June 13, 2020

I have finally acquired enough parts to build at least 3 of these lap counters. Now I just need to build them, hopefully while taking photos/videos.


Originaly Designed by: Craig S. from I-Lap Timing Systems
For use with: PC Lap Counter software.

The WOS hardware and app for timing is horrible, incomplete, and useless; something else was needed. Virtual Raceways in listed the help of Craig from I-Lap Timing Systems to design and make a custom lap counting device SCX WOS.

This will help you modify your WOS base unit, so it may interact with PC Lapcounter, and intercept and manipulate the data going to and from the cars.

Craig made and sent me the units I have been using for events, so I have not yet made my own, so some of these instructions are a little incomplete. I have so far only re-organized his original instructions to fit this page, while trying to make them easier to follow.

Original Instructions: As Posted On SlotCarIllustrated Forum

Partially brought on by SCX dumping WOS for the new ADVANCE system right when he first released the instructions for this, Craig has become disinterested and frustrated with slotcars, and no longer wants anything to do with them, or making lap timing devices for them. So, please do not bug him about this project, he is no longer devoting any time to it. So... it is up to my lazy ass to continue it, thus the creation of this page.


The AliExpress links below are what Craig originally posted in his instructions. I am currently searcing for more up to date links using Amazon, etc.

Arduino "Blue Pill": This is the main CPU board that will do all the work between the WOS Base Unit and PC Lap Counter.
STM32F103C8T6 [Buy On AliExpress] [Buy On Amazon]

USB-Serial adapter:
This is used to allow the USB port to be placed anywhere. The on board USB has bugs, and is disabled in the current firmware.
CP2102 [Buy On AliExpress] [Buy On Amazon]

Chip programmer:
This is required to install the firmware onto the Arduino board. This is only done the first time the board is setup.
ST-LINK V2 [Buy On AliExpress] [Buy On Amazon]

433mhz Remote Control & Reciever:
This is required to control the device remotely. It was difficult to find the right items on Amazon, so you may have to do some extra searching.
2KT01 & RX480E-4 [Buy BOTH On AliExpress]

Mini 128X64 Pixel Display:
This shows the current speed setting for all 6 cars.
SSD1306 or UT-0206-P05 [Buy On AliExpress] [Buy On Amazon]

APA102 LED Strips:

[Buy On AliExpress] [Buy On Amazon]


This is Craig's image from his original instructions posted on the forums. Wires must be added to all ground pins (GND) and connected together. There are no lines drawn from or between the ground pins in this image; updated image soon.
[SCX WOS Base Unit Board]
[Arduino GND]
[LCD Display]
[LED Strip]
[USB Board]
[Remote Reciver Board]

... and 5 volts from the base. ?? I need to double check & update what I write for this.


All of the components and wires can be fit inside the base unit case, or under the start track, one way or another. It does not have to be done this way, this is just one way to do it. Do it however you can get the most use out of it.

You should plan this out before you start to avoid cutting wires too short.


You will need to find this poorly labeled resistor and unsolder it from the board. Then re-solder it back onto the board so only 1 side of it is connected to the board. This opens up this location and provides a place to add 2 wires.

It may be easier/safer to solder the resiter so it is sticking out from the board.


This is the connections for the track data intercept, the trickiest of all the soldering.

A wire must be attached or soldered to each A & B location shown on the previous schematic. The other end of wire A must be soldered on the solder joined exposed by removing the resistor. The other end of wire B must be soldered to the detached solder joint on the resister itself.


This is the connections to get the lap data.

A wire must be soldered to location C shown on the previous schematic. The other end of wire C must be soldered as shown in this photo.

A wire must be soldered to location GROUND shown in this photo. The other end of wire C must be soldered to the rest of the ground pins.

You must be carful to make sure each of these wires only make contact with one leg of the chip, and are not shorting out by touching any of the other chip legs.


This firmware file created by Craig is required.
[Download SCX_WOS_BP_1.0.bin from Craig's]
[Download SCX_WOS_BP_1.0.bin from]

This USB device is required to install the firmware:
[Buy On AliExpress] [Buy On Amazon]

This is connected to the arduino by the 4 supplied wires. The two yellow jumpers should be on the "0" side. Connect:
3.3V to 3.3V

This software is required to use the USB device: ST-Link .
[Download from]
[Download from]

1. Run ST-Link utility
2. Click "File" and "Open" the firmware file
3. Click "Target - Connect" (3rd Icon)
4. Wait a few seconds and it should show it is connected
5. Click "Target - Program & Verify" (6th Icon)


If the status window displays the following, then the firmware has been installed correctly.

12:04:40 : [SCX_WOS_BP_1.0.bin] opened successfully.
12:04:40 : [SCX_WOS_BP_1.0.bin] checksum : 0x0030F68B
12:04:52 : ST-LINK SN : 48FF73066578555548392067
12:04:52 : ST-LINK Firmware version : V2J29S7
12:04:52 : Connected via SWD.
12:04:52 : SWD Frequency = 4,0 MHz.
12:04:52 : Connection mode : Normal.
12:04:52 : Debug in Low Power mode enabled.
12:04:52 : Device ID:0x410
12:04:52 : Device flash Size : 64KBytes
12:04:52 : Device family :STM32F10xx Medium-density
12:05:30 : Memory programmed in 5s and 601ms.
12:05:30 : Verification...OK
12:05:30 : Programmed memory Checksum: 0x0030F68B


Pressing button A, will start a new race. Pressing button A while a race is running will pause the current race. Pressing button A while a race is paused will resume the current race.

Pressing button B, will cancel the current race.

BUTTONS C & D (+-)
The system will default to speed step #13 when powered on. The current speed step will be displayedon the small LCD screen. Pressing button C, will increase the speed of all 6 cars by 1 step. This can be increased up to step #24, any further and it will reset to step #0. Pressing button D, will decrease the speed of all 6 cars by 1 step. This can be decreased to step #0, any further and it will jump to speed #24. This is ideal for kids that do not understand that going slower in corners is faster then flying off the track in every corner. This adjusts ALL 6 cars at the same time, not individually.


Craig had the current firmware setup to out put to APA102 RGB LED light strips to create a starting light, as well as a fuel gauge for each car that is generated bythe PC Lap Counter software.

These fuel gauges have nothing to do with the fuel counter in the WOS BASE Unit or the WOS hand control LEDs. It is possible to use either fuel gauge, or even both. However, using any the WOS base unit features means having to setup the WOS base unit in infinate lap race mode.

My units that I use, were made before the LED option were added, so this is a feature I have yet to use. So... I cannot offer any more info until I get around to trying the LEDs myself...

"LED STRIP" and "CLK" are shown on the schematic, add a 3rd wire from the "GRND", and you should have the 3 wires needed to hook up most RGB LED strips...

I do not recal if it was decided to stop the car, sputter the car, or slow it down, flash the lights, stop counting laps, or do nothing when out of fuel.


At the start of a race cars will not move, until the race starts. This is a feature to keep kids from jumping the start at events, or just going while the cars are being setup on the track.

When the race is completed, the very next time each car crosses the finish line, it will stop a few track sections after the line, provided the driver is still giving it throttle input. The cars will remain stopped, until the next race starts.

!!! If you think something is broken while testing cars, make sure a race is running, or the car will not go. I do this alot when distracted at events.

I believe Craig added a way to toggle this on and off.


The screen appearance of PC Lap Counter can be customized within PC Lap Counter. The default setup is a very messy, over populated, and boring gray windows table. This photo is how I customized my own, so it is simple and to the point.

I still need to pull the file off of the lap counter computer and share it online.


After I test verify the parts I find actually work, I will bundle parts together and sell them as a D.I.Y kit.

Arduino + Programmer + BlueTooth Module + Remote Control + Reciever + LCD Display

LED Upgrade for D.I.Y. KIT
LED Light Strip for making star lights and fuel gauges.

New WOS Base Unit
Taken from new WOS set. Firmware upgraded to latest version.


Craig wanted this to be an open source conversion that people can do themselves. He is too busy and is not interested in making these, so please do not ask him.

I currently have a few extra, New WOS Base Units, that I intend to eventually convert and sell on ebay, and this website. However, I will not sell any until I have them made, and that will require me to get off my lazy butt and actually see if my soldering skills are still up to the task.

When I get a few made, I will update this so it is a purchase button through PayPal.

Without LED Upgrade:

With LED Upgrade

This device does NOT currently work with SCX Advance. However... The WOS base unit can be used as a dumb power base for an SCX Advance track. When an advance car runs over the track sensors of a modified WOS+PCLC base unit, it does detect a reading from the car's IR sensor, however it is very distorted and it confuses the heck out of the modified PCLC device, due to the car sending a different IR data packet.

It is my hope that the firmware of the PCLC device can be updated to understand the IR packets sent from the ADVANCE cars. If this can be done, this could work with advanced cars, and there might even be a slim chance it may even work with advance and wos cars at the same time. However, any feature that relies on the data signal in the WOS track would be lost with Advance cars. Access to an Advance car's speed and headlights would be impossible through this pclc device. So car's will not stop at the end of a race, or stop, slow down, or sputter when out of fuel. The only thing that WILL work, is the sensor for detecting a complete lap, and pit entry/exit, which in a way are the most important.

As previously mentioned in the beginning of this page, Craig is not working on this project any further, and I do not understand enough of this to be able to update the firmware, so it may not happen... Unless someone else steps in, or I learn more about this.