your PC to the Raspberry Pi via SSH using the built-in SSH client on Linux and macOS or PuTTY on Windows. See to how connect your PC to Raspberry Pi via SSH.
Make sure you have the RPi.GPIO library installed. If not, install it using the following command:

sudo apt-get update sudo apt-get install python3-rpi.gpio

Create a Python script file touch_sensor_servo.py and add the following code:

# This Raspberry Pi code was developed by newbiely.com # This Raspberry Pi code is made available for public use without any restriction # For comprehensive instructions and wiring diagrams, please visit: # https://newbiely.com/tutorials/raspberry-pi/raspberry-pi-touch-sensor-servo-motor import RPi.GPIO as GPIO import time # Constants won't change TOUCH_SENSOR_PIN = 18 # Raspberry Pi GPIO pin connected to the motion sensor's pin SERVO_PIN = 20 # Raspberry Pi GPIO pin connected to the servo motor's pin # Variables will change angle = 0 # The current angle of the servo motor prev_motion_state = None # The previous state of the motion sensor motion_state = None # The current state of the motion sensor # Setup GPIO GPIO.setmode(GPIO.BCM) GPIO.setup(TOUCH_SENSOR_PIN, GPIO.IN, pull_up_down=GPIO.PUD_UP) GPIO.setup(SERVO_PIN, GPIO.OUT) # Create PWM instance for servo servo_pwm = GPIO.PWM(SERVO_PIN, 50) # 50 Hz frequency # Initialize servo position servo_pwm.start(0) try: while True: prev_motion_state = motion_state # Save the last state motion_state = GPIO.input(TOUCH_SENSOR_PIN) # Read new state if prev_motion_state == GPIO.LOW and motion_state == GPIO.HIGH: print("The sensor is touched") # Change angle of servo motor if angle == 0: angle = 90 else: angle = 0 # Control servo motor according to the angle duty_cycle = (angle / 18) + 2.5 # Convert angle to duty cycle servo_pwm.ChangeDutyCycle(duty_cycle) time.sleep(0.1) # Add a small delay to avoid rapid sensor readings except KeyboardInterrupt: servo_pwm.stop() GPIO.cleanup()

Save the file and run the Python script by executing the following command in the terminal:

python3 touch_sensor_servo.py

Tap the touch sensor multiple times.
Check out the servo motor's angle changing.

The script runs in an infinite loop continuously until you press Ctrl + C in the terminal.

Video Tutorial

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