Technical Field

The present invention relates to a controller for operating an electrically driven pump associated with a liquid supply system. It also relates to a method for pressurising a liquid supply in a liquid supply system. The invention is applicable for example to a water supply system in which water is drawn from a source of water, for example a holding tank, dam, reservoir or the like, and is supplied under pressure for household, farm, commercial or industrial use. The invention will be described with reference to its use in a water supply system, however it could also be used in other liquid supply systems.

Background

A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was, in Australia, known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims.

Households that are not connected to a municipal (mains) water supply may rely upon water supplied from a storage tank and pressurised by a pump. The pump may be activated by a controller which uses detection of pressure to switch the pump on and off, for example two pressure thresholds may be set, that is an upper threshold at which the pump is switched off and a lower or "cut-in" threshold at which the pump is switched on. However if the difference between the two thresholds is relatively large, the pressure fluctuation in the water supply system may be unacceptable.

To alleviate this problem, a controller that automatically measures a pump's maximum output pressure when installed in a system (also known as its closed head pressure) and establishes a lower pressure threshold that is a certain percentage (say 80%) of this maximum output pressure has been proposed - see international publication WO 03/029656 A1 (PCT/AU02/01334). Although this can provide a relatively smaller pressure output variation (for example 20%) than with pre-set pressure thresholds, it may result in a higher "standby" pressure in the household's water supply system which increases the likelihood of leaks in pipe joints and taps etc. of the water supply system. The pressure drop occasioned by any such leaks with the higher cut-in pressure threshold (that is, the threshold value at which the pump is switched on) can lead to frequent switching on and off (that is, cycling) of the pump - which is undesirable. Thus, choosing the appropriate value of a cut-in (pump on) pressure is a compromise between the pump cycling when set too high and large pressure variation when set too low.

One proposal to avoid frequent cycling, such as when there is a slow leak in the water supply system, is to have two pre-set cut-in pressure thresholds, the higher one of which (say 80% of the pump's output pressure) is set when no leakage is detected, and the lower one of which (say 50% of the pump's output pressure) is set when leakage in the system is detected, that is when uniform pressure drops and repeat frequencies typical of slow leaks such as a dripping tap for example are detected.

Although a re-setting of the cut-in pressure threshold to a lower value may alleviate the slow leak, the householder will again experience a significant variation in supply pressure until the higher cut-in threshold is re-set. Also, the leakage response may be unnecessarily triggered by equipment with a slow but constant demand for water, for example an evaporative cooler.

The invention, according to one embodiment, seeks to provide a controller for the pump which alleviates the significant pressure variation problem yet still provides for effective detection of and response to leaks in the liquid supply system.

Other embodiments of the invention seek to satisfy other objects. Thus another embodiment seeks to provide a controller having parts that are relatively easily assembleable and may therefore save manufacturing costs. Yet another embodiment seeks to provide a controller through which the liquid flow is directed to allow for improved flow characteristic measurements. A further embodiment seeks to provide a pressure unit which allows an observer (for example a user of a water supply system) to ascertain the status of the pressure within the unit.

Summary of the Invention According to a first embodiment the invention provides a controller for operating a pump associated with a liquid supply system, the controller including: a pressure unit including a housing having an inlet for connection to the liquid supply and an outlet for delivery of the liquid to a consumer, a control circuit mounted on the housing and including a sensor, wherein the pressure unit and the sensor are operatively associated such that the sensor generates signals related to pressures within the pressure unit, and wherein the control circuit is operative to determine from the signals generated by the sensor a rate of pressure change within the pressure unit to vary, in dependence upon the rate of pressure change, a threshold pressure value at which the control circuit is operative to switch on the pump to pressurise the liquid supply for delivery to the consumer.

An aspect of the invention which may be associated with the above described first embodiment is the provision of a method for pressurising a liquid supply in a liquid supply system having a closed head pressure, the liquid supply system including a pump for pressurising the liquid supply wherein the pump is operated when the liquid supply pressure falls to a threshold value below the closed head pressure, the method including the steps of: (i) determining the closed head pressure of the liquid supply,

(ii) measuring changes in pressure of the liquid supply due to a flow of liquid from the liquid supply, (iii) calculating a rate of pressure change from the measurements of step

(iv) varying the threshold pressure value for operating the pump in dependence upon the calculated rate of pressure change, wherein the threshold pressure value is increased for relatively large rates of pressure change and is decreased for relatively low rates of pressure change.

The pressure unit may include a diaphragm within the housing and the diaphragm may have a permanent magnet associated therewith to which the sensor is responsive. Such a sensor may be a Hall effect device which generates a variable voltage signal related to pressures within the pressure unit in dependence upon the position of the diaphragm and thereby the permanent magnet.

The liquid supply system will have a closed head pressure, and preferably the variable threshold pressure at which the control circuit is operative to switch on the pump is a percentage of the closed head pressure (% _cu t-ιn), and wherein the rate of pressure change ^ and the % _cut - _ιn are linearly, logarithmically or exponentially related. Preferably the % _cu t-ιn and the ^- are linearly related between a maximum % _cu t-ιn

(for example 90% of the closed head pressure) and a minimum % _cu t-ιn (for example 30% of the closed head pressure) and wherein for pressures above and below, respectively, the maximum and minimum % _cu t-ιn values, the respective % _cu t-ιn value is constant.

The water supply system may include an external accumulator, and in this case the % _cu t-ιn may be a function of ^ and the liquid flow rate Q, that is:

%cut-.n = f (-f , Q).

According to a second embodiment, the invention provides a controller for operating a pump associated with a liquid supply system for the pump to pressurise the liquid supply, the liquid supply system having a closed head pressure, the controller including: a pressure unit including a housing having an inlet and an outlet, a diaphragm within the housing which is biased to act against the pressure of the liquid supply between the inlet and the outlet when a liquid supply is connected to the inlet, wherein the bias on the diaphragm is such that the diaphragm remains in substantially one position whilst the liquid supply pressure within the housing is at the closed head pressure, (wherein said one position depends upon the closed head pressure and may differ for the controller in different liquid supply systems), a circuit structure carrying a control circuit for operating the pump for supplying liquid to and through the housing, the control circuit including a sensor which is mounted on the circuit structure such that it is operatively associated with the diaphragm for sensing positions of the diaphragm as the diaphragm moves away from said one position in response to liquid pressures within the housing below the closed head pressure, wherein the sensor provides signals to the control circuit indicative of liquid pressures within the housing for the control circuit, whilst there is a liquid flow through the housing, to operate the pump when the sensor provides a signal indicative of a liquid pressure within the housing that is a predetermined value below the closed head pressure, such that the liquid supply pressure is maintained within a predetermined range from the closed head pressure. The closed head position of the diaphragm (that is, the said "one position")has a direct relationship with the supply pressure. This allows the controller to automatically adapt to a large range of different pumps and pressures.

The sensor may be a Hall effect device which is responsive to a permanent magnet that is associated with the diaphragm, as is described above for the first embodiment.

In the first and second embodiments, the circuit structure may include a liquid flow sensor as part of the control circuit, in which case the housing includes an aperture and the circuit structure is mounted on the housing such that the liquid flow sensor is exposed to a liquid flow through the housing from the inlet to the outlet.

When the liquid pressure within the housing is the predetermined value below the closed head pressure, the control circuit will operate the pump. The liquid flow sensor provides a flow signal to the control circuit to recognise when there is a liquid flow through the housing and if this signal is present, operation of the pump is continued. However if the flow signal is not present, operation of the pump is stopped after a short time in the order of seconds (e.g. 5 seconds). When liquid flow is present, operation of the pump is continued until the flow stops. Thus primarily the flow signal is used by the control circuit to determine a no-flow condition through the housing at which time the control circuit will turn the pump off. In some circumstances the flow sensor may also be used to turn the pump on when there is sufficient flow through the housing but no detectable pressure change (for example, if there is no water in a system, and hence zero pressure, and then water is returned to the system by, say, rain).

Also in both embodiments, the inlet of the housing may include a valve for preventing reverse liquid flow into the inlet. Such a valve may include a moveable closure member which contacts a valve seat when the valve is closed and the moveable closure member may be shaped such that a flow of liquid into the housing when the valve is open is directed towards the liquid flow sensor.

According to a third embodiment the invention provides a controller for operating a pump associated with a liquid supply system, the controller including: a pressure unit including a housing having an inlet for connection to the liquid supply and an outlet for delivery of the liquid to a consumer, a circuit structure carrying a control circuit for operating the pump for supplying liquid to and through the housing, the control circuit including a liquid flow sensor, wherein the housing includes an aperture and the circuit structure is mounted on the housing such that the liquid flow sensor is exposed to liquid within the housing, wherein the inlet of the housing includes a valve for allowing a flow of liquid into the housing from the inlet and preventing a reverse flow of the liquid from the housing into the inlet, wherein the valve is shaped such that a flow of the liquid into the housing is directed towards the liquid flow sensor, wherein the liquid flow sensor provides a flow signal to the control circuit to recognise there is a liquid flow through the housing. The above described third embodiment of the invention may include one or more of the additional features associated with either the first or second embodiments of the invention.

Preferably the design of the valve and its positioning within and size relative to the housing is such as to minimally affect pressure loss within the housing. In all embodiments, the aperture of the housing may be adjacent the valve, and thus adjacent the inlet, allowing any arrangement and number of outlets. In one embodiment, the inlet and the outlet of the pressure unit may be in-line and the aperture may be laterally located between the inlet and the outlet for the directed liquid flow to pass over the liquid flow sensor. In all embodiments, the circuit structure is preferably a printed circuit board on which the pressure sensor (for example a Hall effect device) and the flow sensor (for example a structure based on thermal techniques) are mounted.

According to a fourth embodiment of the invention, there is provided a pressure unit for a liquid supply system for delivery of the liquid to a consumer, the liquid supply system having a closed head pressure, the pressure unit including: a housing having an inlet and an outlet, a diaphragm within the housing which is biased to act against the pressure of the liquid supply between the inlet and the outlet when a liquid supply is connected to the inlet, wherein the bias on the diaphragm is such that the diaphragm remains in substantially one position whilst the liquid supply pressure within the housing is at the closed head pressure (wherein said one position depends upon the closed head pressure and may differ for the controller in different liquid supply systems) and the diaphragm moves away from said one position when the liquid supply pressure within the housing decreases, wherein the diaphragm is associated, on its side that is not exposed to the liquid supply, with a moveable member having pressure indicia, wherein the housing includes a window and the window and moveable member are such that for the diaphragm in said one position a pressure indicium indicating the closed head pressure is exposed through the window and for movement of the diaphragm away from said one position, a pressure indicium indicating a decreased pressure is exposed through the window.

The indicia that are viewable through the window advantageously provide a relatively simple means for several pieces of information as to the liquid supply pressure condition within the pressure unit to be conveyed to a consumer without providing a quantitative pressure measurement. Thus it shows whether liquid is available - for example, if there is no liquid, the pressure will be zero and this could be indicated by red indicia being exposed in the window. For normal pressures, the exposed indicia could be green and if, for example, there is a leaking tap, and thereby reducing pressure within the pressure unit, the associated movement of the diaphragm may be indicated by green to red indicia being exposed. Use of quantitative pressure measurements is deliberately avoided because there may be a range of "normal" operating pressures which may not be realised by consumers.

For a better understanding of the various embodiments of the invention and to show how they may be performed, a preferred embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings. It is to be understood that various of the features of the preferred embodiment may be omitted to realise exemplifications of the first to fourth embodiments of the invention as broadly described above.

Brief description of the drawings

Figure 1 illustrates a liquid supply system with which the preferred embodiment is useable.

Figure 2 is an isometric view of a controller according to the preferred embodiment.

Figure 3 is an exploded view of the controller of figure 2 viewed from one direction.

Figure 4 is an exploded view of the controller of figure 2 viewed from another direction to that of figure 4. Figures 5 and 6 are longitudinal cross-sections of the controller of figure 2 illustrating its diaphragm in two different locations.

Figures 7 and 8 are transverse cross-sectional views through a pressure chamber of the controller of figure 2, illustrating the inlet and outlet and a valve arrangement therewith, figure 7 illustrating the valve in a closed position and figure 8 illustrating the valve in an open position.

Figures 9 and 10 are isometric views of a portion of the controller of figure 2 illustrating the valve arrangement in two positions, similarly to figures 7 and 8.

Figure 1 1 is a block diagram illustrating functions of an electronic control circuit of the controller of figure 2.

Figure 12 is a circuit diagram of the control circuit.

Figures 13 and 14 are graphs illustrating operational regimes for a controller of figure 2.

Detailed description of the preferred embodiment

Figure 1 illustrates a simple liquid supply system 20 with which the embodiment of a controller to be described below may be associated. The liquid supply system is a water supply system and the preferred embodiment will hereinafter be described with reference to its use in such a system. The water supply system 20 includes a reservoir 22 for a supply for the water

23, for example a household rainwater tank, having a pump 24 driven by an electric motor 26 in an outlet for pumping the water to various consuming outlets 28, for example a tap, toilet, shower and/or laundry. The electric motor 26 of the pump 24 is controlled via a controller 30 which controls the operation of the pump 24 based upon water pressure and water flow parameters that are determined via the controller 30.

As shown in Figures 2 to 6 the controller 30 includes a pressure unit 32, which is made up of a housing 34 having an inlet 36 for connection to the water supply from the pump 24 and an outlet 38 for delivery of the water to the consumer devices 28. The figures show a priming cap 128 screwed onto the outlet 38. In use, the outlet 38 would be connected to a pipe leading to the consuming outlets 28. The housing 34 may also include additional outlets for supply of water to additional consumers, for example a second outlet 130 is illustrated. If only one outlet 38 is to be used, the additional outlets would be blocked, for example by priming caps 128. The housing 34 is composed of three portions, that is, an end portion 34a which principally contains a helical compression spring 42, an intermediate portion 34b which principally defines a pressure chamber 44 and a cover portion 34c.

The housing 34 contains a diaphragm 40 which is biased via the helical compression spring 42 to act against the pressure of the water within the pressure chamber 44 between the inlet 36 and the outlet 38 when a water supply is connected to the inlet 36. Thus the portion 34b of the housing 34 and the diaphragm 40 define the pressure chamber 44 with which the inlet 36 and the outlet 38 (which are formed in the intermediate portion 34b of housing 34) are in communication. The end portion 34a of the housing 34 and the diaphragm 40 define another chamber 46 within which the spring 42 is located. A still further chamber 48, which is adjacent to the pressure chamber 44 and opposite the diaphragm 40, is defined by the intermediate portion 34b and the cover portion 34c of the housing 34. A circuit structure 50 carrying a control circuit 140 (to be described in detail below with reference to figures 1 1 and 12) is mounted within the chamber 48. The end portion 34a of housing 34 includes an inwardly extending tubular part

52 (see figures 5 and 6) over which the spring 42 locates. A guide member 54 for operative association with the housing 34 end portion 34a, the spring 42 and the diaphragm 40 comprises a central stem 56 which extends through a cylindrical part 58 having an end cap 60. One end of the spring 42 locates over the inwardly extending tubular part 52 of the housing end portion 34a and the other end locates within the annular space between the rearward portion of the stem 56 and the cylindrical part 58 of the guide member 54, with part of the rearward portion of the stem 56 fitting inside the inwardly extending tubular part 52 and able to slide therein. The outside diameter of the cylindrical part 58 of the guide member 54 is sized such that it also is a sliding fit within an internal diameter defined by ribs 62 in the housing 34 end portion 34a that surround the inwardly extending tubular part 52. The guide member 54 furthermore includes an outermost cylindrical skirt 59 which is shorter than the cylindrical part 58 and provides an end rim 61 which serves a purpose to be described below. The end cap 60 of the guide member 54 provides a solid supporting seat for a raised central area 64 of the diaphragm 40. The diaphragm 40 has an outwardly flared wall 66 (best seen in figure 5) which extends from the periphery of its central area 64 and which joins with a curved outer wall 68 having a circumferential flange 70. The flange 70 formation seats within a complementary shaped recess 72 defined by the housing 34 end portion 34a and is clamped in position by a complementary shaped facing end 74 of a rib 76 on the housing 34 intermediate portion 34b when the housing 34 is assembled. The contact regions between the flange 70 of the diaphragm 40 and the complementary recess 72 of the end portion 34a and the end 74 of rib 76 of the intermediate portion 34b are such that when the pressure chamber 44 contains water under pressure, the junctures are sealed to prevent the pressurised water from leaking into the spring chamber 46.

The diaphragm 40 also includes, protruding centrally from its central area 64, a blind cylindrical extension 78, within which fits the forward portion of the stem 56 of the guide member 54. A permanent magnet 80 is mounted within the stem 56 at its forward end.

The inlet 36 and the outlet 38 of the pressure chamber 44 include there between a valve arrangement 82 for allowing water to flow into the pressure chamber 44 of the housing 34 from the inlet 36 and preventing a reverse flow of the water from the pressure chamber 44 into the inlet 36. The valve 82 includes a closure member 84 which is held captured within a tubular part 85 which fits through and screws into an internal thread of the outlet 38. The tubular part 85 includes legs 86 having a smaller diameter ring 87 at their ends which captures the closure member 84 whilst allowing it to reciprocate towards and away from the inlet 36. The closure member 84 includes a shaped end 88 (which is generally conical with a rounded apex - best seen in figure 8) which has a peripheral groove that retains an O ring 91. The O ring 91 seals onto a valve seat 90 on the inlet 36. A helical compression spring 92 (see figures 7 and 8 - the spring 92 has been omitted from the other figures for clarity) surrounds the smaller diameter ring 87 of the tubular part 85 and acts between the ends of the legs 86 and a rear surface 89 of the shaped end 88 of the closure member 84 to bias the closure member 84 towards the inlet 36 into engagement with the valve seat 90.

The inlet 36 comprises a conduit 94 which extends into the pressure chamber 44 and is moulded as part of the intermediate portion 34b of the housing 34. A connector fitting 96 (see figures 3 and 4), which includes at one end a screw thread 98 and a nut formation 100 and at the other end the valve seat 90 below which is a groove 102, is fitted through the conduit 94 and held captive therein by a circlip 104 which sits within the groove 102 and bears upon an end rim of the conduit 94 within the pressure chamber 44. Thus the connector fitting 96 is rotatable within the conduit 94 which allows ready attachment of piping from the pump 24 onto the threaded end 98.

In normal operation of the pressure unit 32 with pressurised water within the pressure chamber 44 and the pump 24 not operating and water present at the inlet 36, the closure member 84 of the valve arrangement 82 is held in sealing engagement against the valve seat 90 of the inlet 36 by the pressure of the water acting on the rear surface 89 of the closure member 84 assisted by the spring 92, thus preventing flow of the water from the pressure chamber 44 into the inlet 36. When the pump 24 is operated, water is pumped into the inlet 36 until its pressure increases sufficiently to force the shaped end 88 of the closure member 84 to unseat from the valve seat 90 and thus open the valve arrangement 82 for the water to be pumped through the pressure chamber 44 from the inlet 36 into the outlet 38.

The design of the valve arrangement 82 and more particularly the shaped end 88 of the closure member 84 within the pressure chamber 44 (which is relatively large compared to the valve arrangement 82) is such that there is minimal loss of head through the pressure chamber 44.

The wall 105 of the intermediate portion 34b of the housing 34 opposite to the diaphragm 40 includes an aperture 106 for a purpose to be described below.

The circuit structure 50 mounted within the chamber 48 is a printed circuit board 108 which includes a liquid flow sensor. The flow sensor is of the type that operates based on thermal techniques and includes sources of heat such as resistive heater elements and temperature sensors, such as thermistors. Examples of such sensors are disclosed in International Publications WO 91/19170 (PCT/AU91 /00239) and WO 03/029656 (PCT/AU02/01334). The electronic circuitry of the flow sensor of the present embodiment is described in detail below with reference to figures 1 1 and 12. Structurally, the flow sensor comprises a metal plate 1 10 (see figures 3 and 4) onto an insulating layer on a rear surface of which the heater elements and thermistors are mounted. The printed circuit board 108 includes an aperture 1 12 and the metal plate 1 10 is attached to the printed circuit board 108 over the aperture 1 12 such that its uninsulated front surface, when the printed circuit board 108 is mounted within the chamber 48 via posts 109 and the cover portion 34c, is exposed to water flow within the pressure chamber 44 via the aperture 106. A ring seal 1 14 is located within the chamber 48 between the periphery of the aperture 106 and the metal plate 110 of the printed circuit board 108 to prevent leakage of water from the pressure chamber 44 into the chamber 48 within which the circuit structure 50, that is the printed circuit board 108 is mounted.

The purpose of the shaped end 88 of the closure member 84 of the valve arrangement 82 is to direct water flow entering the pressure chamber 44 from the inlet 36 towards the flow sensor, that is towards and over the surface of the metal plate 1 10 which is exposed through the aperture 106. The flow sensor provides a flow signal to the control circuit 140 (to be described below with reference to figures 1 1 and 12) to recognise there is a water flow through the pressure chamber 44 of the housing 34 for the control circuit 140 to continue to operate the electric motor 26 of the pump 24.

As shown in figure 1 1 the control circuit 140 also includes water pressure detection circuitry 146 which includes a Hall effect device 116 as a sensor (see figures 3, 5 and 6). The Hall effect device 1 16 is mounted on the printed circuit board 108 such that when the printed circuit board 108 is mounted within the chamber 48, the device 1 16 is located closely adjacent to wall 105 of the housing 34 intermediate portion 34b and is positioned to lie on the central axis of the diaphragm 40/guide member 54 arrangement, such that it is influenced by the magnetic field of the permanent magnet 80 that is mounted at the forward end of the stem 56 of the guide member 54 as the diaphragm 40 moves. Thus, as the water pressure within the pressure chamber 44 decreases, the permanent magnet 80 moves towards the Hall effect device 116 and as the liquid pressure increases, the permanent magnet 80 moves away from the Hall effect device 1 16. When a current is flowing through the Hall effect device 1 16, the movement of the permanent magnet 80 and thereby its magnetic field relative to it generates voltage signals which, as will be described below, are utilised to determine rates of pressure change within the pressure chamber 44 of the pressure unit 32.

Two limits are defined for the movement of the diaphragm 40/guide member 54 arrangement. One limit, for high pressure within the pressure chamber 44, is set by the end rim 61 of the outer most cylindrical skirt 59 of the guide member 54 bearing upon a step 1 18 inside the end portion 34a of the housing 34 (see figure 6). The other limit, for low pressure within the pressure chamber 44, is set by a laterally extending head 122 of a screw 120 in the rearward end of the stem 56 of the guide member 54 bearing against a shoulder 124 formed within the bore of the inwardly extending tubular part 52 of the end portion 34a of the housing 34 (see figure 5). A protective cap 126 is fitted to the end portion 34a to close the bore of the tubular part 52.

As shown in the exploded views of figures 3 and 4, a sealing ring 132 is interposed between the intermediate portion 34b and the cover portion 34c of the housing 34 to ensure that the circuit structure 50 is sealed within the chamber 48.

The control circuit 140 comprises several sections that serve different functions, as shown by the functional blocks in figure 1 1. Thus there is a microcontroller and its support circuitry 142, and power supply circuitry 144 for operating the various functions via the microcontroller. There is water pressure detector circuitry 146, of which the Hall effect device 1 16 is a component, and water flow detector circuitry 148 of which the metal plate 1 10 is a part. The microcontroller and support circuitry 142 determines the operation of pump driver circuitry 152 for operating the pump 24 via its electric motor 26. Additionally there is LED and LED driver circuitry 154 for indicating various control conditions. With reference to figure 12, the water flow detector circuitry 148 is made up of resistors (H1 , H2, H3, R12, R15, R19, R22 and R23), thermistors (TH1 , TH2 and TH3), capacitors (C10, C1 1 and C12) and transistor Q3.

The resistors H1 , H2 and H3 are mounted on the rear surface of the metal plate 1 10 over an insulating layer and are connected in series and form the basis of the primary heat source. The power dissipated by these three resistors is regulated by the microcontroller IC1 , through pulse width modulation on the switching of the transistor Q3. The three thermistors, TH1 , TH2 and TH3, are strategically located on the metal plate 1 10 of the printed circuit board 108, also over the insulating layer, and are designed to measure the temperature at the surface on which they are mounted. As the insulating layer of the metal plate 1 10 is a poor thermal conductor, the power dissipated by the resistors, H1 , H2 and H3, will be distributed unevenly along the surface of the metal plate 1 10, hence the three thermistors, TH1 , TH2 and TH3 will register slightly different temperature measurements. The microcontroller IC1 continuously monitors the temperature differential between the thermistors TH1 and TH2. The metal plate 1 10 of the printed circuit board 108 is in constant contact with water, hence water flow will improve the thermal conduction along the surface of the metal plate 1 10 and a reduction in the temperature differential between TH1 and TH2. The microcontroller IC1 will use this information in an algorithm to determine whether water is flowing or not. The thermistor TH3 is used to compensate for an additional temperature effect due to the Triac Q1 while the pump is in operation.

The water pressure detector circuitry 146 comprises the integrated circuit IC2 and capacitor C13. The integrated circuit IC2 is a Hall effect device that translates the magnetic field it senses from the permanent magnet 80 into an analogue voltage that is presented to pin 2 of the microcontroller IC1.

The pump driver circuitry 152 comprises resistors (R4, R6, R7, R8, R9 and R10), transistor Q2, Triac Q1 and integrated circuit IC6. When a logic high level signal is outputted at pin 7 of IC1 , transistor Q2 will switch on and cause current to flow through the LED of the optocoupler IC6. This forward current that flows through the LED will generate infrared radiation that triggers the detector. Once triggered, the detector stays latched in the "on state" until the current through the detector drops below the specified holding current. The detector's "on state" will cause sufficient current to flow into the gate of the Triac Q1 and cause it to switch on and start conducting, hence operating the pump motor. A logic low level signal outputted at pin 7 of IC1 will switch off transistor Q2 and subsequently the pump motor.

The microcontroller and support circuitry comprises the integrated circuit IC1 , resistors (R5, R1 1 , R24) and capacitor (C1 ). The integrated circuit IC1 is an 8-bit microcontroller with flash memory. With the firmware loaded into its flash memory, IC1 will perform the control algorithm.

The power supply circuitry 144 comprises the Varistor (VDR1 ), capacitors (C2, C3, C4, C5, C6, C7, C8, C14, C15, C17 and C18), resistors (R1 , R16, R25, R26, R27, R28, R29 and R30), diodes (D1 , D2, D3, D4, D5, D6, D7, D8, D9 and D10), inductors (L1 and L2), transformer (T1 ) and integrated circuits (IC3, IC4 and IC5). VDR1 and C1 provide protection against electrical noise spikes at the mains supply input. Diodes D1 , D2, D3 and D4 form a full bridge rectifier which rectifies the input mains supply voltage to a full-wave rectified DC voltage. Components C2, L1 and C3 form a pi-filter network that provides filtering to the rectified DC voltage from the bridge rectifier a well as differential mode EMI filtering. A flyback power supply is formed by the integrated circuit (IC3), resistors R16,

R25, R26, R27 and R28, diodes D5, D6 and D10, capacitors C4, C18 and C19 and transformer T1. Diode D5, capacitors C3, C5, and resistors R26 and R27 form a clamp circuit limiting the leakage inductance turn-off voltage spike on pin 4 of IC3 to a safe value. The rectified and filtered input voltage is applied to the primary winding, pin 1 , of the transformer T1. The other side of the transformer primary, pin 2, is driven by the integrated circuit IC3.

The AC voltage at the secondary winding of the transformer T1 is half-wave rectified by the diode D9 and converted into a filtered DC voltage by a pi-filter comprised of L2, C15 and C14. The filtered DC voltage is regulated by the zener diode D7. When the filtered DC voltage exceeds the sum of the zener diode's voltage and optocoupler LED forward voltage, current will flow in the coupler LED and will cause the transistor of the optocoupler to sink current. When this current exceeds the threshold level at pin 1 of IC3, IC3 will inhibit the next switching cycle. When the filtered DC voltage falls below the threshold, IC3 will initiate a conduction cycle and by adjusting the number of enabled cycles, output regulation is maintained.

Components D6, R28, R16, C4, D10 and C18 provide over-voltage protection to the power supply. When an over-voltage condition occurs and the bias voltage exceeds the sum of the zener diode's voltage, D10, and the threshold voltage level at pin 2 of IC3, current begins to flow into pin 2 of IC3. When this current exceeds the threshold of IC3, IC3 will shut down until the voltage level at pin 2 of IC3 drops below a pre-determined level.

The AC voltage across the pins 10 and 8 of the transformer T1 is half-wave rectified by the diode D8 and converted into a filtered DC voltage level by capacitors C6 and C7. The integrated circuit IC5 is a voltage regulator that converts the filtered DC voltage at its input pin 3 into a regulated lower voltage level, say 5 Vdc, suitable for the rest of the electronics to operate in. The capacitor C8 provides further filtering at the output of IC5 to eliminate any voltage level fluctuations.

The resistors (R13, R14 and R17) and LEDs (LD1 , LD2 and LD3) form the LED and LED driver circuitry 154. A high logic level at pin 3, pin 9 and pin 15 of IC1 will turn on the LED LD1 , LD2 and LD3 respectively. Resistor R24 and push button S1 form the user input circuit. Pressing S1 will present a logic level low signal at pin 1 1 of lCL

Upon installation of a controller 30 in a water supply system 20, the pump 24 is operated to establish a closed head pressure for the system, that is the maximum water pressure within the pressure unit 32 that is established with all of the consuming outlets 28 closed. The pump 24 is then turned off and the pressure unit reverts to a normal standby condition wherein, as illustrated by figure 6, the diaphragm maintains a first position against the bias of the spring 42 whereat the magnet 80 is maximally spaced from the Hall effect device 1 16 and, as illustrated by figure 7, the valve arrangement 82 is closed. When a consuming outlet 28 is open, the pressure within the pressure chamber 44 reduces and the diaphragm 40 (and thus the magnet 80) is moved by the bias of spring 42 towards the Hall effect device 1 16 (see figure 5) and thus the pressure drop is detected. So long as there is prime at the inlet 36, the valve arrangement 82 will open (see figure 8) and water will flow over the metal plate 1 10, thus a water flow will be detected by circuitry 148. When the pressure within the pressure chamber 44 reduces to some predetermined level of pressure below the closed head (called the cut-in pressure) the pump driver circuitry 152 of the control circuit 140 will switch on, via the Triac Q1 , the electric motor 26 and thus the pump 24, provided the water flow detector circuitry 148 detects water flow over the metal plate 110 and the water level detector circuitry 150 detects that there is a supply of the water. The switching on of the pump 24 ensures that the water supply pressure in the water supply system 20 is maintained within a predetermined range from the closed head pressure. When the consuming outlet or outlets 28 is/are closed, the flow signal ceases and the controller 30 reverts to the normal standby condition.

In the fault situation of a loss of prime at the inlet 36, the bias of the diaphragm registers zero pressure, no water flow will occur over the metal plate 1 10 and thus there will be no detection of flow by the water flow detector 148 and the pump will be switched off after possibly being on for a very short period.

In another fault situation of a leak in the water supply system 20, for example a dripping tap 28, then from the standby condition of the controller 30, there will occur a slow loss of pressure within the pressure chamber 44 which will result in movement of the diaphragm 40 (and thus its associated magnet 80) towards the Hall effect device 1 16 and thus detection of the reducing pressure via the circuitry 146. According to an embodiment of the present invention, such detection of the reducing pressure is operative to vary the cut-in pressure, that is, generally to reduce it to avoid frequent switching on and off of the pump 26. The LED and LED driver circuitry 154 is operative for the LEDs to indicate different conditions, for example green for "on", red for "standby" and yellow for "fault". The push button S1 is a manual start button for priming the pump.

In the preferred embodiment of the present invention, the control circuit 140 is operative to determine from the signals generated by the Hall effect device 1 16, a rate of pressure change within the pressure unit 32 (specifically within the pressure chamber 44) to thereby vary the threshold pressure value at which the control circuit 140 is operative to switch on, via the Triac Q1 , the electric motor 26 of the pump 24 to pressurize the water supply 23 for delivery to the consumer. The rate of pressure change may be determined by the microprocessor from, for example, five voltage readings from the Hall effect device 1 16 per second. Thus, if the demand from consuming outlets 28 is high, there will be a large rate of pressure change and the cut-in pressure threshold can be high, whereas if the consumer demand is such as to create a slow rate of pressure change, such as for example may be caused by a leaking tap 28, then the cut-in pressure threshold can be low. Thus a cut-in pressure can be determined as a percentage of the closed head pressure (% _cu t-m) dependent upon a rate of change of pressure (^ , where P is pressure and t is time).

The relationship between the % _cut . _ιn and the ^ can be linear, for example as shown by line 160 of the graph of figure 12. Alternatively it may for example be logarithmic (see curve 162 of figure 12) or exponential (see curve 164 of figure 12).

Also the relationship need not be a continuous function, for example a maximum and/or a minimum % _cut - _ιn (for example 90% and 30% respectively as illustrated by the graph of figure 13) may be provided where values respectively above and below these %cut-ms are set to a constant value. The relationship 1 16 illustrated by figure 13 is linear between the maximum and minimum % _cut . _ιn values.

A water supply system 20 may include a relatively large external accumulator tank (not shown). If such an accumulator tank is present in the system 20, the rate of pressure change will be slower for any given flow rate than in a system without such a tank. The controller 30 may be adapted for such a system by making the % _cu t-ιn a function of not only the rate of change of pressure but also the water flow rate, for example:

%cut-ιn = f (IT . Q) where Q is the volumetric flow or

%cut-.n <x (-f +Q). With this regime, the higher the flow rate Q or the rate of change of pressure, the higher the cut-in percentage and vice versa. Of course, how the two parameters of flow rate Q and the rate of change of pressure ^- are combined and weighted would be tailored to suit the target water supply system. The controller 30 may include indicia viewable by a consumer to give an indication as to the water supply pressure condition within the pressure chamber 44. Thus, as shown in figure 2, the housing portion 34a may include a window 170 and the guide member 54 may include, on its outermost cylindrical skirt 59, indicia 172 that are viewable through the window 170. The visible indicia may be green for the diaphragm 40/drive member 54 arrangement positioned as illustrated in figure 6 (that is for normal pressure within the pressure chamber 44) and may show red for pressures that are reduced, for example for the diaphragm 40/guide member 54 arrangement positioned as illustrated in figure 5. It is envisaged that a controller 30 according to embodiments of the invention may be used for "mains boosting", that is, for example with a mains supply system to a household where the mains pressure is low or unacceptably variable. Using the control regime described above and with the mains pressure applied to the pressure chamber 44, so long as the mains pressure is above a threshold cut-in value, the pump will not start. However should the pressure fall below the cut-in pressure, then according to the rate of pressure change, the pump will be started at some lower threshold ready to boost the supply pressure.

The preferred embodiment described above is illustrative of the various embodiments of the invention as initially summarised. These generally described embodiments, and the specifically described preferred embodiment, are susceptible to variations, modifications and/or additions other than those specifically described and it is to be understood that the invention in all its various embodiments includes all such variations, modifications and/or additions which fall within the scope of the following claims.