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How can I wire this to my car?

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  • How can I wire this to my car?

    If I have an electronic device that I want to put in my trunk, and it's already in DC and the wires are split so I have a positive and negative wire. The current that it needs is 5.1V and 3A. What do I need to make this work so I can hard-wire it to my car?

    TIA

  • #2
    you can use the 5v line off your PSU
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    • #4
      Yes, my plan is to connect that "docking device" to my laptop. However, that "docking device" only needs 5.1V and 3A, so I guess I need something that will take the 12V down to 5.1V. Question is, where do I find such a thing?

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      • #5
        I would just suggest using a DC/AC inverter, then using the AC/DC inverter that came with the setup. Unless you want to set up a transformer to drop the voltage, then find a way to dissipate a few hundred amps.
        Quick! To the Popemobile!

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        • #6
          Try a pair of LM317T's

          I had the same problem and used a pair of LM317T's in parallel. If you're willing to build and solder a bit, you'll need a couple of resistors to set the proper output voltage.

          Available from Radio Shack. Use a heat sink.

          http://www.radioshack.com/product.as...%5Fid=276-1778
          Originally posted by ghettocruzer
          I was gung ho on building a PC [until] just recently. However, between my new phone having internet and GPS and all...and this kit...Im starting to have trouble justfiying it haha.
          Want to:
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          • #7
            Originally posted by Bugbyte
            ...you'll need a couple of resistors to set the proper output voltage...
            Use Ohm's law: V=IR
            V = voltage
            I = Amperage
            R = Resistance
            Quick! To the Popemobile!

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            • #8
              BiohazrD

              please stop posting on this topic as it is clear you aren't really sure what you are talking about.

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              • #9
                Originally posted by MrPerfectionest
                BiohazrD

                please stop posting on this topic as it is clear you aren't really sure what you are talking about.
                WTF are you talking about dude? He even got Ohm's Law right. Not to mention he called the part by name...

                sheesh...

                BTW, if you were joking, then please disregard
                Mind Scream out

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                • #10
                  Like BugByte said, a DIY is the easiest.

                  Here's a diagram that can work.


                  Use for the 78xx a 78S05

                  edit: now i see its a AC diagram, im not sure if it will work for DC..
                  05155'30"N 0434'31"E

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                  • #11
                    Originally posted by mindscream
                    WTF are you talking about dude? He even got Ohm's Law right. Not to mention he called the part by name...

                    sheesh...

                    BTW, if you were joking, then please disregard
                    what? i agree with mrperfectionist, i dont see how ohms law is applicable, and how the **** do u dissapate a few hundred amps

                    unless you were joking? ok now i'm confusing myself
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                    • #12
                      You would probally be best off just buying an inverter and going DC(car)->AC(inverter)->DC(wall plug that comes with base station) It is inefficient but is the easiest solution and you can always use the inverter for other appliances later on.

                      Otherwise you could build (buy?) a simple circuit....I'm pretty sure there are already plenty on this forum if you just search for em. (Don't use the one a few posts above.)

                      Finally if you don't like any of those ideas build your own. I did some really basic research that would get you started. This uses linear regulators because they require the least amount of pieces and are the easiest to build in my opinion.

                      A search with National shows the LM1084 series. It can put out 5 amps max at various voltages. You would want the LM1084IT-5.0 in particluar. Check the datasheet for the sample circuit - it will basically be like the changed around one I've attached. You can get free samples @ http://www.national.com/pf/LM/LM1084.html

                      "DISCLAIMER": I haven't tested this circuit. I'm NOT an Electrical Engineer...hell, I didn't even get accepted into engineering at my college. I'm skeptical if that regulator can do 5A constant without getting way too hot (even with a heatsink.) It would be possible just to hook a couple up in parallel with each chip having its own heatsink to be on the safe side. ALWAYS test voltage output with a multimeter before attaching to device!!! And a small fuse before the circuit couldn't hurt either. So don't whine if it doesn't work or breaks stuff.
                      Attached Files

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                      • #13
                        I would probably add to the big *** heatsink a big *** fan. This is a linear regulator, which dissipates all wasted power as heat, so if you draw 4 amps at 5 volts, you are dissipating 28 watts in the device!!!
                        Carputer currently 'ghettoed' into car!!!

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                        • #14
                          if you go the inverter route make usre you get onw that survives crank or when you start your car you may get issues with the dock going dead and windows complaining you have disconnected devices without turning them off. Likewise if you use hibernation make sure the power to the dock is resumed when the laptop starts to wake up or devices may not work properly. What do you need the dock for? can you make do with somehting else that is unpowered like a USB2 pcmcia card and then power individual devices off smaller dc-dc convertors? Or even just use a USB hub - might save yourself some money too!

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                          • #15
                            Also, the company who make the dock make dc-dc convertors, why not ask them if they do one suitable?

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