Spinning LED display

[lwilliams]

We're making a spinning LED display which consists of 8 LEDs connected to a spinning arm on a DC motor, the LEDs are connected to a PIC16F88 microcontoller with an optical sensor triggering every revolution. The idea is the LEDs will flash on and off while the arm spins to provide an image, we need some help with the programming to set the sequences for the LEDs to light, can anyone help?

 

[birdman0_o]

Make a big table!

 

[OlPhart]

Depends on image type...

Graphics? I'll 2nd birdman: a big table, unless it's repetitive and/or symmetrical. Mine is built into a ceiling fan and spells messages. It took a solid month for me to get the code right, partly due to lower case descenders in the upper vs lower arc. The "static" pix (see attachments) are time lapsed, the .avi is from a camcorder.

Funniest part of these things: people over ~35 have a Really Difficult time reading it, under 30 get it instantly. I think it's the younger can let the motion "paint" the image, yet older can't resist following the motion. One older (~50s) man INSISTED there was something wrong with the device; after 3 patient explanations of "how" to read it, I gave up.

A genuine trick is how to download new data while running. I'm on my 4th approach. Good Hunting, it's a Great toy once working... <<<)))

 

[gabeNC]

Now that is a slick idea. Very nice! Now how about some specs? How many leds? What's your controller etc etc.

 

[OlPhart]

For real lower case descenders, 15 LEDs are used in a 7 X 12 character matrix, the "floating" 3 are the descenders for the opposite arc. This is so the upper case matrix stays spatially stable. Controllers are a pair of Freescale 908 series. One runs the text->output w/offset & color changes through constant current drivers to the RGB LEDs. The other manages the messages to be displayed and the comm link to the programmer.

The "blade" software runs upper & lower arcs of 32 characters each and allows for full rotational offset. There're also color toggling aspects on a # of rotations/change basis. It's all I could do with the RAM available, an updated 9S08 version could do a Lot more. It runs in both rotations & all 3 speeds (index pulse timing checked every rotation & corrected as necessary). The programmer is a Windows VisualBasic application.

Generating the font tables is straightforward, outputting the formatted data is easy. You'll earn your stripe in reading/formatting the text for output. It requires both forward & reverse table use and inversion with vertical offset. I found it a Real brain scrambler. Good Hunting... <<<)))

P.S. There're variations I've built that have a vertical arm and rotate as scribing a section of a drum. Tradeoff: much easier display formatting, but much harder mech to build.

 

[MrAl]

Hello there,

Yes, that's nice. I always meant to try building a simple oscilloscope along those same lines but instead went a different route. Still think it would be cool though.
Dont forget that you are not limited to circularly oriented images either. A sort of simple set of graphics transformations will get the lines straightened out even if not as well near the center. The chip can do the processing or the host computer can do the processing.