Computer Controlled LEDs

Purpose : The main purpose of this project is to use a DB25 connnector and make one or more LEDs light up using the computer's parallel port and pascal programming language.

Hypothesis : It is possible to light up LEDs using computer's parallel port and pascal programming language. When you send commands like 'writeport(888, 255);' all the lights connected to pins D0 to D7 will light up.

Materials :

1. 18 guage Red and Black wires(2 feet)
2. Two LEDs(3V)
3. DB25 connector
4. DB25 connector securing case
5. Electrical tape
6. A safety box!
7. Three parallel port pins. (You may need more unless you have skils)
8. A pair of needle nose pliers
9. A wire stripper
10. A philips screw driver
11. A hand drill
12. A #12 drill bit

Procedure :

1. -> Get all the material ready to be used.
2. -> Read all the safety procedure.
3. -> Get a #12 drill bit and put it in a hand drill.
4. -> Drill two holes one inch from each of the two side of the safety box.
5. -> Drill one hole at the back of the safety box for the wires to come out from.
6. -> Put two LEDs in from the TOP of the holes.
7. -> Solder two red wires to the bigger ends of the LEDs.
8. -> Solder two small black wires to the smaller ends of the LEDs.
9. -> Solder one end of 150ohm resistor to the black wires and attach a longer black wire to the other end of the resistor.
10. -> Get all three(two red and one black) wires out of the box from the hole at the back of the safety box.
11. -> Get three parallel port pins and attach them to the three open wires.
12. -> Get a DB25 connector and put the black wire in pin 18.
13. -> Put the one of the red wire in 'D0' while inserting the remaining red wire into 'D1.'
14. -> Wherever you see open solder and/or wire, put electrical tape around it to prevent it from short circuiting.
15. -> Carefully enclose the DB25 connector into a DB25 connector securing case.
16. -> Using a glue gun, put some glue right on the bottom of the LEDs from the inside to prevent them from moving.
17. -> Tape all the wires down inside the safety box in a neat manner so that you do not find random tangling wires.
18. -> Make sure that you put put tape on the three wires that run from the DB25 connector to the safety box.

Diagram : Take a look at the following diagram to properly wire your LEDs.

Observation / Results : After I finished constructing the hardware, I made a really simple sophisticated Pascal program that will ask the user how many times do they want the LEDs to blink and whether they want both LEDs to blink or alternate LEDs to blink. When I attached the DB25 connector to the computer's parallel port, and executed the Pascal program, my LEDs blinked the way I wanted.

Conclusion : As I hypothesized in the begining, it is possible to use computer's parallel port and DB25 connector along with other tools to light up LEDs using Pascal programming language. It is also possible to take input from the parallel port and use it to run the program. Command 'writeport(888, 255);' did indeed send power to all the pins between and including 'D0' and 'D7.'