[mowbot] Back on track

Dave Everett (deverett nospam at idx.com.au)
Fri, 24 Apr 1998 13:51:59 +1000

Hello Everyone,

I've been pretty slack with my mowbot development. I've been waiting for
some parts and I've used that as an excuse to bludge.

I've also been developing a vision system that is showing very promising
results, and I have considered using it on the robot if the ambient IR
energy doesn't interfere with the system.

Last year I was looking for a decent bumper system to use on the perimeter
of 'Grassy' and decided to build a membrane type switching system. This has
the advantage that I can pack many more sensor points per square cm, and
the switches remain essentially sealed.

What I've done is bend a 3cm aluminium strip around the robot, that makes
the common for the switching system. At the top and bottom of the aluminium
I have places 1cm wide plastic that is double sided to the strip, the
plastic running all the way around the strip. Then I have 281 3.5cm strips
of 0.5mm wide nickel-silver spaced at 7mm intervals running vertically.
Over the whole thing is a spongy foam strip. I have yet to find a suitable
final strip that needs to be 1cm or less wide, and attached around the

Each strip can be wired to others nearby to make switching regions, and
because of the narrowness of the Nickel-silver strips, I can go around
rounded corners easily.

By now you're probably imagining millions of dollars spent and a large
engineering team to make it work ;-) Actually it is so bloody simple, It
would have been much harder to implement with normal switches and not as

This all makes much more sense in pictures, I will be updating the page in
a few days time with the whole story, I'll let you all know when it's done.

The bumper switches are quite sensitive and will allow the robot to stop
before pushing too hard into an obstacle.

This will allow me to complete the first phase of Grassy, making him
operational within a hard-bounded area.

I hope to hear how everyones personal projects are progressing.

Dave Everett.