GB2349208A

GB2349208A - Signalling device

Info

Publication number: GB2349208A
Application number: GB0005139A
Authority: GB
Inventors: David Mayer
Original assignee: ELECTRONIC SOLAR PRODUCTS LIMI
Current assignee: ELECTRONIC SOLAR PRODUCTS LIMI
Priority date: 1999-03-06
Filing date: 2000-03-06
Publication date: 2000-10-25
Also published as: WO2000054233A3; GB0005139D0; GB9905155D0; WO2000054233A2; AU2927800A

Abstract

A signalling device comprises means for storing electrical energy <I>eg</I> a battery (41) connected to signalling means (48) <I>eg</I> an LED, and control means (45) to prevent actuation of the signalling means when charging current is supplied to the storage means but activate the signalling means if that current falls below a threshold. The control means comprises an oscillator (45) which is prevented from oscillating when the current is above the threshold. The current may be supplied to both the storage means and the oscillator via a pair of parallel diodes (D1,D2) from a solar cell connected across terminals (35), and the signalling means (48) may be a visual or audible alarm or an emergency light which is operated when ambient light level falls. Alternatively the oscillator may be controlled by a pressure contact to indicate low pressure in a fire extinguisher, or by the presence or absence of water between electrical contacts to indicate low water level.

Description

2349208 Title - SigLialling Device This invention relates to a sensing and

signalling device, and in particular to a device which emits a visual or audible signal in response to a stimulus such as the absence of ambient light or some other parameter.

There are many situations in which the absence of ambient light may make it desirable for visible or audible signals to be used, eg to provide guidance along a path or to provide warnings of an obstruction or hazard. For instance, such a situation can arise after nightfall or in an emergency in which artificial lighting fails in a building or other enclosed environment (eg in a coal mine, or in a ship or aircraft).

In order to function satisfactorily in such applications, a signalling device should be compact and robust, should be capable of emitting the visual or audible signal for as long as the absence of ambient light persists, and should not require frequent maintenance, eg by replacement of batteries or the like.

There has now been devised a signalling device which satisfies these and other requirements.

According to the invention, there is provided a signalling device comprising storage means for storing electrical energy, signalling means operably linked to said storage means and adapted to be supplied with an electric current by said storage means, and control means operably linked to said signalling means to prevent actuation thereof, said control means being in the form of an integrated circuit containing an oscillator, wherein when the current supplied to the control means is above a predetermined threshold the oscillator is prevented from oscillating and supply of current to the signalling means is prevented, and when the curTent supplied to the control means is below the predetermined threshold the signalling means is actuated.

In one preferred embodiment of the invention the device further comprises collecting means 2 for collecting light energy and converting that light energy to an electric current. In such an embodiment the electric current is preferably supplied to the storage means (so as to charge the storage means) and may also be supplied to the control means so that the control means is sensitive to the presence of ambient light.

Such a device is advantageous in that the storage means is charged when ambient light is present, and the signalling means is actuated automatically when the ambient light is absent. Thus, for a device located outdoors the device is actuated at nightfall; for a device within a building, vehicle or other structure the device is actuated when the ambient lighting is switched off or fails. Because the switching means is responsive to the presence or absence of a current from the collecting means, it is not necessary to provide any additional means for sensing the presence or otherwise of ambient light.

Thus, according to another aspect of the invention there is provided a signalling device sensitive to the presence of ambient light, said device comprising collecting means for collecting light energy and converting that light energy to electrical energy in the form of an electric current, storage means for storing said electrical energy, signalling means operably linked to said storage means and adapted to be supplied with an electric current by said storage means, and control means operably linked to the collecting means so as to cause said storage means to charge when said collecting means generates an electric current and to actuate said signalling means when the current produced by said collecting means falls below a predetermined threshold.

The signalling means most commonly emits a visual signal. The signalling means in such a case comprises means for converting the electrical energy back to light energy. For reasons of compactness, low cost, and low maintenance requirements, such means most preferably comprise one or more light emitting diodes (LEDs).

For other applications, the signalling means may emit an audible signal. In such a case, the 3 signalling means will comprise a loudspeaker or the like. Again, for reasons of compactness and low cost the signalling means preferably comprises a simple piezoelectric loudspeaker. In other applications, the signal may not be produced locally but may be generated at a remote location, eg by being transmitted using cellphone technology, down a conventional 5 telephone landline, eg to a remote computer, or by radio transmission.

The signalling means may emit a continuous signal. However, for many applications it is preferred that the emitted signal should be intermittent, ie the signal will be a flashing light or an intermittent audible tone.

The collecting means for collecting light energy and converting that light energy to electrical energy most preferably comprises one or more solar cells, which are preferably in the form of compact solar panels. The collecting means is preferably capable of collecting light energy from both sunlight and artificial light sources, thereby enabling the device to be used in situations in which there is no natural light, eg in the interior of buildings, vehicles, ships etc or in mines. The collecting means should generally be capable of charging the storage means satisfactorily even at relatively low ambient light levels. Typically, the device will be capable of being charged sufficiently to operate through a full period of darkness (eg overnight) by a few hours illumination at an intensity of 100 Lux or more (which is typical of artificial lighting). Obviously, at higher levels of illumination (eg a few thousand or tens of thousand Lux, which is typical of natural sunlight) the time required to charge sufficiently will be reduced.

Most preferably, the solar panels are capable of absorbing light over a relatively wide wavelength spectrum, and of generating current of at least 8uA. One example of a suitable solar panel is that supplied by Sanyo under the designation AM1414. The performance characteristics of the solar panel may be enhanced by the application of suitable surface coatings, or other modifications known per se.

The storage means for storing electrical energy is preferably an electrical battery connected to the collecting means (where this is present), ie to the solar panels or the like. The battery 4 preferably has a low charge resistance to minimise power losses, and should have sufficient capacity to supply the signalling means for as long as ambient light is absent (which might typically be overnight). Nickel hydride batteries are preferred.

As described above, the control means most preferably comprises an integrated circuit containing an oscillator which is prevented from oscillating when current is generated by the collecting means and thereby prevents current being supplied to the signalling means.

Suitable integrated circuits include DC-to-DC voltage converters. Such a circuit will generally need to be able to operate at the current levels produced within the device. One suitable integrated circuit is that designated TC7660 (Telcorn Semiconductor Inc).

The predetermined threshold at which the signalling means is actuated is most conveniently zero current or a current which is close to zero.

The detection of the presence of ambient light is performed by the collecting means, ie the absence of ambient light is indicated by cessation of electric current generation. Preferably, actuation of the signalling means occurs only after a short delay, to avoid the signalling means being actuated by a temporary loss of illumination intensity, eg due to a passing shadow. Similarly, deactivation of the signalling means is preferably also subject to a delay, to prevent deactivation by a passing light (eg a car headlamp or torch).

For applications other than sensing of ambient light, current may be supplied to the control means directly from the storage means. In such a case, the current path may include a switch or the like which is sensitive to a parameter which is to be monitored. For instance, the switch may be pressure-sensitive and may open in the event that pressure falls below a threshold, thereby cutting off the supply of current to the control means and actuating the signalling means. In another embodiment the device may be used as a water level sensor, the switch comprising a pair of contacts immersed in the water. In such a case the water creates electrical connection between the contacts, that connection being broken when the water level falls.

Thus, according to a further aspect the invention provides a low-pressure indicator comprising storage means for storing electrical energy, signalling means operably linked to said storage means and adapted to be supplied with an electric current by said storage means, and control means operably linked to the storage means via a pressure- sensitive switch, the arrangement being such that when the pressure-sensitive switch is closed current flows to the control means and actuation of the signalling means is prevented, and when the pressure-sensitive switch is open the signalling means is actuated.

Such a low-pressure indicator may be incorporated into an enclosed vessel, actuation of the signalling means providing an indication of a fall in pressure within the vessel. One example of such a vessel is a fire extinguisher, actuation of the signalling means (eg in the form of a flashing light) indicating that the fire extinguisher needs to be recharged.

In such a case, the pressure-sensitive switch is preferably held closed by the influence of pressure applied to the switch, and opens if that pressure falls below a threshold.

In another aspect, the invention provides a water level sensor comprising storage means for storing electrical energy, signalling means operably linked to said storage means and adapted to be supplied with an electric current by said storage means, and control means operably linked to the storage means via a pair of electrical contacts, the arrangement being such that when water is present between the electrical contacts, thereby establishing electrical conduction between them, current flows to the control means and actuation of the signalling means is prevented, and when no water is so present the signalling means is actuated.

In such a case, the pair of electrical contacts may be disposed at the desired minimum water level within a vessel, eg a plant tray or trough, such that the device is actuated if the water level falls below that level. This may prompt manual replenishment of the water in the vessel 6 or may trigger automatic delivery of water to the vessel.

Another particular application of the invention is as a position marker for doorways such as fire doors, emergency exits and the like. In such an application the device is preferably sensitive to the presence or absence of ambient light. Thus, in another aspect the invention provides a door fitted with a position marker comprising collecting means for collecting light energy and converting that light energy to electrical energy in the form of an electric current, storage means for storing said electrical energy, signalling means operably linked to said storage means and adapted to be supplied with an electric current by said storage means, and control means operably linked to the collecting means so as to cause said storage means to charge when said collecting means generates an electric current and to actuate said signalling means when the current produced by said collecting means falls below a predetermined threshold, In this case, the position marker may be mounted on the surface of the door, or may be housed in a recess within the door. In the latter situation, the recess may be provided with a transparent or partially transparent cover which may carry lettering or other information.

For many applications, it is beneficial for the device according to the invention to be encapsulated in a sealed housing. Such a housing may conveniently be fabricated in plastics material, and for a device in which the emitted signal is a visible signal at least part of the housing will be transparent.

For many applications, the device according to the invention is affixed to a suitable substrate. For this purpose the device may be provided with fixing means to facilitate such attachment. For instance, the device may have a housing with a planar surface which is provided with self-adhesive means for affixing the housing to a suitable substrate. Alternatively, or in addition, the housing may have fixing holes by which the device can be secured to a substrate using screws. For many applications the device will have the form of a completely enclosed 7 and self-contained unit which can be affixed to a substrate either pen- nanently or temporarily.

The device according to the invention finds application in many varied fields. These include safety and security applications in areas in which position indicators are used, particularly in conditions of darkness or environments in which ambient lighting can fail. Typical fields of application include fire fighting, mining, the oil and gas industry, railways, aviation, highways and marine applications. Applications may also be found in other areas such as telecommunications (eg standalone security monitoring devices, remote sensing, Internet and cellphone carried warning devices etc), agriculture (water monitoring and control, solar powered irrigation control systems, etc) and consumer goods (safety clothes, toys, burglar 10 and intrusion alarms, remote monitoring and horticultural applications).

The device according to the invention may be attached to a fixed substrate or may be attached, either temporarily or permanently, to items such as clothing. For example, the device may be attached to a helmet wom by workers in an industrial environment or one or more devices may be attached to work wear such as jackets or fluorescent vests or armbands.

The invention will now be described in greater detail, by way of example only, with reference to the accompanying drawings, in which Figure 1 is a plan view of a light-emitting device according to the invention; Figure 2 is a sectional view of the device of Figure 1, on line AA; Figure 3 is a sectional view of the device of Figure 1, on line BB; Figure 4 is a circuit diagram of a circuit board forming part of the device of Figure 1; Figure 5 is a circuit diagram of a second embodiment of a device according to the invention; Figure 6 is a circuit diagram of a third embodiment of a device according to the invention; 8 Figure 7 is a schematic, partial view of a fire extinguisher fitted with a low-pressure indicator incorporating the circuitry of Figure 6; and Figure 8 is a partial sectional view of a door incorporating a device similar in functional terms to that shown in Figures I to 4.

Referring first to Figures I to 3, a light-emitting device according to the invention is generally designated 1 and comprises a clear plastics housing 10 which cooperates with a planar clear plastics base 20 to define an internal cavity in which two solar panels 30 (Sanyo - type AM 1414) and a circuit board 40 are received.

Figure 4 shows the circuit diagram of the device 1. The solar panels 30 are connected to the contact pads 35 positioned at the four comers of the circuit board 40. The current from the cells 30 is passed through a first diode DI and a second diode D2. The second diode D2 is connected directly to a battery 41 to prevent the battery 41 from discharging through the solar cells 30.

DI is connected to an RC oscillator on pin 7 of an integrated circuit 45 (TC7660 - Telcom Semiconductor, Inc), and is used to stop the oscillation whilst there is current from the solar cells 30. A resistor RI is used to reduce the current from the solar cells 30 to within the range of the oscillator and provides the ground for a capacitor Cl when the solar cells 30 are not producing current. D2 is used to pass the current to the battery 41 to keep it in a state of charge. Therefore, whilst there is current at RI the integrated circuit 45 is unable to oscillate and cannot provide a current to an LED 48 and the battery 41 is charged.

When the current at the solar cells 30 decreases (due to lack of light) the oscillator capacitor Cl is charged to the input voltage (battery) by using RI as the ground (the solar cells are no longer producing current causing the positive to become ground). This current on Cl is in turn connected to an output capacitor C2 via analogue gates within the integrated circuit 45.

This output capacitor C2 is then discharged through the integrated circuit 45 into the LED 48. R2 is a zero ohm resistor used for bridging the track only and serves no purpose in the 9 operation of the circuit.

In effect, CI controls the frequency of flash of the LED 48, and C2 controls the duration of the flash.

When ambient light returns, the current increases at the resistor RI and the integrated circuit 45 ceases oscillating and the LED 48 stops flashing. The current from the solar panels 30 then recharges the battery 41.

Details of the individual components used are as follows:

Solar cells 30 Sanyo energy AM 1414 enhanced Amorton Integrated circuit 45 Telcom TC7660 COA surface mount Battery 41 12.5mA nickel metal hydride DI, D2 standard current limiting diode RI I mega ohm standard resistor R2 zero ohm bridge resistor LED 48 standard ultrabright CI 47nF ceramic capacitor C2 47RF electrolytic capacitor The LED 48 is positioned centrally on the circuit board 40. The internal surface of the housing 10 is formed with an integral, downwardly-depending, generally triangular projection 12 which terminates adjacent the upper surface of the LED 48. The projection 12 serves as a light guide which transmits the light from the LED 48 in such a fashion that the light is emitted as a flashing bar.

The housing 10 is also provided with two preformed fixing holes 14 by which the device I can be fixed to a substrate with screws (not shown), corresponding apertures being provided in the base 20. Alternatively, or in addition, a self-adhesive patch (eg of doublesided adhesive tape) may be provided on the underside of the device 1 for attachment to a substrate.

The embodiment shown in Figure 5 can be used as a water level sensor, eg in a plant watering tray. Components corresponding to those of the embodiment described above are indicated by the same reference numerals. In this embodiment, the battery 41 is again charged by the solar panel(s) 30 via the contact pads 35. However, the current to the RC oscillator on pin 7 of the integrated circuit 45 is supplied from the battery 41 via a pair of contacts 51 which are immersed in water contained within, for example, a plant watering tray 52. So long as the water level is sufficient for the contacts to be immersed in the water, the current path is established and the oscillator of the integrated circuit 45 is prevented from oscillating, thereby preventing the flow of current in LED 48. If the water level falls, the flow of current to the oscillator is interrupted, and current flows through the LED 48. In this embodiment, the solar panels 30 serve only to charge the battery 41 and operation of the device is independent of the presence or absence of ambient light.

The embodiment shown in Figure 6 does not utilise solar panels at all. As for the second embodiment, the supply of current to the RC oscillator of the integrated circuit 45 is from the battery 41, in this case via a switch 61. The switch 61 may be, for instance, a pressure sensitive switch, the device thus providing a warning of a fall in pressure. One application for such a device would be to monitor the internal pressure of a canister, eg a fire extinguisher. Figure 7 shows in schematic form such a fire extinguisher which is generally designated 70 and comprises a canister 71 on which is mounted a handle/dispenser assembly 72. An outlet hose 73 extends from the assembly 72. The fire extinguisher thus far described is entirely conventional. Where the fire extinguisher 70 differs from the prior art is in the provision of a low-pressure sensor 74 which incorporates the circuitry of Figure 6. The sensor 74 is received in the assembly 72 such that the pressure-sensitive switch 61 is exposed to the interior of the canister 71 and the externally visible part of the sensor 74 houses the LED 48. So long as the pressure inside the fire extinguisher 70 is above a certain threshold, the switch 61 is held closed and the LED 48 is prevented from actuating. If the pressure falls below the threshold then the switch 61 opens and the LED 48 flashes, providing a visual indication that the fire extinguisher 70 needs to be replaced or recharged.

I I Finally, Figure 8 shows a section of a door 80 incorporating a solarcharged device 88 which is similar in functional terms to that described above in relation to Figures I to 4. The door 80 comprises a pair of leaves 81,82 which are separated by battens 83. A recess 84 is defined by an opening in one of the leaves 8 1. The device 88 is mounted in the recess 84, and has a transparent front cover 86 which overlaps the opening and is fixed to the leaf 81, eg by screws. So long as ambient light is incident on the device 88 the LED 48 which it contains is inactive. Should the ambient light level fall, however, the LED 48 flashes, providing a visual indication of the location of the door 80 and illuminating any lettering printed on the cover 86.

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Claims

1. A signalling device comprising storage means for storing electrical energy, signalling means operably linked to said storage means and adapted to be supplied with an electric current by said storage means, and control means operably linked to said signalling means to prevent actuation thereof, said control means being in the form of an integrated circuit containing an oscillator, wherein when the current supplied to the control means is above a predetermined threshold the oscillator is prevented from oscillating and supply of current to the signalling means is prevented, and when the current supplied to the control means is below the predetermined threshold the signalling means is actuated.

2. A device as claimed in Claim 1, ffirther comprising collecting means for collecting light energy and converting that light energy to an electric current.

3. A device as claimed in Claim 2, wherein the electric current is supplied to the storage means and also to the control means so that the control means is sensitive to the presence of ambient light.

4. A device as claimed in any preceding claim, wherein the signalling means emits a visual signal.

5. A device as claimed in Claim 4, wherein the signalling means comprise one or more light emitting diodes (LEDs).

6. A device as claimed in any one of Claims I to 3, wherein the signalling means emits an audible signal.

7. A device as claimed in any preceding claim, wherein the signalling means emits an 13 intermittent signal.

8. A device as claimed in Claim 2, wherein the collecting means for collecting light energy and converting that light energy to electrical energy comprises one or more solar cells.

9. A device as claimed in Claim 8, wherein the solar cells are capable of generating current of at least 8gA.

10. A device as claimed in any preceding claim, wherein the storage means for storing electrical energy is an electrical battery.

11. A device as claimed in Claim 10, wherein the battery is a nickel hydride battery.

12. A device as claimed in any preceding claim, wherein the control means comprises a DC-to-DC voltage converter.

13. A device as claimed in any preceding claim, wherein the predetermined threshold at which the signalling means is actuated is zero current or a current which is close to zero.

14. A device as claimed in any preceding claim, wherein activation and/or deactivation of the signalling means is subject to a delay.

15. A device as claimed in Claim 1, wherein current is supplied to the control means directly from the storage means.

16. A device as claimed in Claim 15, wherein the current path includes a switch or the like which is sensitive to a parameter which is to be monitored.

17. A device as claimed in any preceding claim, wherein the device is encapsulated in a 14 sealed housing.

18. A device as claimed in Claim 17, wherein the housing is of plastics material.

19, A device as claimed in Claim 17 or Claim 18, wherein at least part of the housing is transparent.

20.A signalling device sensitive to the presence of ambient light, said device comprising collecting means for collecting light energy and converting that light energy to electrical energy in the form of an electric current, storage means for storing said electrical energy, signalling means operably linked to said storage means and adapted to be supplied with an electric current by said storage means, and control means operably linked to the collecting means so as to cause said storage means to charge when said collecting means generates an electric current and to actuate said signalling means when the current produced by said collecting means falls below a predetermined threshold.

21. A device as claimed in Claim 20, wherein the control means comprises an integrated circuit containing an oscillator which is prevented from oscillating when current is generated by the collecting means and thereby prevents current being supplied to the signalling means.

22. A device as claimed in Claim 21, wherein the integrated circuit is a DC-to-DC voltage converter.

23. A device as claimed in any one of Claims 20 to 22, wherein the collecting means for collecting light energy and converting that light energy to electrical energy comprises one or more solar cells.

24. A door fitted with a position marker comprising collecting means for collecting light energy and converting that light energy to electrical energy in the forrn of an electric current, storage means for storing said electrical energy, signalling means operably linked to said storage means and adapted to be supplied with an electric current by said storage means, and control means operably linked to the collecting means so as to cause said storage means to charge when said collecting means generates an electric current and to actuate said signalling means when the current produced by said collecting means falls below a predetermined threshold.

25. A door as claimed in Claim 24, wherein the position marker is housed in a recess within the door.

26. A door as claimed in Claim 25, wherein the recess is provided with a transparent or partially transparent cover.

27. A low-pressure indicator comprising storage means for storing electrical energy, signalling means operably linked to said storage means and adapted to be supplied with an electric current by said storage means, and control means operably linked to the storage means via a pressuresensitive switch, the arrangement being such that when the pressure-sensitive switch is closed current flows to the control means and actuation of the signalling means is prevented, and when the pressure-sensitive switch is open the signalling means is actuated.

28. Am indicator as claimed in Claim 27, wherein the pressure-sensitive switch is held closed by the influence of pressure applied to the switch, and opens if that pressure falls below a threshold.

29. A fire extinguisher incorporating a low-pressure indicator as claimed in any one of Claims 25 to 28.

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30. A water level sensor comprising storage means for storing electrical energy, signalling means operably linked to said storage means and adapted to be supplied with an electric current by said storage means, and control means operably linked to the storage means via a pair of electrical contacts, the arrangement being such that when water is present between the electrical contacts, thereby establishing electrical conduction between them, current flows to the control means and actuation of the signalling means is prevented, and when no water is so present the signalling means is actuated.

31. A signalling device substantially as hereiribefore described and as illustrated in Figures I to 4.

32. A water level sensor substantially as hereinbefore described and as illustrated in Figure 5.

33. A low-pressure sensor substantially as hereiribefore described and as illustrated in Figure 6.

34. A door substantially as hereinbefore described and as illustrated in Figure 8.