What is "charlieplexing"? (a short demo using the Raspberry Pi)

While I was reading Raspberry Pi Cookbook, I came across a few things that looked interesting to demo. One of them was the concept of “charlieplexing“. On past projects, when I needed multiple LEDs (like in my Simon clone), I just connected each individual LED to its own GPIO pin. I was fully aware that current had to travel through the LED in one direction and that it wouldn’t light in the other direction, but it hadn’t occurred to me to take advantage of that fact. This is where charlieplexing comes in – we arrange multiple LEDs such that »

Creating a Flickering Candle Using an RGB LED on the Raspberry Pi

After getting PWM (pulse-width modulation) to work with an RGB LED last week, I was trying to think of what else I could do with an LED that demonstrated changes in color as well as intensity. I’m not sure why – maybe it was because we lost power in our neighborhood recently – but I thought a flickering candle could be an interesting little challenge… Materials In order to test this out, you’ll need a few things. An RGB LED A button A breadboard A T-cobbler (optional, but makes life easier when wiring up to GPIO pins) A range of »

How to Use an RGB multicolor LED with Pulse Width Modulation (PWM) on the Raspberry Pi

If you buy a kit with random LEDs, wires, switches, etc, like this one I purchased from CanaKit, you’re likely to end up with one or two of those funky little LEDs that appears to be white, and has 4 wires instead of 2. I had set mine aside and made a mental note to figure it out later… well, I’m bored with regular LEDs so that time has come! It’s a special kind of LED that consists of 3 separate LEDs… red, green and blue. By adjusting each color independently, you can create any color (similar »

How to Flash an LED on Your Raspberry Pi When You Get New Email

This week we’ll create an email notification system using the Raspberry Pi. The idea is to check for new email, and flash an LED when we get one. Connecting to Gmail The circuit will be extremely straight-forward, so let’s focus on the more difficult part first – connecting to an email service. We need to create a secure connection to our email provider, so we can find out when new mail arrives. Do a quick search, and you’ll likely find scripts like this one where you just connect with your username, password and a few other pieces of »

Generating Morse Code on the Raspberry Pi Using a Button on a Breadboard

Last time, I created a morse code generator. It took user input from the console, translated it into morse code, and blinked an LED to “transmit” the message. I decided to build on that a bit, adding a button to the circuit that allows me to generate morse code from a button click. The clicks are read in by a GPIO pin, and interpreted by a Python script. Defining the Rules We should always figure out what a program is going to do before we start writing it, so here are a few rules to guide us: Dots and dashes »

Building a Morse Code Transmitter on a Raspberry Pi

Last week, I made the Raspberry Pi blink an LED a few times. As thrilling as that was ;) I almost immediately wanted something more. Note: Source code for this project is available on GitHub. Goals Setup a simple circuit (LED and resistor) using a breadboard Learn about Morse Code in order to correctly translate a sentence Manipulate the GPIO pins on the Raspberry Pi to send signals at intervals Get familiar with basic Python constructs, like dictionaries, functions and loops Setup To do this, a few things are necessary: Install Raspbian on the Pi (comes with Python 3 preinstalled) Get »

Hello World for the Raspberry Pi (Making an LED Blink)

I finally unboxed my Pi a few weeks ago, and since then I’ve been learning some Python, which is the primary language of the Pi. You can do fun things with it out-of-the-box, like running and modifying the Python games that install with Raspbian (as well as writing your own), or playing around with MIT’s Scratch program (which also comes preinstalled). Or you could try another OS, like the OpenElec media platform that turns your Pi into a photo gallery / movie streamer (something a few of us were playing around with at the last AkronCodeClub meetup). But a »