On 18/04/20 21:41, larkim wrote:
Recently got a dose of laziness and bought a robot mower. Works really nicely

One thing I haven't got clear in my head is how it knows whether it is inside or outside of the charged boundary wiring.

I can power down the whole system, move the robot to just outside the boundary loop, and when it is all powered back up it instantly detected as being outside the wire.

Anyone know how this works? What goes down the low voltage cable that is the boundary wire to allow the robot unit to detect where it is in relation to being inside or outside?

Have a look at the article he
https://www.ardumower.de/index.php/en/induktion

In particular, see the section "Sender/receiver principle using polarity
change ("Perimeter v2")" which appears about two thirds of the way down.
Quote:
"While crossing the perimeter loop, something interesting happens:
signal changes polarity, that means negative and positive voltages
reverse each other. By using this principle, crossing the perimeter wire
will be detected. The robot knows its current perimeter state all the
time (inside/outside)."

I'm not sure if crossing the wire is the detection for inside/outside,
or simply being outside is different from being inside - it's a bit
ambiguous. To my way of reading it, however, it tends towards always
knowing where it is, whether it actually crosses the wire or not.

--

Jeff