Digital Slot Car Racing
Digital control for racing with slot cars.
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.
History and Background
Scalextric is a brand of Slot Car manufactured by Hornby, a British company. See Wikipedia
Long 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