PicPOV is a project based on “persistence of vision”. A PIC microcontroller blinks 8 LEDs on and off so that when waved through the air, a message appears to float in front of the viewer.
Design and Implementation
The design goals were:
- be simple to use;
- capable of storing multiple messages;
- simple to change between messages;
- simple to load new messages.
A small microcontroller like the PIC18F1220 does this job just fine! It has only 18 pins, an internal oscillator, eeprom and a serial port.
- The internal oscillator removes the need for a crystal;
- Multiple messages are stored inside the eeprom;
- One button changes to the next message (8 in total);
- New messages can be loaded through the serial port using any terminal program.
The serial port connection is usually implemented using a MAX232 or similar IC but to reduce the costs even more, a simple 2 transistor solution is used.
The circuit is divided in three areas:
- Microcontroller, LEDs and button on the left side are the basic POV circuit;
- Two transistors and 4 resistors on the bottom right implement a level shifter to to interface with the serial port;
- and finally at the top right a power supply.
For more detail: PicPOV – Persistence of Vision with a PIC18F1220