Raspberry Pi Program to Control DC Motor

Use Python with the RPi.GPIO library to control a DC motor by setting GPIO pins high or low; for example, import RPi.GPIO as GPIO, set pin mode, and use GPIO.output(pin, GPIO.HIGH) to run the motor.

Examples

InputRun motor forward for 5 seconds

OutputMotor spins forward for 5 seconds then stops

InputRun motor backward for 3 seconds

OutputMotor spins backward for 3 seconds then stops

InputStop motor immediately

OutputMotor stops spinning

How to Think About It

To control a DC motor with a Raspberry Pi, you use GPIO pins to send signals that turn the motor on or off and control its direction. You connect the motor to a motor driver circuit, then write a program that sets the GPIO pins high or low to spin the motor forward, backward, or stop it.

Algorithm

1

Import the GPIO library and time module

2

Set GPIO mode to BCM

3

Set motor control pins as output

4

Turn motor on by setting pins high or low to control direction

5

Wait for desired time

6

Turn motor off by setting pins low

7

Clean up GPIO settings

Code

python

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)

motor_pin1 = 17
motor_pin2 = 18

GPIO.setup(motor_pin1, GPIO.OUT)
GPIO.setup(motor_pin2, GPIO.OUT)

print("Motor running forward")
GPIO.output(motor_pin1, GPIO.HIGH)
GPIO.output(motor_pin2, GPIO.LOW)
time.sleep(5)

print("Motor stopped")
GPIO.output(motor_pin1, GPIO.LOW)
GPIO.output(motor_pin2, GPIO.LOW)

GPIO.cleanup()

Output

Motor running forward
Motor stopped

Dry Run

Let's trace running the motor forward for 5 seconds then stopping it.

1

Setup GPIO mode

GPIO mode set to BCM numbering

2

Setup motor pins

Pins 17 and 18 set as output

3

Run motor forward

Pin 17 = HIGH, Pin 18 = LOW; motor spins forward

4

Wait 5 seconds

Program pauses for 5 seconds

5

Stop motor

Pin 17 = LOW, Pin 18 = LOW; motor stops

6

Cleanup GPIO

GPIO pins reset to default state

Step	Pin 17	Pin 18	Motor State
Setup	N/A	N/A	Pins configured
Run forward	HIGH	LOW	Spinning forward
Wait	HIGH	LOW	Spinning forward
Stop	LOW	LOW	Stopped
Cleanup	N/A	N/A	GPIO reset

Why This Works

Step 1: GPIO Setup

We use GPIO.setmode(GPIO.BCM) to select the pin numbering system and set the motor pins as outputs to control voltage signals.

Step 2: Motor Direction Control

Setting one pin HIGH and the other LOW makes the motor spin in one direction; reversing these signals spins it the other way.

Step 3: Stopping the Motor

Setting both pins LOW cuts power to the motor, stopping it safely.

Step 4: Cleaning Up

Calling GPIO.cleanup() resets the pins so they don't stay active after the program ends.

Alternative Approaches

Using PWM for speed control

python

import RPi.GPIO as GPIO
import time

GPIO.setmode(GPIO.BCM)
motor_pin = 17
GPIO.setup(motor_pin, GPIO.OUT)
pwm = GPIO.PWM(motor_pin, 100)  # 100 Hz
pwm.start(0)

print("Motor speed ramp up")
for speed in range(0, 101, 20):
    pwm.ChangeDutyCycle(speed)
    time.sleep(1)

print("Motor stop")
pwm.ChangeDutyCycle(0)
pwm.stop()
GPIO.cleanup()

This method controls motor speed by changing the power level with PWM but requires a motor driver that supports PWM input.

Using GPIO Zero library

python

from gpiozero import Motor
from time import sleep

motor = Motor(forward=17, backward=18)

print("Motor forward")
motor.forward()
sleep(5)

print("Motor stop")
motor.stop()

GPIO Zero simplifies motor control with easy methods but adds a dependency and is less flexible for complex setups.

Complexity: O(1) time, O(1) space

Time Complexity

The program runs a fixed sequence of commands without loops that depend on input size, so it runs in constant time.

Space Complexity

Uses a fixed number of variables and GPIO pins, so memory use is constant.

Which Approach is Fastest?

All approaches run quickly; using GPIO Zero adds abstraction but simplifies code, while PWM adds complexity for speed control.

Approach	Time	Space	Best For
Basic GPIO control	O(1)	O(1)	Simple on/off motor control
PWM speed control	O(1)	O(1)	Controlling motor speed smoothly
GPIO Zero library	O(1)	O(1)	Easy and readable motor control