Repost: Robotic Lawn Mowere

Hello
I was looking for a simple low cost robotic lawn mover.
Now I decide to design and build my one...
A 3Ah 14.4 V Roomba battery, 4 wheels 4 motors, the cut motor, 15
photovoltaic battery in such a way it could work without charging when sun
shine (hope it will be enough for the whole year)
The brain is based on 3 relay and a timer system: 2 front mechanical
sensors: if left one, backward on the right way for 5s, if right one,
backward on the left way for 7s, every 2mn, bacward right.
I experiment this very simple and stupid algoritm with my home designed
vacuum robotic: very efficient. (and easy to program!)
I think robot can be full charged in about 5 days in summer for a 3h cut:
that means lawn is cut every 5 or 6 days in summer, perhaps every 2 weeks in
winter.
I can charge it through mains if necessary... (hope not)
I am looking for an idea to prevent to cut wet grass.
Another problem: I must check that robot doesn't rest in the tree shadow...
Any comments, suggestions, web site, video, pictures... welcome...

--
hpspt

There are robotics dissussion groups on Yahoo, which are focused on
robotic lawn mowers.  They tend to discuss the commercially sold ones,
but I've seen some discussion about making your own.  That may be a
better place to talk.

Joe Dunfee