"Ryan Kremser" schreef in bericht
s.com...
Hello I am new to computer interfaces and i need something which i can
drive
at least 29 devices via relay. No inputs with this though. Nothing fancy
just either on or off. What hardware would i need to do this? what kind
of
price range are we talking? Thanks in advance



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


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