PC controlled starter solenoid? Possible?

**Shoryuken** · 01-29-2004, 12:54 PM

I'm fairly new here, I hope this is in the right place. I've been browsing the forums a good bit poking around (read i've searched) looking for a way to control the engine start via in-car computer.

I'm farily certain its possible, based on my very limited knowledge of actual automotive engineering. I know that voltage is passed through the solenoid on the starter to start the car. I know that there are keychain remote-starters.

So my question is, how would you create a device that takes input (a click/button press) from the computer and transfers that to voltage to the solenoid? I'm not much of a hardware guy, and even less a car guy, so I turn to you all for advice.

My ultimate idea is to have a thumbprint scanner start the car, with the option of entering a code on the keypad for valets, and mechanics/etc. I confident that I could handle the software part, its mostly the hardware end that I need help with.

Since this is really a far-out idea, I mostly pose the question for discussion purposes. I'm aware that even if possible, its probably not all that smart to put the ignition of your car in the hands of windows... Just think it would be damn cool!

**wizardPC** · 01-29-2004, 01:18 PM

Parallel Relay control for XP coming soon

**Shoryuken** · 01-29-2004, 01:35 PM

Thanks for the response, I didn't really think to search on 'relay control', I was mostly looking at starter/solenoid specific terms.

Do you have any thoughts on the project? Other than the lack of windows reliability (and perhaps boot-up time), are there other reasons to keep the key rather than go to a PC controlled option?

**W6-Ryan** · 01-29-2004, 01:47 PM

what it someone steals the pc

**Custommx3** · 01-29-2004, 01:56 PM

what if starting it from the PC is optional?

**wizardPC** · 01-29-2004, 02:12 PM

a couple of big things about having the computer control the starter:

first, when the PC boots, all the relays will come on, then go off, then come back on until you turn them off. If you have this connected to your starter, that is BAD.

Second, you must ensure that the computer will "survive the crank" which means either installing a second battery or a tank circuit.

Third, you will still have to put your key in to unlock the steering column.

So, whilst this seems like a cool idea, its not really practical.

**deadweasel** · 01-29-2004, 02:41 PM

Originally Posted by wizardPC

a couple of big things about having the computer control the starter:

first, when the PC boots, all the relays will come on, then go off, then come back on until you turn them off. If you have this connected to your starter, that is BAD.

Second, you must ensure that the computer will "survive the crank" which means either installing a second battery or a tank circuit.

Third, you will still have to put your key in to unlock the steering column.

So, whilst this seems like a cool idea, its not really practical.

Well how about having the PC trigger a preinstalled remote starter then? You would still have to worry about surviving the crank, but then you could get around the steering column lock. When all's said and done however, there isn't much practicality to having the PC start the car. That's putting the cart before the horse.

**Shoryuken** · 01-29-2004, 02:44 PM

Thanks Wiz, valid points. I've known that this wasn't a particularly smart idea, but the coolness factor of it makes it seem worth persuing.

The second option:
Remove the ignition switch and locking mechanism from the steering column.
Add in a push-button to 'start' the starter, which is in active until identification is verified (fingerprint/passcode)

Option 2 seriously reduces the headache of this project, though the extra step isn't quite as cool, probably is necessary, even if only because sometimes it takes 2 seconds of cranking to start, and sometimes it takes 5 seconds. With a push button, you can hold until the car is started..

On the topic of tank circuits/extra batteries, I was under the impression that a dc/dc PSU solved that problem? Did I mis-read that someplace? A second battery doesn't seem all that difficult, and perhaps would allow my other idea (lots of ideas, very little common sense = me), which is to have the PC hibernate (i've read the issues with hibernate, and experienced them in my home PC) for 12-24 hours between starts, unless manually shut down. But thats a topic for another thread.

**Shoryuken** · 01-29-2004, 03:02 PM

deadweasel, there are a couple of points to this for me.
Number one is to get rid of keys all together. At the moment, my 1 car key is the only thing I have to carry. My house has a combination plate, my office is a key card that lives happily in my wallet (don't even have to take my wallet out to open the door).

My car doors have a keypad, so no need for a key there, and my trunk (boot) pops from inside the car, so no real need for a key for that.

The second is purely the coolness factor, which I evidently think is much higher than the people who've replied to this thread. (I often think things are much cooler than other people though, the joys of living in my own little world).

**wizardPC** · 01-29-2004, 04:56 PM

Originally Posted by deadweasel

Well how about having the PC trigger a preinstalled remote starter then? You would still have to worry about surviving the crank, but then you could get around the steering column lock. When all's said and done however, there isn't much practicality to having the PC start the car. That's putting the cart before the horse.

the steering column lock is the mechanical (not electrical) part for needing the key. You can start the car without the key in the ignition (read hotwire), but you cant turn the wheel. That is the steering column lock.

To have the computer start the car you need at a minimum 2 relays on the card--one to make the car think that the key is in the "on" position (which powers on the fuel pump, accessories, etc) and one for the starter.

The first relay controls 2 other relays (get some instructions for a remote start car alarm to understand this fully) and is on as long as the car is running. Cut that one off and the car turns off.

The second one needs to stay on just long enough to start the car, and immediately turn off. This presents the biggest problem, because if the car battery has a low charge then the relay wont activate long enough to start the car. If you lengthen the time the relay is on, then if the battery is fully charged the starter will be on too long, which can cause damage over time.

The best thing to do, in my opinion, is to set up one of the computer relays to control power to the fuel pump. tis a long, drawn out explanation of exactly how I would go about doing that, and I think I have said too much for one post