Abstract:
A water detection system for detecting water and activating an alarm is provided. The water detection system includes an alarm relay and a water sensor. The water sensor includes a solid state switching and amplifying circuit for detecting low levels of current flow and amplifying the signal to activate the alarm relay. In one embodiment, the water detection system further includes an alarm panel, including visual and audible alarms activated by the alarm relay. In one embodiment, the water detection system includes multiple water sensors for providing zone protection. In one embodiment, the alarm relay is configured to shut-down the device causing the presence of water. A method for implementation of the water detection system is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     None. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a system and method for detecting the presence of water. More particularly, it relates to a solid-state electronic circuit for detecting the presence of water and a method for using the circuit. 
     Undetected water leaks can cause property damage, equipment shutdowns, and expensive clean-up costs. Furthermore, these leaks can create a hazardous working environment for persons in the vicinity of a leak. Typical uses for water detection systems include placement beneath air conditioning systems to detect condensation overflow, placement in homes to detect water overflow onto the floor from a sump, and placement in selected locations in various-commercial processes to detect undesired water leaks and overflows. 
     One type of water detection system, a closed-circuit-type system, includes a sensor having two conductive probes. The sensor is placed at the location that water detection is desired, and the presence of water is detected when the water closes an electrical circuit by connecting the two probes. This closed-circuit-type water detection system is capable of detecting a thin film of water. The amount of water necessary for proper operation of this type of water detection system depends upon the sensitivity of the circuit and its ability to detect a flow of electrons between the two probes. 
     Closed-circuit-type water detection systems, known in the prior art, all have shortcomings that limit their effectiveness, reliability, and safety. One system uses a high voltage applied to the probes in a series circuit, along with a relay. While the high voltage may help to detect the presence of smaller amounts of water, it has several disadvantages, including creating an unsafe condition for persons in the operating environment. Other systems apply high current levels to the probes, which can result in an unsafe operating condition and can cause deterioration of the probes due to electrolysis. Still other water detection systems use highly sensitive solid-state circuitry, but the design limits the possible distance between the sensor and an alarm. This distance is limited because the use of long wires creates a voltage drop, a capacitive effect, and an inductive effect which can act to create false alarms. 
     There remains a need in the art for an effective and safe water detection system that can detect very small amounts of water, and for a system that allows the sensors to be placed at substantial distances from an alarm. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is a water detection system for detecting water and activating an alarm. In one embodiment, the system includes a sensor and an alarm. The sensor includes a first probe and a second probe coupled to an amplifying and switching circuit. The sensor further includes first and second terminals located across the amplifying and switching circuit. The first probe and second probe are configured to contact any of the liquid present in the operating environment. The alarm housing includes an alarm circuit for activating an alarm and is electrically coupled to the first and second terminals of the sensor. 
     While several alternative embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, wherein is shown and described only the embodiments of the invention, by way of illustration, of the best modes contemplated for carrying out the invention. As will be realized, the invention is capable of modification in various obvious aspects, all without departing from the spirit and scope of the present invention. 
    
    
     Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing components of a water detection system according to a first embodiment of the present invention. 
     FIG. 2 is a schematic diagram showing the circuitry of the water detection system shown in FIG.  1 . 
     FIG. 3 is a perspective view of a water detection system according to a second embodiment of the present invention. 
     FIG. 4 is a schematic diagram of the circuitry of the second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 is a block diagram of a water detection system  10  according to a first embodiment of the present invention. As shown in FIG. 1, the water detection system  10  includes a voltage source  12 , a relay coil  14 , and a water sensor  16 , connected in series. The voltage source  12  provides the electricity to power the circuit. The relay coil  14  activates when a sufficient level of current flows through the circuit and operates to control an alarm or other auxiliary device. The water sensor  16  is placed at the detection site and operates by closing a circuit upon detection of the presence of water. In one embodiment of the present invention, all of the components shown in FIG. 1 are contained within one housing, which is then placed directly at the detection site. In another embodiment of the present invention, the voltage source  12  and the relay coil  14  are located in a separate housing and are coupled to the water sensor  16  by an electrical conductor. The voltage source  12  is typically either a battery or a direct current power supply. 
     FIG. 2 is a schematic diagram showing the water detection system  10 . As shown near the top of FIG. 2, the voltage source  12  includes a first conductor  18   a , coupled to a negative terminal, and a second conductor  18   b , coupled to a positive terminal. As shown near the middle of FIG. 2, the water sensor  16  includes a first terminal  20   a  and a second terminal  20   b . The first conductor  18   a  is coupled to the first terminal  20   a  of the water sensor  16 . The second conductor  18   b  is coupled to the relay coil  14 , which in turn is coupled to the second terminal  20   b  of the water sensor  16 . 
     As shown near the bottom of FIG. 2, the water sensor  16  includes a first probe  22   a , a second probe  22   b , a first resistor  24   a , a second resistor  24   b , a transistor circuit  26 , a capacitor  28 , and a diode  30 . The probes  22   a  and  22   b  act as the terminals of a switch that is closed by the presence of water. In one embodiment, the probes  22   a  and  22   b  are placed about one half inch apart. The resistors  24   a  and  24   b  are biasing resistors and have appropriate values to allow proper operation of the transistor circuit  26 . The values of the resistors  24   a  and  24   b  control the sensitivity of the transistor circuit  26 , and one of ordinary skill in the art can select appropriate resistance values. The transistor circuit  26  is connected across the probes  22   a  and  22   b . The capacitor  28  acts to smooth any ripple voltage in the signal coming from the voltage source  12 . The diode  30  acts to prevent the circuit from damage if the terminals of the voltage source  12  are connected to the water sensor  16  in reverse polarity. 
     In one embodiment of the present invention, the water detection system is contained within one housing, which is placed at the water detection site. In other words, each of the voltage source  12 , the relay coil  14 , and the water sensor  16 , are placed within the same housing. The relay coil  14  includes additional leads (not shown) that couple to an alarm device. 
     During operation of the water detection system  10  of the present invention, the water detection system  10  is placed at the water detection site. When no water is present, or insufficient water is present to create a conduction path between the probes  22   a  and  22   b , no current from the voltage source  12  will flow in the circuit. At this point, the electric potential of the voltage source  12  between the positive and negative terminals is present across first terminal  20   a  and second terminal  20   b , as the potential will move through the relay coil  14 . This electric potential then enters the water sensor  16  where the diode  30  prevents a reverse polarity connection, and the capacitor  28  smooths the signal. This smoothed voltage signal is then communicated to the emitter and collector terminals of the transistor circuit  26 . The electric potential is further transmitted to the probes  22   a  and  22   b . At this time, however, as no water is present, the current does not flow through the circuit, as it is open at the probes  22   a  and  22   b.    
     When water is present between the probes  22   a  and  22   b , it will close the circuit and cause current to flow. Because of the high resistance of water, only a small amount of current will flow. In the case of distilled water, it is possible that only a very small level of current will flow through the circuit. This current flow is detected at the base of the transistor circuit  26 . 
     As shown in FIG. 2, in the center of the water sensor  16 , the transistor circuit  26  includes an amplifying transistor  32  and a switching transistor  34 . The small current flow, now present across the probes  22   a  and  22   b , reaches the base of the amplifying transistor  32 , which then operates to allow a current to flow from the voltage source  12  through the amplifying transistor  32  and out its emitter. The emitter of the amplifying transistor  32 , as shown in FIG. 2, is coupled to the base of the switching transistor  34 . This current flow, reaching the base of the switching transistor  34 , allows a larger current from the voltage source  12  to be amplified through the switching transistor  34 . When the switching transistor  34  is activated, it allows a larger amount of current to flow through the circuit from the voltage source  12 , thereby effectively acting to close a switch between the first terminal  20   a  and the second terminal  20   b . In one embodiment of the present invention, the transistor circuit  26  is a Darlington transistor, as known to those of skill in the art. 
     The switching transistor  34 , however, has an internal resistance which allows some amount of the current to continue to flow, through the probes  22   a  and  22   b , to the base of the amplifying transistor  32 , which ensures that the switching transistor  34  remains active as long as water is present. At this point, a majority of the current from the voltage source  12  will flow through the relay  14  and the switching transistor  34 , thereby activating the relay. 
     In one embodiment, the relay coil  14  needs seventy percent of its rated voltage to activate. Therefore, any extremely small current that are amplified by the transistor circuit  26  do not cause the relay coil  14  to activate. Once the current level reach the necessary level, the relay coil  14  is activated, and remains activated until it is reduced to five percent of its rated voltage. Thus, once the relay coil  14  is activated, the voltage at the first terminal  20   a  and the second terminal  20   b  can vary widely without causing the relay coil  14  to deactivate. 
     In one embodiment of the present invention, the circuitry components of the water sensor  16  are encapsulated in epoxy, and the entire housing is sealed to prevent water damage. 
     FIG. 3 is a perspective view of a water detection system  100  according to a second embodiment of the present invention. The water detection system  100  includes an alarm panel  102 , a water sensor  104 , and a power supply  106 . The alarm panel  102  is electrically coupled to the water sensor  104 . The alarm panel  102  is further electrically coupled to the power supply  106 . The power supply  106 , in one embodiment, is designed to convert one hundred twenty volts alternating current into nine volts direct current, and is plugged into a standard wall receptacle. In other embodiments, the power supply  106  is designed to convert power having a wide variety of voltages and frequencies to nine volts direct current. This allows the water detection system  100  to be used with power outlets around the world. In another embodiment, the power supply  106  is a battery. The power supply  106  provides the power needed for operation of the water detection system  100 . The design of the present invention allows the water sensor  104  to be placed at a large distance from the alarm panel  102 , by using conductive wire. Excessive wire length is not a problem, as it is in the prior art, because the circuitry that performs the sensing is located in the water sensor  104 . Therefore, false positive signals are not created by long wire length, in the design of the present invention. 
     The alarm panel  102 , as shown near the top of FIG. 3, includes an audible alarm  108 , abnormal indicator light  110 , an alarm indicator light  112 , a test switch  114 , and a silence switch  116 , all contained within a housing  118 . The components of the alarm panel  102  will be described in greater detail below with reference to the circuit diagram shown in FIG.  4 . The water sensor  104  includes probes  120 A and  120 B on a bottom surface of a housing  122 . 
     FIG. 4 shows a circuit schematic for the water detection system  100  of the present invention. As shown near the top of FIG. 4, the alarm panel  102  is connected to the power supply  106 . Power from the power supply  106  flows into the circuit as indicated. The circuitry of the alarm panel  102  include an alarm relay coil  124  and a silence relay coil  126 . The alarm relay coil  124  includes a first set of contacts  128  and a second set of contacts  130 . The first set of contacts  128  includes normally closed contacts  128   a  and normally open contacts  128   b . The second set of contacts  130  include normally closed contacts  130   a  and normally open contacts  130   b . The silence relay coil  126  includes a first set of contacts  132  and a second set of contacts  134 . The first set of contacts  132  includes normally closed contacts  132   a  and normally open contacts  132   b . The second set of contacts  134  includes normally closed contacts  134   a  and normally open contacts  134   b . The circuitry of the alarm panel  102  further includes a battery  136  connected to the negative terminal of the power supply  106 , by a first diode  138 , when external voltage is present at the power supply  106 . A second diode  140  connects the battery  136  to the positive terminal of the power supply  106  when external voltage is absent. Also, when external voltage is absent, the first diode  138  acts as an open circuit to prevent the battery  136  from energizing the normal indicator light  110 . This indicates to the operator that power has failed, and also acts to conserve the energy of the battery  136 . As shown near the bottom of FIG. 4, the wires  142   a  and  142   b  are designed for coupling to the water sensor  104 . The internal circuitry of the water sensor  104  is not shown in FIG. 3, because it is the same as that of the water sensor  16  shown in FIG.  2 . 
     During operation, when no water is present across the probes  22   a  and  22   b  of the water sensor  104 , power from the power supply  106  will flow through the normal indicator light  110 , the normally closed contacts  128   a , and the normally closed contacts  132   a . This will cause the normal indicator light  110  to glow, indicating a normal operating condition. At this time, current is not flowing through any other portion of the circuit in the alarm panel  102 . As explained above, with reference to FIG. 2, the electric potential from the power supply  106  is transmitted to the terminals  20   a  and  20   b  of the water sensor  104  through the alarm relay coil  124 . When water is present across the terminals  22   a  and  22   b , the water sensor  104  will operate, as described above with reference to FIG. 2, and current will begin to flow through the water sensor  104  circuitry. At this point, with water present between the probes  22   a  and  22   b , the water sensor  104  essentially acts to close the path between contacts  20   a  and  20   b  and allow current to flow through the circuitry in the alarm panel  102 . 
     This closed path allows current to flow through the alarm indicator light  112 , causing it to glow, indicating an alarm condition. It further allows current to flow through the alarm relay coil  124 . Once current reaches seventy percent of the rated level of the alarm relay coil  124 , it will activate. Because the alarm relay coil  124  is not activated until seventy percent of its rated level is reached, it acts to cancel out minor current fluctuations that may be present in the system. The alarm relay coil  124  is not activated until it a sufficiently high current level is reached. When the alarm relay coil  124  activates the first set of contacts  128  switch so that the normally closed contacts  128   a  open, and the normally open contacts  128   b  close, this switch causes the normal indicator light  110  to shut off, indicating that water has been detected. It also allows current to flow through the buzzer  108  to create an audible alarm signal. The second set of contacts  130  of the alarm relay coil  124 , as shown near the bottom right in FIG. 4, are intended for use with an auxiliary device. For instance, they could be connected to a device that is the cause of the water leak and the leak detection will act to shut down the device. 
     If the operator of the water detection system  10  wishes to shut off the audible alarm created by the buzzer  108 , he may press the silence switch  116 . Pressing the silence switch  116  will energize the silence relay coil  126 , causing actuation of its first set of contacts  132  and its second set of contacts  134 . The normally closed contacts  132   a  will open and the normally open contacts  132   b  will close. Opening of contacts  132   a  will cause the buzzer  108  to be cut off from the power supply  106 . The closing of the normally open contacts  132   b  causes the silence relay coil  126  to latch on as it creates a coupling to the power supply  106  even after the silence switch  116  is released. The activation of the silence relay coil  126  will also cause the normally open contact  134   b  to close and the normally closed contact  134   a  to open. The opening of the normally closed contacts  134   a  will deactivate the alarm relay coil  124 . The current will now flow through the silence relay coil  126  instead of the alarm relay coil  124 . 
     When water is removed from the probes  22   a  and  24   b , the current will stop flowing through the water sensor  104  and the silence relay coil  126  will deactivate, returning the system to its initial state. In one embodiment, the circuitry of the alarm panel  102  includes a test switch  114  which may be used to test the various indicators on the alarm panel  102 . 
     In an alternative embodiment of the present invention, the alarm relay coil  124  is located in a housing separate from the alarm panel  102 . In another embodiment of the present invention, multiple water sensors  104  can be connected to the alarm panel  102  to provide zone protection. The circuitry of the alarm panel  102  is capable of monitoring multiple water detectors  104  by connecting each of the water detectors to the terminals  20   a  and  20   b  in parallel. The presence of water at any set of probes of any of the water sensors  104  will cause the alarm circuitry to activate. The design of the present invention allows the use of multiple water detectors  104 , because the water detectors  104  do not draw current until water is present. Therefore, there is essentially no limit on the number of water detectors  104  than can be used. In another of the present invention, a float switch is connected in parallel with the water sensor  104 . When either the water sensor  104  or the float switch detects the presence of water, or water at a specified level, it will activate the alarm circuitry. 
     While the above description describes the present invention with reference to water detection, it should be appreciated that the present invention may also be used to detect the presence or the level of other conductive liquids. Although the present invention has been described with reference to preferred embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.