GB2202358A

GB2202358A - Water leak detector, alarm and controller

Info

Publication number: GB2202358A
Application number: GB08706350A
Authority: GB
Inventors: Robert William Dawe
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-03-17
Filing date: 1987-03-17
Publication date: 1988-09-21
Also published as: GB8706350D0

Abstract

Freezing conditions can cause water tanks and pipes to rupture. The subsequent thaw allows water to flow freely onto the surrounding environment. This water, when in contact with one or more of a number of strategically placed detectors 11 cause the electrically isolated conductors of the detector sensor to short circuit. The detectors are parallel interconnected and further connected to a control unit 14. The sensor short circuit causes an electrical current to turn on a transistor located in the control unit. This in turn energises a two pole changeover relay, the contacts of which apply power to an audible and visual alarm along with applying 240 VAC power to close a Solenoid or motorized valve 16 installed in the mains water supply. This stops the flow of water to the ruptured pipe. Each detector, (Fig 2, not shown), comprises a housing having drain holes (22) in the top side and a base which is open and to which is secured a p.c.b. sensor (18) or an electrical copper strip board sensor, both sides of which have two electrically isolated paths (21) of electrically conductive material. <IMAGE>

Description

WATER LEAK DETECTOR, ALARM AND CONTROLLER This invention relates to a water leak detector, alarm and controller.

Freezing conditions frequently cause water pipes in buildings to freeze and burst. The subsequent thawing causes water to flow freely onto the surrounding environment. The occupier's first indication of such a burst is when he observes water seeping through ceilings, floors and walls, whereupon he will take the necessary action to isolate the mains water feed to the building.

According to the present invention there is provided a number of parallel inter-connected strategically placed water detectors, each comprising a printed circuit board sensor having two unconnected paths of electrically conductive material etched on both sides. An electrical short circuit is made when two or more consecutive paths on one side or the other are in contact with a conductive element such as water.

The conductive path of all the detector sensors form the input to an electronic circuit housed in a remotely located control unit. The shorting together of any two or more consecutive conductive paths causes an electrical current to flow through a resistor onto the base of a transistor located in the control unit. The transistor is turned on and energises a double pole changeover relay. One set of contacts applies power to an audible alarm and light emitted diode, the other contact allows power to be applied to a Solenoid valve remotely located in the mains water supply pipe.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which Figure 1 shows in perspective five detectors interconnected and further connected into the control unit, along with connections from control unit to Solenoid valve and 240 VAC mains voltage supply.

Figure 2 shows a drawing of the detector.

Figure 3 shows a drawing of the control unit.

Figure 4 shows a circuit diagram of the control unit.

Referring to Figure 1 of the drawings, the water leak detector, alarm and controller comprises a number of detectors 11 interconnected in parallel with a two core cable 13 via a two way connector block 12. One detector is connected to a control unit 14. A Solenoid valve 16 is connected to the control unit via a suitable cable 15. Power to operate the Solenoid valve is supplied from a conventional 240V A.C. single phase power supply 17. (Fused).

Referring to Figure 2 of the drawings, the detector 11 comprises several drain holes 22 drilled in the top side. The base is open and has a lip 20 recessed on all sides to enable the sensor 18 to sit flush with the base of the detector. The sensor 18 is constructed of a flat printed circuit board or electrical copper strip board, both sides of which have two paths of an electrically conductive material 21, running together.

The two paths are electrically isolated from each other. The sensor 18 is rigidly fixed to the lip 20 of the detector 11. Two wires 19 connect top and bottom rails and are connected into a connector block 12 (Refer to figure 1).

There is normally no electrical continuity between the two wires 19.

There will be electrical continuity between the two wires 19 when two or more conductive paths 21 on the top or bottom of the sensor 18 are electrically shorted together. Such a short will occur when any two or more paths are in contact with water, either from the top via drain holes 22, or the bottom of the detector.

Referring to Figure 3 of the drawings, the control unit comprises a suitable box which internally houses the electronic circuitry.

Externally, there is mounted a power on/off switch S1, a power "on" indicating light emitting diode L1, a visual alarm indicating light emitting diode L2, an audible alarm cover 27 and an audible alarm silence switch S2. Cables are entered through the drilled cable entries 37.

Referring to Figure 4, the control unit circuit comprises 2 light emitting diodes, 4 resistors, 2 switches, 1 diode, 1 double pole changeover relay, 1 P.N.P. transistor, 1 piezo electric buzzer, 1 fuse and holder, 1 battery and external connections to the detectors, Solenoid valve and 240V AC power supply.

When any one, or combination of detectors come into contact with water the input terminals I/P are effectively shorted out. Under this condition, and with the power supply switch S1 closed, a small current is allowed to pass through R3 to switch on transistor T1. This causes relay Rel 1 to energise and close contacts C1 and C2. Contact C1 applies battery power to an alarm buzzer Sp and alarm indicating light emitting diode L2. Contact C2 applies 240V AC power to the external Solenoid valve. The switch S2 enables the alarm to be silenced without shutting off power to the Solenoid valve.

Power on indicating LED L1 indicates that the internal battery power is healthy.

In order to detect a water leak, raise an alarm and initiate the necessary control action to isolate the leak, the detectors must be strategically placed around the route of water pipes or water holding tanks. The control unit must be powered, and the Solenoid valve must be connected and installed in the mains water supply pipe to the building.

Claims

1 A water leak detector, alarm and controller comprising a number of parallel interconnected strategically placed water detectors, a control unit and a Solenoid valve. The detectors each comprise a protective housing onto the base of which is fixed a printed circuit board sensor having two unconnected paths of electrically conductive material etched on both sides.

An electrical short circuit is made when two or more consecutive paths on one side or the other are in contact with a conductive element such as water.

The conductive paths of all the detector sensors form the input to an electronic circuit housed in a remotely located control unit.

The shorting together of any two or more consecutive conductive paths causes an electrical current to flow through a resistor onto the base of a transistor located in the control unit, the transistor is turned on and energises a double pole changeover relay.

One set of contacts applies power to an audible alarm and light emitted diode, the other set of contacts allows power to be applied to a Solenoid valve remotely located in the mains water supply pipe.

2 A water leak detector, alarm and controller as claimed in claim 1, wherein the sensor is constructed from electrical copper strip board and the two electrically isolated rails are formed from interconnecting wires between the copper strips.

3 A water leak detector, alarm and controller as claimed in claim 1 or claim 2, wherein the relay is latched such that the detection of water causes the relay to latch closed and remain closed after the detector is dry.

A manual reset switch located on the control box enables the relay to be reset.

4 A water leak detector, alarm and controller as claimed in claim 1 or claim 2 or claim 3, wherein the controller is powered from an AC voltage source implementing an AC/DC power supply converter.

5. A water leak detector, alarm and controller, as claimed in claim 1 or claim 3 or claim 4, wherein the Solenoid valve is replaced by a motorised valve.

6. A water leak detector, alarm and controller, as claimed in any preceding claim, wherein the sensor has a number of unconnected paths of electrically conductive material etched on one side of the printed circuit board only.

7. A water leak detector, alarm and controller as claimed in any preceding claim, wherein the internal battery power supply is recharged via the mains supply to form a battery back-up facility.

8. A water leak detector alarm and controller as claimed in claim 4, wherein a battery is supplied to form a D.C. supply back-up (via a suitable means) in the case of an A.C. mains failure.

9. A water leak detector, alarm and controller as claimed in any preceding claim, wherein the sensor has several holes drilled in the centre away from the electrically conductive paths to enable water to drain through the sensor.

10. A water leak detector, alarm and controller as claimed in any preceding claim, wherein the alarm signal is transmitted to an external alarm.

11. A water leak detector, alarm and controller substantially as described herein with reference to Figures 1-4 of the accompanying drawings.