Installing the Perimeter Wire for your Automatic Robotic Lawnmower

One of the trickiest tasks when you first install your automatic robotic lawnmower is getting the perimeter wire right.In fact, there are usually two wires:

• perimeter wire round the outside (stops the robot leaving the lawn)
• guide wire (helps the robot get back to the charging base)

We'll deal with the guide wire in a later article, for now let's look at the perimeter wire. The easiest example is a rectangular lawn.

Placing the Perimeter Wire Around a Rectangular Lawn

Many lawns are basically rectangular - even our lawn, which has two zones (front and back) and an 'upper back' lawn, some swings, raised flower beds and a patio, is essentially rectangular.

The only concerns are:

• having enough wire
• what to do about corners

The first is easy enough - just measure the perimeter, and buy more wire if necessary! The second needs some explanation. The picture on the left shows my initial installation attempt, next to the patio.

Incorrect Perimeter Wire Placement

The blue line shows the wire, and you can assume that the area to the left and below the picture are out of bounds for the mower.

The red line shows the path that the mower consistently took. The result was that it would keep stopping with an "Outside mowing area" error!

In the manual, the instructions were quite clear to avoid sharp corners, but somehow I ignored this advice.

Clearly, you do need to follow it, so I adjusted the wire to look like the picture below.

Now, the robot doesn't exit the mowing area, and all is well. Of course, I had to buy extra clips because it's a more complex shape, but Husqvarna sells them in packs of 100, so although it was an extra expense, it wasn't insurmountable.

Correct Perimeter Wire Placement

Plus, it was cheaper than replacing the blades which were grinding themselves on the coping that runs around the edge of the lawn!

Another point to watch when laying the perimeter wire is the distance between the wire and the edge of the lawn.

The temptation is to get as close as possible to the edge, to avoid having to use a strimmer or edge cutter, but it's a false economy, as the robot needs space to turn, and not leaving enough space means that it will also exit the mowing area.

For those who have a raised edge, and are using that to limit the robot, that's fine, but it does cause wear and tear to the bumper.

Of course, if you are lucky enough to have a robot mower that uses ultrasound, that doesn't apply!

The Perimeter Wire and Obstacles

It is also possible to branch the perimeter wire out, and use it to go around an obstacle in the lawn (such as a valuable bush, or tree). The only thing to watch is that the wire is kept close to itself when it is doubled back (to return to the perimeter) so that the robot ignores it. Otherwise, it can get stuck in an area bounded by the outgoing wire, and the edge of the mowing area.

My preference was to build a small wall around things like shrubs and trees, because:

• it would take a lot of wire to go round every obstacle
• it increases the risk of problems with the wire breaking.

Again, following the instructions is paramount!

Setting Up The Perimeter Wire with Multiple Zones

Our lawn is essentially split into three parts, two are connected by a passageway, but the other is at the front of the house and not reachable by the robot mower automatically. We carry it between the back and front zones, manually!

The front zone is created by a perimeter wire that is taken off the main charging station, and runs completely around the lawn, bounding it.

At the back, the perimeter wire runs around the edge of the first zone, and then along the edge of the passageway, around the second zone, and back to the charging station.

The gap between the wires at the closest point of the passageway is less than a meter; this isn't ideal, as the robot sometimes doesn't quite make it through (in either direction) and therefore:

• gets stuck in the second zone, or
• never mows the second zone!

I'm still looking for the best solution for this, but I suspect I'll end up widening the passageway. I'll keep you posted...