I want to make vehicles crawl around a LEGO town following a path I define -- but in some invisible way, so the onlookers can't see how it works. What are my options? Here are some I've thought of, but perhaps you can think of something better:
- Put strong magnets under the road, every few cm, maybe closer together on the curves. Magnetic sensors of some sort (maybe just reed switches would do?) in the car would use this to steer, much like a traditional optical line-follower. Problems: the road can be almost a cm thick itself, which would necessitate the use of strong (and therefore expensive) magnets.
- Put cheap iron bars or balls (or whatever) under the road, and a strong magnet on a swivel in the car. The magnet should point at the nearest iron, and we can detect that (maybe by bouncing an LED off it) and use it to steer. I'm not sure if this would work reliably.
- Er... getting short on ideas here, but if we could embed some sort of navigation beacons in the town layout, then in principle you could make the cars "programmable" by manually pushing them once around the path you want them to follow, and they should be able to repeat that path again and again. But I'm not sure what sort of navigation beacons would be appropriate -- remember, neither the car nor the town is supposed to have any visible gadgetry; it's supposed to look like the minifigs are just driving their cars.
- Really scraping the barrel, could we do some sort of optical line-follower but not in the visible light range? Something we could use to paint a line on the road that would be invisible to humans, but visible to the car's sensors?
Any insight on the above ideas, or new ideas I haven't considered?
Many thanks,
- Joe