miniPOV Persistance of Vision Toy

intro

This is based off of a toy by Lady Ada. I ported her code to the 16F84A because this is the easiest chip for me to use.

• I already have some that I sampled from Microchip.
• The 16F84A already has an 8 pin port capable of driving the LED's
• There is a timer that causes an interrupt at overflow
• I'm not building 100 of them for freshmen to build as kits

results

i am happy enough with this toy. it's not very pretty and it doesn't work as well as the ones at the Discovery Store but it's good enough since i really just wanted to do a non-trivial PIC project. The image i created is the Boston Engineering logo which i chose for it's lateral symmetry. this means the same image is drawn whether i wave the wand to the left or right. I tried doing 'Boston Engineering' but it was too long to read and the words were written backwards on the back-stroke (i wave the wand wildly back and forth). hardware

POV Wand:

like i said it's not much to look at. I am using my BetaPicDevelopmentBoard with a POV module. All of this is fancy talk for I hacked some things together with perf board and some Cat5 cable. The POV Wand is made from eight LED's soldered to a strip of perf board. All the ground leads are soldered together and connect to the ground header on the development board.

I used a Cat 5 cable for the data lines because I have tons of it and i needed eight wires in a bundle. Furthermore the cable provides some mechanical support for the flimsy perf board.

In the picture you can see the line of LED's on the far right. If you squint and tilt your head a bit you can almost make out the POV Wand (don't forget to hold your breathe). If you are really clever you will realize the POV image is upside-down too.

software

Like I said I ported the code to the 16f84a. While it may have required some knowledge of the chip and assembly it really wasn't that hard. you can look at the assembly code here: bec-logo-pov.asm and if the hex file here.

-- ChristopherPepe - 17 Mar 2006