Using an Encoder with Raspberry Pi

Introduction

A position encoder is a device used to measure and track the position of a moving object with high precision. When combined with a Raspberry Pi microcontroller, it enables accurate position sensing and control in a wide range of applications. A position encoder typically consists of a sensor and a rotating or linear scale. As the object moves, the sensor detects the position changes and converts them into electrical signals. These signals are then processed by the Raspberry Pi to determine the object's exact position. Position encoders offer reliable and real-time feedback, allowing for precise control over the movement of robotic arms, CNC machines, 3D printers, and other automated systems. By leveraging the power of the Raspberry Pi and its GPIO pins, the position encoder provides an efficient and cost-effective solution for position sensing and control. 

Problem statement

Controlling position encoder using a Raspberry Pi. 

Requirements

1. Raspberry Pi

2. Position encoder

3. Jumper wires

Working

The position encoder, when integrated with a Raspberry Pi, enables precise and reliable position sensing and control. The Raspberry Pi utilizes its GPIO pins to interface with the position encoder and interpret the position information it provides. The position encoder generates electrical signals proportional to the position or displacement of the moving object, whether it's a rotary or linear motion.The Raspberry Pi reads and processes these signals to determine the current position accurately. It compares the desired position with the feedback obtained from the position encoder. If any deviation is detected, the control algorithm implemented in the Raspberry Pi adjusts the output signals to bring the object to the desired position. This closed-loop control system ensures precise positioning by continuously monitoring and adjusting the position based on the feedback obtained from the position encoder. The Raspberry Pi offers a flexible and powerful platform for implementing various control algorithms and applications that require accurate position sensing.

Circuit Diagram

Follow the circuit diagram below to connect position encoder and Raspberry Pi: 

• Connect the 3V3(PIN1) of Raspberry Pi to VCC of position encoder

• Connect the GND(PIN9) of Raspberry Pi to GND of position encoder

• Connect the DOUT of position encoder to GPIO17(PIN 11) of Raspberry Pi

Code

Now let's write the Python code to connect position encoder with Raspberry Pi. Follow the steps below:

1. Connect to your Raspberry Pi using VNC or Desktop environment.

2. Launch the Geany Python IDE or open a text editor to write the code.

3. Create a new file named positionencoder.py and save the following code into it:

4. You can copy and paste the following code from here into the file.

import RPi.GPIO as GPIO

# Set GPIO mode and pins

GPIO.setmode(GPIO.BCM)

encoder_pin = 17

count = 0

# Set up interrupt handler

def encoder_interrupt(channel):

    global count

    # Increment the count

    count += 1

    print("Interrupt detected! Count:", count)

# Configure interrupt on rising edge

GPIO.setup(encoder_pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

GPIO.add_event_detect(encoder_pin, GPIO.RISING, callback=encoder_interrupt)

# Main program loop

try:

    while True:

        pass

except KeyboardInterrupt:

    GPIO.cleanup()

4. After saving the file execute it by clicking on messenger like icon on geany editor or open terminal and navigate tothe folder you saved the file, execute it by typing  python encoder.py 

5. After running the code swipe an object between receiver and transmitter of position encoder to verify the count and working of position encoder.

Output

The system initializes and starts counting the slots changed upon rotation of the encoder wheel. The count value is continuously printed on the terminal whenever a pulse is detected. Rotate the encoder shaft to observe changes in the count value. Each rotation or movement of the encoder generates pulses, resulting in a change in the count value.

Conclusion

By following this guide, you have successfully interfaced an encoder with Raspberry PI 3B+ using interrupts. You have learned how to track the position and movement of the encoder by counting the pulses generated. This knowledge can be applied to various applications such as motor control, robotic systems, and position sensing, which can be used to control robots and cars precisely.