It was christened “Magic Wand” by the sub editor of the magazine. Nowadays this sort of thing is referred to as a POV or persistence of vision project.
Nevertheless it is simple to make and fun so I though it was a good candidate to adapt for the Pi.
Incidentally, not only did I make the cover photo that month, but also the Fractal graphics article was mine as well.
The concept is simple, a column of LEDs flash out a message displaying one column at a time in a rapid sequence. You then move the LEDs so that each column lights up in a slightly different physical location. Then the persistence of vision that the eye possesses makes it look like there are LEDs in each position where they were like up. In other words waggle some LEDs on a stick and see words appear in mid air.
The concept can take many forms, perhaps the most impressive is where the whole unit is spun on a bicycle wheel but here I just want to show how to make the simplest version and let you explore the many possibilities of this effect.
My original circuit had 5mm LEDs arranged in a column, now you can get the LEDs closer together and get a more solid looking display if you use surface mounting LEDs. These come in many sizes but an 0806 or 0605 package will fit nicely on adjacent tracks of veroboard. As well as being many different colours to choose from there are also many different styles. I chose an LED with a diffuser built in to spread the light over the whole area of the package, and not just have a point source. I thought this might be better for photography. However, I don’t think you can go wrong with what ever sort you choose.
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