Re: [mowbot] Active borders.

Monta Elkins (monta nospam at
Tue, 25 May 1999 18:53:53 +0000

adamdb nospam at wrote:
> Having recently joined this list, I am sure this subject has been
> discussed before, but I wasn't around to hear it.
> Does anyone have any schematics or references for an "active border"
> system? (You know, kind of like the invisible dog fence, only for my
> mowbot). I am building my mowbot with the intention of using grass
> sensors to try and stay in the uncut grass, but just in case I would also
> like an active border so I don't mow down the wife's garden by accident.
> As I understand the concept, some kind of wire or wires are buried around
> the perimeter of the lawn, an AC signal is injected into the wire, and
> the mowbot has some form of sensor that will detect this signal. I would
> like to do this as cheaply and simply as possible.
> Any ideas?

Use a dog fence.
There are some cheap invisble dog fences that could be modified.
(less than $100 if memory serves).

I tried building one on my own but didn't have any luck.
Of course I'm not a "radio guy".

There are some folks who use ultra low frequency for long distance