Computer startup/shutdown logic

That still won't work if you're running a Windows O/S. or any other OS that requires a shut-down sequence. HOWEVER, if you want to spend MORE money, get a UPS with the interface that saves all work, and shuts down the PC automatically when power is lost to the UPS. There is software that is installed, with a Serial cable. OR, use a Keyboard with the a button for powing off the PC, newer ones have them, I know, I have one! If I want to shut down, all I do is press the button on the Kayboard, and down she goes. Use that to PULSE the key, and the thing will shut-down, with your relays and stuff (just not TOO much voltage!). The turning on is the simple part, just apply the voltage to the POWER button pins on the Motherboaard when you power up the car. Newer BIOSs in PCs also have power on by MOUSE or KEYBOARD buttons as well, but not with USB Keyboards or Mouse. You must use the PS/2 ports in order for that to work. All the ATX supply does is sense a signal from the Motherboard after Windows shuts down to POWER OFF the unit. Sure, you can hard ware a shut-off, but you'll het your improperly shut-down screens with the Windows O/S. You can "CLOSE" the ATX power switch pins, but it can't be a CONSTANT, it must be a momentary contact for powering OFF. ALSO, the BIOS must be set for INSTANT OFF, and not the 4-Sec Delay (which would mean the pins are closed for FOUR seconds before the PC shuts off). Like I said, with a Windows O/S, you just wun into those shut-down issues.

There's a bunch of guys selling "shutdown controllers" that will do what you want.  Average $ is $40, however there's also schematics to be found on the Web.   Here's a site with schematic and parts list. I've not built one because I simply have an icon that I hotkeyed. One button push and my BenzPC shuts down quickly.

Powerslave0 wrote: That still won't work if you're running a Windows O/S. or any other OS that requires a shut-down sequence. HOWEVER, if you want to spend MORE money, get a UPS with the interface that saves all work, and shuts down the PC automatically when power is lost to the UPS. There is software that is installed, with a Serial cable. OR, use a Keyboard with the a button for powing off the PC, newer ones have them, I know, I have one! If I want to shut down, all I do is press the button on the Kayboard, and down she goes. Use that to PULSE the key, and the thing will shut-down, with your relays and stuff (just not TOO much voltage!). The turning on is the simple part, just apply the voltage to the POWER button pins on the Motherboaard when you power up the car. Newer BIOSs in PCs also have power on by MOUSE or KEYBOARD buttons as well, but not with USB Keyboards or Mouse. You must use the PS/2 ports in order for that to work. All the ATX supply does is sense a signal from the Motherboard after Windows shuts down to POWER OFF the unit. Sure, you can hard ware a shut-off, but you'll het your improperly shut-down screens with the Windows O/S. You can "CLOSE" the ATX power switch pins, but it can't be a CONSTANT, it must be a momentary contact for powering OFF. ALSO, the BIOS must be set for INSTANT OFF, and not the 4-Sec Delay (which would mean the pins are closed for FOUR seconds before the PC shuts off). Like I said, with a Windows O/S, you just wun into those shut-down issues.

Actually you are wrong on that issue.  If your computer is ACPI compliant then if you tap the power switch on an atx power supply by default it will initate a windows shutdown.  Works perfectly on my Windows PC here.

I live my live a quarter mile at a time. For those 10 seconds or less I'm free.