Comment Controlling Relays (Score 1) 453
The simplest (not safest :) ) way of doing what you want is getting 5V switchable relays that basically turn on in the presence of 5V (really ~4) and turn off when seeing 0V.
Then hook up a pin from your parallel port to each of the relays, also hook up the ground pin to the control ground for the relay. You'll need a diagram of a parallel port from http://www.beyondlogic.org/index.html#PARALLEL
or anywhere else to choose pins from the data byte. After that, turning on and off the relay is as simple (in linux) as getting perms to the port with ioperm (http://www.rt.com/man/ioperm.2.html) and making a bit go up or down in a certain byte in your memory space (the possible locations are in the parallel port doc above I believe).
I've done this, it's simple and it works... but don't mess up and put 120V through your parallel port. You will regret it :)
Then hook up a pin from your parallel port to each of the relays, also hook up the ground pin to the control ground for the relay. You'll need a diagram of a parallel port from http://www.beyondlogic.org/index.html#PARALLEL
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I've done this, it's simple and it works... but don't mess up and put 120V through your parallel port. You will regret it
