Actually, an even better desing would be to sense the moisture in the soil.  If
it rained a lot last night, you shouldn't need to rain all day, and maybe even
the next.  It will also tell your system when you need to water more than usual,
and less than usual

I know you can get a pretty accurate reading by simply sticking two probes in
the soil, and measuring the resistance between them.

-Adam

John Waters wrote:
>
> Hi All,
>
> I have built an automated lawn spraying system for my backyard. A PC is used
> to turn ON and OFF the water valve periodically according to a preset
> schedule. The problem now is, it may sometimes be raining during, or shortly
> before the spray time, which would simply waste water. Is there any
> commerically available rainfall detector that could be interface to my PC? I
> want to use it to stop unnecessary spraying. Or, I could build my own
> circuit for doing this, does anyone get such a circuit?
>
> Thanks in advance
>
> John
>
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