Abstract: A micro-switch is mounted within a housing and is electrically connectable to an irrigation controller. The switch has a spring biased actuating lever pivotable between ON and OFF positions. A single disc made of a hygroscopic material is mounted within the housing adjacent the inner end of the lever for absorbing rainfall and rapidly expanding a sufficient amount to move the actuating lever from its ON position to its OFF position to thereby cause the watering program of the irrigation controller to be interrupted. A stack of moisture absorptive discs made of the same hygroscopic material is mounted in the housing adjacent an outer end of the lever. When the stack of discs receives rainfall it slowly expands and maintains the actuating lever in its OFF position after the single hygroscopic disc has dried and contracted to ensure that watering is not re-initiated too soon after a storm.

Abstract: A micro-switch is mounted within a housing and is electrically connectable to an irrigation controller. The switch has a spring biased actuating lever pivotable between ON and OFF positions. A single disc made of a hygroscopic material is mounted within the housing adjacent the inner end of the lever for absorbing rainfall and rapidly expanding a sufficient amount to move the actuating lever from its ON position to its OFF position to thereby cause the watering program of the irrigation controller to be interrupted. A stack of moisture absorptive discs made of the same hygroscopic material is mounted in the housing adjacent an outer end of the lever. When the stack of discs receives rainfall it slowly expands and maintains the actuating lever in its OFF position after the single hygroscopic disc has dried and contracted to ensure that watering is not re-initiated too soon after a storm.