My Parallel Port Interface.

This page discusses the "universal interface" that I built for my various projects so I can control them from my computer's parallel port. I got the plans from Robot Builder's Bonanza 2nd Edition. Basically it routes the Control, Status, and Data lines from a computer's parallel port through three Hex Buffer Driver ICs (74367) so that the ICs rather than the parallel port are driving whatever device is attached to the interface. For now its configured to drive some LEDs and all of the input lines are tied low.

	A cropped picture of the entire interface on my prototyping board. Was 1600x1200x24bit before I cropped it, but now its 16bit and I didn't use a flash.
	This is where the parallel cable is wired to the board. Was 1600x1200x24bit before I cropped it now its 16bit. The pins start at pin 1 on the left and 18 on the right.
	Here is where the outputs are tied to LEDs through various resistors. I didn't have 330ohm resistors so I used what I could find so there are some 100s, 68s, and the blue one is a 101 rated at 1W. The LEDs don't seem to be getting hot from over current so I'm not worried. The first output is on the left.
	If you would like to download my rendition of the test program given in the book you can run it on any machine with a Basic interpreter like Qbasic on Windows.
	Here is my second Basic program that will count up the various output lines if your interface is configured like mine. I tried to comment this code so that you (and I) can see (remember) how the ports various lines interact.

Recently I hooked up a small DC motor from an old toy to see if I could control it from the STROBE (first) line. I ran a program that basically turned the line ON/OFF every few seconds. Well it didn't work until I said "D'oh!" and remembered to use a 2N3055 Power Transistor rather than a lower powered one. Using the right transister kind of helped but I still had a problem getting it to turn on. When I motor first starts it needs more current than it does once its moving. The 5V 1A power supply I'm using with the protoboard doesn't have enough output to reliably power the ICs and give the motor a good kick. Sometimes it works and sometimes I have to give the axle a little twist to get it moving. Once its moving it will keep going until the line turns off. I basically need to hook up a separate power supply to the protoboard to supply the motors and other things I hook up to it. I recently burnt out a 250W PS in my PC and replaced it with a 350W. As far as I can see the 250 only blew 2 or 3 caps which I should be able to replace and although I wouldn't trust it to power a PC again, I would trust it for fairly rugged components like small hobby motors and such.