FC.Drag-PRO is a two-lane slot car drag racing system with start and finish sensors, a Pro Tree, reaction time (RT), elapsed time (ET), bracket settings, red-light detection, and winner indication. It operates on its own. Compatible FC.Protocol units can also connect to FC.Platform for race management.
Important power rule: use only one power input at a time. Power FC.Drag-PRO through either its rear barrel power connector or its USB-C port. Never connect both. When using FC.Platform, disconnect the barrel supply and power the system through USB only.
Quick start
- Install one start sensor and one finish sensor in each lane. The start sensors go near the staging line; the finish sensors go at the end of the strip. Keep all four sensors facing upward and well illuminated.
- Connect each sensor cables in the orientation permitted by its plug.
- Mount the main unit securely, connect the sensors, and choose one power input: the rear barrel connector for standalone power or USB-C. Do not connect both power inputs.
- At startup or after Restart, set a bracket for either lane if needed. Leave both brackets at zero for a heads-up race.
- Stage both cars over their start sensors. After the staging delay, watch the tree. Leave on your lane's green light and drive across its finish sensor.
- Read RT and ET on the corresponding displays. The winning lane is indicated by its green winner light; a false start produces a red light for that lane.
What's included
The current product listing includes the two-lane timing unit, sensor cables for the start and finish lines, a spare sensor lead, a USB-C cable. The cable assemblies serve as each lane's start and finish sensors. Cable length or stand style may vary by order or product version; check your package before installing the strip.
Get to know the system
Each lane has a bracket button, an RT display, an ET display, and tree lights that indicate its starting and race status. The main unit also has a rear Restart button, sensor connector sockets, the rear barrel power connector, and a USB-C connection.
- Start sensors: detect when each car is staged and when it leaves the line.
- Finish sensors: detect each car at the end of the strip for elapsed-time measurement.
- RT: the car's reaction time relative to its starting light.
- ET: the time measured for its run to the finish.
- Bracket buttons: set a lane's starting delay in 50 ms steps during standalone bracket configuration.
Remove the protective film from the displays before first use.
Install the start and finish sensors
FC.Drag-PRO uses light-dependent resistor (LDR) sensors. At startup it takes a light reading as a reference. A car covering a sensor reduces the light that reaches it, allowing the system to recognize staging, launch, or finish. Provide steady light and keep your head, hands, and cars from shading the sensors during startup or Restart.
- Choose the staging position in each lane and a finish line at the same distance along both lanes. Confirm that your cars cover the intended sensor positions.
- Drill a 5 mm hole for each of the four sensors. For HO track, the printed guide places sensors between the rail and slot; for larger scales, beside the rails and close to them.
- Install the light-sensitive faces upward, aligned with the track surface according to the printed guide. Make sure no sensor protrudes into the car's path.
- Secure the sensors without covering their faces. Run the cables under the track and protect them from pulling, pinching, or passing cars.
- Connect the two sensor cable plugs, holding their solid connectors rather than pulling on the wires.
You have short start-line leads and longer finish-line leads, approximately 3 ft and 21 ft respectively. Confirm the lengths supplied with your particular order before finalizing the track layout. Keep the sensor faces clean and illuminated during racing.
Assemble and secure the main unit
FC.Drag-PRO can be installed using a single stand, or two fixed-width stands for HO. Assemble the supplied stands for your track and secure the unit to its base with appropriate screws, double-sided tape, or adhesive so it cannot move during a race. Route every sensor cable where drivers and cars cannot catch it.
Choose one power connection
Never use the rear barrel power connector and USB-C at the same time.
- Standalone with a barrel supply: connect the suitable supply to the rear barrel input. Keep USB disconnected.
- Standalone with USB: connect USB-C for power. Keep the barrel supply disconnected.
- With FC.Platform: disconnect the barrel supply first, then connect the unit to the Windows computer by USB. USB must be its only power input during the connection.
Before changing from one input to the other, disconnect the current power source. Never plug in the second input while the first is connected.
Set brackets for a standalone race
After power-on or Restart, you have bracket configuration time window. All four displays initially show 0. You have up to 60 seconds to set a lane's bracket. Each press of that lane's bracket button adds 50 ms; holding it increases the value continuously. The selected bracket appears on its RT display.
A bracket delays the starting-light sequence for that lane. Leave both values at zero when both cars should receive the same start. If you stop adjusting for about 5 seconds, or the 60-second window expires, the system moves to the pre-stage phase and shows 0000 on the RT displays.
Restart to prepare a new standalone run and check the bracket displayed before staging. When FC.Platform controls a compatible FC.Protocol device, set the required race configuration in the software and follow its race view instead of assuming an earlier manual bracket value remains active.
Stage, start, and read the race
- Move each car onto its start sensor. The corresponding ET display shows 0000 when that lane is staged.
- Once both cars are staged, the system waits 5 seconds and applies any configured bracket delay.
- For the Pro Tree, the yellow lights illuminate together. The green lights follow 400 ms later, according to each lane's configured start.
- Leave when your lane turns green and drive through its finish sensor.
- At the end of the run, read each lane's RT and ET. The winning lane is indicated by its green light.
If a car leaves before its green light, that lane receives a red light and is disqualified for the run. You will see 8888 on its displays while the opponent's RT and ET remain visible.
The system resets automatically approximately 20 seconds after a race. You can also use the rear Restart button to prepare another run.
Connect to FC.Platform 2.0
FC.Platform provides Drag Single Races, elimination tournaments, driver and car records, a race view, and saved results for compatible FC.Protocol FC.Drag-PRO devices. The hardware manages the physical staging, starting lights, timing, red lights, and official winner. FC.Platform receives those results and manages the event. FC.Platform 2.0 does not read or display speed from FC.Drag-PRO.
- Disconnect any barrel power supply. FC.Platform connection must use USB as the device's only power source.
- Open FC.Platform on the Windows PC, then connect FC.Drag-PRO by USB.
- Confirm that it appears in Device Manager. If a new FC.Protocol unit shows UNASSIGNED, use Advanced → Assign Device ID, reconnect or restart as instructed, and confirm its unique ID before using it in a saved setup.
- Create the Drivers and Cars needed for the event. Each Car belongs to an existing Driver.
- Open Drag Single Race or Drag Tournament, select the participants and cars, and set brackets where the format requires them.
- Stage and race on the physical system. FC.Platform shows stage status, RT, ET, red-light information, and the winner reported by the hardware. Save or advance the official result through the race view.
In a Drag Tournament, FC.Platform can arrange entrants by entry order, random order, or manual seeding and manages the elimination queue through the final. Follow the FC.Platform 2.0 User Guide for the full software workflow. A legacy FC.Drag-PRO without FC.Protocol cannot be assumed to work with FC.Platform 2.0; contact FC Slot-Cars if you are unsure about the firmware in your unit.
Troubleshooting
The system does not stage a car
Check that the car fully covers the intended start sensor. Verify that its cable and white connector are seated, the sensor is clean, and it received unobstructed light during startup. Restart with no hands or cars shading any sensor, then test one lane at a time.
A car reaches the finish but no ET appears
Check the corresponding finish sensor's location, cleanliness, illumination, and cable connection. Confirm that the car passes directly over it. Test both lanes separately to identify the affected sensor or cable.
The bracket or start seems different from the previous race
Check the bracket values during configuration before staging. Restarting or an automatic reset may return a FC.Protocol v1.3 device to a new bracket configuration with zero values. If using FC.Platform, set the desired bracket in the software for the current race.
A red light appears
The system detected a car leaving its start sensor before that lane's green light. Reset and make sure both cars are properly staged before the tree begins. If a red light occurs without a car moving, inspect lighting and the start sensor's position.
FC.Platform cannot communicate with the device
First disconnect the barrel supply and use USB only. Check the USB cable and Windows Device Manager. If the USB serial device has a yellow warning icon or no valid COM port, install the official WCH CH341SER.EXE Windows driver, reconnect the unit, and try FC.Platform again. Also confirm that the device has FC.Protocol firmware; the printed standalone manual alone does not establish software compatibility.
Frequently asked questions
Can I connect the barrel power supply and USB at the same time?
No. Never connect both inputs simultaneously. This PCB does not have protection for two power sources. Use one input only. For FC.Platform, disconnect barrel power and connect through USB.
Do I need FC.Platform to race?
No. FC.Drag-PRO can stage cars, run its starting sequence, measure RT and ET, indicate red lights, and show the winner as a standalone system.
How many sensors do I install?
Four: one start sensor and one finish sensor for each of the two lanes.
What does the bracket button change?
During standalone configuration, each press increases that lane's start delay by 50 ms. Leave both brackets at zero for the same start in both lanes.
Why does the system reset after a race?
It automatically prepares for another run approximately 20 seconds after the race. You may also press Restart to prepare a new run.
Will FC.Platform show the car's speed?
No. FC.Platform 2.0 shows the supported drag race results, including RT, ET, red light, and winner, but it does not read or display speed from FC.Drag-PRO.
Care, support, and further reading
Keep all four sensors clean and well illuminated, secure their cables under the track, and hold the solid connector when unplugging a sensor assembly. If you need help, email fc.slotcars@gmail.com with your purchase details, firmware version if known, track scale, photos of the sensor placement and power connections, and a short video of the issue.
Fernán Castillo
FC Slot-Cars