forcing the PC to do a "Super Power OFF" is..., I do not recommend
[as butitoy mentioned..., lu-oy ka-ayo ang components sa cpu specially the HDD ].
anyways, just correct me if I am wrong, ang allan timer kay duha ang iya relays:
-> one you can use to power off the monitor
-> one that you can use to 'force shutdown' your pc, just use this particular relay to 'switch' your "power button" as to effect of pressing it.
sakto ba?
as an alternative to the "shutdown" method..., you can just create a power management script that if 'idle' ang user..., it will (possibly terminate any user programs) loggoff the user.