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DC DC converter extending connection cable possible?

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  • DC DC converter extending connection cable possible?

    Hi!

    I wanna know if can modify my DC DC converter (12 V to 5V) i plan to put on my car.
    I wanna know if its possible to extend the cable that goes from the DC DC to the device i wanna connect to. I mean, this cable needs more 30 cm at least to get on the device i plan to install but what i need to know is if there is any problem with the voltage/current that will have, since i am making changes to the original one.
    The DC DC goes for 2 Ampere current and i really need the 2A cause i will connect a DVD drive and its really 2A.

    THANKS!

  • #2
    why not extend the converter to the location of the dvd drive? that way, your extending it before the voltage regulator, so the dvd drive can get the full power without a problem..
    My OLD 2001 Mitsubishi Eclipse GT:
    "The Project That Never Ended, until it did"


    next project? subaru brz
    carpc undecided

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    • #3
      Originally posted by soundman98 View Post
      why not extend the converter to the location of the dvd drive? that way, your extending it before the voltage regulator, so the dvd drive can get the full power without a problem..
      I dont have room for the converter....any thoughts?

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      • #4
        what model converter are you using?
        My OLD 2001 Mitsubishi Eclipse GT:
        "The Project That Never Ended, until it did"


        next project? subaru brz
        carpc undecided

        Comment


        • #5
          Originally posted by soundman98 View Post
          what model converter are you using?
          HQ converter its PSP suitable too.

          Its a 12 V to 5 V dc dc with car lighter socket

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          • #6
            the only reason i ask is because member Oldspark pointed a site out a while back that makes a very small converter that might work for you to put near the dvd drive:

            http://www.lightobject.com/DC-to-DC-...V-2A-P540.aspx

            at only 50mm X 40mm footprint, it is really small, and should do 2A (though it might need a heat sink)




            anyways..

            technically, 30-40cm should be ok for extending the wire, though i am a little concerned because you need the maximum amperage that the psu puts out-- so any little drop will directly affect the device..
            My OLD 2001 Mitsubishi Eclipse GT:
            "The Project That Never Ended, until it did"


            next project? subaru brz
            carpc undecided

            Comment


            • #7
              Disconnect the converter's sense point and extend that to the the load.

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              • #8
                Originally posted by OldSpark View Post
                Disconnect the converter's sense point and extend that to the the load.
                What is sense point ??

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                • #9
                  Switched-mode converters sample the output voltage to increase or decrease (regulate) their output.

                  It is usually a resistive (voltage) divide at the output.
                  EG - the converter circuit's (IC or chip's) may have an internal reference voltage of 1.2V. For a 5V output, make 5V look like 1.2V - ie, a 1.2:5 divider - eg, a 3.8k & 1.2k resistor (see Wiki - voltage or resistive divider).

                  Rather than change the resistors to boost the voltage, it's better to extend them to the output. IE - disconnect the "top" resistor (to its +5V output) and use a wire from its "top" to the load +5V. A thin wire should be fine (it's only uA or mA), though you may have to be careful with interference....
                  (It the same in principle as linear regulators, alternators etc. This "extended" sense line is equivalent to the Sense terminal of a car's regulator/alternator.)


                  Reality depends on the chip (converter) being used. It may have sufficient noise filtering etc.

                  Comment


                  • #10
                    ^^ great idea!! in laymans terms, you are making the power supply account for the longer power wire, instead of you trying to work around it..
                    My OLD 2001 Mitsubishi Eclipse GT:
                    "The Project That Never Ended, until it did"


                    next project? subaru brz
                    carpc undecided

                    Comment


                    • #11
                      Yep. And it is SO OBVIOUS isn't it - now that you have thought about it.

                      And in retrospect, it is so obviously used everywhere - like 4-wire sensors, voltage regulation at PSU outputs (after current shunts, copper losses, transistors etc), and any good distribution system.

                      You can extend most regulators - even LM317 3-terminal adjustable voltage regulator (but not the LM 78xx & 79xx - they are "fixed").


                      For cars etc, if you do NOT have the single-wire D+ type alternator/regulator, you can usually extend the reference to the battery - even if it is in the boot/trunk.
                      Then who cares if their is a 1V or 2V drop from the alternator - the battery voltage will be spot on (eg, 14.2V).
                      That's why I like the (newer - ie, 30 year old) S-types - usually only a few uA is consumed to a long thin wire can be used. (Some like might be ~10mA-15mA - akin to a LED, but that is still a small wire - you can even omit the fuse!)


                      If over-voltage at the alternator is a problem for the front battery or front loads, then a chopper will reduce the voltage.
                      And that MUCH simpler and cheaper than up-converting from front to back. IE - over-set your alternator and then cut back excess voltage.
                      (Australians tend to buy $300 & $500 20A & 40A dc-dc converters to boost voltage to the back instead, but that's 'cos they are gullible or stupid.)

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