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  • AC-DC and DC-DC PSU's together?

    So I've gotten a EPIA M for christmas, and I'm drafting out a case for it, and I've again come to thinking about using both a DC-DC PSU and a AC-DC psu, so I could ditch the inverter in the car, and still have it usable indoors without having to disassemble the case and put a ac-dc psu on it. My question is this, do I need to switch (spdt) all the wires so that only the powered psu is connected to any given device (motherboard, dvd, hdd), or could I connect them both without the switches and use diodes to impeede the flow of power from the powered psu to the unpowered? Or could I simply connect two psus together sans switches or diodes and have it work? Only one psu would be powered at any given time. And if using diodes would work, what do i need in a diode? (ratings, etc, im unfamaliar with them).
    -Nick

    _____________________________
    Since when is insanity a bad thing?
    www.mp3vw.com

  • #2
    Anyone? With all the electronics gurus about, I figured someone else had atleast given this thought.
    -Nick

    _____________________________
    Since when is insanity a bad thing?
    www.mp3vw.com

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    • #3
      Why not build a case with external PS?
      Just a multi pin connector on the side of the case and plug it in to a AC/DC indoors, an a DC/DC in the car.

      Get 1 male and 2 female industrial connectors and connect the females to the PS, male to computer.

      Gives you a smaller computer box too.

      But there is a lot of pins to be connected...

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      • #4
        Yeah, I had though of that, but for sheer ease of use (anywhere, anytime), two in the same case would be better. That and the case that im currently building has a 7x7 empty spot, which would be more than enough for a second psu.
        -Nick

        _____________________________
        Since when is insanity a bad thing?
        www.mp3vw.com

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        • #5
          Originally posted by MP3DUB
          Yeah, I had though of that, but for sheer ease of use (anywhere, anytime), two in the same case would be better. That and the case that im currently building has a 7"x7" empty spot (can't be any smaller, due to the maximum depth of the case being 14"), which would be more than enough for a second psu.
          -Nick

          _____________________________
          Since when is insanity a bad thing?
          www.mp3vw.com

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          • #6
            Hi,

            An average ACDC psu has rectifier diodes on the main outputs 5V, 12V. When line power is not connected, these will behave as blocking diodes.

            You can check your DCDC psu for having output rectifiers also. If it has, then I don't see big problems in connecting them together.
            When it has simple step-down converters like in Sproggy, then I suggest placing (schottky)diodes in series with the DCDC outputs, or use a decent relais (will give less voltage drop).

            The auxillary power supplies -5V and -12V are probably generated by different circuits, probably even linear (7905...). In that case you can use diodes there to be sure (1N4001 for <1A, 1N5401 for <3A).

            Henk

            white bream
            working on a trilogy: CARGO - UNIGO - MERGO
            CARGO = the Car Computer
            Intel Celeron M, [P]SDC, uBlox GPS, GPRS, WLAN, Silabs FM, RDS, TMC,
            Dual-audio, Onecable TFT, Microsize: 45 x 108 x 168mm (1.8 x 4.3 x 6.6")

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            • #7
              why not just make a simple power connecter... then when you are in the house use a transformer to make a DC power supply and get some nice 12v to connect to the dc-dc?

              There is any number of already existing power connectors that you could use to pull this off with minimal effort.

              --==edit==--

              editing my edit here... I found a transformer, but when I phoned the company they said it was AC.
              aka Kumaneko
              "Don't make me moderate your ***!"
              Maxima of Doom - project thread - photo gallery
              mp3car system is currently FUBAR and finances do not allow for a correction of that situation
              Real computer hackers use a rotary cutting tool on their motherboard.

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              • #8
                I have a EPIA-M and OPUS (should have been here already). I want the same functionality that you want so what I'm going to do is stick the OPUS (DC-DC) supply into the case and when I yank the computer out of the car (if ever) I'm going to plug it into this (http://www.aaacamera.com/pyramid_ps15kx.html). You can also use a AT power supply and make a connector for the cig. lighter. Itís quick and easy. Also 34 bucks for that supply isn't bad at all. As Larkar said, make some sort of quick connector. Radio shack as some triple pin connectors (automotive so they are kinda heavy duty which is good).

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                • #9
                  Originally posted by ShinkunoNamida
                  why not just make a simple power connecter... then when you are in the house use a transformer to make a DC power supply and get some nice 12v to connect to the dc-dc?

                  There is any number of already existing power connectors that you could use to pull this off with minimal effort.

                  --==edit==--

                  editing my edit here... I found a transformer, but when I phoned the company they said it was AC.
                  My ideal was for it to be completely contained, so that I could pull it out anywhere (ie not just my house) and use it and not have to lug an external atx power supply or a 12vdc 10amp power supply out with it.
                  -Nick

                  _____________________________
                  Since when is insanity a bad thing?
                  www.mp3vw.com

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                  • #10
                    You have a point in that, using a transformer at home to supply 12V to the computer would just reverse your current situation.

                    Do you have info on your DCDC converter?

                    Henk


                    BTW. Happy 2003 to you all!! (here within 20 mins... )

                    white bream
                    working on a trilogy: CARGO - UNIGO - MERGO
                    CARGO = the Car Computer
                    Intel Celeron M, [P]SDC, uBlox GPS, GPRS, WLAN, Silabs FM, RDS, TMC,
                    Dual-audio, Onecable TFT, Microsize: 45 x 108 x 168mm (1.8 x 4.3 x 6.6")

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                    • #11
                      Thanks for all the help so far, and I don't have a dc-dc yet, as I wasn't sure what would be required in making it work I just have a 1U ATX AC-DC psu. But if I go that route I was considering the Opus.
                      -Nick

                      _____________________________
                      Since when is insanity a bad thing?
                      www.mp3vw.com

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