Automatic soil watering system

Claim 2

In an irrigation control system, the combination comprising: first and second sensors located underground at different levels and each having an electrical current controlling resistance characterized as changing in response to a change in the rate of heat loss from the sensor induced by a change in the moisture content of the underground formation adjacent the sensor; and means for effecting electrical current flow to be controlled by changes in said resistance and responsive to a change in such current for controlling an irrigation water valve, said means including a valve controlling actuator, a first relay connected with the first sensor and in controlling relation with the actuator to operate the actuator to open the valve in response to a decrease in said current flow corresponding to relative drying of said formation adjacent the first sensor, and a second relay connected with the second sensor and in controlling relation with the actuator to operate the actuator to open the valve in response to a decrease in second sensor current flow corresponding to relative drying of said formation adjacent the second sensor.

Claim 3

The combination of claim 1 wherein the first and second sensors are located underground at lower and upper levels, respectively.

Claim 4

The combination of claim 1 wherein the first and second relays have contact interconnections characterized in that a single source of power is connectable with said relays to be controllably connected with said actuator in response to operation of either relay.

Claim 5

The combination of claim 3 including a power line connected with one relay arm, said one relay having a pair of contacts, one of which is connected with the actuator and the other of which is connected to the arm of the other relay, said other relay having a pair of contacts, one of which is connected with the actuator.

Claim 6

The combination of claim 4 in which said actuator comprises a solenoid with a plunger having valve open and closed positions, said one contact of said one relay and said one contact of said other relay being connected with the solenoid electrical winding to pass current for energizing the solenoid to move the plunger to valve open position.

Claim 7

The combination of claim 3 wherein said means comprises said single source of power in the form of a transformer winding which is also electrically connected with said sensors.

Claim 8

The combination of claim 3 includes said single source of power in the form of a transformer winding, and said means includes another transformer winding electrically connected with said sensors which are in electrical parallel relation.

Claim 9

The combination of claim 3 including another pair of sensors, another pair of relays and another actuator as defined in claim 3, the two pairs of relays having electrical interconnection whereby said single source of power is operable to energize either actuator to valve open position via said relays.

Claim 10

The combination of claim 8 including a timer electrically connected to control electrical power application from said source to all of said relays.

Claim 11

The combination of claim 1 including another pair of sensors, another pair of relays and another actuator as defined in claim 6, and including said single source of power across which said pairs of sensors are connected in parallel.

Claim 12

The combination as defined in claim 1 wherein said means includes a battery power source.

Claim 13

In an irrigation control system, the combination comprising: first and sEcond sensors located underground and each having an electrical current controlling resistance characterized as changing in response to a change in the rate of heat loss from the sensor induced by a change in the moisture content of the underground formation adjacent the sensor; and means for effecting electrical current flow to be controlled by changes in said resistance and responsive to a change in such current for controlling an irrigation water valve, said means including a valve controlling actuator, a first relay connected with the sensor and in controlling relation with the actuator to operate the actuator to open the valve in response to a decrease in said current flow corresponding to relative drying of said formation adjacent the first sensor, a second relay connected with the second sensor and in controlling relation with the actuator to operate the actuator to open the valve in response to a decrease in second sensor current flow corresponding to relative drying of the formation adjacent the second sensor, and there being resistance electrically connected with the sensors such that second sensor current required to operate the second relay is different from the first sensor current required to operate the first relay and by a predetermined factor.

Claim 14

In an irrigation control system, the combination comprising: first and sEcond sensors located underground and each having an electrical current controlling resistance characterized as changing in response to a change in the rate of heat loss from the sensor induced by a change in the moisture content of the underground formation adjacent the sensor; and means for effecting electrical current flow to be controlled by changes in said resistance and responsive to a change in such current for controlling an irrigation water valve, said means including a valve controlling actuator, a first relay connected with the sensor and in controlling relation with the actuator to operate the actuator to open the valve in response to a decrease in said current flow corresponding to relative drying of said formation adjacent the first sensor, a second relay connected with the second sensor and in controlling relation with the actuator to operate the actuator to open the valve in response to a decrease in second sensor current flow corresponding to relative drying of the formation adjacent the second sensor, and there being resistance electrically connected with the sensors such that second sensor current required to operate the second relay is different from the first sensor current required to operate the first relay and by a predetermined factor.