Good points. I believe the first (bringing up a timed shutdown dialog with the option to extend/cancel) could be done entirely in software (in principle there's no reason why it can't - but it might require kernel changes). I'm still looking into that possibility - I can write a user mode app such that the PC doesn't shut down and brings up the dialog instead but the odd app might close immediately. I'm trying to work out how to avoid even that happening.Originally Posted by Cobelli
I've got a use for the hardware aspect though. My car turns off the switched 12v during the crank. So if I drive my (planned) auto pc off the switched voltage, I am protected against voltage spikes. I just need a small lead acid battery to avoid the drop to zero. I still want an automatic shut down. So I'm wondering if there's any way that I can continuously monitor for the 13-14V switched voltage and if it disappears for long enough (i.e. more than just during the crank), turn the computer off.
That way, when I switch the car on, the PC starts resuming from hibernate immediately and survives the crank. When I later switch the car off, it starts hibernating again ~10 seconds later unless I switch it back on again. That could be done with electronics, but a software solution + a custom serial cable would be simpler and cheaper.