Method and apparatus for optimizing soil moisture

• US 7,574,284 B2
• Filed: 10/31/2006
• Issued: 08/11/2009
• 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
• Primary Examiner(s): Masinick; Michael D
• Application Number:
  US11/555,200
• Publication Number:
  US 20070055407A1
• Time in Patent Office: 1,015 Days
• Field of Search: 700/284, 137/78.2, 137/78.3, 239/63
• US Class Current: 700/284
• 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 determining the field capacity of an irrigated soil, comprising the steps of:

providing an irrigation controller coupled to a sprinkler system arranged to distribute water over said soil;

executing a calibration cycle on said irrigation controller;

said calibration cycle directing said irrigation controller to repeatedly irrigate said soil for short periods of time at predetermined intervals;

said calibration cycle directing said irrigation controller to measure the moisture level of said soil at each of said intervals;

said calibration cycle comparing successive measurements to each other; and

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

creating an irrigation schedule with the newly calibrated irrigation controller based, in part, on said determined field capacity.

2. The method of claim 1, 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.

3. A method of establishing a field capacity value of a region of soil comprising:

providing an irrigation controller coupled to a sprinkler system for distributing water over said region of soil;

executing a calibrating cycle routine on said irrigation controller;

said calibration cycle routine directing said irrigation controller to water said region intermittently at predetermined periods of time;

said calibration cycle routine directing said irrigation controller to obtain a moisture value at each of said period of time;

said calibration cycle routine comparing said moisture values;

said calibration cycle routine establishing a field capacity value when said comparing of said moisture values results in successive moisture values differing by less than a threshold amount;

calibrating a moisture sensor with said irrigation controller based on said field capacity value.

4. A method of evaluating field capacity of a volume of soil comprising:

providing an irrigation controller coupled to a sprinkler system arranged to distribute water over said volume of soil;

executing a calibration cycle on said irrigation controller;

supplying water to said volume of soil at short intervals at predetermined periods of time with said irrigation controller;

obtaining a moisture value for each of said period of time;

comparing successively obtained moisture values with said irrigation controller;

establishing a field capacity value when said comparing of said successively obtained moisture values results in said moisture values differing by less than a predetermined amount;

irrigating said volume of soil with said newly calibrated irrigation controller based in part on said determined field capacity value.