You can’t build a line follower without a test track to run it on. The proposed UK rules for this competition specify the track to be on a 300mm grid with fixed turn radii of 150mm. Well, I don’t have room for that and I don’t want to make tiles either so a little lateral thinking is called for…
What I do have room for is a sheet of MDF measuring 1220mm by 610mm. This is a standard size and should cost only a few pounds from the local DIY store. I bought a piece 6mm thick. It will be less stable than it might be and will curve towards the painted side but it is light and will do for my purposes. If the board were divided into six tiles, I could only make the simplest of tracks. However, one of the most important parts of the rules is the specification of the turn radius at 150mm. My line follower is quite small at 100mm wide and, unlike some of the South East Asian followers would be happy to run on tracks with only 60mm or so clearance to either side. After a bit of doodling, I decided I could fit this track into my piece of MDF:
View the PDF here. All the turn radii are 150mm and the length of the straights is whatever will fit. I am not using the turn markers and there is no odometry on the robot. A space of 100mm around the edge should be plenty one (if) I get it under control.
Ordinary matt black emulsion is used as the background of the track. This does not cover too well and MDF is pretty absorbent so three coats were needed and the surface has raised from the moisture. This pant will not be very durable but it is cheap and easy to use. The brushes wash out under warm water without any need for detergents and there are no noxious fumes. Proper blackboard paint would have been better but is quite unpleasant to use.
The centres of the turns and ends of the straights are marked out in pencil. An ordinary pair of compasses with a pencil in them can be used to mark out the turns at the 150mm radius. Lay down some 19mm white PVC electrical tape along the straights, taking care to place it centrally on the pencilled lines. Now you can take the compasses and set them to draw the inside edge of the turns. This will give you an edge to lay the tape against. Only the inside edge is needed.
Lay the tape by stretching it off the roll, smoothing down as you go. It should be quite easy to make it follow the turn. The whole job took about 20 minutes. Take your time and get it right as lifting the tape may well damage the paint surface. Once finished, mine looked like this: