Newsgroups: sci.electronics.design
Subject: Re: Control of 120VAC using a Parallel Port
References: <[email protected]>
"Michael M. Sawalski"  writes: 
> Does anyone have any ideas on design of the circuit (what do I need to
> connect the parallel cable to) for controlling the power on the
> electromagnet.  This would replace the 120VAC push button switch.

The simplest and most reliable way to replace a pushbutton
with computer control is to use a relay controlled form computer.
A relay works as controlled siwtch and provides necessary 
isolation between mains voltage and computer.

You can find details how to control a relay to PC parallel
port and how to control it form your own programs at
http://www.hut.fi/Misc/Electronics/circuits/parallel_output.html
That document is written my me and it includes the necessary
schematics, test program, tested source code (Pascal and C) and
programming tips (Assembler, Basic, C). The document includes 
executable test program and source code for DOS. There is also
source code cor Linux and information also related to Windows.

Further information and example programs related to Windows are wellcome.
Does anyone have a simple free Windows example program like the ones
above wichi I could add to my pages (with permission from the author)
or link to (in this case I hope that tis is a stable link which does
not dissapear quicly).

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web pages at http://www.hut.fi/Misc/Electronics/