Water sensing apparatus

A water sensing apparatus has a housing and a circuit within the housing. An alarm, e.g. a piezoelectric horn, is driven by the circuit. An elongate sensor is secured to the housing and is connected to the circuit. The other end of the sensor is adapted for sensing the presence of water, to activate the alarm. The sensor is both sufficiently rigid to enable it to maintain a configuration in which the apparatus is hung by the sensor, and is sufficiently flexible to enable it to be bent manually to a desired configuration.

FIELD OF THE INVENTION 
This invention relates to a water detection apparatus. This invention more 
particularly relates to a water detection apparatus suitable for domestic 
or industrial use, for detecting floods and high water levels in baths or 
other containers. 
BACKGROUND OF THE INVENTION 
The problem of flooding in domestic housing and industrial buildings is 
well known. This is particularly the case in structures that have 
basements. Flooding can be caused by a variety of sources. For example, it 
can be caused by a burst pipe, heavy rainfall, or water backing up through 
the drains. In many cases, flooding is only discovered after a significant 
amount of water has collected, causing considerable damage. 
It is desirable that any flooding should be detected as soon as possible. 
In many cases, the actual water accumulation is relatively slow, so that 
early detection enables remedial action to be taken. For example, in the 
case of a burst pipe, the main water supply can be turned off. 
Alternatively, if the water is coming from outside, then, in extreme 
cases, one could use a pump to pump out the basement. 
Also, some houses and industrial buildings are located in areas that have a 
high water table. In such a case, it is relatively common to provide a 
sump pump or the like, to prevent excessive accumulation of water in a 
basement. This is an adequate solution, provided the pump works as 
required. However, if the pump fails, then a considerable quantity of 
water can accumulate before the failure is detected. 
It is also to be realized that, apart from domestic and industrial usage, 
there are situations where it is desirable to monitor the filling of a 
vessel. Thus, for example, in the domestic situation, it is desirable to 
be able to monitor the filling of a bath tub, sink and the like. 
Also, for external use, it is common to have a tub or container that is 
filled with water from one source or another. Again, it is often desirable 
to monitor the filling of the container. 
For marine use, it is desirable to monitor the water level in the bilges of 
a vessel. This can provide an early warning of failure of a sump pump or a 
leak occurring. 
Whilst proposals have been made for flood alarms or water level detectors, 
many earlier proposals suffered from many disadvantages. Such detectors 
were often intended either to be fixed in position, or were intended for 
being moved around from location to location. However, earlier detectors 
were not suitable for both types of use. Some earlier detectors did not 
include any lead with the actual sensor on it, thus effectively preventing 
their use for detecting bath tub levels etc. For use in monitoring bath 
tub levels and the like, a water sensing apparatus should be capable of 
being readily mounted on the edge of the bath tub. This was not possible 
with known devices. 
BRIEF SUMMARY OF THE PRESENT INVENTION 
In accordance with the present invention, there is provided a water sensing 
apparatus comprising a housing, a circuit within the housing, an alarm 
connected to and driven by the circuit, and an elongate sensor, one end of 
which is secured to the housing and is connected to the circuit and the 
other end of which is adapted for sensing the presence of water, to 
activate the alarm, which sensor is sufficiently rigid to enable it to 
maintain a configuration in which the apparatus is hung by the sensor and 
which is sufficiently flexible to enable it to be bent manually to a 
desired configuration. The other end of the sensor has two exposed 
contacts. 
The sensor can be in the form of an elongate extruded plastic strip, with 
two solid copper conductors molded into it along its edges. The ends of 
the copper conductors are exposed at the other end of the sensor, for 
contacting water. The copper conductors provide the desired degree of 
stiffness and resiliency. The copper conductors can be of approximately 
1/16" diameter and spaced approximately 1/2" apart. 
For a water sensing alarm, it is also desirable that the user can be 
confident that the unit or apparatus is operative. To this end, the 
apparatus can further include an indication that it is operative. It is 
also preferably powered by a battery, and in this case can include an 
indication that the battery power is getting too low. 
This can be achieved by providing a light emitting diode (LED), connected 
to and controlled by the circuit. The LED can be flashed briefly at set 
intervals, for example every 45 seconds, to indicate that the unit is 
operative. This uses little power. Additionally, when the power level gets 
too low, then the alarm can be sounded intermittently, to warn the user 
that the battery needs replacement. By this means, the user can be 
confident that the apparatus is operative.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
A water sensing apparatus is indicated by the reference 20. The apparatus 
20 has a housing 22 and an elongate sensor 24. As shown in FIG. 1, it is 
provided with a mounting bracket 26. 
Referring to FIG. 4, the housing 22, in known manner, comprises a rear 
housing half 22a, and a front housing half 22b, secured together by screws 
23. The rear housing half 22a includes an opening closeable by a cover 
plate 28, in known manner. 
Within the housing 22, a printed circuit board 30 is mounted. The circuit 
board 30 is secured by screws 32 to the rear housing half 22a. These 
screws 32 engage cylindrical projections 34. 
The rear housing half 22a includes a profiled recess 36 for one, upper end 
of the sensor 24, indicated at 120. A similar recess 37 is provided in the 
other housing half 22b. The housing half 22a additionally includes a 
downwardly extending extension 40 including a hollow cylindrical 
protrusion 42. 
As described in greater detail below, the sensor 24 includes a body 122 
including conductive leads 124. As shown, upper ends 124a of the leads are 
stripped and curved through 90.degree. for mounting in holes 44 in the 
printed circuit board 30. 
Additionally, the sensor upper end 120 includes a pair of holes 126, and 
below them an opening 128, the opening 128 being larger than each of the 
holes 126. 
During assembly, the sensor upper end 120 is fitted onto the projections 34 
and protrusion 42, which extend through the holes 126 and opening 128 
respectively. The circuit board 30 is then secured by the screws 32 to the 
projections 34, thereby clamping the sensor upper end 120 in position. 
The hollow cylindrical protrusion 42 extends below the main part of the 
housing 22, and can be used for permanent mounting of the device. Thus, a 
screw can be inserted through it to permanently fix the apparatus 20 to a 
wall. 
To the front housing half 22b, a piezoelectric horn 44 is mounted. This 
piezoelectric horn 44 is mounted by means of an annular ring 46 of foam 
material, coated on both sides with adhesive. It is secured to a 
corresponding annular projection 48. This greatly facilitates mounting of 
the horn 44 as compared to conventional techniques. The piezo horn 44 can 
be of known construction and includes contact surfaces on its back. The 
housing 22 includes an opening 50 for the sound generated by the horn 44. 
On the printed circuit board 30, flexible contacts, indicated generally at 
52 are provided, for contacting the piezo horn 44, in known manner. 
Also mounted on the printed circuit board 30 are an integrated circuit 54, 
which forms the basis of the circuit, and a light emitting diode (LED) 56. 
The other components on the circuit board 30 are detailed in relation to 
the diagram of FIG. 5. 
In known manner, the top of the housing 22 defines a battery compartment 
58, in which a battery 60 is located. The cover plate 28 provides access 
to the battery 60. The battery 60 is connected by a lead 62 to the printed 
circuit board 30. The battery 60 is a nine volt battery. 
Referring to FIG. 3, there is shown the internal circuit, in schematic 
form, of the integrated circuit 54. The fourteen pins of the integrated 
circuit 54 are given the reference numerals 1-14. The integrated circuit 
54 can be any suitable circuit and can have varying characteristics. It is 
a low power CMOS integrated circuit. It has built-in hysteresis and a 
reduced input differential voltage, to make it stable yet sensitive. 
The circuit includes an input 1 for a low voltage reference signal. This is 
connected to an internal voltage reference 70, which in turn is connected 
to a differential amplifier 72. The other input of the amplifier 72 is 
connected to an input 7 for the power supply voltage. 
Input lead 3 is for an input from the sensor 24, whilst input lead 5 is for 
a sensor reference input. These inputs 3, 5 are connected to a further 
differential amplifier 74. The outputs of the two differential amplifiers 
72, 74 are connected to two inputs of an OR gate 76. The input 4 is blank. 
The input lead 6 is connected to another input of the OR gate 76, and also 
to ground as indicated. 
Input lead 2 is connected to a horn modulating oscillator 78, which is in 
turn connected to a horn oscillator 80. An output of the OR gate 76 is 
connected to and controls the horn modulating oscillator 78 and the horn 
oscillator 80. 
Input lead 9 serves as an output for the piezoelectric horn 44 and is 
connected to the output of the horn oscillator 80; the output of the 
oscillator 80 is also connected by an inverter 81 to another horn driver 
output at lead 13. 
Lead 10 is a feedback lead from the horn 44, whilst lead 8 is an inverse 
feedback lead from the horn 44. 
Lead 14 is connected to the LED 56, and is connected via a gate transistor 
82 to ground. 
Lead 11 is a ground connection. 
Lead 12 is connected to a trouble clock oscillator 84, whose output is 
connected to the differential amplifier 72 and the gate transistor 82. 
Referring to FIG. 5, the integrated circuit 54 and its leads 1-14 are 
shown. 
Of the battery leads 62, the positive lead 62a is connected via a resistor 
86 and the LED 56 to the lead 14, with the lead 62b connected to ground. 
This positive lead is also connected via a resistor 88 to the lead 12 
setting the trouble clock 84 frequency. The input lead 12 is also 
connected via a capacitor 90 to ground indicated at 92. The ground lead 11 
is also connected to ground 92. 
The first lead 1, for a low voltage reference is left opened, so that the 
internal voltage reference 70 is used. 
The input lead 2 is connected via a capacitor 94 to ground. By providing a 
capacitor, this gives a pulsed output for the piezoelectric horn 44, as 
opposed to continuous. 
For the sensor 24, one lead is connected to the positive battery lead 62a, 
whilst the other sensor lead is connected to a resistor 96, which in turn 
is connected to the sensor input 3. The sensor input 3 is also connected 
via a resistor 98 to ground. The values of the components are marked on 
FIG. 5, and as indicated, the resistor 96 has a much lesser value than the 
resistor 98. 
The positive battery lead 62a is also connected by two resistors 100, 102 
in series to ground 92. The sensor reference input 5 is connected to the 
junction between the two resistors 100, 102. This thus provides a 
reference voltage at the sensor input 5, of approximately one third the 
battery potential. 
The lead 4, which is blank in any case, is left open, as is the lead 6 for 
connection to other units. In a situation, for example industrial usage, 
where many such units are provided, they could be connected together via 
the leads 6. The power supply lead 7 is connected to the battery lead 62a. 
The piezoelectric horn 44 is connected to the horn driver output 13. The 
feedback lead 10 and the inverse feedback lead 8 are also connected via 
resistors 104 and 106 to one input 108 of the horn 44. Another input 110 
of the horn 44 is connected to the other horn driver lead 9, with a 
capacitor 112 provided between the horn inputs 108, 110. 
The mode of operation of the water sensing apparatus 20 will now be 
described. In use, a suitable battery is connected to the lead 62. 
The trouble clock oscillator 84 controls the amplifier 72 and gate 
transistor 82, so as to maintain them normally open. At set intervals, for 
example 45 seconds, it closes them briefly. This has the effect of turning 
the LED 56 on briefly, to provide a visual indication that the unit is 
operative. Simultaneously, as the amplifier 72 is activated, it conducts a 
voltage check. It compares the voltage at the lead 7 with the internal 
reference voltage from the unit 70. If the voltage at the lead 7 is too 
low, then a signal is sent to the OR gate 76, which in turn activates the 
horn modulating oscillator 78 and the horn oscillator 80. Thus, if the 
battery level falls too low, at the interval set by the trouble clock 
oscillator 84, the horn 44 is switched on briefly. This provides a warning 
to the user that the battery 60 should be replaced. This intermittent 
"beeping" at 45 second intervals can continue for 30 days. If battery is 
not replaced, then the horn 44 will sound continuously for a shorter time. 
Simultaneously, the sensor input at lead 3 is continuously compared with 
the reference input at the lead 5. If the sensor leads 20 contact a body 
of water, then an electrical connection is made between them. This raises 
the voltage at the sensor input 3. This differential between the voltage 
at the input 3 and the reference at the input 5 is detected by the 
amplifier 74. It sends a signal through the OR gate 76 turning the horn 
modulating oscillator 78 and the horn oscillator 80 on. The horn 44 is 
then powered through leads 8, 9, 10 and 13, to provide a pulsed sound, 
warning the user that water has been sensed. 
The sensor 20 is elongate and has a body 122 formed of extruded plastic 
material. As shown in FIG. 4, the cross section of the body 122 has a 
central planar portion of uniform thickness, and two edge portions, which 
are generally circular and whose diameter is larger than the thickness of 
the central portions. Located within the circular edge parts are the 
sensor leads 124. Each lead 124 is formed from solid copper and has a 
diameter of approximately 1/16". The leads 124 are spaced by approximately 
1/2". This construction of the sensor 124 enables it to be readily flexed 
or bent by hand to any desired configuration. At the same time, the solid 
leads 124 enable it to maintain the shape that it is bent into. The lower 
ends of the leads 124 are exposed to form contacts for water. 
With reference to FIGS. 1 and 2, a description of the mode of use of the 
water sensing apparatus 20 will now be given. 
As shown in FIG. 1, the apparatus 20 can be mounted by means of the bracket 
26. For this purpose, the bracket 26 has mounting holes 27 for screws. The 
sensor 24 is manipulated to a straight configuration, and the apparatus 20 
is placed in the bracket with the extension 40 of the housing held by the 
bracket 26. 
As shown, a sensor lower end 121 is then located at a level 130 above a 
floor 132. For example, the sensor 24 could be located in the basement of 
a house, in which case, the level 130 would be just above the basement 
floor at 132. Whilst the lower end 121 is shown spaced just above the 
floor, it could actually be touching the floor, so as to give an 
indication of the presence of any water. 
If flooding should occur, causing water to accumulate on the floor 132, 
when the depth of water reaches the level 130, this will close the two 
leads 124 of the sensor 24. Accordingly, the apparatus 20 will be 
activated, and the alarm 44 sounded. 
FIG. 2 shows an alternative use of the device. Here, the sensor 24 has been 
manipulated into a generally inverted U-shape. This enables the apparatus 
20 to be hung on the side of a bath tub, indicated at 134. The sensor 
lower end 121 is then at a level 136 within the bath tub. The bath tub can 
then be left to fill, without the user being worried about it overflowing. 
Once the water reaches the level 136, the sensor leads 124 will again be 
connected, triggering the alarm 44. The user can then return to turn off 
the water. 
This latter function is expected to be particularly useful for jaccuzzis, 
hot tubs and the like, whether indoors or outdoors, as they take a long 
time to fill. Consequently, most people do not like to wait while they are 
filling. However, if left unattended, there is the danger that one can 
forget that they are filling, resulting in flooding etc. It will thus be 
realized that the water sensing apparatus of the present invention can be 
used for a variety of applications, indicating the presence of water from 
various sources. 
For domestic use, it can be used in the basement, to indicate storm sewer 
backup, leakage from pipes or through outside walls, or failure of sump 
pumps. It can also indicate overflow of a laundry tub etc. In the kitchen, 
it can again detect leakage of pipes or an overflow, for example, from a 
sink. It can also detect leakage from a dishwasher or trouble with an 
automatic ice making machine. 
In a laundry room, it can be used to detect broken or leaking hoses, or 
overflow or a leaky washing machine. In a bathroom, it can detect overflow 
from a bath tub. This both saves the damage caused by water overflow, as 
well as saving on hot water, by simply ensuring that the bath is not 
overfilled. It can also detect overflow or leakage from a toilet, or again 
broken or leaking piping. 
It is also to be noted that in an apartment, if flooding occurs, the loud 
piezoelectric alarm can alert neighbors and security patrols passing 
outside the apartment. This can be particularly useful when the occupant 
is on vacation etc. 
In an industrial or farm situation, it can be used to detect overflow of a 
variety of vessels. It can also detect accumulation of condensation, or 
again the failure of sump pumps. 
For marine applications, it can be used to detect accumulation of water in 
the bilges of a boat. 
The apparatus requires little or no maintenance. The provision of an 
automatic battery warning means that no regular, independent check of the 
battery condition should be needed. However, it is recommended that the 
apparatus is tested once a month, eg. by immersing the sensor in water. 
Also, the end of the sensor should be maintained free from lint and dirt, 
for example by cleaning with a stiff brush. It should also be ensured that 
it is always mounted as required. Water should not be allowed to drip over 
the housing 22, nor should the housing 22 be immersed in water.