RGB-slider is an application to control a RGB LED on your Raspberry Pi using a web interface.
Ok, but what is it exactly?
Rgb-slider is using NodeJS to provide a web interface to send some command to a Pi-Blaster daemon to control the intensity of the three colours of a RGB LED using Pulse Width Modulation (PWM).
When you run the application, it will start a web server listening for connections on the port 3000. The server is hosting a single web page (index.html) displaying 3 horizontal sliders: one for each colour: red, green and blue. The page is a clone (with tiny modifications) of the Jquery UI slider demo you can find here.
When you access the page and move a slider, the value of this particular colour is sent to the server using a web service. The value, between 0 and 255, is divided by 255 to get a value between 0 and 1. This final value is passed as a PWM value to the pi-blaster daemon.
The default GPIO pin configuration is:
Colour | GPIO Pin Number --- | --- Red | 17 Green | 18 Blue | 22
You just have to wire your LED on the above pins (don't forget the resistors), start the application and use a browser to connect to the page to play with the sliders.
On your Raspberry you need the following programs:
- NodeJS and npm, I'm using the version available here, it's working fine on my Raspberry A+.
- pi-blaster daemon, available here.
- git, to clone the repository - on Raspbian you can simply do
sudo apt-get install git- alternatively you can download a zip file from my Github.
You also need a RGB LED wired to the GPIO. Have a look at this video.
Installation and usage
- Clone the repo:
git clone https://github.com/Kylir/rgb-slider.git
- Optional: Edit the index.js to change the GPIO pins
- Install the dependencies using the command
- Start the application by typing
- Go to the slider page (point your browser to the IP of your Raspberry - port 3000). You can use the command
sudo ip addr showto see what your IP is. Add the
http://prefix and the
:3000suffix. For instance, I can access my application using
http://192.168.1.74:3000. Please note that depending on your network configuration, your application is potentially accessible to anyone in the world...
The application is using two modules:
- Express JS to create the server and the web services.
- Pi-blaster.js to talk to the pi-blaster daemon.
What to do next?
This toy application demonstrates that it is not really difficult to have a web interface to control something plugged on your GPIO. You can use the same kind of idea to control a robot remotely or to switch on and off your lights at home while you are on holiday. Use your imagination!
Also, because it is so easy to build a web application using NodeJS, there are a lot of articles on the subject. Have a look for instance at the Adafruit tutorial here.
There is another NodeJS module really nice to use to play with the GPIO: onoff. With this module you can read from the GPIO, opening a lot more possibilities.
MIT License: see LICENSE.txt