Raspberry Pi - Stepper Motor Limit Switch
This tutorial instructs you how to use Raspberry Pi to control a stepper motor via a limit switch and an L298N driver. Specifically, we will cover:
- How to program Raspberry Pi to stop the stepper motor when a limit switch is touched.
- How to program Raspberry Pi to change direction of the stepper motor when a limit switch is touched.
- How to program Raspberry Pi to change direction of the stepper motor by two limit switches installed in opposite position.
Hardware Preparation
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 Stepper Motor and Limit Switch
If you are unfamiliar with stepper motor and limit switch (including pinout, functionality, programming, etc.), the following tutorials can help:
- Raspberry Pi - Limit Switch tutorial
- Raspberry Pi - Stepper Motor tutorial
Wiring Diagram
This tutorial provides the wiring diagram for two cases: One stepper motor + one limit switch, One stepper motor + two limit switches.
- Wiring Diagram between Raspberry Pi, stepper motor and, and a limit switch
This image is created using Fritzing. Click to enlarge image
- Wiring Diagram between Raspberry Pi, stepper motor and, and two limit switches
This image is created using Fritzing. Click to enlarge image
※ NOTE THAT:
The wiring connection between the stepper motor and L298N may vary depending on the type of stepper motor. Carefully examine the Raspberry Pi - Stepper Motor tutorial to learn how to properly link the stepper motor to the L298N motor driver.
Raspberry Pi Code - Stop Stepper Motor by a Limit Switch
A stepper motor is programmed to spin continuously with the following code, and will stop instantly when a limit switch is touched, and resume moving if the limit switch is released.
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 stepper_limit_switch.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-stepper-motor-limit-switch
import RPi.GPIO as GPIO
import time
# Define GPIO pins for L298N driver and limit switch
IN1 = 12
IN2 = 16
IN3 = 20
IN4 = 21
LIMIT_SWITCH_PIN = 27
# Set GPIO mode and configure pins
GPIO.setmode(GPIO.BCM)
GPIO.setup(IN1, GPIO.OUT)
GPIO.setup(IN2, GPIO.OUT)
GPIO.setup(IN3, GPIO.OUT)
GPIO.setup(IN4, GPIO.OUT)
GPIO.setup(LIMIT_SWITCH_PIN, GPIO.IN, pull_up_down=GPIO.PUD_UP)
# Define constants
DEG_PER_STEP = 1.8
STEPS_PER_REVOLUTION = int(360 / DEG_PER_STEP)
# Function to move the stepper motor one step forward
def step_forward(delay):
GPIO.output(IN1, GPIO.HIGH)
GPIO.output(IN2, GPIO.HIGH)
GPIO.output(IN3, GPIO.LOW)
GPIO.output(IN4, GPIO.LOW)
time.sleep(delay)
GPIO.output(IN1, GPIO.LOW)
GPIO.output(IN2, GPIO.HIGH)
GPIO.output(IN3, GPIO.HIGH)
GPIO.output(IN4, GPIO.LOW)
time.sleep(delay)
# Function to check the limit switch status
def is_limit_switch_pressed():
return GPIO.input(LIMIT_SWITCH_PIN) == GPIO.LOW
try:
# Set the delay between steps
delay = 0.001
while not is_limit_switch_pressed():
# Move the stepper motor forward endlessly
step_forward(delay)
except KeyboardInterrupt:
print("\nExiting the script.")
finally:
# Clean up GPIO settings
GPIO.cleanup()
- Save the file and run the Python script by executing the following command in the terminal:
python3 stepper_limit_switch.py
- If the wiring is correct, the motor should rotate in a clockwise direction.
- When the limit switch is touched, the motor should stop immediately.
- Then if the limit switch is released, the motor rotates again.
The script runs in an infinite loop continuously until you press Ctrl + C in the terminal.
By changing the value of delay variable in the code, you can change the speed of the stepper motor.
Code Explanation
Check out the line-by-line explanation contained in the comments of the source code!
Raspberry Pi Code - Change Direction of Stepper Motor by a Limit Switch
A stepper motor will be set in motion continuously and its direction will be altered when a limit switch is touched.
Detailed Instructions
- Create a Python script file stepper_direction.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-stepper-motor-limit-switch
import RPi.GPIO as GPIO
import time
# Define GPIO pins for L298N driver and limit switch
IN1 = 12
IN2 = 16
IN3 = 20
IN4 = 21
LIMIT_SWITCH_PIN = 27
# Set GPIO mode and configure pins
GPIO.setmode(GPIO.BCM)
GPIO.setup(IN1, GPIO.OUT)
GPIO.setup(IN2, GPIO.OUT)
GPIO.setup(IN3, GPIO.OUT)
GPIO.setup(IN4, GPIO.OUT)
GPIO.setup(LIMIT_SWITCH_PIN, GPIO.IN, pull_up_down=GPIO.PUD_UP)
# Define constants
DEG_PER_STEP = 1.8
STEPS_PER_REVOLUTION = int(360 / DEG_PER_STEP)
# Global variable to store the previous state of the limit switch
prev_limit_switch_state = GPIO.HIGH
# Function to move the stepper motor one step forward
def step_forward(delay):
GPIO.output(IN1, GPIO.HIGH)
GPIO.output(IN2, GPIO.HIGH)
GPIO.output(IN3, GPIO.LOW)
GPIO.output(IN4, GPIO.LOW)
time.sleep(delay)
GPIO.output(IN1, GPIO.LOW)
GPIO.output(IN2, GPIO.HIGH)
GPIO.output(IN3, GPIO.HIGH)
GPIO.output(IN4, GPIO.LOW)
time.sleep(delay)
# Function to move the stepper motor one step backward
def step_backward(delay):
GPIO.output(IN1, GPIO.LOW)
GPIO.output(IN2, GPIO.LOW)
GPIO.output(IN3, GPIO.HIGH)
GPIO.output(IN4, GPIO.HIGH)
time.sleep(delay)
GPIO.output(IN1, GPIO.HIGH)
GPIO.output(IN2, GPIO.LOW)
GPIO.output(IN3, GPIO.LOW)
GPIO.output(IN4, GPIO.HIGH)
time.sleep(delay)
try:
# Set the delay between steps
delay = 0.001
# Set the initial direction
direction = 'forward'
while True:
# Check if the limit switch state changes
limit_switch_state = GPIO.input(LIMIT_SWITCH_PIN)
# Change direction if the limit switch changes from HIGH to LOW
if limit_switch_state == GPIO.LOW and prev_limit_switch_state == GPIO.HIGH:
direction = 'backward' if direction == 'forward' else 'forward'
# Move the stepper motor based on the direction
if direction == 'forward':
step_forward(delay)
elif direction == 'backward':
step_backward(delay)
# Update the previous state of the limit switch
prev_limit_switch_state = limit_switch_state
except KeyboardInterrupt:
print("\nExiting the script.")
finally:
# Clean up GPIO settings
GPIO.cleanup()
- Save the file and run the Python script by executing the following command in the terminal:
python3 stepper_direction.py
- If the wiring is correct, the motor should spin in a clockwise direction.
- When you touch the limit switch, the stepper motor's direction will change to counterclockwise.
- Touch the limit switch again and the stepper motor's direction will go back to clockwise.
Raspberry Pi Code - Change Direction of Stepper Motor by two Limit Switches
Let's see the code that makes a stepper motor spin continuously, and when either of two limit switches is touched, switches the motor's direction.
Detailed Instructions
- Create a Python script file stepper_two_limit_switches.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-stepper-motor-limit-switch
import RPi.GPIO as GPIO
import time
# Define GPIO pins for L298N driver and limit switches
IN1 = 12
IN2 = 16
IN3 = 20
IN4 = 21
LIMIT_SWITCH1_PIN = 27
LIMIT_SWITCH2_PIN = 19
# Set GPIO mode and configure pins
GPIO.setmode(GPIO.BCM)
GPIO.setup(IN1, GPIO.OUT)
GPIO.setup(IN2, GPIO.OUT)
GPIO.setup(IN3, GPIO.OUT)
GPIO.setup(IN4, GPIO.OUT)
GPIO.setup(LIMIT_SWITCH1_PIN, GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.setup(LIMIT_SWITCH2_PIN, GPIO.IN, pull_up_down=GPIO.PUD_UP)
# Define constants
DEG_PER_STEP = 1.8
STEPS_PER_REVOLUTION = int(360 / DEG_PER_STEP)
# Global variables to store the previous state of the limit switches
prev_limit_switch_1 = GPIO.HIGH
prev_limit_switch_2 = GPIO.HIGH
# Function to move the stepper motor one step forward
def step_forward(delay):
GPIO.output(IN1, GPIO.HIGH)
GPIO.output(IN2, GPIO.HIGH)
GPIO.output(IN3, GPIO.LOW)
GPIO.output(IN4, GPIO.LOW)
time.sleep(delay)
GPIO.output(IN1, GPIO.LOW)
GPIO.output(IN2, GPIO.HIGH)
GPIO.output(IN3, GPIO.HIGH)
GPIO.output(IN4, GPIO.LOW)
time.sleep(delay)
# Function to move the stepper motor one step backward
def step_backward(delay):
GPIO.output(IN1, GPIO.LOW)
GPIO.output(IN2, GPIO.LOW)
GPIO.output(IN3, GPIO.HIGH)
GPIO.output(IN4, GPIO.HIGH)
time.sleep(delay)
GPIO.output(IN1, GPIO.HIGH)
GPIO.output(IN2, GPIO.LOW)
GPIO.output(IN3, GPIO.LOW)
GPIO.output(IN4, GPIO.HIGH)
time.sleep(delay)
try:
# Set the delay between steps
delay = 0.001
# Set the initial direction
direction = 'forward'
while True:
# Check if limit switch 1 state changes
limit_switch_1 = GPIO.input(LIMIT_SWITCH1_PIN)
if limit_switch_1 == GPIO.LOW and prev_limit_switch_1 == GPIO.HIGH:
direction = 'backward'
# Check if limit switch 2 state changes
limit_switch_2 = GPIO.input(LIMIT_SWITCH2_PIN)
if limit_switch_2 == GPIO.LOW and prev_limit_switch_2 == GPIO.HIGH:
direction = 'forward'
# Move the stepper motor based on the direction
if direction == 'forward':
step_forward(delay)
elif direction == 'backward':
step_backward(delay)
# Update the previous states of the limit switches
prev_limit_switch_1 = limit_switch_1
prev_limit_switch_2 = limit_switch_2
except KeyboardInterrupt:
print("\nExiting the script.")
finally:
# Clean up GPIO settings
GPIO.cleanup()
- Save the file and run the Python script by executing the following command in the terminal:
python3 stepper_two_limit_switches.py
The script runs in an infinite loop continuously until you press Ctrl + C in the terminal.
- If the wiring is correct, the motor should spin in a clockwise direction.
- When you touch limit switch 1, the stepper motor's direction will be reversed to anti-clockwise.
- Touching limit switch 2 will cause the stepper motor to rotate clockwise again.