idea for auto startup/shutdown controller
So I'm almost ready to start ordering the pieces to get my build underway, and I started contemplating on a startup/shutdown controller. Since we are dealing with a boot time on a carpc, it would be awesome to have the computer start to boot up maybe 10-15 seconds at least before I even get into the truck. I've seen the remote systems that you have to latch a remote to your key ring, install the receiver into the car, wire it in, and all that jazz, but then I started thinking about how that could be bypassed and basically make use of the existing keyless entry system on a car/truck. I came up with an idea that I'd like to run by you guys.
Basically, take a standard shutdown controller such as uSDC20D. Here's where my idea comes into play though. It involves using two diodes and a feed from the factory door locks. Basically as follows:
Basically you'd wire it like normal only with a diode in line with the switching ignition signal wire, and you'd also tap into the factory door lock wiring and pull the +12v that occurs when the doors are unlocked (since most if not all cars simply reverse the polarity on the door lock actuators in order to lock or unlock), and then wire it in also with a diode into the same input. Then set the shut down controller to keep the computer running for at least a minute or so after the input goes away. In theory, this would trick it into powering up the PC when you unlock the doors via a factory keyless entry system, and as long as you turn the ignition on within a minute (or however long you desire to set the auto shutdown time at), the computer would stay up and running. This way the computer would already be half way booted up, if not all the way booted by the time you get the engine started, maybe even before you sit down in the driver's seat!
The only complication I see in it right now (and it may not even be an issue) is feed back between the two inputs if the ignition is on and sending +12v to the input, and the doors are locked which would then be grounding out the other input. The diodes are in place to keep +12v from feeding from one source to the other, but I'm not sure how they would fair keeping +12v away from ground; it may work fine or it might just send the diode up in a puff of smoke, lol. BUT, that's why I'm asking this here first :) I guess another option I would have is instead of using a door lock input which reverses between lock and unlock, I could use the running lights or turn signal +12v as the momentary input, since they flash when unlocking the car. The only thing with that is then it would cause unwanted booting every time I so much as lock the doors, and that is sometimes 10-15 minutes after I get out of the truck. It may not be that big of a problem for that to happen though.
Now I can't be the only person who's ever though of this, but if I am I'll be very surprised, and I'd like to know what you guy's thoughts are on it. Look simple enough to work?