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186 foot layout wiring questions

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  • 186 foot layout wiring questions

    Hi All, I've already read thru the many threads here at SCI covering track wiring and power taps.
    http://slotcarillustrated.com/portal...light=zippydog
    I'm a "newbie" and would like you guys to "sign-off" on my plans to provide track power to "Project Talladega" (see my thread in the Carrera section).
    I have a Pyramid PS26KX 22 amp power supply, 250 feet of 4 conductor 16 guage stranded wire and four heavy duty 8 lug terminal blocks from Slot Car Corner.

    http://www.slotcarcorner.com/product...nal-Block.html

    Here's the game plan...
    1. Cut the wire that connects the Carrera supplied power supply to the BB. Plug the connector end (of the wire I just cut) into the BB as usual but the "cut" end will now go to the Pyramid output instead of the factory wall transformer. I plan on inserting an "in-line" fuse on the positive lead of 7 amps. I remember reading here with six cars you may approach a 6 amp current draw...Yes/No?
    2. Go underneath the main piece of power track and connect four wires. Each wire will be run to one side (jumpered together) of an 8 lug terminal block. From those four terminal blocks I will connect eight 4 wire "trunk-cables" that will feed current to different sections of my 186 foot layout.
    3. I may (if you think I should) insert another "in-line" fuse on the power side of each lane between the terminal block and the underside of the power track. Lets say 3 amp each lane. Yes/No?
    4. Each of the eight "trunk cables" will be run out to different sections of the layout. I will "splice" the end of each "trunk cable" with two more 4 conductor 16 guage wires and use these to "branch-out" 12 feet in either direction thereby giving me a total of 24 power taps.
    5. I will strip each end of the 16 guage wire (that is color coded for proper connection points) about 2 inches, fold it over and tuck it into the underside of the Carrera tracks. Then duck tape the area for a secure fit.






    If you guys would please let me know what changes or additions I need to make to these wiring plans before I goof up I would really appreciate it. Thanks for any input.
    Last edited by Wet Coast Racer; 04-03-2011, 04:20 PM. Reason: Deleting non-Advertiser Amazon & eBay Links. Fixing the Photobucket ones.

  • #2
    Are you ever planning to run analog cars? If not, then there's no reason to run four wires all over the place; two would be fine. And I completely agree with using a central distribution point for the power.

    Have you test-driven this track? My reading of the plan has the "four-lane" section in the upper right going in two different direction, with the outer two lanes going clockwise and the inner two lanes going counter-clockwise. This is very cool in theory - one of my early designs had it, too - but it leads to some really nasty accidents. Or will there be a separator wall between the two pairs of lanes?

    Comment


    • #3
      Originally posted by Iowa999 View Post
      Are you ever planning to run analog cars? If not, then there's no reason to run four wires all over the place; two would be fine. And I completely agree with using a central distribution point for the power.

      Have you test-driven this track? My reading of the plan has the "four-lane" section in the upper right going in two different direction, with the outer two lanes going clockwise and the inner two lanes going counter-clockwise. This is very cool in theory - one of my early designs had it, too - but it leads to some really nasty accidents. Or will there be a separator wall between the two pairs of lanes?
      Great reply and information...exactly what I need to hear from you guys. Now, boy ... in all the threads I came upon here at SCI and track wiring I never read only two wires were needed for the digital (I told you guys I'm green) I thought 4. Analog?...probably not. That right there made things easier for me already.
      I've been advised about on-coming traffic in the left set of curves so I will be using a barrier between lanes to avoid nasty head-ons...although that would make for some spectacular collisionsif only the dang cars weren't so pretty ....
      and expensive.

      Comment


      • #4
        Originally posted by Ponderwilu View Post
        I plan on inserting an "in-line" fuse on the positive lead of 7 amps. I remember reading here with six cars you may approach a 6 amp current draw...Yes/No?
        An "in-line" fuse on the positive lead is an excellent idea, 7 amps may be a bit low.
        When accelerating from rest each car will take well over one amp. As speed rises, the current falls.
        I'd say try it and see, but don't be surprised if you need a higher current fuse.

        Originally posted by Ponderwilu View Post
        3. I may (if you think I should) insert another "in-line" fuse on the power side of each lane between the terminal block and the underside of the power track. Lets say 3 amp each lane. Yes/No?
        Not for digital.
        For analogue the lanes should be fused individually.

        In digital all the lanes are electrically the same, so trying to fuse them separately isn't going to work. Depending on exactly how you wire it, you could end up with all or nearly all the cars taking current through one 3 amp fuse (so it'll blow).

        Comment


        • #5
          Originally posted by Al's slotracing View Post
          An "in-line" fuse on the positive lead is an excellent idea, 7 amps may be a bit low.
          When accelerating from rest each car will take well over one amp. As speed rises, the current falls.
          I'd say try it and see, but don't be surprised if you need a higher current fuse.


          Not for digital.
          For analogue the lanes should be fused individually.

          In digital all the lanes are electrically the same, so trying to fuse them separately isn't going to work. Depending on exactly how you wire it, you could end up with all or nearly all the cars taking current through one 3 amp fuse (so it'll blow).

          Thank you sooooooo much for this. Yep .... didn't know any of that either. See ... you guys already saved my butt twice.

          Comment


          • #6
            Shouldn't the fuse be between the transformer and the CU, not after the CU?. Yes, a fuse after the CU will also prevent too much current from being pulled through the CU, but only after it has already happened for a moment, right?

            Comment


            • #7
              The fuse should be wired between the power supply and anything else.
              That way, once the fuse is blown no further current can flow, so everything is protected.

              It is true that fuses only blow once high current has flowed through them for a short period. Some electronics can be damaged by the high current in the short period before the fuse blows. At least the fuse will prevent further damage if the electronics were to fail.

              Comment


              • #8
                That matches my thoughts. The only argument I could see someone making in favor the fuse being after the CU is that they didn't want to lose the laps, etc, for the race in progress. But I'd rather lose one race than a CU.

                Comment


                • #9
                  Originally posted by Iowa999 View Post
                  That matches my thoughts. The only argument I could see someone making in favor the fuse being after the CU is that they didn't want to lose the laps, etc, for the race in progress. But I'd rather lose one race than a CU.
                  Good point, You could have two fuses, one between the CU and the track and a higher current one between the CU and the power supply.
                  The most likely fault is a short circuit across the rails, what would blow the lower value fuse but still leave the CU connected. This lower value fuse would still need to take all the cars, which as I've said could be over 7 amps.
                  The higher value fuse would only blow if the fault was in the CU.

                  Comment


                  • #10
                    16 gauge wire is only rated for a maximum of 5 amps. You would never have a problem unless there was a short, in which case the wire could burn up if you use a 7 amp fuse. If you have a lot of taps it probably would be safe to use 16 gauge wire from the distribution point to the track, but you should use at least 14 gauge wire from the power supply to the distribution point.

                    Comment


                    • #11
                      Thicker wire from the power supply to the distribution point is a good idea to keep the resistance down.

                      As for the adequacy of a 7 amp fuse
                      According to the 16th Edition IEE Regulations, 1.0 mm2 conductors (approx 18AWG) are safe for 11 amps in conduit in thermal insulation (which is about the worst case for "burning up"). The thicker 16 AWG (about 1.3 mm2) will take more current. 7 amp fuse wire is approximately 31 AWG (0.04 mm2 )

                      So there is no way 16 AWG will "burn up" when protected with a 7 amp fuse.

                      Comment


                      • #12
                        The AWG chart that I use seems to be very conservative. Wire is fairly cheap, so it seems to me that it could not hurt to use thicker wire. I did watch a very nice Bowman track burn up a few years ago because it had no fuses. The resistance of 16GA wire is 4 ohms/1000 feet, 14GA wire is 2.5 ohms/1000 feet.

                        Comment


                        • #13
                          Ponder -

                          Before you get too far ahead and use some,not so good info...
                          Here ya go...(in the internet !)

                          To make sure you get even power to ALL parts of the track layout, go to this site and fill out the required info in the little boxs and hit the "calculate" button.

                          Continue to recalculate as you change the wire size and amount (= locations on the track), until you get "0" voltage drop. Oras low as you feel you can live with..!
                          Then...wire the track accordingly.
                          Me...I'd rather have too much power tap redundancy thAn not enough.

                          http://www.nooutage.com/vdrop.htm

                          Mike

                          Comment


                          • #14
                            Originally posted by Mike- View Post
                            Ponder -

                            Before you get too far ahead and use some,not so good info...
                            Here ya go...(in the internet !)

                            To make sure you get even power to ALL parts of the track layout, go to this site and fill out the required info in the little boxs and hit the "calculate" button.

                            Continue to recalculate as you change the wire size and amount (= locations on the track), until you get "0" voltage drop. Oras low as you feel you can live with..!
                            Then...wire the track accordingly.
                            Me...I'd rather have too much power tap redundancy thAn not enough.

                            http://www.nooutage.com/vdrop.htm

                            Mike
                            The link Mike shows is good for normal wiring installations where there is a single wiring run from point to point. Unfortunately it is of little use for calculating what happens in a slotcar track with power taps. I'll explain why -
                            It doesn't cover the resistance changes round a "ring main" which is how a slot car track without taps works ("ring main" is the standard way house power sockets are wired in the UK).
                            Each power tap that is added forms another parallel path with a different resistance feeding in someway round the lap.
                            So with multiple power taps there are multiple paths through the taps and track rails. The current shared between all of them and the proportion of the current through each conductor is different for each point round the lap.
                            All this can be calculated from the basic physics of adding parallel and series resistances, but once you get past one or two power taps there is quite a lot of number crunching required.
                            It's also worth mentioning you never get 0 voltage drop (except at zero amps, which of course is of no use to a slot car) and it is virtually impossible voltage to get the same drop all the way round the lap.

                            Comment


                            • #15
                              Provided that there are no breaks in the braid it is easy to get uniform power all around the track. Connect all of the positive leads in one spot and connect all of the negative leads half way around the track. When you do that you will always have the same amount of braid and wire between the car and the power supply. Another thing to remember is that the voltage drop through both the wire and the track braid will vary as the load varies. Since the combined resistance of the wire and braid should be very low that is not a very important factor.

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