idea for auto startup/shutdown controller

**iamsuperbleeder** · 05-31-2012, 11:44 PM

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?

**dmcdlrn** · 06-01-2012, 06:47 AM

I'm assuming you have the factory alarm? Aftermarket alarms often have accessory functions... that might be a better choice. My system takes about 2 seconds to resume (laptop in standby) and I find at least once a week I want to roll up my windows and really don't want the system to wake up and kinda wish I had put my bypass switch in a more accessible location. I'm wondering if you will see similar frustrations.

I could see situations where you unlock your truck to get a widget out of it and then lock it and walk away. Now your computer is running. Even 10 or 15 minutes like that and your battery will be weak for the next start.

Definitely not bashing your idea as I know people here have done similar things. Just giving my 2 cents.

**duncanator24** · 06-01-2012, 07:19 AM

You could wire a switch in the circuit as well (or a pushbutton might work better) that would allow you to perform the regular car funtions without the pc turning on. Basically when the switch is in the on position, the pc would turn on when your chosen method of power is applied and when the switch is off, the pc would stay off instead. I would think that since both the ignition and the door lock are powered from the same source (your battery), you should not have any grounding issues because they are also grounding back to the battery eventually. I am not very knowledgeable on this though lol. Post here if you make it work, sounds interesting!

**iamsuperbleeder** · 06-01-2012, 10:33 AM

yeah its a 2006 Tacoma and just has the factory passive alarm, so I doubt there's any optional outputs that'll let me power it up. another thing I thought about would be hooking it to the passenger door or rear door unlock circuit since you have to double tap the unlock on the keyfob to make them unlock, but then I'd still be stuck with the grounding issue, if that is in fact going to be an issue. the bypass switch may be an option though. there's some little pockets in the bed of the truck

**iamsuperbleeder** · 06-01-2012, 10:36 AM

oops, hit reply early... stupid phone, lol

I could hide a momentary switch in one of the pockets in the bed and use it to disable the start up of the PC if I just had to unlock the doors and grab something out of the truck or roll the windows up

I'll have to do a little more research, maybe some breadboard testing, and see if the feedback through the diodes would be a problem

**iamsuperbleeder** · 06-02-2012, 08:47 PM

just though of something else. I could just use this as an excuse to get a remote start kit that I've been wanting to get; that would solve this problem, lol

OR, I could just tap into the dome light feed since it kicks on with the door unlocking too. then I wouldn't have to deal with the ground feedback issue

choices, choices, choices... I actually think I'm liking the dome light tapping option the best now, possibly in conjunction with the override disable switch

**kolton5543** · 06-11-2012, 06:41 PM

The dome light option sounds a bit more feasible. Not only will it turn on the PC when you unlock the doors but it will turn it on when you open the door if it is already unlocked.