The Display is an array of 5×24 Leds. I used Shift registers to light up every column, DO NOT USE ANY 74LSXXX TTL. The 74LS is a Low Power TTL that doesn’t light up the leds very well. Use the 74HCXXX series or 74FXX series.
Config: WDT Off, TIMER On, OSC Internal RC, MCRL Off, LVP Off
After almost 2 weeks sleeping only 5 hours every night, the circuit is working. Is hard to get a picture while the display is scrolling the message.
This LED Display allows up to 128 Characters, Just write your message in the EEPROM Data and it will be displayed. If the Display is “blinking”, the power is not enough, Put a 470mF capacitor in the positive and Gnd. If some Dots are brighter than the others, you need to use another TTL series (like 74FXX). Some TTL have not enough power to light up many leds.
It was really hard to develop. The function is similar to any video cards on computers. The program in the PIC have: RAM Section: Contains the data to display. ROM Section: Contains the characters and symbols. Converts any letter to binary data. Scroll process: Scrolls the data in the RAM Section and send the data to LEDs. Display Process: Takes the info from EEPROM, Converts the data to Bits (using the ROM Section) and put it on the RAM section.
The next one will be a full display (maybe a color display) with 8×40 led array. This one was really hard to build and took more than 56 work hours. The good thing is: For less than $ 20.00 USD, I built my own led display. I Paid: three 5×8 leds array for ony $6.00 USD, 1 Microcontroller PIC for $ 3.00 USD, three Shift registers (TTL) $ 2.50 USD. A 5.5 volts AC adapter for $ 3.00 USD and miscellaneous: $2.70 USD.
REMEMBER TO WRITE THE MESSAGE IN THE EEPROM DATA BEFORE PROGRAM THE MICROCONTROLLER. If the message is too short, use the “LF” Character (Ascii: 10, Hex: 0A) as “End of message”.
The character 01 (01h) is used to create a 4 seconds pause in the display.