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    Help me understand something I thought I understood about electricity

    Yesterday, I was dinking around with the idea of using devices, which are powered by AC to DC wall-warts, but require 12V like a car, in a car without their wall-warts. I thought of things, which seemed obvious, such as the fact that voltage fluctuates to a pretty great degree in a car so it may require tighter regulation at the device. Then I was curious about whether a current limiter or fuse would have to be added to protect the device, which would normally, only call for a 1A or 2A wall-wart.

    I ran this question by a relative who is savvy to much in computers and electronics, and he said that I can't just do that, and I would require an inverter, and would still need to use the wall-wart that came with the device.

    What's up?
    Presonus Audiobox USB, Schiit Magni 3, Sony MDR-V700

    #2
    Re: Help me understand something I thought I understood about electricity

    Most things should work as long as they won"t mind the voltage changing between 10 to 13.8 volts. If you hook it directly to the battery or other direct connection it would be better to have a 1 amp or 2 amp fuse. If you hook it thru the cigarette lighter jack, it will already be fused, but it could be fused much higher than 2 amps.

    Comment


      #3
      Re: Help me understand something I thought I understood about electricity

      Originally posted by Logistics View Post
      Yesterday, I was dinking around with the idea of using devices, which are powered by AC to DC wall-warts, but require 12V like a car, in a car without their wall-warts. I thought of things, which seemed obvious, such as the fact that voltage fluctuates to a pretty great degree in a car so it may require tighter regulation at the device. Then I was curious about whether a current limiter or fuse would have to be added to protect the device, which would normally, only call for a 1A or 2A wall-wart.

      I ran this question by a relative who is savvy to much in computers and electronics, and he said that I can't just do that, and I would require an inverter, and would still need to use the wall-wart that came with the device.
      The wall wart/brick is just an "AC-DC converter" with some (dubious) regulation of its output voltage and current. If you can create a DC that resembles the sort of DC that a particular device expects to encounter, then the device has no way of knowing that it is NOT being powered by it's original wall wart.

      Note that some wall warts are little more than transformers -- even going so far as to supply AC to the device (relying on the device to internally rectify, filter and regulate, as required).

      Others are genuine "power supplies" -- but, may have really loose load regulation characteristics (as the load changes, the voltage sourced from the wall wart may change as well!).

      One less obvious aspect of all this is that most (active) devices want a certain amount of POWER to perform their tasks. So, a voltage source that is a bit lower than the expected could still allow the device to operate correctly; but, could increase the amount of current flowing into the device or the duty cycle of any switching devices in its internal circuitry. Unless you know the range of conditions over which the device was expected to be operated (which can be wider than the range that is explicitly specified), your safest bet is always to mimic the power source that was designed for the device.

      Comment


        #4
        Re: Help me understand something I thought I understood about electricity

        What was pointed out to me during the aforementioned conversation is that the device will be expecting a particular sine wave or square-wave due to being converted from house mains, and moving to the cars battery would screw it up.
        Presonus Audiobox USB, Schiit Magni 3, Sony MDR-V700

        Comment


          #5
          Re: Help me understand something I thought I understood about electricity

          Originally posted by Logistics View Post
          What was pointed out to me during the aforementioned conversation is that the device will be expecting a particular sine wave or square-wave due to being converted from house mains, and moving to the cars battery would screw it up.
          Your device is expecting DC Voltage to operate, the so called wall wart convert 120VAC (US) AC to low Voltage DC required by your device.
          Never stop learning
          Basic LCD TV and Monitor troubleshooting guides.
          http://www.badcaps.net/forum/showthr...956#post305956

          Voltage Regulator (LDO) testing:
          http://www.badcaps.net/forum/showthr...999#post300999

          Inverter testing using old CFL:
          http://www.badcaps.net/forum/showthr...er+testing+cfl

          Tear down pictures : Hit the ">" Show Albums and stories" on the left side
          http://s807.photobucket.com/user/budm/library/

          TV Factory reset codes listing:
          http://www.badcaps.net/forum/showthread.php?t=24809

          Comment


            #6
            Re: Help me understand something I thought I understood about electricity

            It would be good to know exactly what device it is, and perhaps know how it's built. Sometimes it will work, sometimes it wont.

            I have a pretty nasty example of what won't work after doing some analysis: I have this lithium ion vacuum cleaner that uses a 15 volt 100mA wall wart charger. Based on the circuitry it was determined that the voltage actually doesn't matter - but the current does. If the wall wart was not current limited, the charging circuit would immolate and that's the end of that circuit...

            But besides that, car alternator power is very noisy. It is not filtered at all, and contains a "harmonic" of your engine speed that your device needs to handle. The voltage peaks during these alternator peaks need to be handled, as well as any troughs whenever the engine isn't started. Perhaps dealing with the droop during engine starting also needs to be accounted for. Car power is pretty nasty IMHO...

            Comment


              #7
              Re: Help me understand something I thought I understood about electricity

              am thinking there are regulated supplies for in cars . phone charger for one .must be more versatile ones

              Comment


                #8
                Re: Help me understand something I thought I understood about electricity

                As eccerr0r indicated, right now we have no idea what the device is and what the power requirement is and how sensitive the device to noisy electrical enviroment.
                Never stop learning
                Basic LCD TV and Monitor troubleshooting guides.
                http://www.badcaps.net/forum/showthr...956#post305956

                Voltage Regulator (LDO) testing:
                http://www.badcaps.net/forum/showthr...999#post300999

                Inverter testing using old CFL:
                http://www.badcaps.net/forum/showthr...er+testing+cfl

                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                http://s807.photobucket.com/user/budm/library/

                TV Factory reset codes listing:
                http://www.badcaps.net/forum/showthread.php?t=24809

                Comment


                  #9
                  Re: Help me understand something I thought I understood about electricity

                  Originally posted by Logistics View Post
                  What was pointed out to me during the aforementioned conversation is that the device will be expecting a particular sine wave or square-wave due to being converted from house mains, and moving to the cars battery would screw it up.
                  If the mains are only used as a POWER source, there's usually nothing that moving to an equivalent (after-wall-wart) DC supply can't accommodate (with similar POWER capabilities).

                  Note, however, that the AC signal on the mains may be used for other, non-power-related uses. For example, I routinely use it as a long-term timebase and/or to frequency lock sampling algorithms to the ACTUAL line frequency (e.g., to remove any components of the AC mains frequency from the signals being sampled).

                  In these cases, the lack of that "timing" signal is seen as an error (in one instrument, I use that fact to indicate that the instrument is running on its internal battery and start measuring the DC voltage as a predictor of when that battery will be exhausted)

                  Comment


                    #10
                    Re: Help me understand something I thought I understood about electricity

                    I apologize, I wasn't intending to be vague. I was considering using a Sound Blaster Extigy in a car, and outputting to monoblock amps.
                    Presonus Audiobox USB, Schiit Magni 3, Sony MDR-V700

                    Comment


                      #11
                      Re: Help me understand something I thought I understood about electricity

                      Would posting the specs on the back of the Extigy's power brick, help determine whether it can be connected directly, to automotive DC?
                      Presonus Audiobox USB, Schiit Magni 3, Sony MDR-V700

                      Comment


                        #12
                        Re: Help me understand something I thought I understood about electricity

                        the more info the better

                        Comment


                          #13
                          Re: Help me understand something I thought I understood about electricity

                          Originally posted by Logistics View Post
                          Would posting the specs on the back of the Extigy's power brick, help determine whether it can be connected directly, to automotive DC?
                          Set up a lab/bench supply to emulate the brick. See if it works on the bench. Then, worry about how you'll deal with the more hostile automotive environment.

                          Comment


                            #14
                            Re: Help me understand something I thought I understood about electricity

                            Originally posted by Logistics View Post
                            Would posting the specs on the back of the Extigy's power brick, help determine whether it can be connected directly, to automotive DC?
                            Also the spec of the device, the more details the better.
                            Never stop learning
                            Basic LCD TV and Monitor troubleshooting guides.
                            http://www.badcaps.net/forum/showthr...956#post305956

                            Voltage Regulator (LDO) testing:
                            http://www.badcaps.net/forum/showthr...999#post300999

                            Inverter testing using old CFL:
                            http://www.badcaps.net/forum/showthr...er+testing+cfl

                            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                            http://s807.photobucket.com/user/budm/library/

                            TV Factory reset codes listing:
                            http://www.badcaps.net/forum/showthread.php?t=24809

                            Comment

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