Low-voltage sprinkler control system

• US 3,195,816 A
• Filed: 03/13/1962
• Issued: 07/20/1965
• Est. Priority Date: 03/13/1962
• Status: Expired due to Term

• Current Assignee: Richard H. Mercer
• Original Assignee: Richard H. Mercer
• Inventors: Mercer, Richard H.
• Application Number:
  US04/179,349
• Time in Patent Office: 1,225 Days
• US Class Current: 239/63
• CPC Class Codes: A01G 25/167 Control by humidity of the soil itself or of devices simulating soil or of the atmosphere; Soil humidity sensors
• CPC Class Codes: G01N 27/048 for determining moisture content of the material
• CPC Class Codes: G05D 22/02 characterised by the use of electric means
• CPC Class Codes: Y10T 137/189 Soil moisture sensing

Claims

2. FOR USE IN CONTROLLING THE MOISTURE CONTENT OF SOIL BY AUTOMATIC OPERATION OF A SPRINKLING SYSTEM WHEN SAID MOISTURE CONTENT FALLS BELOW A PREDETERMINED VALUE, A PAIR OF NONPOLARIZABLE ELECTRODES ADAPTED TO BE BURIED AT SPACED-APART LOCATIONS IN THE SOIL, A SOURCE OF ALTERNATING CURRENT NOT EXCEEDING ABOUT 7 VOLTS CONNECTED ACROSS SAID ELECTRODES, A CURRENT- AND POTENTIAL-LIMITING RESISTOR IN SIERES WITH SAID ELECTRODES AND SAID SOURCE TO PREVENT THE POTENTIAL ACROSS SAID ELECTRODES EXCEEDING ABOUT2 VOLTS A.C., A POTENTIAL-SENSING BRIDGE CIRCUIT HAVING ITS INPUT TERMINALS CONNECTED DIRECTLY ACROSS AND IN PARELLEL WITH SAID ELECTRODES, THE ARMS OF SAID BRIDGE CIRCUIT COMPRISING CONDENSER MEANS AND RECTIFIER MEANS CONNECTED TOGETHER TO CONVERT SAID A.C. CURRENT FLOW BETWEEN SAID ELECTRODES TO AN AMPLIFIED DIRECT-CURRENT VALUE AT THE OUTPUT TERMINALS OF SAID BRIDGE CIRCUIT, AND AN INDEPENDENT POWER CIRCUIT FOR SUPPLYING AN OIPERATING POTENTIAL TO SOLENOID VALVE MEANS FOR CONTROL OF A SPRINKLER SYSTEM OPERATIVE OVER THE AREA WHERE SAID ELECTRODES ARE BURIED, SAID POWER CIRCUIT INCLUDING A TRANSISTOR, THE CONTROL TERMINALS OF SAID TRANSISTOR BEING CONNECTED TO SAID OUTPUT TERMINALS OF SAID BRIDGE CIRCUIT SO THAT SAID TRANSISTOR AND SAID PAIR OF ELECTRODES ARE MUTUALLY ISOLATED FROM EACH OTHER BY SAID BRIDGE CIRCUIT AND THE POWER TERMINALS OF SAID TRANSISTOR BEING CONNECTED IN SERIES CIRCUIT WITH SAID POWER CIRCUIT.