8x8 Scrolling LED display (Simple example)

[wellyboot]

Hello,

I have built a simple 8x8 LED matrix that scrolls a message, in my example i am scrolling " D J W " followed by a smiley face.

I used standard yellow leds, which are ok, I would however recomend using higher brightness leds and adjusting the PORTB output resistors to suit.

I have attached a text file of code, I warn you now im no expert at writting code and not as experienced as some guys on here are, i have based it around 16F872 as i had 1 handy, and hope someone finds it useful!

Ill try and post a circuit diagram later

Dave

[wellyboot]

attached a picture of display, and a circuit diagram

[wellyboot]

oppps its too late to edit last post,

The circuit appears to show all the columns in the matrix are connected directly to the top row, this is an error,


have attached a revised circuit.

note: that i have used the standard diode symbol instead of the LED symbol just to make it easier to draw, as i used the 'paint' program to do it!

[earltyso]

nice work!

I had lots of problems shifting through my rows when I built an ascii lookup table.

I have not tried shifting through colums, now I am motivated again to bust out the 8x8 matrices I have lying aroud my electronics cuboard again.

[wellyboot]

Hi

Have added a LM35 Temperature sensor to the above circuit, connecting the output from the sensor to AN0 (pin2) of the PIC.

Now i have a scrolling temperature reading in degrees C on my display.

I have stored the data for the numerical characters in the internal eeprom, as i didnt have enough memory to store it in a varible array .

The characters for the numbers look a bit naff, but can easlierly be altered to look better.

Again im no expert, and only put this together this evening! but seems to work quite well.

[hoggefx]

Nice !

Thanks.

[wellyboot]

Hi again, Thanks for your replys, have made a couple of alterations

1st) I noticed when the digits 1st came onto the display on the right hand side column, the left hand side column some of the LEDs lit very dimmly when they should have been off.
I have modified the 'LOOP' section of code as follows to fix this problem and speed up the scrolling a bit too.

LOOP:
FOR scroll = 0 TO 35
FOR scan = 0 TO 15
PORTC = 1
FOR counter = 0 TO 7
PORTB = leddata [counter]
PAUSEUS 1500
PORTB = 0
PORTC = PORTC * 2
NEXT
NEXT
FOR counter = 0 TO 34
leddata [counter] = leddata [counter+1]
NEXT
NEXT
GOTO START
END


2) I have improved the look of the characters in the eeprom locations as follows:

eeprom 0,[%00111110,%01010001,%01001001,%01000101,%00111110] '0
eeprom 5,[%00000000,%01000010,%01111111,%01000000,%00000000] '1
eeprom 10,[%01000010,%01100001,%01010001,%01001001,%01000110] '2
eeprom 15,[%00100001,%01000001,%01000101,%01001011,%00110001] '3
eeprom 20,[%00011000,%00010100,%00010010,%01111111,%00010000] '4
eeprom 25,[%00100111,%01000101,%01000101,%01000101,%00111001] '5
eeprom 30,[%00111100,%01001010,%01001001,%01001001,%00110000] '6
eeprom 35,[%00000001,%01110001,%00001001,%00000101,%00000011] '7
eeprom 40,[%00110110,%01001001,%01001001,%01001001,%00110110] '8
eeprom 45,[%00000110,%01001001,%01001001,%00101001,%00011110] '9

3) I have noticed that if the LM35 is too close to the PIC IC the output is higher than normal resulting in a higher temperature being displayed, the PIC IC is cold so i have no idea why this is happening. I have soldered my LM35 onto 3 wires about 4cm's from the board which seems to have corrected the problem.

Hope this covers all the bugs!

[prasanna]

Hi, Please let me know how to program this IC PIC16F872 as I am new to this area.
My email: [email protected]
Appreciate your help

[krish69]

Hi, Please let me know how to program this IC PIC16F872 as I am new to this area.
My email: [email protected]
Appreciate your help

u got lot to learn dear.u need a programmer n programming software to do this..
[r u from srilanka o uk?]

[priya5]

sir plz send me the code and ckt diagram of LED moving display using ATmega 16

[Ioannis]

This is a PIC controller forum. Not AVR.

Ioannis