I have seen many smart home systems that enables you to hook up your appliances to your PC and control it right from your desktop. They are all very comprehensive and above all very expensive. I was thinking of doing something similar without using a micro controller ( i know they are the fashion today but a layman has an aversion to it ). I kept thinking and thinking and tey suddenly it stuck me...the good old PARALLEL port!!!!...
I have used it to light an LED using a c program when i was 15...then i left it as soon as i layed my hands upon my first microchip pic project.
But i thought i better dust it back up...come one guys..let us do it....
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Step 1: Basic Ideas of a Paralell Port
Everybody knows what is parallel port, where it can be found, and for what it is being used. the primary use of parallel port is to connect printers to computer and is specifically designed for this purpose. Thus it is often called as printer Port or Centronics port (this name came from a popular printer manufacturing company 'Centronics' who devised some standards for parallel port). You can see the parallel port connector in the rear panel of your PC. It is a 25 pin female (DB25) connector (to which printer is connected). On almost all the PCs only one parallel port is present, but you can add more by buying and inserting ISA/PCI parallel port cards.
the Pin outs are simple...
pins 2-9 are the 8 data pins which we will be using to control up to 8 switches.
Step 2: The Circuit
IN4148 Diode - 1
6V Relay -1
1KOhm Resistor - 1
202Kohm Resistor - 1
BC547 Transistor -1 (BC548 Will also do)
LED - 1
DB25 Male connector ( Usually comes with a 25/18 wire cable)
6V Power Supply - 1 ( I used a old charger from Nokia, It worked pretty well)
Working Board - 1 ( you can also do it in Christmas tree style...but i prefer doing it in a board )
Pins 18-25 Usually comes shorted together in the connector itself..else do it in the connector and use a single wire to the ground to minimize complications...
Step 3: The Software to Run It.....
I am not venturing into the details of the programming..
Google for inpout32.dll to get the details :)