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… Contents 1 Materials 2 Concepts 2.1 Pulse-Width Modulation 2.2 The RGB Color Wheel 2.3 Algorithms 3 Circuit Design 4 Da Codez 5 See it in Motion 6 Now What? Materials In order to »

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. Contents 1 Connecting to Gmail 1.1 Find the Official API 1.2 Authenticating 1.3 Getting the Unread Mail Count 2 Designing the Circuit 3 More Reading 3.1 Gmail 3.2 Raspberry Pi 3.3 Python 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 »

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. Contents 1 Defining the Rules 2 Designing the Circuit 3 Writing the Script 3.1 Metronome 3.2 Success or Failure 3.3 Detecting Button Clicks 4 More Resources 5 Final Thoughts »

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. That led me to… Note: Source code for this project is available on GitHub. Contents 1 Goals 2 Setup 3 What is Morse Code? 4 Coding the Translator 4.1 The Circuit 4.2 Mapping Characters to Morse Code 4.3 Mocking Out the GPIO Module 4.4 Distinguishing Dots from Dashes from Letters from… 5 Trying it Out 6 What else did I learn this week? 6.1 Circuit Design Tools 6.2 Tutorials 6. »

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 »