LED Sign

Here's how to make a microcontroller based 7 letter (or less) LED sign.  Each letter is individually controlled and so you can program it to display many different patterns.  It uses the darling transistor array ULN2003A to switch letters on and off.  The DC voltage you use will determine the maximum number of LED's in series.  For example, I used a 9 volt DC adapter and since each  LED drops 2 volts, I used at most 4 LED's in series (9/2 = 4 rounded).   You then connect an appropriate resistor in series and extend the number of LED'S per letter by connecting additional series sets in parallel.  For example, using a 9 volt supply, a letter with 9 LED's would consist of 3 series sets: 4, 4, and 1 which are then connected together in parallel.  A resistor of 50 Ohms is connected in series for each of the 4  LED's to allow 20 miliAmps of current.  (9 - 2*4)/0.02A=50.  The single LED gets (9 - 2)/0.02 = 350 Ohm resistor in series.   As long as your power source can deliver enough current, your letters can include more LED's if necessary.
You will need to design your LED board separately since the sign will be any word or name you choose.

Step 1 Bill of Materials

Components

• Capacitor .1uf
• Capacitor 10uF
• Capacitor 1uF
• PIC16F88
• 7805T TO220H 
• Resistor 4.7K
• 5MM LED's
• Several resistors: 50, 150, 250, 350 Ohms

Hardware

• Wire 
• Single sided copper clad board large enough for the LED sign
• 3" x 3" Single sided copper clad board
• PIC burner
• 9 Volt DC adapter

Software

• Jal compiler: http://www.casadeyork.com/jalv2/
• Eagle software: http://www.cadsoftusa.com/
• LEDSign.jal
• LEDSign.hex

PCB making

• Paint thinner
• Hydrogen Peroxide
• Meuratic acid
• Laminator
• Laser Printer
• LEDSign.sch and LEDSign.brd