poriet:
Thanks for that. So, it could operate in a number of ways.
Our garden is so higgley-piggledy I cant see either method working very well.
At present we have a low-tech method of automatically cutting the lawn:
two rabbits and two guinea-pigs.Bruce
Use a shovel to make a slit in the dirt and bury a couple meters of wire a few inches down. Pulse DC through the wire (makes a changing field as opposed to a static field, say 10 to 100 short pulses per second) and see if you can detect it with a Hall sensor.
If you can get it to work then use 3 sensors to make a line-follower robot, the robot follows the path laid out. Only THEN should you think about whirling cutting blades and more sensors to stop for objects/animals.