EditDigital Slot Car Racing
Digital control for racing with slot cars.
EditDigital Control
In brief, the Scalextric protocol leverages a square-wave 12v p-p high current signal driven onto the track. The signal is balanced, such that each 'side' of the lane is driven in opposite voltage, allowing the car to rectify this waveform and recover (with some small losses) a DC voltage for the motor.
Inside the car is mounted a small decoder which recovers the control signal, interprets it, and drives the power back to the motor. Motor speed and braking is controlled via the decoder - unlike analog where the speed is directly controlled within the hand controller.
Full details on the control signal provided by the controller are discussed on
Scalextric Digital Control page. This also provides a link to circuit diagram and PIC18 programming code to create your own 6 car power base.
EditInCar Chip
The In Car 'Chip' is a small decoder which recovers the control signal, interprets it, and drives the power to the motor. Motor speed is PWM (Pulse Width Modulated) and braking is controlled via shorting out the motor. The Car ID is constantly supplied through the infrared LED mounted on the base of the car. The chip also provides brake-light control which comes on when the brakes are applied, and also what appears to be Head Lights control, however no way has been discovered to contol this.
The circuit diagram for the Scalextric 'chip' is below:
 In Car 'Chip' - Rev E - Click to download |
EditCar Detection
Beneath the car is mounted a small Infra-Red LED which constantly pulses the car's ID downwards onto the track. Detectors mounted under the slot pick up the signal, and can decode which car is passing over them. The same signal carries detail on whether a car should change lanes or not, and when detected by a special lane-change track-piece, a physical 'flipper' will cause the car to move from one lane to another.
The car detection is also used for lap counting, as simple car-pass detection methods from analogue racing cannot be used as more than one car can be driving in the same lane.
Full details on the decoding of a car's ID are provided on the
Scalextric Car Decoding page. This includes circuit diagrams and PIC12 programming code to decode and deliver the car ID.
For those who wish to review the detector circuit, and the micro-controller code, move straight to
SSD Decoder page.
EditPowerbase 6 Repair
The six-car powerbase (PB6) is somewhat underdesigned, with an output driver stage which does not efficiently power the final transistors. This caused those driver transisitors to become overheated under heavy load, and then prone to failure should a short-circuit occur.
Repairing a blown powerbase when the one of more output drivers have failed, is not a tricky task. However replacing the MOSFETs with the same part and returning to the same environment can only mean another failure. This repair up-rates the MOSFETs with common components, extending the headroom for the powerbase.
See the
PB6 repair page for step-by-step instructions to repair a blown PB6 (v1.5 design)
EditPro Upgrades - PB-Pro and PitPro
A group of enthusiasts have invested significant time and energy to up-rate the Scalextric core components with more power and better facilities. The Pro range of tools take the Scalextric experience away from toy level, into something that serious slotters can race, and the not so serious can really enjoy.
ElectricImages has the facilities to upgrade your equipment to the Pro tools, so you can really extend and enjoy your slot-car experience without the headaches of the limits imposed upon Scalextric by the toy industry legislators.
See the
Pro Upgrade page for details on what these are, and how to buy.
History and Background
Scalextric is a brand of Slot Car manufactured by Hornby, a British company. See
WikipediaLong considered the original designers of 1/32 scale slot racers, they recently (well, 2004 to be exact) entered the market with a Digital offering called Sport Digital. Technologically, it was based upon the model train digital protocol, DCC, and allowed up to 6 cars to travel in the same slot.
The real draw of Digital car racing is the ability to change lanes, and run more than one individually controlled car on a single lane.
While the electrical system is based on DCC, Scalextric has created their own unique version of this protocol, by adding on facilities such as car ID detection and lane change control. Lane change and manual brakes can be triggered from the handheld throttle controller controlling the car.
Ian Harding, Christchurch, New Zealand