GB2404474A - Emergency lighting monitoring system with lighting control - Google Patents

Description

Lighting System This invention relates to a lighting system.

Lighting control systems can be designed to enhance the effect of the lit environment through altering the light level (dimming), changing the colour, highlighting the features or providing some movement of light; or to save energy by turning lights off when people are not present or when there is sufficient natural light.

The first systems achieved dimming by altering the voltage applied at the lamp - but this is only suitable for certain lamp types. Fluorescent lamps (one of the most efficient and most common types) require special ballasts.

Initially ballasts were designed with analogue control where a pair of terminals were connected to a variable resistor to control the level of dim. A variable voltage (1-lOv) could be applied to the same terminals to change multiple ballasts at the same level.

Digital ballasts (such as those made by Tridonic) were introduced to improve the reliability and repeatability of the control; the 1-lOv analogue signal was replaced by a digital command to tell the ballast to operate a specific light level, turn on or off etc. A simple control system was introduced where a simple push switch can be connected onto the control wires to turn on, turn off or dim up and dim down by a quick push or a push and hold of the switch.

Latterly, the Digital Addressable Lighting Interface (DALI) has been introduced as an irdustry standard where an agreed protocol is used to address specific ballasts and turn them on, off, to a given light level or change by a certain amount. Feedback is provided to allow the ballast to signal if a lamp is faulty and it is possible to monitor the amount of energy used by each ballast. 63 addresses are allowed on each system so larger systems must be made up of multiple lots of 63.

All of the above lighting control systems are very cost effective for small areas or even reasonably large offices, but additional equipment is needed to provide some of the more sophisticated functions or to apply the system to a whole building. As the systems become larger the control elements become progressively more complex and expensive particularly where a large number of discreetly controlled areas (zones) are required or where the wiring must run separately from the areas to be controlled.

Patents EP 940,904 and GB 2,331,1390 (the contents of which are incorporated herein by reference) describe an emergency lighting monitoring system which is characterized by a control panel which is used to power, operate and monitor multiple interfaces where the interfaces are connected to the panel via a loop of cable (for reliability). The interfaces are powered from the voltage on the loops - so as to minimise cost and size - have a similar interface to the panel but are designed for specific luminaire types. One interface is used for NiCd battery self-contained emergency luminaires, one for VRLA battery self-contained luminaires another type for central battery slave luminarires etc. Each interface has a unique address on the loop allowing individual control and monitoring of the luminaires and large systems can be built up by networking multiple panels.

It is an object of the present invention to provide a low cost system for controlling lighting systems.

According to a first aspect of the invention a lighting system comprises: a main power supply; a first plurality of lighting units, each having mains failure circuitry to monitor the main supply and to connect the lighting unit for operation to an auxiliary power supply in the event of a failure of the main power supply, and a testing circuit operative to assess the condition of operational readiness of the lighting unit; at least one control unit; a signal line connected to the at least one control unit and to the testing circuit of one or more of the lighting units; wherein the first plurality of lighting units each have a lighting control circuit also connected to the signal line and wherein the at least one control unit is operable to apply signals to the signal line for control of the testing circuit and the lighting control circuit; wherein each one of the testing circuits and each one of the lighting control circuits is identified from the others by an address. \\

The system may include a second plurality of lighting units each having a lighting control circuit. The second plurality of lighting units preferably do not have the mains failure circuitry or the testing circuit.

The system advantageously provides the features of an emergency lighting system with the additional functionality of lighting control. Thus, once emergency lighting is present, lighting control functionality can be implemented for very small additional outlay, because the same control panel is used for both types of controls.

Only a proportion, preferably about 5%-10%, of the lighting units would have the emergency functions, with the remainder simply having lighting control.

The testing circuit and the lighting control circuits in the first plurality of lighting units may be a combined lighting and testing circuit.

The testing circuit and/or the lighting control circuit advantageously incorporate the address, rather than lighting gear of the luminaire, or the address being provided by selected wiring.

The lighting control circuit preferably receives power from the signal line, which preferably receives power from the at least one control panel.

The lighting control circuit thereby advantageously does not draw power from the existing main supply to the lighting unit, instead power is supplied separately.

Thus, no change to the existing power supply to the lighting unit is required.

The same communication protocol is preferably used for the testing and lighting control circuits.

The lighting control circuit is preferably implemented in an interface, which interface is preferably tailored to a particular type of lighting unit, depending on ballast of a particular lighting unit for example. The interface may include the testing circuit. The testing circuit and the lighting control circuits preferably have different addresses.

The testing circuit addresses are preferably in a first range and the lighting control circuit addresses are preferably in a second range.

The lighting control circuit preferably allows for dimming, brightening, colour change and/or switching on/off of its associated lighting unit.

The or each control unit is preferably programmable to allow for lighting control of groups of lighting units substantially concurrently.

Preferably one lighting control unit is provided for lighting control and emergency lighting of a set of lighting units. Further control units are preferably provided for lighting units beyond a capacity of a first lighting control unit.

The invention extends to a lighting control circuit as described in the first aspect.

According to a second aspect of the invention a kit for converting an emergency lighting system to an emergency lighting and lighting control system comprises a first plurality of lighting control circuits and a control unit operable to provide control signals to the lighting control circuits, wherein each lighting control circuit is operable, in use, to be associated with a lighting unit.

The lighting control circuit may be combined with an emergency lighting testing circuit in an interface unit, to allow replacement of an existing emergency lighting interface unit with the interface unit combining the lighting control circuit and the emergency lighting testing circuit. Preferably, approximately 5-10% of the existing emergency lighting testing circuits may be replaced with combined lighting control and emergency lighting testing circuit.

All of the features described herein may be combined with any of the above aspects, in any combination.

For a better understanding of the invention and to show how the same may be brought into effect, a specific embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic block diagram of an emergency lighting system; Figure 2 is a block diagram of a lighting unit included within the system; ( J 7 Figure 3 is a circuit diagram showing the main components of a conversion circuit being part of the lighting unit of Figure 2; Figure 4 is a schematic block diagram of a second emergency lighting system) and Figure 5 is a schematic view of an emergency lighting system having general lighting control capabilities.

A lighting control system is proposed which takes the features of the emergency lighting monitoring system for example as described in EP 940, 904, the description from which is incorporated herein as Annex 1. Those features being low cost, addressable, simple tailored interfaces are applied to lighting control. An interface is fitted in each luminaire - to give maximum flexibility, the same or different interfaces can be used for system inputs from light sensors, movement detectors or switches and the control panel is programmed to provide overall system control (timing and sensitivity functionality).

The interfaces described herein can be the conversion circuits 40 of Annex 1 with suitable minor changes to allow for the additional functionality described herein.

Figure 5 shows schematically an emergency lighting system having additional lighting control functionality.

In the example shown a combined emergency lighting and lighting control panel 2 is connected to a series of luminaires 3. Each luminaire has an interface 4 which allows signals from the control panel 2 to be passed to ) 8 the luminaires 3 by their respective interfaces 4, via signal line 6. About 5-10% of the luminaires 3 have emergency lighting functionality as described in Annex 1 and below, whereas all or a majority of the luminaires have lighting control functionality as described below.

The system shown in Figure 5 has the same functionality as the emergency lighting system described in Annex 1. In addition the interfaces 4 allow the luminaires 3 to be dimmed, brightened, switched on/off in groups or individually that are specified using the control panel 2 which can be easily programmed by a computer 5. Switching on/off may be in response to light sensors, movement detectors, control switches, and the like.

In the example shown in Figure 5 a single combined emergency lighting panel and lighting control panel 1 is provided where the number of addresses required is based on one address being needed for the emergency lighting control features and another, different, address being required for the lighting control for each luminaire, where there are no more than 255 emergency units and 255 lighting control units per panel. Each control panel 2 has a maximum of 255 units of each type due to losses along the signal line 6. Different numbers may easily be achieved by simple specification changes, to allow for example 511 or 1047 units per panel.

The lighting control is provided by any of the systems for e.g. varying brightness of fluorescent lamps or switching eta that are currently known. )

When a user wishes to change settings for the control of the luminaires 3, such as automatic timings, sensitivity levels eta he will perform the changes via the control panel 2 or via the PC 5 connected thereto. The interfaces 4 may be directly addressable by a portable unit temporarily plugged into the interface 4 for setting the interface addresss.

It is the inventive realization of the applicant that the presence of an emergency lighting system in a building provides a very cost effective infrastructure for adding lighting control functionality to a building. Thus, when a user has specified emergency lighting being available for a building it is very straightforward in the system described in the present application to provide lighting control functionality. This would not be the case if a user wished to start a lighting control system from scratch other than in the limited cases for small numbers of luminaires discussed above. When fitting a system from scratch adding lighting control functionality to an emergency lighting system adds very little or no additional wiring. Only different interfaces are required to allow for emergency and lighting control signals to be provided, depending on the address used, as described below.

Interfaces 4 can be provided specific to the gear used in the luminaire 3 so as to provide maximum flexibility on choice of gear but with an identical system interface so that the gear type is transparent to the control panel 2.

The size of the system is determined by the number of panels 2 interfaced together with each panel having a maximum of 255 interfaces 4 of each type allowed. Other examples may allow 511 or 1047 interfaces. The cost is minimised by the system architecture (single power supply in the panel, simple pair of cables 6, polarity insensitive). System configuration is carried out off line via PC software and the configuration is loaded onto the system one panel at a time. Suitable amendments for lighting control can be made to the configuration system described in Annex 1.

The interfaces 4 are specific to the luminaires 3 that are used. For example different interfaces are used for different lighting gear, such as 1-lOV gear, or digital gear etc. The addressing of the interfaces 4 is such that different address ranges are used for emergency monitoring and lighting control. This allows the same control panel 2 to carry out both functions on one pair of wires 6. The interfaces 4 can be addressed using the same programmer and the system loading limitations (number of addresses) is not affected by whether emergency lighting monitoring and lighting control is carried out on the same panel or not.

Lamp monitoring has in the past only applied to emergency lighting control. In the present system however, given that each luminaire communicates via the signal line 6, lamp monitoring can be provided to luminaires even where no emergency lighting control is provided. In this case the interface may be with DALI, digital control with a separate current monitor, or the 1-lOV analogue system with a separate on/off switch and a current monitor.

The system is characterized by the capability of a large number of luminaires 3 and a relatively slow response to specific inputs or outputs. This makes it ideal where a large or complex area requires to be lit, but where there are relatively few manual inputs, i.e. where the user expects an instant response (e.g. immediate turning off of the light). A typical and ideal application is a large retail "shed" where the operator wants to be able to control the light level in each aisle separately, but where the light does not need to be changed quicker than every few minutes.

Because each luminaire 3 is individually addressed areas in the building are accommodated by system programming.

Therefore changes in operation are a case of changing the software rather than moving wires, changing connection etc. Operational control of the system can be via the control panel, via manual inputs connected to the system, via automatic sensors or via programmed timer response.

Isolation is provided from control wires to local mains supply. This gives total flexibility on the phase connection to each light.

Luminaire 4 addresses are set during installation but can be subsequently changed using the control panel 1/2 or the programmer. Addressing need not be sequential, but addresses must not be duplicated.

New lamp gear can be accommodated via the design of a new interface 4.

Monitoring of the luminaire 3 operation can be provided by using DALI, using the input function on the interface 4, or using a separate interface.

Additionally, the interface 4 in the luminaire 3 could be used to provide a system input to make wiring easier. For example, if a local switch was needed, rather than a separate switch and interface, it could be possible to take the local switch to a local luminaire. Similarly it might be possible to use the input to monitor passive infra-red PIR movement detectors, light detectors etc. Alternatively, a separate interface for each luminaire could be provided for easier understanding of the system.

The above described system provides a cost effective way of providing lighting control to an existing emergency lighting system, or to combine the two functionalities on a new installation. A kit can be provided, comprising a panel and interfaces for each lighting unit to allow conversion from emergency lighting to emergency lighting and lighting control.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features

disclosed in this specification (including any

accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Annex 1 With reference to Figure 1, an emergency lighting system comprises a plurality of emergency lighting units 10 which, for the purpose of this example, each of which is a self-contained luminaire comprising a fluorescent lamp and a rechargeable battery.

Each of the luminaires 10 is connected to a main electrical supply 12. Depending upon the particular requirements of the installation, any or all of the luminaires may be illuminated permanently, switchable, or extinguished permanently during such time as the main electrical supply 12 is operational. In the event of failure of the main electrical supply 12, the luminaires become illuminated automatically.

The system further comprises a central control unit 14. A signal line 16 extends from the central control unit 14 in a loop, to connect to each luminaire in turn, finally to return to the central control unit 14. As well as carrying data signals, the signal line 16 also supplies power to components within the luminaires.

Additional components of the system include a personal computer 20 which can be connected to the central control unit 14, and a network controller 22 by means of which several central control units can communicate with one another.

The central control unit 14, in this embodiment, is similar to an addressable fire alarm control panel, suitably re-programmed. In this way, it is possible for the circuits which apply data to and read data from the signal line 16 to be of a nature which is conventional in the technical field of fire alarm systems. As in the case of a fire alarm control panel, the central control unit is provided with user controls by means of which its operation can be controlled by a user.

With reference now to Figure 2, a lighting unit for use in the system of Figure 1 can be constructed as a modification of a conventional selfcontained emergency luminaire. In Figure 2, the box 30 represents a conventional self-contained emergency luminaire. The luminaire comprises battery input terminals 32, a lamp 34 and a switching circuit 36. The luminaire has four input terminals, conventionally labelled L, L1, N and E. The L terminal is connected to a supply of mains electricity which is live at all times other than during a mains failure. The L1 terminal is optionally connected to a switched mains supply which can be used to illuminate the lamp 34 at any time as required. The N and E terminals are respectively connected to the neutral line and the earth line of a mains supply.

In its conventional condition, the switching circuit 36 serves to provide a charging current to the battery terminals 32 to charge a battery connected to them and to supply power to the lamp 38 from the L1 terminal. However, in the event that power to the L terminal ceases, the switching circuit 36 connects the battery terminals 32 to the lamp 34 so as to illuminate the lamp by means of power from a battery connected to the terminals. (It is well understood that further circuitry will be required if the lamp 34 is a fluorescent lamp, but that is not of relevance to the present invention.

In a lighting unit for use in a system of the present invention, the luminaire described above is provided with a conversion circuit, shown at 40 in Figure 2.

The conversion circuit 40 is constructed as a small encapsulated unit which can be readily fixed within a case of the luminaire. The conversion circuit 40 has four input terminals labelled L, L1, N and E respectively. During installation, these are connected exactly as described above in relation to the conventional luminaire.

The conversion circuit 40 has two further pairs of input terminals, within each pair a first terminal being labelled 1 and a second being labelled 2. Wires of the loop circuit 16 from each of the adjacent devices in the loop are connected to a respective pair of input terminals 1 and 2.

The conversion circuit 40 has four output terminals 48, each of which is connected to a respective one of the input terminals L, L1, N. E of the conventional luminaire 30. The conversion circuit is constructed such that its input terminals N and E are connected directly to the corresponding input terminals on the conventional luminaire 30, and such that its input terminals L and L1 are connected to the corresponding input terminals of the conventional luminaire 30 through switch contacts 42 of a relay.

The conversion circuit 40 is provided with a pair of battery input terminals 46 and a battery output lead 44. A rechargeable battery 33 (as would be used with the conventional luminaire 30) is connected to the battery input terminals 46. The battery output lead is connected to the battery terminals 32 on the conventional luminaire 30, such that current flowing between the battery 33 and the switching circuit 36 flows through the conversion circuit 40.

A two-colour indicating LED 52 is provided which is visible externally of the conversion circuit 40.

The conversion circuit further includes a microcontroller which controls all aspects of its operation. The microcontroller 50 of this embodiment has multiple analogue and digital input/output capability and has internal memory for storage of a program and a small amount of data.

The operation of the conversion circuit 40 will now be described with reference to Figure 3, (Note that the connections for the neutral and earth lines, and many minor components are not shown in Figure 3 in the interest of clarity).

The conversion circuit 40 is based around a programmable microcontroller 50. The microcontroller 50 controls all of the other stages of the circuit. These will now be described. A power supply (not shown) provides a OV DC level and a positive DC supply at Vcc.

The conversion circuit 40 includes a mains switching stage 54. The mains switching stage 54 comprises a double-pole latching relay 56. The relay interconnects the mains input at L and L1 to the mains output terminals at 48 through respective normally-closed switch contacts 42. The relay 56 is controlled by a pair of solenoids 58,59 each of which is connected to a respective digital output 60, 62 of the microcontroller 50 through suitable interface circuitry 64. Energisation of a first of the solenoids 58 causes the relay to open its contacts, and energisation of the other solenoid 59 causes the relay to close its contacts. It is the nature of a latching relay that subsequent de-energisation of a solenoid does not cause the state of the relay contacts to change. By means of this arrangement, the microcontroller can selectively connect or disconnect the luminaire 30 and the mains supply, without the need to maintain a solenoid in an energised state.

Under normal operating conditions, the relay 56 is latched closed to complete the connection between the mains input terminals and the mains output terminals 48. The relay 56 is opened only when a test is being carried out as will be described below. However, it is desirable that in the event of a failure occurring during a test, the relay 56 is closed to return the luminaire 10 to its normal operating condition. To this end, a capacitor 65 is provided a first input of the second solenoid 59 which can store sufficient charge to energise the solenoid 59 sufficiently to close the relay 56. A fail-safe circuit 57 is connected to a second input of the second solenoid 59, the fail-safe circuit 57 being operative to discharge the capacitor 65 through the solenoid 59 in the event of a power failure.

Within the conversion circuit, conductors 66,68 interconnect the battery input terminal 46 and the battery output lead 44. In a first of these conductors 66 (connected to the negative side of the battery) comprises two series connected resistors R39,R21. The values of the resistors R39,R21 are sufficiently low that they do not significantly reduce the light output of the lamp when it is under battery power. A point between the resistors at 68 is connected to the OV level of the conversion circuit 40. A second of the conductors 70 directly interconnects the positive battery input terminal 46 and the positive battery output lead 44 with negligible series resistance.

A current measurement stage 72 is provided in the conversion circuit 40 to measure current flowing through the first conductor 66. The current measurement stage 72 has two input lines 74,76, each connected to the first conductor 66 such that both of the resistors R39,R21 are disposed between the inputs lines 74,76.

Within the current measurement stage 72 (the circuit for which is not shown in full detail in Figure 3) there is provided an amplifying circuit of high input impedance based on an operational amplifier IC. The output of the amplifying circuit provides an output at 78 of the current measurement stage 72. The output 78 of the current measurement stage 78 is fed to a first analogue input 80 of the microcontroller 50.

It will be seen that the voltage appearing across the input lines 74,76 of the current measurement stage 72 will be substantially proportional to the current flowing through the first conductor 66, provided that the resistors R39,R21 are selected such as to exhibit ohmic behaviour under the current which will flow through them during operation of the lamp 34. By proper selection of the gain of the amplifying circuit, it is therefore readily possible to ensure that the voltage at the output of the current measurement stage 72 is proportional to the current in the conductor 66.

A voltage measurement stage 88 is provided to measure the voltage of the second conductor 68. (It should be remembered that the first conductor 66 is tied to OV, therefore the voltage of the second conductor 68 is, essentially, the voltage across the battery 32.) The voltage measurement stage 88 has an input line which is connected to the second conductor at 84. The input line is connected through two series connected resistors R26,R27 to OV. An output line 86 of the voltage measurement stage 88 is connected to a point between the resistors R26,R27. The output line 86 is connected to a second analogue input 82 of the microcontroller 50. An oscillator stage 90 provides a clock input for the microcontroller 50.

The oscillator stage comprises a crystal oscillator which is entirely conventional and will therefore not be described here further.

The LED 52 is connected between first and second digital outputs 92,94 of the microcontroller 50. Each of the first and second outputs 92,94 can independently be driven between OV and Vcc in order that the microcontroller can selectively illuminate the LED 52 in either of its two colours.

A memory device 100 is provided within which the microcontroller 50 can store data for subsequent retrieval. In this embodiment, the memory device 100 is a 128-bit serial access EEPROM device.

Within the conversion unit, the signal line terminals marked 1 are interconnected, as are the signal terminals marked 2. A signal input to the conversion circuit is derived across the pairs of terminals 1 and 2.

A Zener diode D14 is connected across the signal input, which is then fed to an arrangement of four diodes D8,D9,D10,D11 configured to act as a bridge rectifier, the output of which appears at a circuit point 160.

The circuit point 160 is connected through a diode D13 and a resistor R25 to a power supply stage 162. The power supply stage 162 incorporates a current source IC3 to provide a regulated output at Vcc.

A signal reception stage 166 has an input connected to the circuit point 160 and an output connected to a digital input 168 of the microcontroller 50. The signal reception stage 166 detects voltage pulses applied to the signal line 16 by the central control unit 14.

The input of the signal reception stage 166 is fed to a series-connected capacitor C9 and resistor R14 to a circuit point 170. The circuit point 170 is connected to the 0V line by a capacitor C1 and through a diode D3 to the base of a transistor T6. Two resistors R15,R16 connect respective opposite sides of the diode D3 to the 0V line.

The collector of the transistor T6 is connected to the positive supply line Vcc through a resistor R16. The emitter of the transistor T6 is connected to the OV line.

The output of the signal reception stage 166 is taken from the collector of the transistor, there being a capacitor connected between the output and the OV line.

The reception stage 166 operates by filtering any steady DC component from the signal on its input by means of the capacitor C9. The transistor T6 can then be turned on and off in the presence and absence of voltage pulses in the signal line. This gives rise to negative-going pulses appearing on the digital input 94 to the microcontroller 50.

A signal generation stage 176 has an input connected to a digital output 178 of the microcontroller and an output connected through a resistor R4 to the circuit point 160.

The signal generation stage 176 comprises a transistor T3 the base of which is connected through a resistor R3 to the input of the signal generation stage 176 and through a resistor R2 to the OV line, and the emitter of which is connected through a resistor R1 to the OV line. The output of the signal generation stage 176 is connected to the collector of the transistor T3.

It will be seen that if the microcontroller 50 raises its digital output 178, the transistor T3 will be turned on.

This will result in current being drawn from the signal line 16, this being detectable by the central control unit 14.

Operation of each of the luminaires 10 will now be described.

Prior to installation, each luminaire must be configured such that it is assigned an address number which is unique within the system. This is done by connecting a programming device 11 to the signal line input of the testing circuit 40 before the testing circuit is connected to the signal line 16. The programming device 11 supplies the testing circuit 40 with power, and also generates a programming signal incorporating an address number chosen by an operator. On detection of the programming signal, the microcontroller 50 operates to store the address number in the memory device 100. The address number will remain stored in the memory device 100 until it is changed by an operator.

In normal operation, the microcontroller 50 monitors signals received from the signal line 16 until it detects a signal which contains its address, as stored in the memory device 100. The content of the signal is then assessed.

If the signal is a routine polling signal, the microcontroller 50 then analyses the signals received from the current measurement stage 72 and the voltage measurement stage 88. If these signals indicate that the current and voltage are within the range expected for a battery being charged normally, the microcontroller 50 places a signal on the signal line 16 to indicate satisfactory operation, and it places signals on its first and second digital output lines 92, 94 to cause the LED 52 to glow green.

In the event that the current and/or the voltage detected by the current measurement stage 72 and the voltage measurement stage 88 indicate that the battery is not being satisfactorily charged, the microcontroller 50 places a signal on the signal line 16 to indicate this fact to the central control unit 14, and it places signals on its first and second digital output lines 92, 94 to to cause the LED 52 to glow yellow.

In the event that the luminaire has become activated by a local mains failure, the battery current flowing in the conductors 66, 68 will be reversed in direction. This will be detected by the microcontroller 50, which will then place a signal on the signal line 16 to indicate this fact to the central control unit 14.

If, during normal operation, the microcontroller 50 detects that a first testing signal has been addressed to it, then a first testing mode of operation will commence.

In the first testing mode, the microcontroller 50 energises its digital output 60 to energise the solenoid 58 to turn off the relay 56, and thereby simulate a local mains failure. This should cause the lamp 34 to be illuminated by power from the battery 32. The microcontroller 50 then maintains this condition for a predetermined discharge period (in this embodiment, 5 minutes) to allow the operating conditions of the lamp 34 to stabilise. The microcontroller 50 then analyses the signals received from the current measurement stage 72 and the voltage measurement stage 88. If these signals indicate that the current and voltage are within the range expected for a battery being discharged so as to satisfactorily illuminate the lamp 34, the microcontroller places a signal on the signal line 16 to indicate satisfactory operation, and it places signals on its first and second digital output lines 92, 94 to cause the LED 52 to glow green. On the other hand, if these signals indicate that the current and voltage are outwith the satisfactory range, the microcontroller 50 places a signal on the signal line 16 to indicate that there is an apparent fault in the luminaire 10, and it places signals on its first and second digital output lines 92, 94 to cause the LED 52 to glow yellow. Finally, the microcontroller 50 energises its digital output 62 to energise the solenoid 59 to turn on the relay 56, and thereby restore the supply of mains power.

If, during normal operation, the microcontroller 50 detects that a second testing signal has been addressed to it, then a second testing mode of operation will commence.

The second testing mode proceeds much as does the first, with the exception that the discharge period is greater.

In this example, the discharge duration in the second testing mode is between 1 and 3 hours such that the battery 32 is discharged to a significant extent.

Operation of the program within the central control unit will now be described below.

During installation, the computer 20 is used to store in the central control unit 14 information about the luminaires 10 of the system. For example, this information may include a description of the location of the luminaire in a building. This information may be used to help a user to operate the system by providing a memorable description of each luminaire 10 thereby removing the need for users to identify luminaires by number alone.

Additionally, it may be used to assign individual luminaires 10 to a group of luminaires which will be tested simultaneously in the second test sequence, to be described below.

In a normal operating mode, the central control unit 14 operates in a cycle to apply to the signal line 16 a polling signal addressed to a first luminaire 10, and awaits the response generated by the microcontroller of that luminaire 10. If the response indicates that the luminaire is in a condition for satisfactory operation, then the procedure is repeated with the other luminaires.

The cycle is repeated indefinitely.

In the event that the response indicates any other condition, the central control unit 14 issues an audible and/or visual warning to alert an operator to the existence of an exceptional condition, and also to identify the particular luminaire at fault or which has detected a mains failure, as the case may be.

Once in a first predetermined period (in this embodiment, weekly) the central control unit 14 automatically initiates a first test sequence in which it sends the first test signal to a first luminaire 10. The central control unit 14 awaits a signal from the luminaire. If this indicates that there is an apparent fault in the luminaire 10, then the central control unit 14 issues an audible and/or visual warning to alert an operator to the fact that a fault has been detected, and together with an indication to identify the particular luminaire at fault.

The procedure is repeated for all luminaires 10 in the system.

A second test sequence is initiated periodically, typically, once per year. The second test sequence is substantially the same as the first test sequence with the exception that the second test signal is sent in place of the first test signal.

It is normally the case that the second test sequence is initiated under manual control of an operator - this is desirable since after the second test sequence some luminaires 10 may be in a completely discharged condition, so it may be preferred to carry out the second test sequence during a time where the inconvenience that this might cause is minimised. The central control unit 14 provides a visual and/or an audible prompt to an operator when the second test sequence is due to be carried out. In the event that the operator ignores the prompt for a predetermined period (e.g. 1 week) the central control unit 14 will initiate the second test sequence automatically.

If the second test sequence were to cause all of the luminaires 10 to enter the second testing sequence at the same time, the possibility could arise of a large number of the luminaires being in a discharged state simultaneously. Therefore, the second test sequence is configured such that luminaires enter the second test sequence in groups. Such groups are chosen so as to minimise the consequences of multiple members of the group being inoperative for a time after the test. For example, groups can be chosen such that they do not contain several luminaires which are disposed close to one another so that there is little risk of a large area being deprived of emergency lighting.

With reference now to Figure 4, there is shown an emergency lighting system of a type commonly known as a central battery system. In the embodiment of Figure 4, each luminaire 110 is supplied with power from a power line 112. The power supply line 112 receives its power from a battery system 120. As with the first embodiment, during installation each luminaire 110 is assigned an address unique within the system by means of a programming unit 36.

The battery system 120 has as an input a supply of mains power 114 which is fed through a latching relay 132. The relay 132 is closed in normal use. As a main supply of power for the luminaires 110, mains power is supplied to the power supply line 112 having had its voltage reduced by a transformer 116 and having been processed, for example by a filter 118. The battery system 120 further comprises a battery module 122 which is connected to the power supply line 112 and to the input supply of mains power 114. Mains power is fed to the battery module 122 in order to maintain the battery module 122 in a charged state. The battery module 122 also contains circuitry to detect failure of the input supply of mains power 114, I which operates in response to supply power from the battery module to the power supply line 112 as an auxiliary power supply for the luminaires 110.

Each battery system also comprises a test module 130, which will be described below.

An entire emergency lighting system may comprise one or more battery systems 120 each associated with a respective power supply line 112 and luminaires.

A central control unit 140 is connected to each of the battery system 120 by a signal line 142 connected in a loop in a manner similar to that of the first embodiment.

Additionally, the central control unit 142 has interfaces for connection to a computer 144 and further similar control units via an interface 146. These connections serve the same function as corresponding features of the first embodiment, and will therefore not be described further.

The test module 130 is connected to the signal line 112, to the power supply line 112, and has an output 134 to control the relay 132. Thus, luminaires 110 within the system can be continually polled and can also be periodically tested in a manner entirely analogous to that of the first embodiment.

In the present embodiments, signals are sent on the signal line 16 to the testing circuit in a protocol which defines a 9-bit address, an 8-bit voltage field, an 8-bit current field, a 3-bit status field and a checksum. A supply voltage in the range 8-24V is applied to the signal line 16. Data is encoded in voltage pulses of 3-17V above this value applied by the central control unit 14 to the signal line 16. The length of each pulse determines whether it encodes a logical 1 or a logical 0.

The testing circuit 40 generates current pulses in between voltage pulses. The presence of a current pulse encodes a logical 1 and the absence of a current pulse encodes logical 0.

In an enhancement to an emergency lighting unit, such an one used in the above described system or a stand-alone unit, an inhibit control signal may be sent from the central control unit 14 to one or more of the luminaires 10 to indicate that the building or other zone illuminated by them is unoccupied. Upon receipt of this inhibit signal, the luminaire 10 enters a mode in which a local mains failure does not change state to cause the luminaire to become illuminated. This prevents the discharge of the secondary power supply for the luminaire. When the building or the zone, as the case may be, becomes occupied once again, a re-enabling signal is sent to the or each luminaire, so that it once again functions to provide emergency illumination in the event of a mains failure.

As will be understood, it is a simple matter to incorporate such a signal into the signalling protocol of a system as described above, or to any other system of emergency luminaires.

Claims (16)

1. A lighting system comprises a main power supply; a first plurality of lighting units, each having mains failure circuitry to monitor the main supply and to connect the lighting unit for operation to an auxiliary power supply in the event of a failure of the main power supply, and a testing circuit operative to assess the condition of operational readiness of the lighting unit; at least one control unit; a signal line connected to the at least one control unit and to the testing circuit of one or more of the lighting units; wherein the first plurality of lighting units each have a lighting control circuit also connected to the signal line and wherein the at least one control unit is operable to apply signals to the signal line for control of the testing circuit and the lighting control circuit; wherein each one of the testing circuits and each one of the lighting control circuits is identified from the others by an address.

2. A lighting system as claimed in claim 1, in which a second plurality of lighting units each have a lighting control circuit.

3. A lighting system as claimed in claim 1 or claim 2, in which the testing circuit and the lighting control circuit in each lighting unit of the first plurality are a combined lighting and testing circuit.

4. A lighting system as claimed in any preceding claim, in which the first plurality comprises approximately 5% to 10% of a total number of lighting units in the system.

5. A lighting system as claimed in any preceding claim, in which the lighting control circuit receives power from the signal line.

6. A lighting system as claimed in any preceding claim, in which the testing circuit and the lighting control circuit are a combined lighting control and testing circuit.

7. A lighting control system as claimed in any preceding claim, in which the testing and lighting control circuits have the same communication protocol with the at least one control unit.

8. A lighting system as claimed in any preceding claim, in which the lighting control circuit is implemented in an interface, which interface is tailored to a particular type of lighting unit.

9. A lighting system as claimed in claim 8, in which the interface includes the testing circuit.

10. A lighting system as claimed in any preceding claim, in which the testing circuit addresses are in a first range and the lighting control circuit addresses are in a second range.

11. A lighting system as claimed in any preceding claim, in which the lighting control circuit allows for dimming, brightening, colour change, and/or switching on/off of the lighting unit.

12. A lighting system as claimed in any preceding claim, in which the or each control unit is programmable to allow for lighting control of groups of lighting units substantially concurrently.

13. A lighting control circuit as claimed in any one of claims 1 to 12.

14. A kit for converting an emergency lighting system to an emergency lighting and lighting control system comprises a first plurality of lighting control circuits and a control unit operable to provide control signals to the lighting control circuits, wherein each lighting control circuit is operable, in use, to be associated with a lighting unit.

15. A kit as claimed in claim 14, in which the lighting control circuits are combined with an emergency lighting testing circuit in an interface unit.

16. A lighting system substantially as described herein with reference to the accompanying drawings.