The PC is now an economic and common equipment at home or office. Due to Open source and GNU Linux, many professional programs and environments are easily accessible. To interface it to the real world is a step in learning Automation and Robotics.
Computer Data Interface - delabs
In Automation we have both Industrial and Home. You can start with home automation, as industrial automation is more complex. But in Home Automation, Safety First should be emphasized, Any neglect in care of electrical hazards will neutralize any advantage of Home Automation.
Do not apply voltage above 5V to any pin of printer port, ensure earthing is good, use opto couplers for inputs and outputs if you are not sure. wrong use will damage motherboard, these circuits should be used only if your basics are very sound.
delabs Technologies 16:16 30-Mar-07
Analog Interface for PC Ports.