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Thread: Laptop power up idea.

  1. #1
    Newbie
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    Laptop power up idea.

    I'm no wiring guru, so you guys may be able to work out the best way to plumb this in.

    I think it should be straight forward enough to make a basic startup/shutdown controller for a laptop, with minimal soldering.
    To power up, you would solder two wires to the power on switch. This is where the wiring chaps would come in. How would you wire this up to a relay to only provide a momentary connection between the two points?
    Once this bit has been figured out, follow this post to fool your laptop into thinking there is a UPS present to activate the shutdown.
    Schematics/Pin Outs/Diagrams

    Here is the thing. In your windows power settings, you can set the behaviour of the power switch once you've booted into windows. If you tell it to "Do Nothing" when the power button is pressed in windows, then everything should work.

    Does this sound OK, or have I lost the plot at 01:33 on a Monday morning?

  2. #2
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    Setting windows to 'do nothing' when the power button is pressed will not help.
    The hardware setting will power down the PC after abut 5 seconds, then up, then down...

    Here is the diagram to build the circuit. I made this exactly and it works 100% on my laptop.

    The capacitor allows the coil of the relay to be energized until the capacitor stores a charge, thus de-energizing the coil. The resistor bleeds off the charge of the capacitor when positive voltage is removed from the other side of the coil. You can increase the output time by simply changing the value of the capacitor. This one will give you about a 1/2 second output.

    http://www.the12volt.com/relays/page5.asp


    Connecting to laptop switch will require you to open it up and locate the switch contacts.
    Use your multimeter to find which 2 pins on the switch have continuity when the switch is pressed. These are the 2 you need to connect to.
    Use the lines from point 87 and 30 on the relay.

    Good luck

  3. #3
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    Not wanting to poo poo your idea, but are you sure those relay terminals are correct?
    Surely if I bridge the power switch buttons with 87 and 30, then I'm going to be putting 12v across the momentary switch.
    As this normally needs no voltage, just to complete the circuit wouldn't this be better to make an earth contact instead?

  4. #4
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    Yep it's all OK.

    12v power runs across 86 & 85, which charge the coil that then creates continuity across 30 & 87, which has NO voltage.

    The diagram does indicate voltage on the line but you just don't need to put any on it for your application.
    You get a 1/2 second of continuity across 30 & 87, when 85 & 86 have 12V.

    I'll build you one if you pay the right price but where is the challenge for you.

  5. #5
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    Have you ever noticed that with any computer holding down the power switch will cause the motherboard to cut the power off completely? Like when your computer freezes and you have to do a hard reboot?

    Anyways apparently this setup has been proven by more than just Cluck. I like the diagram he posted up btw.

    http://www.mp3car.com/vbulletin/user...rn-module.html

    I would recommend using the USB feature posted there.

  6. #6
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    I do like a good challenge!

    The only part of this project I'm not looking forward to is fabricating a screen in the dash!

  7. #7
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    Have you got a shutdown and AMP turn on delay sorted yet ?
    These were painful for me.

    What car?
    Where you located ?

  8. #8
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    It's going to go in a 1994 Toyota soarer.
    The power off should be straight forward enough as long as shoving 5v to Pin 8 on the RS232 port fools the computer into thinking there is a UPS connected.

    Remove 5v, computer initiates shut-down. Where this thread uses an inverter and regular PC power supply to give out 5v, I'm going to use a second 12v socket running a usb charger plug to give me the 5v. I'm cheating and I'm still going to keep the headunit, so this will take care of remote power on for the amplifier. I've got some component speakers, and a Vibe 10" subwoofer to power.

    I've got plans to build a couple of "Hot Plates" in the boot, so that I can connect directly onto one and have a switched 12v source, or connect to the other and have constant 12v, but not worked out how I'm going to mount it all yet.

    I'm in Sheffield.

  9. #9
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    Sheffield hey, my stomping ground for about 8 months in 2004. Had to get back down under for some sunlight.
    Car and plans sound sweet.

  10. #10
    Constant Bitrate
    Join Date
    Apr 2005
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    121
    instead of wiring it to s switch and adding a relay to make it "momentary", why not just wire it to a "monetary" switch?

    then you can skip the relay, no?

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