FC.Quad User Manual

FC.Quad is a four-lane slot car lap counter and timer. It uses four optical sensors installed in the track and displays lap count, lap times, and race progress for each lane. The system works on its own; a Windows computer and FC.Platform are optional.

This manual covers the physical installation, the starting sequence, the four lane displays, the external Restart button, and computer connection. Each FC.Quad is assembled and tested by FC Slot-Cars in Colombia. If you need help with your particular track, you can contact me using the details at the end of this guide.

Quick start

  1. Choose one timing line across all four lanes. Check with several cars that each car will pass directly over its lane's proposed sensor position.
  2. Drill four 5 mm holes, one per lane. Install the sensors facing upward and recessed about 0.5 mm below the track surface. Route and secure both pairs of cables beneath the track.
  3. Connect the two white sensor plugs to the corresponding ports on FC.Quad. If your unit has the supplied external Restart button, connect it to the separate reset port.
  4. Connect both USB-C power cables. Before startup or Restart, make sure all four sensors receive steady light and the cars are positioned about one inch before the timing line.
  5. Wait through the display check and start sequence. Begin racing when the displays turn off again. The first pass in each lane shows 0 as that lane's starting reference; later passes count completed laps.

What's included

The current FC.Quad product package lists the four-lane timing system, sensor cables, an external Restart button, two USB-C cables, and a spare sensor lead. Check the contents of your particular order before installation. A 5 mm drill bit and materials for securing the sensors to your track are needed for installation.

Get to know your FC.Quad

The main unit has a Restart button, a rear Average/Best selector, USB-C connections, a connector for the external Restart button, and two white sensor connectors. Each white connector carries a pair of sensor leads, for four sensors in total.

On the front, each of the four lanes has three display positions:

  • Top row: Lap count.
  • Middle row: Average lap time or best lap time, selected with the rear switch.
  • Bottom row: Last lap time.

The front columns show all four lanes. Before your first race, pass one car through each lane separately and confirm which display column and position respond. This also verifies that the sensor pairs have been assigned to the intended physical lanes.

Install the four sensors

FC.Quad uses light-dependent resistor (LDR) sensors. Light reaches each sensor when its lane is clear. A passing car briefly shades that sensor, and the system detects the crossing. Sensor position and consistent lighting are essential for reliable lap counting.

Choose the timing line

Choose a location where all four cars will cross their sensors at approximately the same point in the circuit. Look at the cars you normally race before drilling. Different body widths, guide positions, and ride heights can change how much light a car blocks.

For HO tracks, it is recommended positioning each sensor between the rail and slot of its lane. For larger scales, position each sensor beside the rails, as close to them as practical. The current FC.Quad listing describes compatibility from HO through 1/24 scale, on plastic and wooden tracks; the exact position still depends on your track and cars.

Drill and mount the sensors

  1. Mark one position in each of the four lanes. Confirm that a car covers each mark as it crosses the timing line.
  2. Drill a 5 mm hole for each sensor.
  3. Install the sensors with their light-sensitive faces pointing upward, recessed approximately 0.5 mm below the racing surface. They must not protrude into a car's path.
  4. Secure them by press-fit or with a suitable adhesive, without covering the light-sensitive faces.
  5. Route both sensor cable pairs under the track. Secure the cables so they cannot be snagged, stretched, or pinched.
  6. Place the main unit where drivers can read it and connect the two white plugs to its sensor ports. Hold each solid connector when connecting or disconnecting it; never pull on the wires.

Place the timing line about one inch ahead of the cars' starting noses. The cars should not cover the sensors when the system powers on or restarts. Keep the sensor faces clean and provide steady light above the track. If your layout requires it, the sensor leads can be bent gently; avoid sharp repeated bends or strain where a lead meets a sensor.

For photographs and a fuller discussion of sensor positioning, see How to Install a Slot Car Lap Counter Sensor.

Connect power and the external Restart button

FC.Quad uses two USB-C connections. Connect both supplied USB-C cables for normal operation. They also provide the optional USB connections used when working with a computer. Do not assume that powering only one side means all four lanes are ready; check the displays and all four sensors before racing.

The rear Restart button is on the main unit. The separate connector is for the supplied external Restart button, which you can position near the drivers. The printed guide states that either Restart control begins a new start sequence. Route the external button's cable where it will not be pulled or interfere with the track.

Start a race

Before powering on or pressing either Restart button, make sure all four sensors are illuminated and that your head, hands, body, or cars are not casting shadows over them.

  1. Power the system or press a Restart button.
  2. The displays briefly show 0000 and turn off as a display check.
  3. The top display row shows 8888, followed by the middle and bottom rows, each stage about 1.5 seconds apart.
  4. When all displays turn off again, the start sequence is complete and the race begins.

If a car crosses its sensor before the start sequence ends, that lane receives a one-lap jump-start penalty. Its initial 0 appears only after the sequence has finished.

Press the rear or external Restart button to start a new race.

Read lap counts and times

After the start, a lane's first pass shows 0. This establishes the starting reference. Its next pass completes the first measured lap. Later passes update the lap count and times for that lane.

Use the selector switch on the back to change the middle row between Average Lap Time and Best Lap Time at any point. The bottom row continues to show the Last Lap Time. Remove the protective film from the displays before use.

Optional connection to FC.Platform

FC.Quad works without a computer. Legacy units send lap information over USB as comma-separated values. The system lists each module's fields as lane (1 or 2), lap count, average lap time, best lap time, last lap time. Because the four-lane system has two sensor pairs, do not interpret a raw lane number on its own as a unique physical lane among all four; identify which connected module produced the data.

FC.Platform 2.0 supports compatible legacy circuit systems and FC.Protocol devices. For FC.Protocol operation, it represents the four-lane FC.Quad arrangement as two FC.Duo devices, each with two sensors. Assign each physical sensor to its corresponding track lane in Track Manager. For example, one device may supply lanes 1 and 2 and the other lanes 3 and 4, but verify your actual wiring by passing a car through each lane separately. A new FC.Protocol device may need a Device ID assigned before it is used in a saved track configuration.

Follow the FC.Platform guide for the steps appropriate to your firmware. If you are unsure whether your FC.Quad is legacy or uses FC.Protocol, contact FC Slot-Cars with your purchase details before changing firmware.

Troubleshooting

One lane misses some cars

Check that its sensor faces upward, is recessed slightly below the track, and is shaded clearly by each passing car. Clean its face, check its cable, and test with steady lighting and several representative cars. Compare its behavior with the other lanes.

An empty lane counts laps

Changing light or shadows may reach that lane's sensor. Restart with all sensors uncovered, leave the lanes empty, and observe the displays. Check nearby lamps, windows, people, and adjacent track sections. If an empty lane continues counting under stable light, contact FC Slot-Cars with a video showing the sensors and displays.

Only two lanes respond

Check both USB-C connections, both white sensor plugs, and the four sensor cables. Test each physical lane with one car at a time and note which displays respond. If the same pair remains inactive, contact FC Slot-Cars with photos of the connections and the results of that test.

The displayed lane does not match the car's physical lane

Test one lane at a time to identify which sensor is connected to each pair. For standalone use, correct the physical sensor connections as appropriate. In FC.Platform, review the Device → Sensor → Track Lane assignments in Track Manager before racing.

Restart appears slow

The 0000 display check and the row-by-row 8888 sequence are normal. Press either Restart button once and wait until all displays turn off again before passing a car over a sensor.

Windows detects FC.Quad but FC.Platform cannot communicate

If a connected side works as a standalone counter but Windows shows a warning icon for its USB serial device, the CH340 driver may be missing or incorrect. Check Ports (COM & LPT) and Other devices in Windows Device Manager. If Windows reports a driver problem, install the official WCH CH341SER.EXE driver, reconnect the USB cables, and confirm that the warning icon disappears and valid COM ports appear. Then reopen FC.Platform. If communication still fails, note which of the two connections is affected and contact FC Slot-Cars.

Frequently asked questions

Does FC.Quad need a computer?

No. Lap counting, timing, displays, and the starting sequence work without FC.Platform. A Windows computer is optional for compatible race management workflows.

Why are there two white sensor connectors?

Each connector carries two sensor leads. Together they provide one sensor for each of the four lanes.

Why does FC.Quad use two USB-C cables?

The current four-lane system uses two USB-C connections. Connect both for normal operation and verify that all four lanes respond before racing.

Can I use the external Restart button?

Yes. Connect the supplied button to the dedicated rear reset connector and place it where drivers can reach it. The rear button on the main unit also starts a new race.

How deep should I install the sensors?

Install them facing upward, approximately 0.5 mm below the track surface. No sensor should protrude into a car's path.

Why does the first pass show 0?

The first pass establishes that lane's starting reference. Its next pass completes the first measured lap.

Why does FC.Platform show two devices for one FC.Quad?

In FC.Protocol, the four timing inputs are represented as two FC.Duo devices with two sensors each. Track Manager connects those four sensor inputs to your four physical lanes.

Care, support, and further reading

Keep the sensors clean and illuminated, secure the cables beneath the track, and hold the solid white connectors when unplugging them. If you need support, email fc.slotcars@gmail.com with your track scale, photos of all four sensor positions and rear connections, and a short description or video of the problem.

Fernán Castillo
FC Slot-Cars