This clock uses the classic video game Pong to tell the time. The 2 players automatically win and lose so their scores show the hours and minutes. It's not too hard to build and should cost less than $100. All the parts are easily available on eBay and the software code is free to download!
The clock can also show the time written in words such as "Ten Past Twelve", or with large or small digits. The date pops up every now and again too, printed out with a retro flashing cursor effect. A menu screen lets you choose the display mode, or you can have the clock pick a random mode every few hours.
The project uses 2 bright LED matrix panels from Sure Electronics (you can choose between red and green). An Arduino runs the main code and a DS1307 clock chip keeps time, even when the power is off.
Step 1: Parts List & Cost
2 x Model 2416 Red or Green LED Matrix Displays from Sure Electronics
You can get these from Sure's eBay store for $15 each: http://www.sure-electronics.net/ Make sure you get the new version of the display which is based on the Holtek HT1632C chip. You can tell the new displays as they have the controller chip and DIP switches on the back. (See pic). My clock is made with the 3mm LED display, but they also make a larger 5mm one.
1 x Arduino Uno / Duemilanove with ATmega 328 CPU
Th Arduino is the brains of the clock. It has a microprocessor that runs the main clock software, plus inputs and outputs we connect to the displays and other components. Ensure you get an Arduino with the ATmega 328 CPU. (Some older boards come with the ATmega 168 with doesn't have enough RAM). You can get Arduino's for about $30. Try Sparkfun Electronics or eBay.
1 x DS1307 Real Time Clock chip (RTC) and IC socket.
1 x Crystal Oscillator for the DS1307
1x 3.3v Coin Cell and holder - battery backup for the DS1307
I found all these bits on eBay bundled as a kit for $10.
1x Arduino Prototyping Shield
The prototyping board or ‘shield’ plugs onto the top of the Arduino making it easy to add components. It brings all the Arduino's input and output pins onto a circuit board that you can solder components to. Get a board which is designed for a chip to go on, i.e. one that brings each pin of the IC out to a solder pad you can connect wires to (see pic). Again places like Sparkfun or eBay are good sources for them. You should be able to pick one up for $15 - $20. If you don't like the idea of soldering, you could get a breadboard and jumper wire to build the circuit on temporarily instead.
1x 16 Pin IDC Socket
We solder this socket to the prototype board so we can plug the display ribbon cable in. They are a couple of dollars on eBay. If you aren't planning to solder, you don't need this.
2x ‘Push to Make’ Buttons.
These are used to set the time / change the display mode. You can get them for a few dollars.
1x USB Lead - Type "A to B"
This is needed to to program the Arduino, and then as a power lead for the clock.
1x Mains to USB Power Adapter
This is used to power the clock and you can pick them up for less than $10. Look for one with an output of 150mA or above.