×

Automatic control of the moisture content of the soil

  • US 4,194,691 A
  • Filed: 11/29/1978
  • Issued: 03/25/1980
  • Est. Priority Date: 11/11/1976
  • Status: Expired due to Term
First Claim
Patent Images

1. A moisture sensing control for a valve in a conduit by which the soil in an area is watered, said control including a pair of contacts to be inserted in the soil, first and second circuits, and input leads, one lead including a voltage divider, said voltage divider comprising a resistor string and a capacitor, leads of substantial length connecting said contacts to said one input lead across the capacitor, said string including first and second adjustable resistors, the first establishing a dry threshold and providing an input for the first circuit and the second establishing a wet threshold and an input for the second circuit, each circuit including a Schmitt trigger and means operable in response to the threshold that circuit monitors to deliver shaped pulses to the associated trigger, and a third circuit including means operable to effect the opening and closing of said valve and means connected to each trigger to respond to the output thereof, that of the first circuit trigger to effect valve opening and that of the second circuit trigger to effect valve closing.

View all claims
  • 0 Assignments
Timeline View
Assignment View
    ×
    ×