Added: July 14 2005
CIRCUITS
This page is still pretty raw. I'll add more as time allows - Benjammin
BASIC PARALLEL PORT
The circuit below should be duplicated for each printer port pin you plan on using. For the most part its pretty straight forward. By turning on a pin you apply a current to the base of the transistor which in turn allows current to flow from Vcc and change the state of the relay. The relay I'm thinking of is a mechanical reed type and the ones I used were fed from 12v+. You may have to adjust the circuit if you're using different relays. The diodes are there for protection and should not be omitted. To make the actual connection you can cannabilize a printer cable or buy a DB25 connector and go to town soldering.
The parts are common place and shouldn't be hard to find. I'll assume you understand some basic electronics and know how to assemble the components properly. Be aware that you can fry a printer port if you aren't careful. I make no claims that my information is completely correct even though its worked for me using several different machines for extended periods of time. I will in no way be liable if you fry your printer port or other parts of your machine. If in doubt don't use this on a machine you care about.
