Computer Driven Slot Cars

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Could a computer drive a slot car faster than you can?   Would you like to be able to race against another car even before anybody else has turned up for a club night?  Would slot racing at an exhibition be spiced up by letting the public race against a car under computer control?

There are some intriguing possibilities for the new system being produced by Jim Delaney.  Many thanks to Jim for demonstrating his prototype system.

What does it do?

It drives a slot car round a track automatically.  There's also an audio - visual countdown, sound effects etc. on the computer.

Think about how you drive a slot car -  the car arrives at the braking point for a corner and move the controller trigger up and down appropriately. The computer uses sensors under the track to know exactly when the car arrived at the braking point for a corner and electronically turns the power up and down appropriately. 

Right now the system is programmed by entering numbers on a computer screen.  The next planned development is a hand controller connected to the computer so that you can drive the car and the system can learn from your fastest lap and reproduce it every time.

How does it do it

Jim's  system for driving the car is a custom made box containing its own electronics to drive the car. (For those whom understand these things, its a Z80 microprocessor).  This is fed with the numbers which tell it when to do what from any suitable PC down a USB connection.  The PC also provides the audio - visual presentation that sits along side it. 

The sensor is placed under the track use reed switches which detect the magnetic field from the car. It was designed to work with magnet traction cars. Cars not designed for magnet traction are not likely to produce a large enough magnetic field to operate the sensors, but this can be overcome by adding a suitable magnet adding to the chassis.

Jim's system is primarily intended to work with magnet traction cars on proprietary plastic track.  We were keen to see how it would work on a club track, so Jim traveled to Bournemouth to test his system on a scratch built track.  The Bournemouth  track  is built from 15mm thick MDF, with the slot routed slot and copper braid pick up - pretty similar construction to most club and raceway tracks.   The sensors were developed to be slipped under the side of proprietary plastic track where they would sit about 5 mm under the track surface. Obviously the detector could only detect the magnet when it was relatively close to the magnetic field from the car.  We used Jim's standard detectors taped to the underside of Bournemouth's MDF surface. Even though it was working around 3 times further below the track surface than originally intended, the system had no problem detecting a magnet traction car.  

Encouraged by this, we did a quick try with something  faster - a 1/32 production car.  These are intended for tracks where magnet traction wouldn't work anyway, so they don't provide a magnetic field for the detector. A motor magnet on top of the chassis didn't provide quite enough magnetic field to operate the detector every time.  Motor magnets are curved to fit round an armature, I guess this is far from the ideal shape for producing a magnetic field 15mm below the track surface.  We'd already found that magnet intended for magnet traction worked fine, - with another test day and the right maagnets there's every chance this would work.

Jim's system provides the track power for the cars - clearly more than adequate for proprietary hard bodied cars, and Falcons.  The potential is there to upgrade it for more powerful motors should the need arise.

A test drive

The system connected to the Bournemouth track.  

An example of the printed circuit board at the heart of Jim's system.

For the Bournemouth track 7 position sensors were needed. The prototype system is built for up to 32 sensors, giving the potential for a very complicated track indeed!  Each sensor required a pair of wire to the main control box.  Having connected up Jim's system and to the track it was time to try a car.  This required a set of numbers to be entered on the computer.  Jim experience gave a good starting point, and a bit of careful observation plus a slice of trail an error got the magnet traction car running round at a decent speed.  Obviously it was no fault of the system that the magnet traction car was not picking up consistently, there was clearly a bit more speed to come with fine adjustment of the system settings once this was sorted..

The prototype system follows the practice of many home sets in not having dynamic braking.  This meant braking quite early on Bournemouth's  long straight to get round the moderately tight corner at the end.   At this stage in the system's development, a skilled human driver can lap the car on this sort of track faster than the system.  A fully developed system clearly has the potential to drive the car faster than this prototype - could that mean even faster than a skilled human driver?  Quite possibly - it'll be fascinating to find out.