Method and apparatus for optimizing soil moisture

• US 20050194461A1
• Filed: 02/10/2005
• Published: 09/08/2005
• Est. Priority Date: 02/11/2004
• Status: Active Grant

• Current Assignee: Toro Company (Toro)
• Original Assignee: Toro Company (Toro)
• Inventors: Zimmerman, James, Hopkins, Larry Kent, Hawkes, Larry, Goldberg, Allan Morris
• Granted Patent: US 7,133,749 B2
• Time in Patent Office: 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: B05B 12/12 responsive to conditions of ambient medium or target, e.g. humidity, temperature position or movement of the target relative to the spray apparatus B05B12/082, B05B12/084 take precedence
• CPC Class Codes: Y10T 137/1866 For controlling soil irrigation
• CPC Class Codes: Y10T 137/189 Soil moisture sensing

Abstract

A self-adjusting irrigation controller takes a pre-irrigation soil moisture reading prior to irrigation, chooses an amount of water to be dispensed corresponding to that reading from a table, and dispenses that amount of water. A predetermined length of time after the end of irrigation, the controller takes a post-irrigation soil moisture reading and compares the value of that reading to a predetermined target value. If the post-irrigation value differs substantially from the target value, the water amount corresponding to the pre-irrigation value in the table is adjusted to reduce that difference on the next scheduled irrigation cycle having that same pre-irrigation soil moisture reading. The target value is determined by watering the soil to field capacity, then computing the target value as a function of the reading of the sensor at field capacity. The controller thus converges toward an ideal runtime and follows changes in the environment. In the preferred embodiment, the soil moisture is indicated by sensor voltages, and the amount of water dispensed is governed by the runtime of the irrigation system.

Claims

1. A method of automatically adjusting, for optimum watering, the water delivery parameters of an irrigation system that waters at least one watering zone of a soil on a selectable watering cycle schedule, comprising the steps of:

a) sensing moisture levels of said soil in said zone and producing a signal having values representative of said moisture levels;

b) establishing a target value of said signal representative of an optimal moisture level;

c) providing a set of values of said signal that correlate with amounts of water delivered by said irrigation system;

d) causing said irrigation system to deliver an amount of water corresponding to the pre-irrigation value of said signal present at the start of a watering cycle;

e) comparing the post-irrigation value of said signal at a selected time after the end of said watering cycle to said target value; and

f) modifying the correlation of said set of values with said amounts of water delivered in accordance with any significant difference between said post-irrigation value and said target value.

2. The method of claim 1, in which said modifying step involves changing the runtime of said irrigation system corresponding to at least one range of said values of said signal.

3. The method of claim 2, in which a change in the runtime corresponding to one value of said set also causes a change in runtimes corresponding to adjacent values of said set such as to prevent inconsistencies in the runtimes corresponding to said set.

4. The method of claim 1, in which said selected time is a time sufficient for the irrigation water to percolate the soil and substantially equilibrate therein.

5. The method of claim 4, in which said selected time is about 2 hours.

6. The method of claim 1, in which said signal values for an optical moisture sensor are in volts, and said significant difference is about 0.01 to 0.2 volts.

7. The method of claim 1, in which said modification step involves changing by a predetermined amount the runtime related to said pre-irrigation signal value if said difference exceeds a predetermined threshold.

8. The method of claim 7, in which said runtime is expressed in integers of time intervals.

9. The method of claim 8, in which said time intervals are minutes.

10. The method of claim 7, in which said time intervals are seconds.

11. The method of claim 1, in which said modification step involves changing the runtime related to said pre-irrigation signal value by an amount substantially proportional to said difference if said difference exceeds a predetermined threshold.

12. The method of claim 1, in which said target value establishing step includes the substeps of:

i) prior to scheduled irrigation, running said irrigation system for predetermined lengths of time at predetermined intervals;

ii) measuring the moisture content of said soil at each of said intervals;

iii) determining the field capacity of said soil as being the moisture content at which the measured moisture content remains essentially constant from one interval to the next; and

iv) establishing said target signal value as a function of the signal value at field capacity.

13. A method of determining the field capacity of an irrigated soil, comprising the steps of:

a) repeatedly irrigating said soil for short periods of time at predetermined intervals;

b) measuring the moisture level of said soil at each of said intervals;

c) comparing successive measurements to each other; and

d) if said successive measurements indicate an increasing moisture level, determining said field capacity as being the moisture level at which successive measurements differ from each other by less than a predetermined threshold.

14. The method of claim 13, in which said periods of time are about three minutes, said predetermined intervals are about one hour, and said predetermined threshold is about 1% of full scale.

15. An irrigation system, comprising:

a) a plurality of zones to be irrigated, one of said zones being a master zone;

b) a moisture sensor positioned in said master zone and arranged to produce a signal representative of soil moisture in said master zone; and

c) a controller operatively connected to said moisture sensor and arranged to irrigate said master zone at selected times for a runtime determined by said signal; and

d) said controller being further arranged to irrigate the non-master zones of said system for a runtime equal to an individually selectable percentage of the master zone runtime.

16. An irrigation system, comprising:

a) at least one zone to be irrigated;

b) a moisture sensor positioned in each said zone and arranged to produce a signal value representative of the soil moisture level in said zone;

c) a controller operatively connected to said moisture sensor and arranged to irrigate each said zone at selected times for a runtime determined by said signal value; and

d) said controller having programmed therein runtimes corresponding to predetermined ranges of said signal values.

17. The system of claim 16, in which said controller is further arranged to

i) record a pre-irrigation signal value prior to starting irrigation,

ii) determine the runtime corresponding to the signal value range into which said pre-irrigation signal value falls;

iii) irrigate said zone for the runtime so determined;

iv) record a post-irrigation signal value at a sufficient time after said runtime for the soil moisture in said zone to stabilize; and

v) if said post-irrigation signal value is significantly different from a precalculated target signal value, reprogram the runtime corresponding to the signal value range of said pre-irrigation signal value in a direction conducive to reducing that difference.

18. The system of claim 17, in which said target signal value is a function of the field capacity of the soil in said zone.

19. The system of claim 18, in which said target signal value is the signal value at field capacity plus a selected multiple of the signal range covered by each of said predetermined ranges of signal values.

20. The system of claim 18, in which said controller is further arranged to periodically redetermine said field capacity.

21. The system of claim 17, in which said runtime is reprogrammed by fixed increments or decrements.

22. The system of claim 17, in which said runtime is reprogrammed by an amount substantially proportional to said difference.

23. The system of claim 17, in which said runtime is reprogrammed by adding to the runtime corresponding to the signal value range into which said pre-irrigation signal value falls, the runtime corresponding to the signal value range into which said post-irrigation signal value falls.

24. The system of claim 23 in which, if said last-named runtime is greater than a predetermined no-water limit runtime, each said zone is irrigated for said last-named runtime without waiting for the next scheduled irrigation cycle.

25. In an irrigation controller in which soil moisture is read by at least one sensor at a predetermined time after the end of each irrigation cycle, and is compared to a predetermined target moisture level, a display showing for each sensor the identity of the sensor, the increase or decrease of soil moisture in successive readings, the current soil moisture level, and the target moisture level with respect to said current soil moisture level.

26. The display of claim 25, in which said readings are rolling averages of a plurality of individual measurements.

27. The display of claim 25, in which said soil moisture increase or decrease is indicated by scrolling indicia, said indicia scrolling in one direction to show moisture increase, and in the opposite direction to show moisture decrease.

28. The display of claim 25, in which said current soil moisture level is indicated by a bar indicium, said target moisture level being indicated by an indicium appropriately positioned along said bar.

29. The display of claim 25, in which said scrolling indicia alternate with a display of the next scheduled irrigation date.

30. In an irrigation controller associated with a sensor providing readings of data values indicative of the moisture content of a soil being irrigated, a display operable to show the currently sensed value and the rolling average of the values sensed during at least one predetermined immediately past period of time.

31. An irrigation controller programmable to establish a selectable regular watering schedule and a selectable new lawn schedule, said controller comprising means for automatically switching from said new lawn schedule to said regular schedule upon the expiration of a selectable grow-in period.

32. A soil moisture-sensing irrigation controller programmed to automatically vary dispensed water quantities in response to conditions sensed by calibrated sensors, said controller being programmed to perform an auto-calibration of said sensors prior to varying said dispensed water quantities.

33. The controller of claim 32 further programmed to allow power-up with a temporary manual or new-lawn schedule operation, said auto-calibration remaining in abeyance pending the completion of said operation and being then automatically performed.

34. The controller of claim 32 further programmed to selectively skip said auto-calibration on power-up if auto-calibration has previously been performed.

35. The controller of claim 32 further programmed to automatically recalibrate said sensor in response to predetermined operating conditions.

36. The controller of claim 35, which contains a lookup table of sensor readings corresponding to desired runtimes, and in which said predetermined operating conditions include sensor readings outside the range of readings encompassed by said table.

37. The controller of claim 35, in which a field capacity value is established for said sensor, and said predetermined operating conditions include a sensor reading indicating a soil moisture level greater than said field capacity.

38. The controller of claim 32, in which said sensors are automatically recalibrated at predetermined time intervals.

39. The controller of claim 32, in which said sensors are automatically recalibrated after a predetermined number of watering cycles.

40. The controller of claim 32, in which the calibration of said sensors is user-initiatable.