actually solid state would probably be a better solution for me, for the
most part all i'll be switching is 5 or 12 volt lines. If you could
point me to some more information with the printer port it would help me
out a lot, so far this seems to be the best option. I was actually
planning on running this through dos, complied used c++ as there will be
no monitor on the system and it will require fast boot and response
times. Any better alternatives to dos or will i still be able to access
the parallel port in the same way. again thanks in advance

petrus bitbyter wrote:
Ryan,

You can use an EPP (printer) port. This way you can use a separate address-
and databyte. Using a 374 type of address register you can enable or disable
up to eight 473 type data registers without address decoding. That gives you
256 output pins which sure will be enough.

Do you really need relays to switch your equipment? They tend to be pretty
expensive and need a good amount of current. So for twentynine relays you
may end up to need some 3A of current. If you want to switch the mains,
solid state relais are a better choice. (Although they are not cheap
either.) You can also use triacs and optocouplers but you will need some
extra parts so you're building your own solid state relais this way.

Except from the hardware you'll also need some software. Newer (NT based)
Windows versions will not allow you to write directly to the output ports.
One of the methods to circumvent these problem is using a special driver.
For instance:
http://www.paraport.net/

pieter