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2.1.6 Rotary Encoder Module

Introduction

In this project, you will learn about Rotary Encoder. A rotary encoder is an electronic switch with a set of regular pulses in strictly timing sequence. When used with IC, it can achieve increment, decrement, page turning and other operations such as mouse scrolling, menu selection, and so on.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Raphael Kit	337	Raphael Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION	PURCHASE LINK
GPIO Extension Board	BUY
Breadboard	BUY
Jumper Wires	BUY
Rotary Encoder Module	BUY

Schematic Diagram

Experimental Procedures

Step 1: Build the circuit.

In this example, we can connect the Rotary Encoder pin directly to the Raspberry Pi using a breadboard and 40-pin Cable, connect the GND of the Rotary Encoder to GND, 「+」to 5V, SW to digital GPIO27, DT to digital GPIO18, and CLK to digital GPIO 17.

Step 2: Open the code file.

cd ~/raphael-kit/python-pi5

Step 3: Run.

sudo python3 2.1.6_RotaryEncoder_zero.py

You will see the count on the shell. When you turn the rotary encoder clockwise, the count is increased; when turn it counterclockwise, the count is decreased. If you press the switch on the rotary encoder, the readings will return to zero.

Code

Note

You can Modify/Reset/Copy/Run/Stop the code below. But before that, you need to go to source code path like raphael-kit/python-pi5. After modifying the code, you can run it directly to see the effect.

#!/usr/bin/env python3
from gpiozero import RotaryEncoder, Button
from time import sleep

# Initialize the rotary encoder and button
encoder = RotaryEncoder(a=17, b=18)  # Rotary Encoder connected to GPIO pins 17 (CLK) and 18 (DT)
button = Button(27)                  # Button connected to GPIO pin 27

global_counter = 0  # Track the rotary encoder's position

def rotary_change():
   """ Update the global counter based on the rotary encoder's rotation. """
   global global_counter
   global_counter += encoder.steps  # Adjust counter based on encoder steps
   encoder.steps = 0  # Reset encoder steps after updating counter
   print('Global Counter =', global_counter)  # Display current counter value

def reset_counter():
   """ Reset the global counter to zero when the button is pressed. """
   global global_counter
   global_counter = 0  # Reset the counter
   print('Counter reset')  # Indicate counter reset

# Assign the reset_counter function to button press event
button.when_pressed = reset_counter

try:
   # Monitor rotary encoder continuously and process changes
   while True:
      rotary_change()  # Handle rotary encoder changes
      sleep(0.1)  # Short delay to reduce CPU load

except KeyboardInterrupt:
   # Gracefully handle a keyboard interrupt (Ctrl+C)
   pass

Code Analysis

1. Imports the RotaryEncoder and Button classes from the gpiozero library, and the sleep function for delays.

   #!/usr/bin/env python3
   from gpiozero import RotaryEncoder, Button
   from time import sleep
   

2. Initializes the rotary encoder with GPIO pins 17 and 18, and a button on GPIO pin 27.

   # Initialize the rotary encoder and button
   encoder = RotaryEncoder(a=17, b=18)  # Rotary Encoder connected to GPIO pins 17 (CLK) and 18 (DT)
   button = Button(27)                  # Button connected to GPIO pin 27
   

3. Declares a global variable global_counter to track the position of the rotary encoder.

   global_counter = 0  # Track the rotary encoder's position
   

4. Defines a function rotary_change to update the global counter based on the rotary encoder’s rotation.

   def rotary_change():
      """ Update the global counter based on the rotary encoder's rotation. """
      global global_counter
      global_counter += encoder.steps  # Adjust counter based on encoder steps
      encoder.steps = 0  # Reset encoder steps after updating counter
      print('Global Counter =', global_counter)  # Display current counter value
   

5. Defines a function reset_counter to reset the global counter to zero when the button is pressed.

   def reset_counter():
      """ Reset the global counter to zero when the button is pressed. """
      global global_counter
      global_counter = 0  # Reset the counter
      print('Counter reset')  # Indicate counter reset
   

6. Assigns the reset_counter function to be called when the button is pressed.

   # Assign the reset_counter function to button press event
   button.when_pressed = reset_counter
   

7. In a continuous loop, the script calls rotary_change to handle rotary encoder changes and introduces a short delay to reduce CPU load. Uses a try-except block to handle KeyboardInterrupts gracefully.

   try:
      # Monitor rotary encoder continuously and process changes
      while True:
         rotary_change()  # Handle rotary encoder changes
         sleep(0.1)  # Short delay to reduce CPU load
   
   except KeyboardInterrupt:
      # Gracefully handle a keyboard interrupt (Ctrl+C)
      pass