I wanted to experiment with persistence of vision ( POV ) and designed this gadget.Briefly, POV is the physiological effect that makes movies and TV possible where films single frames are shown one after the other and TV scenes are composed by an electronic beam travelling left to right, top to bottom on the screen and still what you see is a fluid image.The clock comes in the shape of a toothbrush case (courtesy of Swissair) with three buttons and 7 LEDs at the top. Inside the case there are two AA (or AAA) batteries with a cardboard homemade battery holder and a piece of perfboard with the circuit on it.
The circuit is based on a PIC16F84A micro, 7 high efficiency LEDs, a 32Khz wrist watch crystal and a few passives.
Pushing one of the buttons (the trigger or 'wand' button) and swinging the wand at the same time right to left this is what you see:
It takes some time to learn and sync button press and swing, but it's easy.At first the image will look distorted but eventually you will be able to get a decent display.
The software include an option to display second as well. The display becomes more complete and the dynamics of the seconds adds interest, but it is also trickier to get a decent display. It is worth a try, but eventually you will probably go for the HH:MM version.
Time is set via two buttons by trial and errors: swing and read time, push mins set button to advance minutes one per second, push hours set button to advance hours one per second, read again and correct if necessary.
The circuit is quite simple, With all parts ready you could do it in a few hours. The batteries last quite long thanks to the low frequency crystal, the low voltage supply and the fact that the display is off most of the time.
The source code and HEX file ready to burn into the PIC togheter with a better picture of the schematic can be found here. The source is commented, so you should not have any problem understanding how this thing works.
Programming software I used successfully are PonyProg or WinPic. The programming interface is the one described in PonyProg.
More pictures here.
