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Carerra Go Track connection piece, current limiting?

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  • Carerra Go Track connection piece, current limiting?

    I've wired an external adjustable power supply to my track. I just cut the end off of one of the wall wart supplies and soldered connectors onto it to connect to the power supply.

    Now, I'm trying to run a car with a different motor. It is an old motor from a Kyosho mini-z.

    With the stock controller, the car won't move at all. I wired up a Parma economy controller and now the car will move, but only for a about 6 inches. The power supply has a display showing the current and voltage. It seems like whenever something tries to draw more than 0.3 amps, something shuts off the power to the car. I can take that same power supply, touch the wires directly to the brushes and the motor spins just fine, so I don't believe it is something the power supply is doing.

    I did some googling, and am not finding anything about current limiting circuitry in the power connector piece, but it seems like something is there.

    Can someone point me in the right direction?

  • #2
    Have you tried using a Carrera Go car?

    Randy

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    • #3
      I should have been more clear. The Carrera Go cars work fine with this arrangement, as they draw very little current. Stock cars with stock controllers work fine. A go car with the Parma controller works fine (with no brakes).

      This car with the higher power motor starts to work, then stops.

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      • #4
        When you open up the piece of track with the power hookups, there is a resistor an a pair of capacitors for each lane. The resistor is a 33 Ohm resistor, and is at least a 1/4 watt rating, maybe higher (it's pretty big). I have been looking at the board traces trying to back how how this thing is really wired, but I suspect this resistor and pair of capacitors is what is causing the current limit.

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        • #5
          Cdub, the resistor in the track is for the turbo button on the controllers.

          go! not digital or go!plus ?
          stock analog track?

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          • #6
            My track is just a plain stock analog track.

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            • #7
              Then why bother with that power base at all? Wire it up for proper power and control. It's pretty easy, even if you've never done it before.

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              • #8
                The short answer is, I didn't know I needed to.

                The longer answer is, I've been trying to keep things pretty simple, as I'm doing this primarily with my young son, so I like the stock power base because it makes it easy for him to hook the track up.

                So, I did a little digging this morning, and I figured out what is really going on. I will document it here for posterity's sake.

                Here is a picture of the circuit board, showing all of the components:


                Yes, the 33 Ohm resistor is there for the Turbo Boost feature.

                There is another component in the mix marked GR72 025 which is a Poly Fuse resettable PTC. This component is always in the circuit, turbo or not, and it does just like what it sounds like. It is a fuse that shuts off the current when around 0.5 amps is drawn. It doesn't reset until the load is removed.



                I believe the third component, marked "105" is just a capacitor.

                So, indeed, the stock analog powerbase has a current limiting fuse in it.



                For completeness, there is how the wire colors map to the pin locations in the connector and what the measured resistances are between the pins with the throttle in different positions.



                In operation, when the throttle is in the neutral position, there is an open circuit in the control handle and no current passes.

                When the throttle is depressed, the resistance in the handle varies from about 36 Ohms down to around 1 Ohm. The current comes back to the base via the Blue wire and passes through the 33 Ohm resistor as well, making them additive in this operation mode. All current that goes through the two resistors also goes through the fuse and on to the rail, Motor, the other rail, and then back to ground.

                When the boost button is pushed, the red and black wires are shorted together, which allows the current to bypass the 33 Ohm power base resistor, but it still goes through the fuse.
                Last edited by Cdub; 11-17-2017, 11:15 AM.

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                • #9
                  than why not bridge the fuse?

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                  • #10
                    I wasn't really thinking about solutions yet when I put that post up. I had gone through the trouble to figure out what was there, and just wanted to share it so hopefully someone else who is wondering doesn't have to go through figuring it out.

                    As far as jumping out the fuse, yes that would be an option. If you do that, now you are relying on the protections integrated into your power supply to protect it and the track. That could go either way. Not sure if I want to test that on my 8 year old. Although since my track is outside if it catches fire it shouldn't take the house with it!

                    The fuse is a commodity item, available in a number of different trip current ratings from the usual places like Mouser and Digikey. If a person wanted to stick with the stock parts, it would be a straightforward soldering job to replace these fuses with higher rated ones. The wire used in the stock power connection piece is quite thin (like hair), so I'd be a little worried about the wire as the next weak link and would probably want to replace it too.

                    I think this is just the step in my journey where I get some different controllers and rewire the track, ditching the stock stuff completely. I thought I would get a little more mileage out of the stock pieces than I have, but that is okay. At least now I know what I'm working with and what I need to do.

                    When I built the table, I didn't really plan for putting in drivers stations, I was more focused on the overall construction and the provisions to cover it when not in use. I just came in from looking at it, and I think I have a decent plan on where to put some drivers stations. I'll go ahead and do call buttons, brake potentiometers, and appropriately sized fuses. I like Anderson Powerpole connectors, so I will likely use those for the connection to the power supply and to the controllers themselves. These items (along with the cars) are stored indoors in a plastic tote.

                    It has been discussed on here that the rails in the Carrera Go track are not stainless steel. They are steel with some coating applied. Are there any special tricks I should be aware of when it comes to soldering to whatever these rails are? I'm assuming I should sand off the coating in the area I'm soldering. Is there anything else I should know?

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                    • #11
                      when i did the power taps for my artin track, i simply turned the track piece over, pushed some wires into the holes on the bottom side and added solder until the spot was filled. good connection.
                      not first class soldering and a correction solution, but it worked fine.

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