Abstract:
The present invention is directed to an irrigation controller, method and software program product for generating valve control signals for energizing a valve. The irrigation controller includes a valve actuation control module selectively coupled each of plurality of control nodes and generating a valve actuation control signal thereon. The valve actuation control signal is a continuous control voltage over a plurality of control signal periods for selectively energizing the selected irrigation valve. Also integrated in the irrigation is a valve chatter module for selectively coupled each of plurality of control nodes and generating a valve chatter control signal thereon. The valve chatter module selectively and, intermittently, energizes the selected irrigation valve. The irrigation controller may further include a remote controller of remotely controlling the irrigation controller.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an irrigation controller. More particularly, the present invention relates to an irrigation controller with a solenoid activator for rapidly pulsing the solenoid actuator. 
   2. Description of Related Art 
   Conventional automated irrigation systems generally comprise two coextensive physical networks that work in concert for the delivery of water. The first is a water delivery network consisting of a water delivery conduit, (e.g., pipe and/or tubing), metering, regulating and dispersing elements for efficiently regulating the flow of water through the conduit and dispersing water over a predetermined area. These elements may include pumps, boosters, irrigation control valves (such as the Weathermatic® Nitro line of diaphragm actuated valves available from Telsco Industries, Incorporated, in Dallas, Tex.) anti-siphon devices, check valves, and various types of water dispersion elements (such as sprinklers, either spray, rotary, drip, bubblers, soaker or misters) for wetting the foliage or surface area with water. At least the conduit, irrigation control valves and certain water dispersion elements are installed below ground, or at least below grade. A conventional irrigation system is divided into discrete irrigation zones (sometimes referred to as stations) and the water flow to each zone is controlled and/or regulated by an irrigation control valve. Each irrigation zone is defined by a plurality of water dispersion elements, each controlled by a separate irrigation control valve, which is coupled in the conduit between the water source and the plurality of water dispersion elements. The conduit and water dispersion elements are installed directly in the ground, but irrigation control valves are protected from the soil by a valve box and cover. 
   The second network is an electrical control network. The purpose of the electrical control network is to generate control signals and transmit the signals to certain components in the water delivery network. Typically, the electrical control network comprises an irrigation controller for generating the control signals (such as the SmartLine™, Weathermatic® Lawnmate or WeatherMate™ controllers, all available from Telsco Industries, Incorporated), and a transmission medium for propagating the signals to the electrical components in the irrigation system. 
   Periodically, it may be necessary for a grounds keeper or operator to gain access to an irrigation control valve to, for example, adjust the amount of water allowed to flow into a particular irrigation zone, or perform preventive maintenance on the irrigation control valve. Often, however, the cover of the valve box will become obscured with dirt, compost, mulch, or some other obstruction, or by vegetation which has been purposely been allowed to conceal the cover. An operator will then probe the ground with a sharpened metal probe around the presumed location in an attempt to find the cover. When the operator receives an indication of an object hidden below the surface, i.e., the probe makes contact with an object below the surface of the ground, the operator excavates the top soil, turf and/or shrubbery to identify the obstructing object. This method of probing and digging is an extremely time consuming process and may involve many hours of probing and digging to locate a particular valve. 
   Often, during the installation of an irrigation system, the installers will create a surface map of the irrigation system. The map shows the layout of the pipes, sprinklers and valves for each irrigation zone, with reference to fixed objects and the topography of the landscape. The operator may then update the irrigation map to incorporate the locations of plants, shrubs, trees and other foliage. With such a map, the operator will have a good approximation of the location for each valve in the system; from which the operator may begin a search for a particular valve; thereby shortening the operator&#39;s searching time. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is directed to an irrigation controller, method and software product for energizing an irrigation valve. The irrigation controller includes at least one control node coupled to an irrigation valve through a control wire, valve actuation control circuitry electrically coupled to the control node for generating a valve actuation control signal on the control node over an actuation period, wherein the valve actuation control signal comprising a plurality of control signal periods each having a continuous control voltage, whereby the valve actuation control signal continuously energizes the control node and a valve over the actuation period, and valve chatter circuitry electrically coupled to the control node for generating a valve chatter control signal on the control node, wherein the valve chatter control signal comprising a plurality of duty cycles, each duty cycle comprising one control signal period and at least one naught signal period, the control signal period comprising a control voltage over a first portion of the control signal period and a naught voltage over a second portion of the control signal period, and the at least one naught signal period comprising a naught voltage, whereby the valve chatter control signal intermittently energizes the control node and the valve over the chatter period. 
   Alternatively, the irrigation controller comprises a control node, a memory for storing processor usable program code for generating a valve control signal for energizing the control node and a processing unit connected to the memory and receptive of the program code, wherein the program code for generating a valve control signal, when executed by the processing unit, causes the irrigation controller to generate a valve actuation control signal on the control node for controlling a continuous control voltage to a valve over an actuation period, and to generate a valve chatter control signal on the control node for a controlling an intermittent chatter voltage to the valve over a chatter period, wherein the intermittent chatter voltage comprises a plurality of duty cycles and each duty cycle comprises one signal voltage period and at least one naught voltage period, the signal voltage period comprises a first voltage level over a first portion of the signal voltage period and a second voltage level over a second portion of the signal voltage period, and the at least one naught voltage period comprises a second voltage level, wherein the second voltage level is less than the first voltage level. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The novel features believed characteristic of the present invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will be best understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings wherein: 
       FIG. 1  is a cross-sectional diagram of a typical subterranean installation of a typical irrigation control valve as installed in an irrigation zone; 
       FIG. 2  is a block diagram of an irrigation system depicting the layout topology of the coextensive water and electrical control networks, including an irrigation controller, in accordance with an exemplary embodiment of the present invention; 
       FIG. 3  is a timing diagram depicting a control signal generated by an irrigation controller and the relative position of a solenoid piston or piston movement in response to the control signal; 
       FIG. 4  is a timing diagram depicting a control signal from control signal generator and the relative position of a solenoid piston or piston movement in response to the control signal as known in the prior art; 
       FIG. 5  is a timing diagram depicting a control signal generated by a valve locator algorithm and the relative position of a solenoid piston or piston movement in response to the control signal, for a valve locator algorithm functionally based on the responsiveness of the solenoid piston in accordance with an exemplary embodiment of the present invention; 
       FIG. 6  is a timing diagram depicting a control signal generated by a valve locator algorithm and the relative position of a solenoid piston or piston movement in response to the control signal, for a valve locator algorithm functionally based on the responsiveness of the solenoid piston and time (i.e., N(t)) in accordance with an exemplary embodiment of the present invention; 
       FIG. 7  is a timing diagram depicting a control signal generated by a valve locator algorithm and the relative position of a solenoid piston or piston movement in response to the control signal, for a valve locator algorithm functionally based on the responsiveness of the solenoid piston, time and an independent function (i.e., f(N(t))) in accordance with an exemplary embodiment of the present invention; 
       FIGS. 8A and 8B  are cross sectional diagrams of a solenoid actuator cooperating with an irrigation control valve, depicted in the solenoid actuator in the unenergized and energized states; 
       FIG. 9  is a block diagram of irrigation system  900  for transmitting control signals using a two-wire control network and a wireless network in accordance with other exemplary embodiments of the present invention; and 
       FIG. 10A  is a diagram of a valve control module (VCM) in accordance with an exemplary embodiment of the present invention; and 
       FIG. 10B  is a diagram of a wireless valve control module (WVCM) in accordance with an exemplary embodiment of the present invention. 
   

   Other features of the present invention will be apparent from the accompanying drawings and from the following detailed description. 
   DETAILED DESCRIPTION OF THE INVENTION 
   An electromechanical irrigation control valve is typically employed to regulate the flow of water between an inlet water source and outlet dispersion elements, such as sprinklers, located in a particular irrigation zone or station.  FIG. 1  is a cross-sectional diagram of a typical subterranean installation of a typical irrigation control valve for a particular irrigation zone. During installation, a trench is dug in soil  138 , in which irrigation pipe  130  and direct burial control wire  140  are laid. Irrigation pipe  130  is typically PVC (polyvinylchloride) in sizes ranging from 0.5 inch to 2.0 inches or more for certain commercial installations. Direct burial control wire  140  is a multi-conductor cable incased in a tough, non-reactive jacket (such as polyethylene, PVC or Neoprene®). Typically, control wire  140  contains an odd number of conductors ( 12 - 16  American Wire Gauge (AWG) diameter), one common conductor wire and an even number of insulated station conductors. Optionally, control wire  140  may also contain a serial communication bus for connecting electronic components in the irrigation system. Irrigation control valve  110  connects an irrigation zone to an inlet pipe. As depicted, irrigation control valve  110  is an inline valve, but other types of automated control vales are available, such as anti-siphoning control valves. The valve, wiring, pipes and connections are all protected from the soil by open-ended valve box  134  and removable cover  132 , which surround the valve and allow for easy access to the valve assembly by an operator or service technician. Often, a single valve box will house 2, 4 or even 6 individual irrigation control valves each coupled to an inlet manifold. 
   Each valve in an irrigation system controls and/or regulates water to a particular irrigation zone that is proximate to the valve, which may be more clearly understood from the irrigation topology depicted in  FIG. 2 .  FIG. 2  is a block diagram illustrating an irrigation system in accordance with an exemplary embodiment of the present invention. Each of valves  110  is connected between the water delivery network and the electrical control network. Water supply  222  produces pressurized water that is fed into pipes  130 , which are connected through valves  110 , and onto water dispersion elements (sprinklers)  242 . Each set of irrigation control valve  110  and associated water dispersion elements (sprinklers)  242  defines a particular irrigation zone  210  (such as irrigation zones  1 ,  2 ,  3 , . . . n). Valves  110  receive a control signal from irrigation controller  202 , via control wire  140 . In many applications, the signal received by valves  110  is a change in voltage level (or more correctly, a change in the current resulting from a voltage change applied across the control wires). This control signal is generated by irrigation controller  202 . A single irrigation controller can control 6, 12, 25 or 46 irrigation zones or more. Irrigation controllers, and the operation of which, may be generally understood from the disclosure of U.S. Pat. No. 6,314,340, issued to Mecham, et al., on Nov. 6, 2001, which is incorporated herein by reference in its entirety. 
   With further reference to  FIG. 2 , a block diagram of irrigation controller  202  is depicted in accordance with an exemplary embodiment of the present invention. Irrigation system  200  comprises at least irrigation controller  202  and optionally, may further comprise other control components such as one or more evapotranspiration module (not shown) and/or remote controller  262 . Some aspects of irrigation controller  202  function generally in the same manner as a conventional irrigation controller. In this regard, an irrigation schedule is programmed into irrigation controller  202  by an operator which specifies not only the day and time of day when irrigation should occur, but also the run time for irrigation in each zone (or program). Irrigation controller  202  then operates to keep track of the irrigation schedule and control the actuation of irrigation control valves  110  in accordance with that schedule for the operator specified run time. 
   An irrigation schedule is programmed into the irrigation controller  202  by the operator which specifies the day and time of day when irrigation should occur. In one implementation, the operator need not pre-program any run time, and the controller chooses an appropriate run time. In another implementation, an operator selected run time is modified by the controller calculated run time if the operator makes this selection. As depicted, irrigation controller  202  operates to process temperature data at the site and calculate a reference evapotranspiration value representing the amount of water lost since a last irrigation. When evapotranspiration modules are in place, a separate temperature sensor is connect to each evapotranspiration module which then calculates a separate reference evapotranspiration value at those remote sites. This information is then communicated to irrigation controller  202 . In response to receipt of the evapotranspiration information, irrigation controller  202  calculates a run time for each zone  210  (or program), and then operates to control the actuation of irrigation control valves  110  in accordance with the irrigation schedule and for the duration of the calculated run time. 
   Irrigation controller  202  includes microprocessor (Main CPU)  212 , programmable read only memory (ROM/PROM)  214  and random access memory (RAM)  216 . ROM/PROM  214  provides a non-volatile storage location for the programming code of the irrigation controller along with certain important (permanent) data necessary for execution of the code. RAM  216  provides a volatile storage location for certain (variable/temporary) data generated during execution of the programming code. Microprocessor  212  communicates with ROM/PROM  214  and RAM  216  in a conventional manner utilizing address bus  218  and data bus  220 . It will be understood that ROM/PROM  214  and RAM  216  may be incorporated within or provided separate and apart from microprocessor  212 . 
   The evapotranspiration module also includes a microprocessor connected to a programmable read only memory (ROM/PROM) and a random access memory (RAM), and functions in a similar manner to the irrigation controller. The ROM/PROM provides a non-volatile storage location for the programming code of the watering time determination module along with certain important (permanent) data necessary for execution of the code. The RAM provides a volatile storage location for certain (variable/temporary) data generated during execution of the programming code, wherein the microprocessor communicates with the ROM/PROM and RAM utilizing an address bus and a data bus. 
   Communication between wired external devices is achieved using serial communications port  232 , which is connected to (or is incorporated in) the microprocessor  212  to support communications between the irrigation controller  202  and external devices such as an evapotranspiration module(s), a portable flash memory drive (not shown), or a personal/laptop computer (not shown). Similarly, a second communications port is connected to (or is incorporated in) any external device or module to be connected to irrigation controller  202 . 
   User interface  246  for supporting data entry into controller  202  is connected to microprocessor  212  through I/O interface  248 . Input data may, if necessary, be stored in RAM  216 . Furthermore, using a serial communications link (not shown), user interface  246  input data may be communicated to an evapotranspiration module (also not shown) for storage in its onboard RAM. The kinds of data input into irrigation controller  202 , and perhaps communicated to the evapotranspiration module include: a preferred time of day when irrigation (if necessary) is to be effectuated; a preferred day (or days) of the week when irrigation (if necessary) is to be effectuated; an identification of soil type for the irrigated area; an identification of the vegetation type (crop coefficient); irrigation system  200  site latitude; sprinkler flow rates; and, a local irrigation adjustment factor. User interface  246  may further be utilized to initiate certain microprocessor  212  and controller  202  activities (such as, for example, manual zone selection and/or irrigation, a self test, or the like) without regard to the current state of programming code execution. 
   Optionally, remote controller  262  may be used by the operator for communications with controller  202  from a remote location. Communication between remote controller  262  and irrigation controller  202  is accomplished using over-the-air RF (radio frequency) signals generated in remote interface  260  that are received by irrigation controller interface  264  (for unidirectional communication). It is anticipated that remote controller  262  will operate as an auxiliary external device and not as a substitute for user interface  246  on irrigation controller  202 . Therefore, only uni-directional transmission to irrigation controller  202  is expected, although bidirectional communication may also be supported in both remote interface  260  and irrigation controller interface  264 . 
   Display  250  (such as an LCD display) for supporting visual data presentation by irrigation controller  202  is also connected through I/O interface  248  to microprocessor  212 . Through display  250 , irrigation controller  202  may present information to the operator (such as time, day and date information). Display  250  may further be utilized by microprocessor  212  to present a variety of menus for operator consideration when entering data into irrigation controller  202  and evapotranspiration module, or inform the operator concerning the errors, status or the state of controller operation. 
   A time of day clock  252  is connected to microprocessor  212  through address bus  218  and data bus  220 . This clock  252  maintains a non-volatile record of month, day, hour of the day, minutes of the hour and seconds of the minute. Clock  252  time data is monitored by microprocessor  212  with the time data driving certain operations by irrigation controller  202  and an evapotranspiration module in accordance with their programming codes. These operations include: reading and storing temperature data; initiating and stopping irrigation activities; and, performing certain irrigation related calculations. 
   In accordance with the execution of the programming code, microprocessor  212  outputs irrigation control signals through I/O interface  248  to control the actuation of irrigation control valves  110 . These control valves  110  operate to either allow or block the passage of water to one or more water dispersion elements  242 . Typically, the control signals to valves  110  are generated directly from the input power signal by transforming the high voltage line input to a lower voltage control signal. Controller  202  receives input line power (typically from 110 VAC or 220 VAC power at 50 or 60 Hz and having a generally sinusoidal character wave). The high voltage AC is typically transformed to a 24 VAC, approximately, continuous full-wave transformed from the line power. Solenoid activation is accomplished by supplying the control wires  140  with the 24 VAC, through a switching device, typically a triac, relay, or mechanical cam-operated switch contacts in irrigation controller  202 . 
   Irrigation controller  202  optionally receives input from other sensors  256  through I/O interface  248 . An example of such a sensor is moisture sensor  256  ( 1 ). When the moisture sensor  256  ( 1 ) detects moisture, this is indicative of a rainfall event. During such a rainfall event, microprocessor  212  suppresses irrigation controller  202  actuation to sprinkle. Another example of such a sensor comprises rainfall gauge  256  ( 2 ). Using rainfall information collected by rainfall gauge sensor  256  ( 2 ), microprocessor  212  adjusts (i.e., reduces or suppresses) its programming code calculated irrigation amount of water which is needed to replace water lost through the effects of evapotranspiration. Temperature sensor  258  is further provided and is connected to microprocessor  212  through input/output (I/O) interface  248 . In accordance with the operation of the programming code, temperature data collected by sensor  258  is stored by microprocessor  212  in RAM  216 . Alternatively, temperature sensor may be coupled to each evapotranspiration module connected to irrigation controller  202 . 
   With further reference to  FIG. 1 , irrigation control valve  110  is comprised of three basic parts, body  112 , diaphragm  114  and solenoid actuator  116 . Operationally, typically valve  110  is of a normally-closed type that prevents the flow of water between the inlet side and outlet side whenever water pressure is present on the inlet side. A port in the valve allows water from the inlet side into a pressure chamber above diaphragm  114  (not shown). The water pressure forces the body of diaphragm  114  downward, securing it against a diaphragm seat and preventing water flow through the valve. The water flow can be switched on by reducing the water pressure above diaphragm  114 , thereby allowing the water pressure from the inlet to push diaphragm  114  away from the diaphragm seat and open a water path through the valve. This may be accomplished in one of two ways. First, water pressure in the pressure chamber can be relieved by manually opening relief screw  118 . This requires an operator to physically open relief screw  118  for water flow and then close the screw to stop the flow. Alternatively, pressure can be drawn off of the upper pressure chamber, remotely, by energizing solenoid actuator  116 . With either action, a pathway is opened allowing the water trapped in the pressure chamber above diaphragm  114  to bleed into the outlet portion of pipe  130  (discussed further below with regard to  FIGS. 8A and 8B ), thereby relieving the pressure above diaphragm  114 . In response to the pressure drop, the pressure of the inlet water forces diaphragm  114  away from the seal and against a stop in the upper portion of the pressure chamber. The position of the stop determines the opening size between diaphragm  114  and the valve seat, and hence the water flow rate through the valve. The position of the stop, and hence the open position of diaphragm  114 , can be adjusted by turning flow control knob  120 . If more or less water is desired for a particular irrigation zone, the operator merely opens cover  132 , exposing valve  110  and knob  120 , and then adjusts the position of the stop with knob  120 , in the amount necessary to change the flow rate to the desired amount. 
     FIGS. 8A and 8B  are cross sectional diagrams of solenoid actuator  116 , shown as seated in valve body  112 , depicted a solenoid actuator in the unenergized and energized states, respectively. Solenoid actuator  116  generally comprises housing  800 , which encases core  808  and coil  806  in a waterproof compartment. Coil  806  is electrically coupled to control wires  140  through wire leads  122 . Below core  808  is cylindrical wear guide  812  surrounding a movable piston  802 . The cross-sectional shape of piston  802  is typically hexagonal, thereby allowing the piston to move freely along the interior surface of wear guide  812  and which provides a path for water displacement during piston movement. Seat  804  is affixed to the lower extent of piston  802 . Spring  810  exerts a downward bias on piston  802  (away from coil  806  and core  808  and toward exit opening  822 ), with both spring  810  and piston  802  being secured in housing  800  by retainer  812 . Water freely flows into cavity  814  through opening  820 , surrounding piston  802  and spring  810 , but is prevented from contacting coil  806 . 
   As can be seen in  FIG. 8A , in the unenergized position, piston  802  is in the closed position with seat  804  forced against exit opening  822  by the biasing force of spring  810 . The force of spring  810 , although relatively weak, is sufficient to provide a watertight seal over exit opening  822 . By sealing opening  822 , the water is prevented from flowing from the pressure chamber above the diaphragm through opening  820  and into outlet opening  822 , thereby maintaining sufficient pressure in the chamber above the diaphragm to keep the diaphragm in the closed/sealed position, which prevents water from flowing through the valve. 
   As can be further understood from  FIG. 8B , when energized core  808  becomes a powerful magnet that attracts piston  802 . Piston  802  moves to the open position against core  808 , and seat  804  is forced away from the normally closed position against exit opening  822 . The magnetic force exerted on piston  802  by energizing coil  806  is many times greater than the downward biasing force of spring  810  on the piston. In response to the magnet force on piston  802 , and immediately after activation, piston  802  is driven into core  808  with a clearly audible “clicking” (or chirping) sound. Water is then allowed to flow through cavity  814  from the pressure chamber above the diaphragm, through opening  820 , into and egresses through opening  822 . 
   The electro-mechanical interactions between the components of solenoid actuator  116  can be better understood with respect to the timing diagrams depicted in  FIG. 3 .  FIG. 3  depicts control signal trace  302 , which varies between E 0  and E out . The relative position of piston  802 , position trace  306 , varies between Z c  and Z 0 , and is responsive to changes in control signal  302 . E 0  represents the unenergized state and E out  represents the energized state during activation, and similarly, Z c  represents the closed position of piston  802  (with seat  804  against exit opening  822 ), and Z 0  represents the full open position of piston  802  (with piston  802  against core  808 ). At normal state, with the irrigation valve closed, the control signal  302  to each control wire is 0.0 volts, or at E 0 , as controller  202  is not generating an activation signal. At activation, controller  202  generates a control signal, or activation voltage, as an AC signal, E out  (typically between 12.0 VAC and 26.0 VAC at 500 mA to 1.5 A), for actuating solenoid actuator  116 . (see trace  302 ). As a practical matter, only a threshold energy of E t  of approximately 5.0 VAC (less than 200 mA) is needed to create a sufficiently strong magnetic force in coil  806  to overcome the mechanical force of spring  810  and compresses the spring. As might be expected, much more voltage is necessary for changing the position of piston  802  (from the rest position against exit opening  822  to the upward most position against core  808 ), than is necessary to maintain piston  802  in the upward most position against core  808 . Furthermore, because the magnetic force exerted on piston  802  by coil  806  is much greater than the biasing force of spring  810 , piston  802  is far more responsive to open control signals than to close signals (i.e., it accelerates faster in response to the magnet than to the spring), as is apparent by comparing the time interval for piston  802  to open (between t 1  and t 3  on trace  306 ) with time interval to close (between t 4  and t 5  on trace  306 ). With piston  802  in contact with, or near core  808 , only a minimal energy E m  is necessary to keep spring  810  in compression (approximately 1.2 VAC at 85 mA or less). Thus, as can be seen from trace  306 , piston  802  will not begin its downward movement until the voltage at coil  806  drops below E m  (time t 4  on trace  306 ). The minimal energy E m , necessary for counteracting the spring tension varies from valve to valve and depends on a number of factors, including the electromotive efficiency of coil  806 , the compressive strength of spring  810  and the frictional resistance of wear guide  812  to piston  802 . Furthermore, as the valve ages, the value for E m  decreases due to spring  810  losing some of its resiliency and also due to an increase in the frictional resistance of wear guide  812  to piston  802  (the increase in the resistance is from dissolved minerals (calcium and magnesium hardness minerals) plating off onto the inner surface of wear guide  812  and the outer surface of piston  802 ). Any condition that resists the force of spring  810  will result is a corresponding increase in the close time for piston  802  and potentially reduce the volume of the resulting click. In any case, the exact values for E t  and E m  vary widely with the type, age and manufacturer of the solenoid actuator and even from solenoid to solenoid of the same type. 
   As mentioned above, during activation an audible clicking sound results from piston  802  striking core  808 , depicted in  FIG. 3  as  308 . It is apparent that the volume of the click sound is proportional to the force with which piston  802  strikes core  808 , and hence the velocity of piston  802 . Therefore, it is expected that louder clicks result from the full stroke movement of piston  802  within wear guide  812 , and weaker, less audible clicks result from less than full stroke movements. 
   Ordinarily, and from time to time, it becomes necessary for an operator to gain access to the irrigation control valve to, for example, adjust flow control knob  120  or perform preventive maintenance on the valve itself. Often, however, cover  132  of valve box  134  will become obscured with dirt, compost, mulch, or some other obstruction  136 , or by vegetation which conceals cover  132 , either intentionally or unintentionally. Traditionally, an operator will attempt to locate a hidden irrigation control valve by probing the ground with a sharpened metal probe around the presumed location of the valve box and cover. Where the operator gets an indication of a hidden object below the surface, i.e., the probe makes contact with an object below the surface of the ground, the operator excavates the top soil, turf and/or shrubbery to identify the obstructing object. This method of probing and digging is an extremely time consuming process and may involve many hours to locate a hidden valve. 
   Often a map of the irrigation system is available from the technicians who originally installed the system that shows the layout of the pipes, sprinklers and valves for each zone, each with reference to local objects and the topography. If the operator has taken care to regularly update the map with topographical changes, such as changes in the locations of plants, shrubs, trees and other foliage, the map may provide the operator with a useful approximation of the location for each valve in the system. This is important because, as mentioned above, some irrigation controllers support  46  or more separate irrigation zones, and, larger estates, parks, golf courses and the like may utilize multiple irrigation controllers to irrigate the entire topology. 
   Another method for locating a hidden valve, usually less time consuming, but more expensive, is to engage the services of an irrigation service professional who employs special-purpose hardware to locate hidden valves. One device traces the underground control wires using RF (radio frequency) signals. The control wires for the affected valve(s) are disconnected or removed, or the service person taps into the control wire at some point between the valve and controller in order to establish continuity between a stand-alone RF generator and the affect valve(s). With the RF powered on, the service person tracks the RF signal emanating from the subterranean control wires using a portable RF receiver. In actuality, this method is employed for locating the control wires, which will eventually lead to the location of a hidden valve. Another method involves using a stand-alone control signal generator for rapidly activating or “chattering” the solenoid actuator. The stand-alone control signal generator can supply a modulated current to produce a rapid oscillation of the solenoid actuator. The rapid cycling produced by the modulated current results in an audible chattering sound that can guide the service person to the actual valve location. However, as with the RF generator discussed above, these units necessitate unwiring affected valve(s), removing the insulation or other methods to establish continuity between the portable device and the affected valve(s). Aside from the expense, this method suffers from another significant drawback; the prior art control signal generator does not reliably induce an audible chattering sound in valve solenoid actuators. Moreover, the service persons cannot know with any certainty whether or not the solenoid actuator is actually chattering until an exhaustive search of the grounds has been undertaken. The reason for this shortcoming can be understood from interactions between the control signal (trace  402 ) and the relative piston movement (trace  406 ), as depicted in  FIG. 4 . 
   The timing diagrams depicted in  FIG. 4  are similar in many regards to those discussed above in  FIG. 3 . However, rather than generating a continuously full wave AV control signal as with the irrigation controller, the control signal generator produces a series of half-wave control signal  402  by clipping the portion of the 24 VAC below 0.0 VAC, resulting in a continuous 50% duty cycle pulsing of the solenoid actuator. Optimistically, that portion of duty cycle  410  which is unenergized provides sufficient time for the spring  810  to force piston  802  back into the closed position (with seat  804  sealing opening  822 ). However, as is apparent from relative position trace  406 , the closing response time of piston  802  (between t 4  and t 5 ) is often far greater than half of the period of the duty cycle. Since piston  802  must have sufficient time to move away from core  808  in order to generate audible successive clicks, only a single audible click  408  results from the initial activation of the control signal generator. Any subsequent chatter produced by the solenoid actuator is a low volume hum from low amplitude clicks  410 . This lower amplitude is due to the close proximity of piston  802  to core  808  at successive time t 1 &#39;s after the initial energizing. This method produces a less than optimum audible sound, which is the sole purpose of the device. As can be appreciated, the reason for the poor results is that the character of the control signal from the prior art signal generator is predicated on the character of the underlying input power signal and is not related, in any way, to the responsiveness of the solenoid actuator. 
   In accordance with one exemplary embodiment of the present invention, a chatter algorithm is integrated directly into the irrigation controller, thereby alleviating the necessity for the use of special purpose equipment. Returning to the block diagram of the irrigation controller in  FIG. 2 , an executable programming code for chattering an irrigation valve solenoid actuator, coupled to the control wires, is stored on programmable read only memory (ROM/PROM)  214 . It is expected that the chatter algorithm, or valve locator routine, will be used infrequently and therefore, should be cost-effectively incorporated in the existing structure of irrigation controller  202  and implemented as an auxiliary diagnostic routine in controller  202 . In accordance with one exemplary embodiment of the present invention, controller  202  employs plurality of discrete bidirectional switching devices  253 , such as a triacs, each coupled between one of a plurality of control wire nodes  254  and a power source (not shown) for controlling actuator control current on each of control wires  140 . The chatter routine provides instructions for I/O interface  248  to apply a control current to a switching device for a particular control wire. The executable programming code stored on programmable read only memory (ROM/PROM)  214  may also include a timing function to automatically terminate the chatting routine after a predetermined duration. Then again, the operator may utilize remote controller  262  for switching on and off the chatter while surveying the area or, as will be discussed below, for changing the chatter tone to help distinguish the solenoid actuator clicks over any background noise that might be present. In any event, when the diagnostic mode is activated, controller  202  will send a modulated current, via node  254 , to the selected control wire that results in a rapid cycling of the solenoid actuator coupled to the selected wire. The rapid cycling produces an audible chattering sound that can be followed to the location of a hidden valve. 
   The presently described integrated valve locator does not require additional steps to establish continuity to the affected solenoid. Since the implementation is an integral of the electrical/firmware design of the controller, no separate unit and no establishment of continuity is required to effectuate the valve location function. This implementation is initiated by selecting this particular diagnostic mode through the standard controller user interface, which combines a dial, LCD and buttons. Alternatively, initiation of the valve locator mode could be reconfigured for one-touch operation by designating a dedicated button on the controller face panel or possibly having a dedicated dial position for the valve locator mode. Valve locator module  270 , or comparable valve locator circuitry, may be integrated directly into irrigation controller  202  as a discrete component which is isolated from the digital components in irrigation controller  202 . In accordance with this exemplary embodiment, valve locator module  270  should be connect directly to control wires  140  and include an separate interface for selecting a zone for testing and activating the chatter function of the module (such as buttons and/or dials). 
   In accordance with another exemplary embodiment of the present invention, the integrated valve locator routine described above includes a chatter algorithm that generates a control signal based on the responsiveness of the solenoid actuator and not on the character of the input signal. As mentioned elsewhere above, piston  802  responds significantly faster in the open direction than in the close direction (because the biasing force of spring  810  is relatively weak). In addition, over time spring  810  becomes weaker and the annular space between cylindrical wear guide  812  and piston  802  becomes clogged with sediment and impurities from the water, which further inhibits the movement of piston  802 . Consequently, piston  802  takes even more time to move from the open position to the close position. The presently described invention compensates for the lag time of the solenoid actuator by increasing length of the duty cycle of the control signal with respect to the control pulse. The benefit of the present exemplary chatter algorithm can be appreciated through a discussion of  FIG. 5 . 
     FIG. 5  is a timing diagram depicting the interaction between a control signal (trace  502 ), which is controlled by a chatter algorithm, and the relative position of the piston or piston movement (trace  506 ), in which the algorithm is a function of the responsiveness of the solenoid piston in accordance with an exemplary embodiment of the present invention. Notice from control signal  502 , that rather than merely clipping the portion of the 24 VAC control signal at 0.0 volts, as in the prior art, the present chatter algorithm modulates the control signal positive for only one half of a cycle every N cycles. Thus, the algorithm causes the irrigation controller to send one control pulse every N cycles, thereby increasing the length of the duty with respect to the control pulse. More time is provided for the piston to recover to the closed position and away from the solenoid core. In response, the solenoid actuator produces one audible click  508  for each N cycles. 
   In order to ensure that a click  508  will be produced for each control pulse (or each duty cycle), the algorithm holds E 0 =0.0 volts for a longer time period than the time necessary for the solenoid piston to return to the closed position Z c , or at least nearly so. Thus, N is selected such that (N/f−|t 4 −t 1 |)≧|t 5 −t 4 |. This can be visualized diagrammatically in  FIG. 5 . There, the period of the control signal is set to NT, where T=1/f, (recall that f is typically 50 Hz or 60 Hz). Consequently, as illustrated by trace  502 , the signal is held at E 0  or 0.0 volts, for at least the time period from t 4  to t 5 , or for the time it takes for the piston to move from the open position, Z 0 , to the close position, Z c . It may be possible to select a value for N min  (the minimum or threshold value for N) such that (N min /f−|t 4 |−t 1 |) is slightly shorter that |t 5 −t 4  during that time period piston  802  separates sufficiently from core  808  to produce an audible clicking sound. However, as a practical matter it is probably not possible to determine an absolute value for N min  that will induce an audible chatter for all solenoid actuators, regardless of their age or physical condition, therefore the value for N min  should include a significant safety factor. 
   Returning again to the diagram of controller  202  in  FIG. 2 , microprocessor  212  and firmware in PROM/ROM  214  control the timing of the conduction of switch  254  by supplying the appropriate control signal to the switch. The valve locator function in firmware enables switch  254  for the selected control wire output and modulates the conductivity to control wire  140  for, for example, one-half of an AC cycle every six AC half-cycles (i.e., N=3). This results in allowing a solenoid current to be applied at a 16.7% duty cycle, with a repetition period of 50 ms with 60 Hz available AC power or 60 ms with 50 Hz available AC power. 
   It should be appreciated that regardless of the value of N, the repeated clicking caused by  802  striking core  808 , will produce an audible chatter tone as a sub-harmonic of 60 Hz (or 50 Hz). Due to constant presence of 60 Hz s a very common background signal generated by many appliances, it is often ignored by habit. This is problematic for locating hidden valves, since the chatter noise from a solenoid piston may be quite faint. Therefore, in accordance with still another exemplary embodiment of the present invention, the chatter algorithm is based on the responsiveness of the solenoid actuator and modulates the control signal to vary the tone of the chatter. 
     FIG. 6  is a timing diagram depicting the interaction between the control signal (trace  602 ) and the relative position of the piston or piston movement (trace  606 ) for a chatter algorithm in which the selection of N is modulated as a function of time (i.e., N(t)), where N(t)≧N min . In accordance with this embodiment, the chatter algorithm is a function of the responsiveness of the solenoid actuator since N(t)≧N min , where N min  is the threshold value of N at which an audible chirp will reliably be produced by the solenoid actuator. However, notice that the frequency of the duty cycle of trace  602  changes over time. That is, the period of control signal, N j T, is shorter at time t 1  and t 3 , and longer at time t 2 , such that N t1 T&lt;N t2 T&gt;N t3 T and N t1 T≈N t3 T. The resulting chatter tone would be perceived to the operator as a higher pitch, followed by a lower pitch and then followed again by a high pitch, as illustrated by the frequency of clicks  608 . Clearly, the chatter tone continues as sub-harmonics of 60 Hz, but with constantly changing pitch and therefore, easier to detect against background noise that might be present in an area. The chatter algorithm can be programmed to modulate the pitch of chatter tone in ascending sequence, a descending sequence, a ditty of pitches or even a random pitch sequence rather than producing a steady state clicking tone. Alternatively, the current signature that produces the actuator movement may be altered to maximize the volume of the chattering sound for a particular solenoid. Here, it would be particularly advantageous to employ remote controller  262  for changing the chatter tone and/or volume rather than repeatedly returning to controller  202 . 
   Finally, in accordance with still another exemplary embodiment of the present invention, and as depicted by the timing diagrams in  FIG. 7 , the chatter algorithm modulates control signal, and hence the chatter tone, by using some complex function (i.e., f(N(t))) where f(N(t))≧N min . In accordance with this embodiment, the chatter algorithm is a function of the responsiveness of the solenoid actuator since f(N(t))≧N min , where N min  is the threshold value of N at which a chirp will reliably be produced by the solenoid actuator. Here, the chatter algorithm is programmed to modulate the pitch of chatter tone as a more rapid and defined sequence of pitch changes, for instance scaling. Thus, as opposed the exemplary embodiment discussed above with regard to the timing diagrams in  FIG. 6 , wherein the pitch changes as blocks of the tones, in accordance with the present embodiment the chatter tone may change period to period, based on a separate function, f(N(t)). 
   With regard to the transmission of other types of control signals and/or transmitting control signals through other transmission mediums,  FIG. 9  is a block diagram of irrigation system  900  for transmitting control signals using a two-wire control network and a wireless network in accordance with other exemplary embodiments of the present invention. Irrigation system  900  comprises irrigation controller  902  for controlling the coextensive water and electrical control networks, and valves  110  contained therein. Irrigation system  900  is similar in many respect to controller  202  described above with regard to  FIG. 2 , and therefore only differences in the two networks have been illustrated in  FIG. 9  and will be discussed below. Irrigation controller  902  generally includes microprocessor (Main CPU)  912 , programmable read only memory (ROM/PROM)  914  and random access memory (RAM)  916 . Microprocessor  912  communicates with ROM/PROM  914  and RAM  916  in a conventional manner utilizing address bus  918  and data bus  920 , and as should be understood that ROM/PROM  914  and RAM  916  may be incorporated within or provided separate and apart from microprocessor  912 . A time of day clock  952  is also connected to microprocessor  912  through address bus  918  and data bus  920 . 
   Communication between wired external devices is achieved using serial communications port  932 , which is connected to (or is incorporated in) the microprocessor  912  to support communications between the irrigation controller  902  and external devices. Communication between most components not connected to address and data buses  918 / 920  and irrigation controller  902  is accomplished using I/O interface  948 . For instance, communication between irrigation controller  902  and each data encoder transceiver  960  (and antenna  962 ), user interface  946 , display  950 , data encoder  970  and optional inputs from other sensors  256  such moisture sensor  956  ( 1 ) and rainfall sensor  956 ( 2 ). 
   System  900  is depicted as having two independent electrical control networks, a wireless electrical control network for controlling of zone  1  and zone  2  and a two-wire electrical control network for controlling zones  3 - 5 . With regard to the two-wire control network, controller  902  includes data encoder  960  coupled between I/O  948  and nodes  954  (of which only two nodes are now necessary for coupling control wires  940  to all values in the two-wire control network). Data encoder  960 , under the direction of CPU  912 , encodes valve addresses (along with other actuation commands and/or actuation data) for transmission on the control wires  940 . Also resident on the irrigation control wires  940 , with the valve address signal, is an actuation current. Generating control signals may be accomplished in a variety transmission methods, a few exemplary methods are discussed further below. 
   Also include in irrigation system  900  is a plurality of valve control modules  980 , each is coupled between the control wires  940  and solenoid  116  of valve  110  for switching the actuation current from the control wires in response to receiving an actuation control signal from data encoder  960 .  FIG. 10A  is a diagram of a valve control module (VCM) in accordance with an exemplary embodiment of the present invention. Located proximate to each irrigate valve  110  (on the two-wire control network) is valve control module  980  that comprises data decoder  1082  and solenoid controller  1084 . Data decoder  1082  decodes incoming signals on control wire  940  and passes the decoded signal information to solenoid controller  1084  (it is expected that the processing capability resides in the solenoid controller, but alternatively the solenoid controller might merely perform the function of a switch under the direction of the a data decoder). Solenoid controller  1084  analyzes the decoded signal information for its own unique hardware address. In accordance with one embodiment, each valve control module  980 , as well as the irrigation controller  902 , is permanently assigned a unique hardware address (similar to a MAC (Media Access Control) address used in computer networks) that uniquely identifies each valve control module as a node of the irrigation control network. Alternatively, the hardware addresses may be manually configurable at each valve control module to suit the operator. Once solenoid controller  1084  detects its own unique hardware address in the decoded signal information, it analyzes the remainder of the decoded control signal information for other information, such as actuation control commands and actuation control data. Solenoid controller  1084  controls the control current between control wires  940  and irrigate valve  110  based on commands it receives in that information. The specific operation of each component in the VCM will vary depending on the transmission protocol imposed by on the control network. 
   In an analogy to the multi-wire irrigation control network discussed above with regard to  FIG. 2 , and accordance with one exemplary embodiment, a hardware address signal itself provides the actuation control current necessary for operating a specific irrigation valve. CPU  912  generates an actuation control signal and identifies a specific valve by the hardware address for a recipient irrigation valve, which is received by the I/O  948  and transformed into a control signal with the actuation control current by data encoder  960 . This embodiment requires very little logic processing capability in VCM  980 . A dumb valve control module is utilized for processing this type of control signal. The actuation control signal is simultaneously received by both the data decoder  1082  and solenoid controller  1084  in VCM  980 . Data decoder  1082  decodes the control signals and passes the decoded control signal information to solenoid controller  1084 . When solenoid controller  1084  recognizes its own hardware address in the decoded control signal information, it allows the actuation control signal (actually the control current) to pass through to the valve&#39;s solenoid. As mentioned above, the process capability may reside in data decoder  1082 , rather than solenoid controller  1084 , which would then merely direct solenoid controller  1084  to allow the actuation control signal to pass through to the valve&#39;s solenoid. In accordance with this exemplary embodiment, in irrigation mode the CPU  912  repeatedly generates actuation control signals faster than the response time of the valve, thus causing the valve to remain open. In valve locator mode, the CPU  912  generates actuation control signals in accordance with the valve locator algorithms discussed above. 
   While the irrigation controller  902  can simultaneously control multiple irrigation valves using the above-described transmission protocol by successively placing different addresses on control wires  940 , throughput is problematic; at some point the succession of repetitious addresses overloads the irrigation control network resulting a premature valve closing. Therefore, in accordance with other embodiments the actuation control signals are implemented in a stacked or layer protocol, with the actuation control current, wherein a valve control information word or packet is formed by an address layer and a command layer. Operationally, and in accordance with this embodiment, the valve address layer provides identification information for a specific hardware address assigned to a single irrigation valve, while the actuation control layer provides actuation control commands. 
   For either of the three exemplary transmission modes described below, a smart valve control module is necessary to process data from control wires  940 . A smart valve control module does more than recognized its own unique hardware address, it also recognizes and parses out command information and actuation data accompanying the address information, and executes the commands as a sequence of control instructions. In accordance with this embodiment, the solenoid controller unpacks the command data from the address layer, analyzes the structure of the control command(s) and then executes the command(s) in accordance with its structure. This greatly decreases the amount of information on the network and simplifies the operation of the network components. 
   In accordance with one exemplary transmission method, irrigation controller  902  generates a symmetrical AC wave (either a sine wave or a square wave) with a peak amplitude large enough to provide power to the valve solenoids and the associated valve control circuit—for example 20 volts peak. The period is similar to that used for prior art solenoids (50 Hz-60 Hz). At a zero time crossing, a brief period of time (approximately 1 mS) is used to encode a digital stream with traditional logic levels. This digital data consists of two components: a solenoid (valve) address and a command. VCM  980  accepts this composite signal, uses the large signal to feed its power supply, data decoder  1082  decodes the digital data from the signal and solenoid controller  1084  interprets the digital data to determine when it should pass the power along to its solenoid. 
   Alternatively, the digital data may be algebraically added to the main signal without special timing to place it near the zero crossing. In accordance with this exemplary embodiment, the data simply “rides on top of” the main power signal and is stripped off using a high pass filter (not shown) in VCM  980 . 
   Finally, other transmission protocols are currently being used in two-wire control networks other than for irrigation control that may be adapted use in an irrigation control network. Of particular importance is a protocol called “Digital Command Control” (DCC), adopted and used by the National Model Railroad Association, Inc. (MRDA) as Electrical Standards For Digital Command Control, All Scales S9.1. DDC is currently used to enable independent simultaneous control of dozens of model trains on the same set of tracks. With regard to an irrigation control network, a symmetrical square wave is used to provide power, but data are embedded in the pulse width by data encoder  960 . The pulse width for each pulse is either “short” or “long.” Data decoder  1082  measures these pulse times and decodes them to binary values. Based on the encoded data, solenoid controller  1084  identifies its own unique hardware address in the binary values and interprets the remaining digital data to determine when it should pass the power from the square wave along to its valve&#39;s solenoid. Alternatively, other transmission modes are known and may also be may be implemented for transmitting and processing logical data for controlling irrigation valves. 
   With regard to any of the logical transmission modes described above, and in accordance with one exemplary embodiment, CPU  912  identifies a specific valve and generates an actuation control command(s) for the valve, which is received by the I/O  948 . I/O  948  passes the information to data encoder  954  which “packetizes” the control command(s) into an address layer for transmission onto the network. In irrigation mode, the irrigation controller  902  generates actuation control “on” command as a logical ON, causing the valve to open, and subsequently separately generates and transmits an actuation control “off” command, as a logical OFF, causing the valve to close. In valve locator mode, the irrigation controller  902  generates a series of alternating ON and OFF commands in accordance with the timing of the valve locator algorithms discussed above. Alternatively, the irrigation controller  902  may instead generate a more complicated control command structure to be executed by the valve control module. For example, in irrigation mode the irrigation controller  902  may generate an ON command, followed by time interval command, and, optionally, followed by an OFF command, to be packed in an address layer of a single packet. Irrigation value control module  980  receives the data packets, identifies a valve address as its own hardware address and parses out actuation commands in the packet. For example, the message may take the form of &lt;hardwareaddress&gt; &lt;messageSTART&gt; COMMAND; COMMAND; ACTIUATIONDATA; COMMAND &lt;messageEND&gt;. The commands are executed in sequence, for example, executing a logical ON command by actuating the value, then tracking the time for the designated time interval command and then closing the valve, or executing a logical OFF command, if present. In valve locator mode, the logical OFF command may be followed by a second time interval command and a logical REPEATX command, instructing irrigation value control module  980  to open the valve for the first time interval, close it for the second time interval, and then repeat the sequence for X-number of repetitions. 
   The use of packetized data transmissions, and a unique hardware addressing scheme, facilities two-way information traffic between the respective irrigation valves and the irrigation controller via a signal encoder/decoder, which replaces address encoder  960  in irrigation controller  902 . The address encoder/decoder (not specifically shown) decodes information from the respective irrigation valves, as well as encodes valve addresses and valve commands destined for the valves&#39; electronics. Bi-directional communication is advantageous for returning an acknowledgment of a command, i.e., a logical ACK command, and for returning status after executing a series of commands, i.e., logical READY command. To further facilitate bi-directional data transmissions the valve control module may also comprises a valve status sensor and/or other appliances (not shown) for monitoring valve functions and a signal encoder/decoder (rather than an address decoder) for encoding valve function information for delivery to the irrigation controller, as well as decoding valve addresses and command information. 
   With regard to a wireless embodiment, the irrigation controller  902  acts as a wireless access point for transmitting (and potentially receiving) radio frequency signals for controlling (and potentially monitoring) the respective irrigation valves. Referring again to controller  902  illustrated in  FIG. 9 , coupled to the I/O  948  is encoder/transceiver  962  and is further coupled to antenna  964  through node  963 . Encoder/transceiver  962  receives control signal command inputs from the I/O  948  and encodes the commands as irrigation value addresses before transforming the addresses, and other data, as electromagnetic signals (typically in the radio frequency range) for transmission on antenna  964 . In operation, the irrigation controller  902  can generate an address command or a more complicated layered message in which an actuation control command is packaged within an address layer, identical to the two-wire embodiment described above. Optionally, the wireless network may operate in uni-or bidirectional modes as also discussed above with regard to the two-wire embodiment. The use of packetized data transmissions enables two-way information traffic between the respective irrigation valves and the irrigation controller via a signal encoder/decoder transceiver (rather than an address encoder transceiver) for decoding information from the respective irrigation valves, as well as encoding hardware addresses and actuation control commands. 
   Also, in accordance with the present wireless embodiment, each valve now also becomes a wireless access point.  FIG. 10B  is a diagram of a wireless valve control module (WVCM) in accordance with an exemplary embodiment of the present invention. Located proximate to each valve  110  in the wireless network is wireless valve control module  990 . WVCM  990  generally comprises solenoid controller  1094  coupled to actuation current source  1096  and also coupled to data decoder/transceiver  1092 , which is connected to antenna  1098 . Antenna  1098  intercepts an electromagnetic waves (typically in the radio frequency range) which are then received by data decoder/transceiver  1098 . The decoder function attempt to decipher any signals in the airwaves, and decode the signals into actuation control signal information for processing by solenoid controller  1094 . Solenoid controller  1094  analyzes the decoded control signal information for its own unique hardware address. When it recognizes its address, it continues analyzing the decoded control signal information for any other actuation commands and actuation control information that might accompany the address. In a typical message, the address is followed by one or more actuation commands, the data necessary to perform the command, such as a time limit, etc., and terminates with a logical END statement. The commands are processed into a control sequence for directing solenoid controller  1094 . Alternatively, solenoid controller  1094  may be embodied as a mere switch for controlling the actuation current, with decoder/transceiver  1098  comprises electronics and logical components for processing into a control sequence. In that case, the decoded commands are executed by data decoder/transceiver  1098 , which then directs the operation of solenoid controller  1094 . 
   Actuation current source  1096  may be replaceable and/or rechargeable battery, or instead may be a separate actuation current wire coupled to a transformer (current step-down) unit remotely located at an AC outlet in relative proximity to the valve (this is more feasible for use with irrigation valve manifolds located in close proximity to wired structures). Wireless valve control module  990 , in accordance with one exemplary wireless embodiment, operates similarly to valve control module  980  described above in the two-wire embodiment with the exception that the source of the actuation control current is not commingled with the control signal in the airway, but is supplied by a separate source (i.e., a battery, separate wired current source, etc.). 
   The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. For instance, although the present invention has been discussed in term of an irrigation controller, the present valve locator may be incorporated into any type of valve controller without regard to irrigation. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.