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  • USB power control

    Because i've got a 12V tot 230V adapter to power my carputer (laptop) I want to make a circuit that powers the laptop and keeps it powered.
    If I turn the car key (car on) a 12V relay put the power to the adapter and I can turn on the laptop. When the laptop is powered a 5V USB relay also switch the 12v parralel. So when I turn off the car the laptop stay's powered. And when I also turn off the laptop the power adapter turns of and the power isn't going anywhere.
    I already got the 12V relay but can't find a relay from 5volt wich can switch 12volt of the car. Does anybody of you know where to get this or how to make his.

    Code:
    car key 12 V      permenant 12V
           |                | 
           |                |---------|
           |                |         |
           |                 /          / 
        [ K1 ] ------------ /          / -----------|
           |                |         |             |
           |                |---------|             |
           |                |                       | 
           |                |                       |  
           |             laptop --> USB 5 volt      |
          GND               |          |            |
                            |        [ K2 ] --------|   
                           GND         |
                                      GND
    K1 and K2 are relay's
    Car: Peugeot 106
    Monitor: K500
    Carputer: Acer Travelmate 661Lmi
    Front-end: RoadRunner
    Skin: Simplistique by LLOYDY
    Navigation: iGuidance 2.1.2 Europe, embedded with iGlaunch
    GPS: BU-353 USB

    ▬▬▬30%▬▬▬▬▬▬▬

  • #2
    This wouldn't be very hard. However, there are a few caveats that you must know of.

    First, powering a relay on off the USB. The USB rail should draw no more than 500 milliamps at 5V. That's the spec from the USB design specs. So, you need a relay with a coil draw of less than 500 milliamps. This shouldn't be to hard, most around around 200 milliamps. But keep it in mind.

    Second, you need to make sure that the relay for the USB is a relay capable of suppling enough power for the 220V inverter. This may be a little bit harder. On the 220V inverter there should be a fuse, what is the value of this fuse? You will want to have a relay that is capable of either higher, or equal to this amount.

    Also, I have seen SOME (VERY RARE) laptops and computers that continue to power the USB rail, even when the pc is off. You will want to check this first.

    As for finding the relay, I'd be more than willing to help, once you find out the specs needed of the relay. 5V relay's are fairly common. And if you can't find a relay that can drive the amount of power needed, you can always use two relays, first one ran off of 5V USB rail, that powers a second, beefier (is that a word?) relay that can directly drive the 220V inverter.

    But I must warn you... if you are relying on software to shut off your laptop, you may find that you have a dead battery when the laptop locks up because of that wonderful unnamed software company that starts with "Micro" and ends with "Soft".

    Knight.
    This message transmitted with 100% recycled electrons.
    -=-=-=-=-=-
    Gravity doesn’t exist. The Earth sucks.
    -=-=-=-=-=-
    Make a man a fire, and he will be warm for the night.
    Light the man on fire, and he will be warm for the rest of his life.

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    • #3
      the converter has a fuse of 20A but thats for the output.
      I still need the 5v relay to switch 12v, can you please help me?
      Car: Peugeot 106
      Monitor: K500
      Carputer: Acer Travelmate 661Lmi
      Front-end: RoadRunner
      Skin: Simplistique by LLOYDY
      Navigation: iGuidance 2.1.2 Europe, embedded with iGlaunch
      GPS: BU-353 USB

      ▬▬▬30%▬▬▬▬▬▬▬

      Comment


      • #4
        Originally posted by KoBolD View Post
        the converter has a fuse of 20A but thats for the output.
        I still need the 5v relay to switch 12v, can you please help me?
        You have to find out how much power you are working with. It's going to be impossible to attempt to find a suitable relay without knowing the amount of power draw from the inverter.

        Have you ever plugged the inverter into the cigarette lighter, and powered the laptop through that? If so, then what is the fuse value on the cigarette lighter from the car?... Most are 20-25. If that's the case, you will probably have to have two relays, one that runs on 5V off the USB, then that powers a larger relay, which controls the 12V to the inverter.


        Knight.
        This message transmitted with 100% recycled electrons.
        -=-=-=-=-=-
        Gravity doesn’t exist. The Earth sucks.
        -=-=-=-=-=-
        Make a man a fire, and he will be warm for the night.
        Light the man on fire, and he will be warm for the rest of his life.

        Comment


        • #5
          That one is 30A
          Car: Peugeot 106
          Monitor: K500
          Carputer: Acer Travelmate 661Lmi
          Front-end: RoadRunner
          Skin: Simplistique by LLOYDY
          Navigation: iGuidance 2.1.2 Europe, embedded with iGlaunch
          GPS: BU-353 USB

          ▬▬▬30%▬▬▬▬▬▬▬

          Comment


          • #6
            Can you please help me with the relays?
            Car: Peugeot 106
            Monitor: K500
            Carputer: Acer Travelmate 661Lmi
            Front-end: RoadRunner
            Skin: Simplistique by LLOYDY
            Navigation: iGuidance 2.1.2 Europe, embedded with iGlaunch
            GPS: BU-353 USB

            ▬▬▬30%▬▬▬▬▬▬▬

            Comment


            • #7
              Do some searching in the forums for RELAYS and LATCHING.
              I saw somethign a while back about rigging two 12v relays that would do what you are taling about.

              You turn on the car, the first relay tuen on power to your converter turns on the second one. The second one keeps the inverter powered on after car is turned off, until you turn off the compuer.

              It sounds like that is what you are tying to do.

              Good luck!

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