How to control (cut off/turn on) laptops PSU by ignition - help needed

hi,
last couple of days trying to figure out how to cut off/turn on laptops psu, mean ignition on-> psu gets 12v, ignition off-> no 12v for psu.
the best (ideal) solution here is mp3car's uSDC20D but ...as I'm Ireland based postage costs is more than controller itself :( (can't justify paying 100$ for it) so looking for simpler solution, DIY like :).
no need here for remote laptop's power on function as I'm using one of 'adopted' oem radios remaining buttons as laptops power button, just simply circuit which doing simply 'thing' hooked up between car's battery and laptop's psu ....
by any chance, have you guys schematic or link to ?
any help and ideas more than welcome
peace
Kris

Hi
Try ebay for cheaper postage(only slightly )
have a look here http://www.mp3car.com/software-and-s...-software.html
for DIY, the links in the first post will take you to a discussion on ideas for auto startup (have alook at the last pages for schematic)

I just used a dc to dc car power adapter that is made for my notebook. I simply switch power on and off to the adapater via a relay. Quick, simple, cheap, reliable.

thanks, guys

@wozza: had a look at these posts but this isn't exactly what I'm looking for (no need for auto start or auto shutdown as it can be done by remote button and Windows' build-in power management)... need to cut off laptops psu only to prevent car's battery going flat when engine is off :) and power it back when engine is on

@dmcdlrn: can you tell me more please :)

stuff.hunter, I replied to your PM but thought I would toss some info here too. To go into greater detail.

My system uses an arduino to monitor ignition and power on and off the laptop. Most people here use some form of startup shutdown controller. Mine is home grown or you can buy one from the store. Both have merits of their own.

If you have the power up and power down of your laptop worked out and all you want is to kill power to laptop when you turn the key off:

You need a standard automotive relay. 4 pin is all you need but you can use a 5, just ignore 87a.

Hook either 85 or 86 to ground and the other to the 12v ignition wire from your steering column.

Hook either 30 or 87 to +12v from battery and the other one to the positive of your laptop power supply. Hook the ground of your laptop power supply to ground. Viola!

mate, you are genius ...seriously thats great solution for me ... just have to figure out where in my cars boot (laptop is going to be mounted there as close to my bmw's battery) is +12v live after ignition :). as going to remove cd changer, ill have some 'extra' wires to plug into - hope one is what I'm looking for :)
many thanks for reply.
kris

You will have to run a small gauge wire from the ignition to the trunk there and mount the relay. You can run the power for the laptop through the relay and directly to the battery (with a fuse of course).

extra wire isn't a problem, thanks mate :)

Quote:

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Originally Posted by stuff.hunter

thanks, guys

@wozza: had a look at these posts but this isn't exactly what I'm looking for (no need for auto start or auto shutdown as it can be done by remote button and Windows' build-in power management)... need to cut off laptops psu only to prevent car's battery going flat when engine is off :) and power it back when engine is on

dmcdlrn

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Hi
What dmcdlrn has said is discussed in the above links with some other Idea's, anyway looks like its sorted :)

If u want total control pf start up and shutdown look into a TR7 pro its from pac electronics its pc or android configurable