Servo - February 2013

Building a Large Scr lling Display — Part 1: Getting One Panel Working

● by Pete Smith

Ioften attend shows where I’m either demonstrating combat robots and bot hockey, or as a sponsor providing prizes of Kitbots products. In order to inform the public about the event or the products, I have several banners to hang up on the walls, plus I also hand out business cards and information sheets when I have the time. It would be useful, however, to have a more eye-catching and informative way of passing on the information.

I’d noticed scrolling LED displays doing just that in shop windows, etc., and even priced them on eBay. They were all pretty expensive, though — especially in the larger sizes. Then, one day I noticed an advertisement for the Freetronics Dot Matrix Display in a magazine.

The Freetronics Dot Matrix Display or DMD (Figures 1 and 2) has 512 LEDS in a 32x16 matrix which is mounted on a PCB (printed circuit board) and protected by a plastic frame — all for about $100 delivered. The display can be controlled using an Arduino, so for about $150 in total one could have a 6” high scrolling display that could be programmed using a PC to display a message about as long as you could desire.

I’m a mechanical engineer and while I have dabbled with the odd electronics project over the years, I have no experience

FIGURE 1. DMD front view.

with small computer boards like the Arduino. One thing that I liked about the Freetronics DMD is that they also make a suitable Arduino board — the “Eleven” — and have excellent beginner’s instructions available on their website at www.freetronics.com.

I ordered a single DMD and an “Eleven” microcontroller board; it arrived in a couple of weeks from Australia (they are also available from resellers in the US).