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Need for testing short something draw 5,10 or 15 amp

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    #21
    Re: Need for testing short something draw 5,10 or 15 amp

    Halogen or regular lamp still have to deal with Hot and Cold resistance, a positive temperature coefficient of resistance. which can be more than 10 times.
    Last edited by budm; 10-24-2014, 04:29 PM.
    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


      #22
      Re: Need for testing short something draw 5,10 or 15 amp

      Get a car headlamp bulb, should be good. It draws about 4-5 amps.
      If you get halogen capsules, make sure you encapsulate it in something for safety in case it ever explodes.

      Comment


        #23
        Re: Need for testing short something draw 5,10 or 15 amp

        Originally posted by macattack600 View Post
        What size type you recommend.
        I think you should get several, 5w, 10w, 20w or so. Start with the lowest and work your way up to prevent board damage.

        Of course, if the filament's cold resistance is too low, you may get the same problems as without it. I am not sure what the cold resistance of those bulbs is.
        Last edited by Agent24; 10-24-2014, 04:29 PM.
        "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
        -David VanHorn

        Comment


          #24
          Re: Need for testing short something draw 5,10 or 15 amp

          Cold:Hot resistance can easily be more than 10 times.
          Learn more here on what to watch out for when using switching device with the lamps.

          I.E.
          2 Lamp Switching
          Before an incandescent or halogen lamp is turned on, the filament temperature and resistance are initially very low.
          At turn-on, the temperature of the filament starts rising from the ambient temperature.
          The low initial resistance causes large inrush current into a lamp, which can be more than 10 times the nominal
          current. The solid-state switch should allow this inrush current to flow in the wiring harness, but only for a specified
          time (<100 msec). Once the lamp is fully on, its steady-state current depends on the supplied voltage.
          Attached Files
          Last edited by budm; 10-24-2014, 04:39 PM.
          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


            #25
            Re: Need for testing short something draw 5,10 or 15 amp

            I'm thinking the car headlight is a bad idea. If I got the math right:


            A car headlight that takes 5A will be 60 watts.

            This means hot resistance will be 2.4 Ohms. That is OK if you want to draw that much current..
            But as budm says, divide that by 10 to get the cold resistance, and the cold resistance is going to be something like 0.24 Ohms.

            This means that when you first apply power, the filament is cold and the resistance is only 0.24 Ohms, we get around 50A of inrush current, this may blow the board and\or shutdown the PSU, and we're back to the same problem we had with no current limiting.
            Last edited by Agent24; 10-24-2014, 04:41 PM.
            "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
            -David VanHorn

            Comment


              #26
              Re: Need for testing short something draw 5,10 or 15 amp

              Thanks, AGENT. see the PDF in my post #24.
              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


                #27
                Re: Need for testing short something draw 5,10 or 15 amp

                So your saying is use a resistor in combination with the led rope light?

                Comment


                  #28
                  Re: Need for testing short something draw 5,10 or 15 amp

                  That would work but would be complicating things, one or the other would work by themselves.

                  Unless you are thinking of getting an LED strip that has no inbuilt current limiting, in which case a resistor or such would be needed to stop the LEDs from burning themselves up (bare LEDs need current limiting too!)
                  Last edited by Agent24; 10-24-2014, 05:14 PM.
                  "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                  -David VanHorn

                  Comment


                    #29
                    Re: Need for testing short something draw 5,10 or 15 amp

                    This is what a benchtop variable power supply is for ? In testing like I'm trying
                    Last edited by macattack600; 10-24-2014, 05:20 PM.

                    Comment


                      #30
                      Re: Need for testing short something draw 5,10 or 15 amp

                      Originally posted by macattack600 View Post
                      Also what about using a 12v that does'nt shut off
                      Originally posted by macattack600 View Post
                      This is what a benchtop variable power supply is for ? In testing like I'm trying
                      Yes, a benchtop\lab power supply with an inbuilt current limiting feature can be used. This is a very good solution, in fact, because you can control exactly how much current you supply and you have no issue with it shutting down.


                      Word of warning: Do NOT use something like a car battery which not only has no current limiting, also has no short-circuit shutoff either. A car battery can and will supply 120A easily, and your board may very well turn to charcoal.
                      Last edited by Agent24; 10-24-2014, 05:23 PM.
                      "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                      -David VanHorn

                      Comment


                        #31
                        Re: Need for testing short something draw 5,10 or 15 amp

                        This is interesting.

                        Comment


                          #32
                          Re: Need for testing short something draw 5,10 or 15 amp

                          There are so many ways:
                          https://www.badcaps.net/forum/showthread.php?t=31683
                          http://www.linear.com/solutions/5297
                          http://electronics.stackexchange.com...h-power-supply
                          http://www.tonystrains.com/tonystips/2011/021011.htm
                          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


                            #33
                            Re: Need for testing short something draw 5,10 or 15 amp

                            Do you think the led light rope need to have a ground wire I believe it's only hot wire and negative on them. Or would I just be running the negative end to the ground of PSU? I do plan on trying this on boards not have much use for first.
                            Last edited by macattack600; 10-24-2014, 06:02 PM.

                            Comment


                              #34
                              Re: Need for testing short something draw 5,10 or 15 amp

                              So is there a way to make variable current device for the psu's 12v rail? The Psu I have says 9.2amp for the 12v.
                              Last edited by macattack600; 10-24-2014, 07:39 PM.

                              Comment


                                #35
                                Re: Need for testing short something draw 5,10 or 15 amp

                                Originally posted by macattack600 View Post
                                So is there a way to make variable current device for the psu's 12v rail? The Psu I have says 9.2amp for the 12v.
                                You can probably use a circuit like this: http://www.eeweb.com/blog/extreme_ci...e-power-supply

                                Not sure if it will output a full 12v though, you might get only 10v, but that should be enough.
                                "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                -David VanHorn

                                Comment


                                  #36
                                  Re: Need for testing short something draw 5,10 or 15 amp

                                  Originally posted by Agent24 View Post
                                  You can probably use a circuit like this: http://www.eeweb.com/blog/extreme_ci...e-power-supply

                                  Not sure if it will output a full 12v though, you might get only 10v, but that should be enough.
                                  I've learned alot today you've been awesome help but I think I can't take it anymore I'm going to buy led strip tape I've read 6ft takes 1 amp.
                                  Last edited by macattack600; 10-24-2014, 10:13 PM.

                                  Comment


                                    #37
                                    Re: Need for testing short something draw 5,10 or 15 amp

                                    Originally posted by macattack600 View Post
                                    I've learned alot today you've been awesome help but I think I can't take it anymore I'm going to buy led strip tape I've read 6ft takes 1 amp.
                                    If you want to be sure on the details, post a link to the one you are thinking of buying and we can see if there's any info to be found about it.
                                    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                    -David VanHorn

                                    Comment


                                      #38
                                      Re: Need for testing short something draw 5,10 or 15 amp

                                      what exactly are you doing again?
                                      i originally thought you were trying to find a short?
                                      now it looks like your trying to load a psu down.

                                      Comment


                                        #39
                                        Re: Need for testing short something draw 5,10 or 15 amp

                                        I believe he wants to try 'smoke out a short' with an ATX PSU, obviously this will trip the SCP or roast the board.

                                        He wants a suitable load in series with the board to limit current and avoid those two things.
                                        "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                        -David VanHorn

                                        Comment


                                          #40
                                          Re: Need for testing short something draw 5,10 or 15 amp

                                          so a milliohms meter is too obvious then?

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