Empeg power on/off based on acc+perm power. How?

Folks,

I'm trying to set up a computer for my car and I want it to behave like the empeg in terms of how it turns on and off depending on whether the car's accessory line has power or not. I don't want to just power it from the accesory because when I turn off the accesory I want it to shutdown properly before power off . Anyone know how this is done? Does it require special hardware? If so, what kind of stuff are talking about?

Thanks!

Anyone know how this is done? Does it require special hardware?

Yeah, I'm pretty sure it does require special hardware. I could swear that I've seen custom hardware boards designed specifically for this task (mounting PCs in cars and having them gracefully shut down on ignition-off). Unfortunately, I don't have a link handy. Anyone?

Well, you could wire the PC directly to the battery, use a serial cable normally used for UPS software, connect the UPS cable to your other equipment and shutdown the PC that way.

Haven't done this myself, just an idea you could play with. Does'nt cost too much either.

TommyE

Thank you Tony. Based on key words in you rmessage I was able to track a web page that says how to build such a thing. Unfortunately its way beyond my capabilities to put such a board together. I'll keep on looking to see if there is something similar that is sold commercially. If anyone runs across something I would appreciate pointers.

why not use the empeg's approach to power-off ... use a simple 12v relay and if the accessory goes off it switches the battery off to your power supply. Then make the software able to handle non-graceful shutdown.. in other words use linux and mount the drives read-only. If using Windows just hope your programs don't clobber your drive and turn off the filesystem check on reboot.

Thank you for the great idea, Tommy. Since reading your message I've been trying to find documentation on how to implement this, no luck yet, but I'm working on figuring it out. I'm hoping its as simple as cutting the power on a pin to inititiate shutdown.

If anyone knows what the protocol to initiate shutdown from a UPS serial is, I would appreciate tips.

Or, if your computer is ATX, then you should be able to do something where the accessory power trips an instantaneous switch/relay that does what a press of the power button would do. Then your OS can shut itself down based on that signal, just as if the front power button were pressed.

Thanks. That may be the info I was looking for. Pardon my ignorance, but I'm only guessing at how a relay works from the context of your message. So essentially I can make this thing cut off power to the computer a specified amount of time after the accessory goes off? Off to google to searching for 12v relay.

Thanks.That would be ideal. I'm using an VIA Epia M mini ITX which should probably support that. Gosh its hard to find documentation on how the simpler things work! I guess that its taken for granted that someone would now about these things.

I'm frustrated after spending numerous hours searching the web for how to do this.

However...., I am happy to hang out in this board because I have received some very promising pointers from the Empeg community...

No a relay would be instantenous, in the sense as soon as the accessory line went dead it would turn off the 12v constant battery line. The point to this would be to make sure your computer is not constantly draining your battery- it would be guaranteed to go off with the accessory line.

To be clear, I don't know that

an instantaneous switch/relay that does what a press of the power button would do

is something that you can buy off the shelf as a packaged component. You might have to build a small circuit to do it. You'd want it to wait for power to go from 12V->0V and have it trigger a normally-off switch to on for a half second or so.

I'm not an electronics engineer by any stretch of the imagination, but this seems like something a 555 timer IC would do.

This is almost certainly going to be your easiest bet, especially if you are an electronics novice (no insult intended, just going by the content of your posts.)
Check out this UPS list for info on UPS connectivity issues. UPS software on your PC will ensure graceful shutdown, which is necessary if you are going to use Windows.

Sounds like you need a combination trigger/delay circuit.