Rain Sensor with Variable Shut Off

• US 20110288775A1
• Filed: 05/19/2010
• Published: 11/24/2011
• Est. Priority Date: 05/19/2010
• Status: Active Grant

• Current Assignee: Hunter Industries Incorporated
• Original Assignee: Hunter Industries Incorporated
• Inventors: Porter, La Monte D., Woytowitz, Peter J.
• Granted Patent: US 8,744,773 B2
• Time in Patent Office: Days
• US Class Current: 702/3
• CPC Class Codes: G01W 1/14 Rainfall or precipitation gauges measuring volume in general G01F

Abstract

An intelligent rain sensor incorporates at least one hygroscopic member and a sensor that generates signals representative of its amount of expansion due to absorption of moisture. A microcontroller executes a pre-programmed algorithm that determines at least the rate of expansion and uses that information to distinguish between actual rainfall events on the one hand, and high humidity, dew or a light sprinkle on the other hand, and sends a shut off command to an irrigation controller.

Claims

1. A rain sensor comprising:

at least one hygroscopic member;

an electronic sensor that detects an amount of expansion of the hygroscopic member upon absorbing moisture;

a processor; and

a memory connected to the processor and pre-programmed with an algorithm that enables the processor to determine the presence of rainfall and generate a shut off command, the determination being based at least in part on the signals generated by the electronic sensor indicating that the hygroscopic member has expanded at a predetermined rate.

2. The rain sensor of claim 1 wherein the electronic sensor is selected from the group consisting of a magnetic sensor and an optical sensor.

3. The rain sensor of claim 1 wherein the electronic sensor is a magnetic sensor and a magnet is operatively coupled to the hygroscopic member to move in an amount proportional to both the amount and the rate of expansion of the hygroscopic member.

4. The rain sensor of claim 3 wherein the magnet is operatively coupled to the hygroscopic member by mounting the magnet on an arm that moves with the expansion of the hygroscopic member.

5. The rains sensor claim 4 wherein the magnetic sensor is selected from the group consisting of a Hall effect sensor, a magneto-resistive sensor, a fluxgate sensor, and a magneto-inductive sensor.

6. The rains sensor of claim 4 wherein the algorithm causes the processor to periodically calculate a dry-to-wet threshold and a wet-to-dry threshold.

7. The rain sensor of claim 6 wherein the algorithm causes the processor to periodically determine a minimum and a maximum set points for a range of travel of the magnet and to generate the shut off command upon the processor determining that the magnet has moved a predetermined percentage away from the minimum set point.

8. The rain sensor of claim 6 wherein the algorithm causes the processor to set up a pre-threshold region within a range of motion of the magnet that is an area just prior to the dry-to-wet threshold and the processor then determines an amount of time that the magnet spends in the pre-threshold area by measuring a predetermined number of successive samples that fall in area, and comparing that number to a predetermined count.

9. The rain sensor of claim 1 wherein the processor and the memory are part of a microcontroller.

10. The rain sensor of claim 1 wherein hygroscopic member is made up of a plurality of hygroscopic discs.

18. The rain sensor of claim 1 wherein hygroscopic member is made up of a plurality of hygroscopic discs.

11. A rain sensor, comprising:

at least one hygroscopic member;

a magnet operatively coupled to move in a manner proportional to both an amount and a rate of expansion of the hygroscopic member upon absorbing moisture;

a magnetic sensor positioned adjacent the magnet that generates signals representative of a position of the magnet;

a processor; and

a memory connected to the processor and pre-programmed with an algorithm that enables the processor to determine the presence of rainfall and generate a shut off command, the determination being based at least in part on the signals generated by the magnetic sensor indicating that the magnet has moved at a predetermined rate.

12. The rain sensor of claim 11 wherein the magnet is operatively coupled to the hygroscopic member by mounting the magnet on an arm that moves with the expansion of the hygroscopic member.

13. The rains sensor claim 11 wherein the magnetic sensor is selected from the group consisting of a Hall effect sensor, a magneto-resistive sensor, a fluxgate sensor, and a magneto-inductive sensor.

14. The rains sensor of claim 12 wherein the algorithm causes the processor to periodically calculate a dry-to-wet threshold and a wet-to-dry threshold based on periodically sampling a position of the magnet.

15. The rain sensor of claim 12 wherein the algorithm causes the processor to periodically determine a minimum and a maximum set points for a range of travel of the magnet and to generate the shut off command upon the processor determining that the magnet has moved a predetermined percentage away from the minimum set point.

16. The rain sensor of claim 14 wherein the algorithm causes the processor to set up a pre-threshold region within a range of motion of the magnet that is an area just prior to the dry-to-wet threshold and the processor then determines an amount of time that the magnet spends in the pre-threshold area by measuring a predetermined number of successive samples that fall in area, and comparing that number to a predetermined count.

17. The rain sensor of claim 11 wherein the magnet is a permanent magnet.

19. The rain sensor of claim 12 wherein the arm is moved by a larger stack of hygroscopic discs or a smaller stack of hygroscopic discs.

20. A rain sensor, comprising:

a housing;

a first stack of hygroscopic discs inside the housing having a first height;

a second stack of hygroscopic discs inside the housing having a second height shorter than the first stack;

a swing arm pivotally mounted inside the housing for movement by either the first and second stacks as they expand and contract due to absorption of water through at least one aperture in the housing and loss of water through evaporation;

a magnet mounted on the swing arm;

a Hall effect sensor positioned inside the housing adjacent the magnet that generates signals representative of a position of the permanent magnet;

a processor; and

a memory connected to the processor and pre-programmed with an algorithm that enables the processor to determine the presence of rainfall and generate a shut off command, the determination being based at least in part on the signals generated by the magnetic sensor indicating that the magnet has moved at a predetermined rate.

21. A rain sensor, comprising:

at least one hygroscopic member;

an electronic sensor operatively associated with the hygroscopic member that generates an output signal representative of a degree of expansion of the hygroscopic member due to the absorption and evaporation of water;

a processor; and

a memory connected to the processor and pre-programmed with an algorithm to discriminate between measurable rainfall on the one hand and dew, high humidity or a light sprinkle on the other hand based on the output signal and for generating a shut off command in response to a determination that measurable rainfall has occurred.

22. A rain sensor, comprising:

at least one hygroscopic member;

an electronic sensor operatively associated with the hygroscopic member that generates an output signal representative of a degree of expansion of the hygroscopic member due to the absorption and evaporation of water;

a processor; and

a memory connected to the processor and pre-programmed with an algorithm for generating a shut off command based on the output signal only upon a determination of measurable rainfall after intermittently sampling the output signal.

23. A rain sensor, comprising:

at least one hygroscopic member;

an electronic sensor operatively associated with the hygroscopic member that generates an output signal representative of a degree of expansion of the hygroscopic member due to the absorption and evaporation of water;

a processor; and

a memory connected to the processor and pre-programmed with an algorithm for generating a shut off command based on the output signal upon detecting the occurrence of varying degrees of expansion of the hygroscopic member to thereby ensure that the shut off command is only generated when measurable rainfall has occurred.

24. A rain sensor, comprising:

at least one hygroscopic member;

an electronic sensor operatively associated with the hygroscopic member that generates an output signal representative of a degree of expansion of the hygroscopic member due to the absorption and evaporation of water;

a processor; and

a memory connected to the processor and pre-programmed with an algorithm for generating a shut off command based on the output signal upon intermittently sampling the degree of expansion of the hygroscopic member and determining a variable dry-to-wet threshold.

25. A rain sensor, comprising:

at least one hygroscopic member;

an electronic sensor operatively associated with the hygroscopic member that generates an output signal representative of a degree of expansion of the hygroscopic member due to the absorption and evaporation of water;

a processor; and

a memory connected to the processor and pre-programmed with an algorithm for generating a shut off command based upon the output signal indicating both a predetermined degree and a predetermined rate of expansion of the hygroscopic member.

26. A rain sensor, comprising:

at least one hygroscopic member;

an electronic sensor operatively associated with the hygroscopic member that generates an output signal representative of a degree of expansion of the hygroscopic member due to the absorption and evaporation of water;

a processor; and

a memory connected to the processor and pre-programmed with an algorithm for generating a shut off command based upon the output signal by measuring a rate of expansion of the hygroscopic member and adjusting when the shut off command is generated based upon the measured rate of change.