This is an interesting thread, and one that I'd like to use if possible to make a cheap-o software monitored PC shutdown and a timed forced shutdown. So I'd like it to send a signal to the comuputer asking it to shut down, using the serial port as people have discussed, but also have a timed shutdown on the power inverter, so after say 1.5minutes it will cut off the power and completely turn off everything.
So having read what I can find in this and other threads, does this look OK? It seems OK by my (extremely limited, high-school level!) electronics knowledge.
Can anyone go over it and see if there's anything wrong?