Wednesday, December 21, 2011

Simple Programmable POV Display

I decided to develop a simple POV display keeping in line with the holiday spirit. the display can be mounted on a motor drive or used by hand.

The POV (Persistence of Vision) displays are based on the principle that the eye cannot discern movement beyond a certain speed. For example, a fast moving light would appear to be a contiguous line. This circuit exploits this principle to flash a straight line of LEDs in rapid succession in order to create words that appear in mid air. The circuit uses a PIC 16F88 microcontroller to control seven LEDs and flashes them based on the word that was programmed.

The project uses a single push button to program different letters into the EEPROM of the microcontroller. The push button is held down for about 5 secs to put it in programming mode. In order to enter different letters, the push button is depressed until the letter you need is reached. The letters are display in their binary format as follows:

The LEDs are represented from most significant to least significant. 0 indicates off and 1 indicates on. After the desired letter is reached, wait for a few seconds for the character to be written to EEPROM. This will be indicated by all the LEDs going off. Repeat this process to program all the characters.

A  0000001
B  0000010
C  0000011
D  0000100
E   0000101
F   0000110
G  0000111
H  0001000
I    0001001
J   0001010
K  0001011
L   0001100
M  0001101
N  0001110
O  0001111
P  0010000
Q  0010001
R 0010010
S 0010011
T 0010100
U 0010101
V 0010110
W 0010111
X 0011000
Y 0011001
Z 0011010
[space] 0011011
'0'   0011100
'1'   0011101
'2'   0011110
'3'   0011111
'4'   0100000
'5'   0100001
'6'   0100010
'7'   0100011
'8'   0100100
'9'   0100101

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