Controlling the LEDs with a 74HC595 chip

I finally got the 74HC595 chips and decided to do a dry run on a breadboard. I used the schematic I made earlier with Fritzing and just rebuilt it, with a couple of LEDs on every chip. I used the code from this blog as a base and it worked on the first try. Now I have to adapt this code for my purposes.

Don’t panic, the test setup looks worse than it is 🙂

Thoughts on connecting the LEDs

This is a summary of some thoughts I had on connecting the LEDs to the Arduino. When I read about charlieplexing I was amazed how many LEDs I could control with so few pins on the Arduino. Then I realized the downside of this technique: Essentially I can only light a single LED at a given time. Sure, there are a couple that can be lit simultaneously when they don’t share any pins, but setting those up would be a nightmare. So I started to group the words. Which words have to be lit when? Continue reading Thoughts on connecting the LEDs

Starting with the front plate

Today I was rummaging through a crafts store and found some dark card board and translucent paper. The paper is available in different colors, so I can customize the color of the words to my liking. I cut some rough letters out of the card board and placed the translucent paper behind it. Continue reading Starting with the front plate

LEDs arrived

Today the LEDs I ordered finally arrived. A couple of days ago I stumbled upon a wiring technique called “charlieplexing”, which is explained quite thorough in this article. If my calculations are correct I’m going to need 12 pins on the Arduino to control the LEDs and another one for the DCF module, so I’ll be good with the regular 14 pins.

So, next I’ll start wiring up some LEDs for testing. As long as I don’t have the DCF module some dummy clock function will have to to.

New project: Wordclock

For some time now I was intrigued by wordclocks. Sadly, all clocks I found so far are quite pricy, so I decided to build my own, using an Arduino for the electronics. The clock is going to be a gift, so I’m going to keep these posts private until the gift is given, so all related posts are going to appear at once.

Yesterday I ordered the first parts for the project, an Arduino Mega 2560 along with a set of white LEDs. Originally I wanted to use an Arduino Nano, but while I was doing the concrete planning of the electronics I realized that would mean quite an excessive amount of soldering on my part. The Nano has only 14 digital pins, but for a minimal german word clock I need to control 19 individual lights, I’ll have 21. My first idea to use a logic gate fell short when I calculated the logic gate.

es ist fünf zehn viertel
zwanzig  nach  vor  halb
eins zwei drei vier fünf
sechs sieben  acht  neun
zehn   elf   zwölf   uhr

There are just too many things that can go wrong here, additionally this would be using quite an amount of space. So I’m going for the Arduino Mega, which has 54 digital pins. A little excessive, but way easier to build. I’m going to add an DCF77 radio clock module so I won’t have to bother with the functions to set the time. The module will reduce the available pins on the Arduino further when it’s connected. Integrating it shouldn’t be too hard, a library to access it from an Arduino already exists.

This is how I want to build it: The top is going to be a layer of acrylic glass, with the words being cut out somehow. I’m not sure yet how I’m going to do this, I have a couple of ideas to try. Below that I want to use a layer of diffuse acrylic, to spread the light from the LEDs more evenly. Maybe I can merge these two layes, I’ll have to try it.

Things to figure out: how to separate the LEDs from each other, how to build the case (probably thin PVC). But first things first, I’ll have to wait for the first parts to arrive. Then I’ll start playing with them.