A 30th birthday is something special. And so a very special present was needed. During a look into the tinkering box I noticed some disassembled dotmatrix displays. For the card shown here, a single display is driven by an ATTINY2313. A text stored in the flash is scrolled through the display. Three AA batteries are used for power supply.

Microcontroller, transistors and a few resistors are mounted as SMD on the backside.

Flo milled the board for me on his CNC. In addition, the 30 is cut out of the board material. That' s a real eye-catcher!

The backside is insulated and protected with plastic 70 from finger pats on the copper.

The circuit is simple. 5 transistors for the columns, series resistors and the AVR. The display has common cathodes for the rows, so you can switch to ground with a NPN transistor. The 7 columns are connected directly to the respective port pins. Thanks to an internal clock, not even a crystal is needed. The input voltage must not exceed 5V.

The firmware was written in C. The microcontroller multiplexes the display column by column. Text and character set are stored in the flash.

Now the only thing missing is a suitable packaging. Together with some other stuff I packed the circuit in a big cardboard box. On the outside of the box you can see a LED, which is powered by an old button cell on the inside. Next to the LED I have written REC to the confusion.

Packaging and especially the contents have provided a lot of fun for the birthday boy and the guests!

Demo video of the prototype

If you want to rebuild the LED Scroller, you can find the files here!

Downloads

• Schematic, Layout, Pictures

Last Update: October 2011