How to Build a Slot-less Lap Counter

Parts List

  • Hall Sensor: Honeywell S&C SS441R (sensitive) X 4
  • Q1,Q2: Transistor PNP S9012 X 2
  • D1,D2,D3,D4: 4148 Signal Switching diode X 4
  • R1,R4: 10K ohm 1/4 watt resistor X 2
  • R2,R3: 3.3K ohm 1/4 watt resistor X 2
  • C1,C2: Capacitor 22uf 35V X 2
    You may be able to go smaller on the capacitor. It depends on what the N-score you have can tolerate before you get false signals. The closer to Zero UF you get the more accurate the lap counter becomes.
  • L1,L2: LED X 2 any standard LED will work
  • Relay: OUAZ-SS-112D 1amp rated X 2
  • Breadboard to build circuit on.
  • N-Scorer Lap Counter

Wiring Diagram

What the Circuit will look like when done


Modifying the N-Scorer Lap counter

It is pretty straight forward open up the N-score unit and remove the lower LEDs from the circuit board, next mark Positive and negative on the IR sensors on the top (larger) PCB board. Then use shielded cable and tap into the N-score PCB board.





Run both shielded cables out the bottom where the LEDs for the IR Beam used to go then solder both cables to your new Trigger PCB.

Placement of Hall Sensors

The black marks show the placement of the hall sensors.


These are Hall sensors. They detect magnetic fields. The have a narrow and a wide face.


You can assemble them 2 ways wide to wide or narrow to narrow. It doesn't matter which way as long as you understand each sensor will be detecting a magnetic feild opposite to the other.


I like to place them narrow side down to start. Glue them to the each other and the track surface with a little crazy glue. Try to line them up as best you can. get them as close to the outside rail plastic surface as you can.


I like to use Futaba Servo connectors here you can see the correct wiring narrow side up, +12V, Ground, Signal


To wire the sensors up you go over/under and the opposite to detect the other car. you can wire both connectors to one side and have the boost track detect both cars in any lane you wish.


All 4 Sensors will be used unlike the Boost track which uses 2 per car.

You wire up The A car connectors to the opposite lanes and opposite Hall sensors.

Car A: Lane 1 Hall sensor Narrow side up

Car A: Lane 2 Hall sensor Wide side up

Car B: Lane 1 Hall sensor Wide side up

Car B: Lane 2 Hall sensor Narrow side up

It is a little confusing but will make sense once your have you lap counter PCB board hooked up and working.


Preparing the 'A' Car

     Using the boost track requires modifing the 'A' Car slightly. You need to reverse the motor direction. This is the same procedure that was needed by the Electronic super booster: How to build a Electronic Super Booster. Just take out the 'A' car motor, flip it over magnets and all and install it back into the chassis.


    In the future if you build a MEGA booster: How to build a Electronic Mega Booster. You will need to slightly modify the mega booster reversing the control wiring for the 'A' car. this is needed to compensate for the reverse steering, it will also be required if you build a lap counter later as well.


     Just a note about optimal placement, due to issues with the 'A' car. If you place the power track/lap counter right after a curve without a wall(1978 command control track) you can ensure you do not miss a lap count with a center lane stall or lane change the curve will force the cars into the outside lane by having the power track the next section after a turn it will ensure a lap counts for both cars will be in the same outside lane due to centrifugal forces. if you will be using the later 1990s TCR track with walls i recommend the power track/lap counter at the end of a long straight to ensure the cars are in separate or the same lane and not in the middle of the lanes. having 2 15" straight seconds before the power track/lap counter is a good minimum.

      Another fun thing. If you want to setup ovals, with this type of power track, Set the Switch to IDEAL mode, then run the race clockwise instead of counter clockwise, in the oval situation this will help the A car with the lane change wiggle problem. the same problem occurs with the IDEAL cars but in the opposite direction. So if you ran the IDEAL cars with the Switch set to T and ran counterclockwise the same wiggle issue would occur as running the TYCO cars counterclockwise.

      This is a good solution for a competition race that does not have even lane lengths. a cross over track would benefit the A car for half a lap as well, it is all a problem with the contact shoe placement design for the A cars shorting the B rail when lane changing from right to left.

      The best placement is right after a curve to ensure accurate lap counts other wise you want it in the middle of a long straight at least 30" (two 15" straight sections away from the curve) to ensure no cars miss the count due to incomplete lane changes.

Lap counter placed after a curve


Problems still working out


     I changed the originalsensor design to a different cirucit board. This change affected my quick fix for the older command control cars. Currently you can not use Lap counter with the older command control cars because the sensors will not see them.


      Now that I finished the trigger design I've started testing. I found an issue with issue with converting the original Command control cars. I changed the sensor layout from the original boost track design to work with the newer 1990s TCR chassis because of this optimization the original Command control are not seen by the hall sensors. One solution was to install extra magnets on the rear bumper so the hall sensors would see the command control cars. The new sensor layout is having trouble picking up the converted command control cars, I'm experimenting with stronger Neo magnets to see if the sensors will pick them up compared to rare earth magnets. if i used larger rare earth magnets the sensors could see them at distance but they will not work well on the original chassis my hope is smaller and stronger magnets will over come the issue. Time will tell.

     I'm working on a fix.


Update: I basically Stacked a smaller Neo magnet on top of a rare earth magnet and glued it to the top of the rear bumper on a CC-02 car this allowed the hall sensors to see the car. i tried a few different magnets but nothing worked as well as stacking 2 magnets on each side of the bumper to trip the hall sensors for each lane. I glued the magnets so they work as 'A' or 'B' and matched them to the chassis.


[insert photo here]

Video of Lap counter

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