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Dual Power supplies

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  • Dual Power supplies

    I did a and maybe I didn't choose the right search words, but what I was looking for was:

    An easy way to have 2 ps's hooked up at the same time with the user being able to switch between the two with the "flip of a switch"

    No power to carputer during "switching" is ok.

    Basically what I want to do is have a dc-dc ps when in the car...and since my installation will be not easily removed...i want a permanently attached ac ps so when in the garage working on the carputer, I can just plug it in to the wall


  • #2
    im sure it can be done...

    you will need to find switch that has the appropriate number of contact, one for each voltage level from your PSU. and it must have 2 sets of contacts... one for the AC-DC and one for the DC-DC. if you want to you can get a switch with 3 positions so that you have a dead set in the middle for an "off" position...

    this site gives a bit of info on switches...

    the other thing to keep in mind is shorting or non-shorting type switches. shorting type will connect BOTH sets of contacts before swtiching from one to the other. this is nice if you dont want to lose power during the switch.. however, i dont know what that would do to the comptuer or the power supply. non-shorting type will break the circuit before it connects to the other set of wires. as you have described in your message, you can use a non-shorting switch.

    basically what you want is a XPDT, non shorting type... substitute the number of voltages you have for the X. and make sure you have the current ratings covered so the switch doesnt fry.

    Single Member of the "1000 Post and No MP3 Car" Club
    2000 Cavalier Z24 [###-------] Only 30% Done ... Still


    • #3
      Get an ATX mobo power connector extention. Plug one end to the mobo and the other end to whatever PSU you want to use. The same thing is for the HD/CDROM drives. I just use a Y drive power connector. Well that is how I do it.
      2004 Matrix XR A7N8X-VM/400 AMD XP-M 2500+, DS-ATX
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      • #4
        The only thing is, wouldn't you have to switch ALL of those wires? All of the ones going to the mobo, all of the ones going to the HD's CD-ROM's drives, etc?

        Or would this create a problem with having voltages and currents going to the output of an inactive power supply?

        Might be worth a try to test with two cheap AC->DC power supplies, but not if you're doing with the expensive opus or anything like that


        • #5
          doh, i need to not open a bunch of threads, read all of them, then 20 minutes later reply to a few of them.


          • #6
            so with this setup, you will need a mobo with 2 atx connector which i believed does not exsist. i have one but that even have an at and atx connector. i am basically on the process of doing something like this, since i already have a dc-dc psu, what i'll do is add another ac psu, have one atx connected to the mobo, and split the wires (+12v +5v -12v -5v 3.3 stby and pg) to both psu's with a rocker switch or something similar to power the mobo based on whichever psu i'm using.

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            • #7
              thanx for the suggestions


              • #8
                what about using an AC to 12V DC powersupply and just hooking it up to the input of DC-DC powersupply, then you can just switch the input of the DC-DC from the car battery to the mains adapter. Saves messin round with loads of wires. Dunno if you could set it up to momentarily have them in parallel so the PC can be left running when switching between the two.

                Just an idea!



                • #9
                  Hmm, you'll struggle to get a cheap 240AC - 12VDC adapter that'll supply more than a few amps at 12V, you're better off having 2 seperate power supplies. I'm using an inverter so i just unplug the ATX PSU from the inverter and into the mains.
                  Mods: 18" Boss rims,Twin custom stainless exhaust,cold air induction.
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                  • #10
                    just get a battery charger and hook it up to the battery when the car is in the garage.
                    Chris Krug
                    owner, turbine minivan


                    • #11
                      wow turbochris,

                      that sounds like the easiest way to do it. You don't think it'll harm the battery to be charging it for prolonged periods.



                      • #12
                        At one time I was switching between the outputs of an AT power supply, and my DC/DC power supply. If I remember right, I think I was using a 4PDT relay, and a DPDT relay just to switch the outputs. Hacked into an AT power supply extension cable, and a couple of drive cables. Wire splices everywhere...what a nightmare. Eventually I ended up rewiring the whole thing.

                        Kept the DC/DC power supply, but got rid of the AT AC/DC power supply. Bought a 12V 13Amp AC/DC power supply off of Ebay and used it to feed the DC/DC power supply when I had the computer in the house. I used a SPDT "automotive" relay to switch the input on the DC/DC power supply. If you prefer, just buy a SPDT switch. It'll do the same thing.


                        • #13
                          NOT THIS AGAIN !!!!!!!!!!!! go to orbit micro .com and get a keypower ATX supply before you fry somthing there only US$200 it's cheeper than a new PC don't ya think


                          • #14
                            I went to orbit micro and i'm having a little trouble trying to understand where you're trying to go with this. $200 is almost what I have in my whole system so far. So I guess in my case- would a power problem cause $200 in damage? No, and it's not likely to get damaged anyway.

                            bh76 has a good solution.

                            Get a good battery charger that has a selectable output. You can put 14 volts into your battery all day long, that's what the alternator does. I have a cheap 2/10 amp battery charger, when I work on the car with the key on I put it on 10 amps, and when I'm done sometimes I'll just leave it on 2 amps for a while to top it off.
                            Chris Krug
                            owner, turbine minivan


                            • #15
                              Thanks guys. Guess that's what I'll do