![\"Raspberry](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/03\/Raspberry-Pi-PWM-output.jpg?resize=1200%2C675&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nTable of Contents<\/h2>\n\n\n\n
Throughout this tutorial, we\u2019ll cover the following main topics:<\/p>\n\n\n\n
- \n
- Introducing the Raspberry Pi GPIOs<\/a><\/li>\n\n\n\n
- Introducing PWM<\/a><\/li>\n\n\n\n
- Connect an LED to the Raspberry Pi<\/a><\/li>\n\n\n\n
- Dim an LED with the Raspberry Pi using PWM<\/a><\/li>\n<\/ol>\n\n\n\n
Prerequisites<\/h2>\n\n\n\n
Before continuing with this tutorial, check the following prerequisites.<\/p>\n\n\n\n
- \n
- Get familiar with the Raspberry Pi board\u2014if you’re not familiar with the Raspberry Pi, you can read our Raspberry Pi Getting Started Guide<\/strong>.<\/a><\/li>\n\n\n\n
- You must know how to run and create Python files on your Raspberry Pi. We like to program our Raspberry Pi via SSH using an extension on VS Code. We have a detailed tutorial about that subject: Programming Raspberry Pi Remotely using VS Code (Remote-SSH)<\/strong><\/a>.<\/li>\n<\/ol>\n\n\n\n
First time controlling the Raspberry Pi Outputs?<\/strong> Get Started by controlling the Raspberry Pi Digital Outputs<\/a>.<\/p>\n\n\n\n
Introducing the Raspberry Pi GPIOs<\/h2>\n\n\n\n
GPIO stands for General Purpose Input Output<\/em> pins and those allow you to connect and control electronic hardware, like LEDs, motors, and sensors to your Raspberry Pi.<\/p>\n\n\n\n
Most models of Raspberry Pi boards have a double row of 40 GPIO pins. The layout of the pins is usually the same for most Raspberry Pi models.<\/p>\n\n\n
\n![\"Raspberry](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/03\/Raspberry-Pi-Pinout-Random-Nerd-Tutorials.png?resize=1024%2C576&quality=100&strip=all&ssl=1\")
Raspberry Pi Pinout<\/figcaption><\/figure><\/div>\n\n\n There are two different ways to refer to a GPIO pin: its name (which is known as GPIO numbering or Broadcom numbering) or its corresponding pin physical number (which corresponds to the pin’s physical location on the header). <\/p>\n\n\n\n
For example, GPIO 25 corresponds to pin 22 (see the picture above). Throughout this tutorial, we’ll refer to GPIO pins by their GPIO numbering (Broadcom numbering).<\/p>\n\n\n\n
To learn more about the Raspberry Pi GPIOs, check the Raspberry Pi Pinout Guide: Raspberry Pi Pinout Guide: How to use the Raspberry Pi GPIOs?<\/a><\/p>\n\n\n\n
Introducing PWM (Pulse-Width Modulation)<\/h2>\n\n\n\n
The Raspberry Pi GPIOs can be set either to output 0V or 3.3V (check this tutorial about the Raspberry Pi Digital Outputs<\/a><\/strong>), but they can\u2019t output any voltages in between. However, you can output \u201cfake\u201d mid-level voltages using pulse\u2011width modulation (PWM), which is how you\u2019ll produce varying levels of LED brightness for this project. PWM is also useful for other applications like varying the speed of DC motors, setting the position of a servo motor, and much more.<\/p>\n\n\n\n
If you alternate an LED\u2019s voltage between HIGH and LOW very fast, your eyes can\u2019t keep up with the speed at which the LED switches on and off; you\u2019ll simply see some gradations in brightness.<\/p>\n\n\n
\n![\"Fade](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2019\/07\/led-fade.png?resize=895%2C182&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nThat\u2019s basically how PWM works \u2014 by producing an output that changes between HIGH and LOW at a very high frequency.<\/p>\n\n\n\n
The duty cycle is the fraction of the time period at which LED is set to HIGH. The following figure illustrates how PWM works.<\/p>\n\n\n
\n![\"How](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2019\/07\/PWM-how-it-works.png?resize=711%2C658&quality=100&strip=all&ssl=1\")
How PWM Works<\/figcaption><\/figure><\/div>\n\n\n A duty cycle of 50 percent results in 50 percent LED brightness, a duty cycle of 0 means the LED is fully off, and a duty cycle of 100 means the LED is fully on. Changing the duty cycle is how you produce different levels of brightness.<\/p>\n\n\n\n
PWM Pins on the Raspberry Pi<\/h3>\n\n\n\n
The Raspberry Pi has 4 hardware PWM pins: GPIO 12<\/strong>, GPIO 13<\/strong>, GPIO 18<\/strong>, GPIO 19<\/strong>.<\/p>\n\n\n\n
You can have software PWM on all pins.<\/strong> You can pretty much choose any pin (except GPIO 0 and 1) to output PWM signals.<\/p>\n\n\n\n
Wiring the Circuit<\/h2>\n\n\n\n
Wire an LED to one of the Raspberry Pi GPIOs. We’ll connect one LED to GPIO 14<\/span> (pin 8). You can use any other pins, except GPIO 0 and GPIO 1.<\/p>\n\n\n\n
Here’s a list of components you need:<\/p>\n\n\n\n
- \n
- Raspberry Pi Board<\/a> – read Best Raspberry Pi Starter Kits<\/a><\/li>\n\n\n\n
- LED<\/a><\/li>\n\n\n\n
- 220 Ohm resistor<\/a> (or similar)<\/li>\n\n\n\n
- Breadboard<\/a><\/li>\n<\/ul>\n\n\n
You can use the preceding links or go directly to MakerAdvisor.com\/tools<\/a> to find all the parts for your projects at the best price!<\/p>
![](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/10\/header-200.png?w=1200&quality=100&strip=all&ssl=1\")
<\/a><\/p>\n\n\n\n![\"LED](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/03\/Wire-LED-to-Raspberry-Pi.png?resize=750%2C544&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nDim an LED with Python on the Raspberry Pi<\/h2>\n\n\n\n
The gpiozero<\/span> library provides a collection of interfaces for everyday components like LEDs, buttons, potentiometers, sensors, and much more. <\/p>\n\n\n\n
So, instead of setting the GPIO properties to dim an LED, the gpiozero<\/span> provides an interface called PWMLED<\/span> with methods that are useful to control LEDs, including a method to produce PWM signals to vary the LED brightness.<\/p>\n\n\n\n
Instead, you can also use the PWMOutputDevice<\/span> interface that can be used to control other digital outputs with PWM. Let’s see how it works.<\/p>\n\n\n\n
The gpiozero<\/span> library should already be installed if you’re running Raspberry Pi OS \u2014 if not, you can run:<\/p>\n\n\n\n
python3 -m pip gpiozero<\/span>.<\/pre>\n\n\n\nPython Script – PWM on Raspberry Pi GPIOs<\/h3>\n\n\n\n
Create a new python file on your Raspberry Pi called fade_led.py<\/em> and copy the following code.<\/p>\n\n\n
# Complete Project Details: https:\/\/RandomNerdTutorials.com\/raspberry-pi-pwm-python\/\r\n\r\nfrom gpiozero import PWMLED\r\nfrom time import sleep\r\n\r\nled = PWMLED(14)\r\n\r\nled.value = 1 #LED fully on\r\nsleep(1)\r\nled.value = 0.5 #LED half-brightness\r\nsleep(1)\r\nled.value = 0 #LED fully off\r\nsleep(1)\r\n\r\ntry:\r\n # fade in and out forever\r\n while True:\r\n #fade in\r\n for duty_cycle in range(0, 100, 1):\r\n led.value = duty_cycle\/100.0\r\n sleep(0.05)\r\n\r\n #fade out\r\n for duty_cycle in range(100, 0, -1):\r\n led.value = duty_cycle\/100.0\r\n sleep(0.05)\r\n \r\nexcept KeyboardInterrupt:\r\n print("Stop the program and turning off the LED")\r\n led.value = 0\r\n pass<\/code><\/pre>\n\tView raw code<\/a><\/p>\n\n\n\n
How the Code Works<\/h4>\n\n\n\n
Continue reading to learn how the code works.<\/p>\n\n\n\n
Importing Libraries<\/h4>\n\n\n\n
First, you import the PWMLED<\/span> component from the gpiozero<\/span> library to control the GPIO that the LED is connected to. Then, you also need to import the sleep()<\/span> function from the time<\/span> module to create delays in the code.<\/p>\n\n\n\n
from gpiozero import LED\nfrom time import sleep<\/code><\/pre>\n\n\n\nInstead of the PWMLED<\/span> component, you can use the PWMOutputDevice<\/span> component which works exactly the same.<\/p>\n\n\n\n
from gpiozero import PWMOutputDevice<\/code><\/pre>\n\n\n\nDeclaring the PWM LED<\/h4>\n\n\n\n
Next, you create a PWMLED<\/span> object called led<\/span> that refers to GPIO 14<\/span>, which is the GPIO that the LED is connected to. Change the number if you’re using another GPIO.<\/p>\n\n\n\n
led = LED(14)<\/code><\/pre>\n\n\n\nWhen you create and use this PWMLED<\/span> object, your program knows that GPIO 14<\/span> is a PWM output that can produce PWM signals with different duty cycle values. After this declaration, you can use led<\/span> to refer to your GPIO 14<\/span>.<\/p>\n\n\n\n
Note<\/strong>: if you want to use the PWMOutputDevice<\/span> component instead, the declaration would be as follows:<\/p>\n\n\n\n
led = PWMOutputDevice(14)<\/code><\/pre>\n\n\n\nNote<\/strong>: if you want to use PWM signals to control DC and servo motors, the gpiozero<\/span> provides the Motor<\/span>, Servo<\/span>, and AngularServo<\/span> classes.<\/p>\n\n\n\n
Control the LED Brightness<\/h4>\n\n\n\n
You can assign a specific brightness level to the LED by setting a specific number to the value<\/span> property as follows:<\/p>\n\n\n\n
led.value = 1 #LED fully on<\/code><\/pre>\n\n\n\nSetting led.value<\/span> to 1<\/span> corresponds to 100% duty cycle, and so the LED will be fully on.<\/p>\n\n\n\n
To turn off the LED completely, you set the value<\/span> to 0<\/span> (0% duty cycle).<\/p>\n\n\n\n
led.value = 0 #LED fully off<\/code><\/pre>\n\n\n\nFor varying levels of duty cycle, and thus varying brightness levels, set the value<\/span> to a number between 0 and 1.<\/p>\n\n\n\n
led.value = 0.5 #LED half-brightness<\/code><\/pre>\n\n\n\nFade In an LED<\/h4>\n\n\n\n
The code then enters a loop where it gradually increases the duty cycle from 0% to 100% in steps of 1% with a delay of 0.05 seconds between each step. This causes the LED to fade in gradually.<\/p>\n\n\n\n
for duty_cycle in range(0, 100, 1):\n led.value = duty_cycle\/100.0\n sleep(0.05)<\/code><\/pre>\n\n\n\nThe range()<\/span> function only accepts integer numbers, that’s why then we divide the duty_cycle<\/span> variable by 100 so that we can have a value between 0 and 1.<\/p>\n\n\n\n
\nThe range(start, stop, increment)<\/span> function in Python generates a sequence of numbers. It accepts as arguments the following:<\/p>\n\n\n\n
- \n
- start<\/span>: the starting value of the sequence (inclusive)<\/li>\n\n\n\n
- stop<\/span>: the last value of the sequence (exclusive)<\/li>\n\n\n\n
- step<\/span>: increment between each value, the default is 1<\/li>\n<\/ul>\n<\/div><\/div>\n\n\n\n
Fade Out an LED<\/h4>\n\n\n\n
We do exactly the same thing to fade out the LED, but we change the arguments of the range()<\/span> function so that it starts at 100 and decreases the duty cycle by 1 in each loop.<\/p>\n\n\n\n
#fade out\nfor duty_cycle in range(100, 0, -1):\n led.value = duty_cycle\/100.0\n sleep(0.05)<\/code><\/pre>\n\n\n\nTry and Except with Keyboard Interrupt<\/h4>\n\n\n\n
To prevent staying with an LED on when you stop the execution of the program, we added a Try <\/em>and Except <\/em>statement. This will catch the KeyboardInterrupt<\/span> exception, which is raised when you press Ctrl<\/strong>+C<\/strong> to stop the program. When this happens, we turn off the LED before exiting the program.<\/p>\n\n\n\n
except KeyboardInterrupt:\n print(\"Stop the program and turning off the LED\")\n led.value = 0\n pass<\/code><\/pre>\n\n\n\nIn summary…<\/h3>\n\n\n\n
1)<\/strong> To output PWM signals on the Raspberry Pi GPIOs, you can use the PWMLED<\/span> or the PWMOutputDevice<\/span> interface of the gpiozero<\/span> library. You need to import it first like this:<\/p>\n\n\n\n
from gpiozero import PWMLED<\/code><\/pre>\n\n\n\nor like this:<\/p>\n\n\n\n
from gpiozero import PWMOutputDevice<\/code><\/pre>\n\n\n\n2)<\/strong> Define the GPIO that you want to control. Using the LED<\/span> interface:<\/p>\n\n\n\n
led = PWMLED(GPIO_NUMBER_OF_YOUR_CHOICE<\/strong>)<\/code><\/pre>\n\n\n\nOr if you use the DigitalOutputDevice<\/span> interface:<\/p>\n\n\n\n
led = PWMOutputDevice(GPIO_NUMBER_OF_YOUR_CHOICE<\/strong>)<\/code><\/pre>\n\n\n\n3)<\/strong> Set the duty cycle (change the LED brightness) with the value<\/span> property:<\/p>\n\n\n\n
led.value = 1 #LED fully on <\/code><\/pre>\n\n\n\nled.value = 0.5 #LED half-brightness<\/code><\/pre>\n\n\n\nled.value = 0 #LED fully off<\/code><\/pre>\n\n\n\nDemonstration<\/h3>\n\n\n\n
Save your python file. Then run it on your Raspberry Pi. Run the following command on the directory of your project file (use the name of your file):<\/p>\n\n\n\n
python fade_led.py<\/em><\/code><\/pre>\n\n\n\nThe LED connected to GPIO 14<\/span> will first turn on, then with 50% brightness, and next, it will turn off.<\/p>\n\n\n\n
Finally, it will start fading in and out continuously until you stop the execution of the program.<\/p>\n\n\n\n
![\"\"](\"https:\/\/i1.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/03\/RPi-Fade-LED-low-brightness.jpg?ssl=1&resize=422%2C422\")
<\/figure><\/div>![\"\"](\"https:\/\/i2.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/03\/RPi-Fade-LED-half-brightness.jpg?ssl=1&resize=422%2C422\")
<\/figure><\/div>![\"\"](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/03\/RPi-Fade-LED-full-brightness.jpg?ssl=1&resize=422%2C422\")
<\/figure><\/div><\/div><\/div><\/div>\n\n\n\nWe added a condition that when the program stops, the LED turns off.<\/p>\n\n\n\n
You can stop the execution of the program by pressing CTRL<\/strong>+C<\/strong>. Notice that the LED will turn off, and a message will be printed on the Terminal shell.<\/p>\n\n\n\n
PWM Output Device<\/h3>\n\n\n\n
If you’re using a Generic PWM Output device, here’s an example using the PWMOutputDevice<\/span> class.<\/p>\n\n\n
# Complete Project Details: https:\/\/RandomNerdTutorials.com\/raspberry-pi-pwm-python\/\r\n\r\nfrom gpiozero import PWMOutputDevice\r\nfrom time import sleep\r\n\r\nled = PWMOutputDevice(14)\r\n\r\nled.value = 1 #LED fully on\r\nsleep(1)\r\nled.value = 0.5 #LED half-brightness\r\nsleep(1)\r\nled.value = 0 #LED fully off\r\nsleep(1)\r\n\r\ntry:\r\n # Fade in and out forever\r\n while True:\r\n #fade in\r\n for duty_cycle in range(0, 100, 1):\r\n led.value = duty_cycle\/100.0\r\n sleep(0.05)\r\n\r\n #fade out\r\n for duty_cycle in range(100, 0, -1):\r\n led.value = duty_cycle\/100.0\r\n sleep(0.05)\r\n\r\nexcept KeyboardInterrupt:\r\n print("Stop the program and turning off the LED")\r\n led.value = 0\r\n pass<\/code><\/pre>\n\tView raw code<\/a><\/p>\n\n\n\n
Other Useful Methods<\/h3>\n\n\n\n
The PWMLED<\/span> and DigitalOutputDevice<\/span> interfaces provide other useful additional methods.<\/p>\n\n\n\n
pulse()<\/h4>\n\n\n\n
The pulse()<\/span> method fades in and out repeatedly. Here’s an example of how you use the pulse()<\/span> method.<\/p>\n\n\n
# Complete Project Details: https:\/\/RandomNerdTutorials.com\/raspberry-pi-pwm-python\/\r\n\r\nfrom gpiozero import PWMLED\r\nfrom signal import pause\r\n\r\nled = PWMLED(14)\r\n\r\n# pulse an LED forever\r\nled.pulse()\r\npause()<\/code><\/pre>\n\t - stop<\/span>: the last value of the sequence (exclusive)<\/li>\n\n\n\n
- LED<\/a><\/li>\n\n\n\n
- You must know how to run and create Python files on your Raspberry Pi. We like to program our Raspberry Pi via SSH using an extension on VS Code. We have a detailed tutorial about that subject: Programming Raspberry Pi Remotely using VS Code (Remote-SSH)<\/strong><\/a>.<\/li>\n<\/ol>\n\n\n\n
- Introducing PWM<\/a><\/li>\n\n\n\n