Parallel Port Box

Back in college I acquired some old DJ light controlling equipment. This included one box with switches and buttons to turn eight channels on and off, two things that looked like big power strips where each outlet was switched by a relay, and two cables, each about fifty feet long to attach the switches and buttons to the relays and outlets.

A few years back I made a box to control the relays from a parallel port. This is used at work to control as many as eight lights that indicate the status of various builds.

I wanted my own to play with the same setup at home, so I made another one. (read: Phone-controlled Christmas lights?)

It looks like this:


It's just eight transistors, resistors, LEDs, and diodes with the necessary connectors in a little box.

It went a lot faster this time. I did all of the soldering and most of the customization of the project box in one night. I think the previous time it took me the better part of a day.

The only thing that prevented it from working the first time I tried it out was that the Centronics connector pinout I was relying on labelled more pins as ground than were actually connected to anything. I moved the ground wire to a different pin and it worked perfectly.

I couldn't find the right kind of Centronics connector, so I ended up soldering to a connector that was supposed to be PCB-mounted. It's ugly, but it's safely tucked away inside the box and works fine.

And finally, when I just about had it ready to test, I realized I didn't have a printer cable. Fortunately, AIT computers provided me with this annoyingly somewhat hard to find cable for a perfectly reasonable price.

In other news, the Python parallel library is about as nice and simple as it gets:

import parallel
import time
p = parallel.Parallel()

Now I need to find something to do with a box of switches and buttons.


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