GB2258571A - Testing emergency lighting systems - Google Patents

Abstract

The system has a plurality of emergency lighting units each having a lamp 15 which is connected to a battery on detection of mains failure and a detector 21 to sense light from the lamp 15, and a central control unit (30) (Fig 2), sequentially sense the outputs from the detector 15. Each lighting unit has a counter 41 counting timing pulses on a data ring 23 and when the counter reaches a programmed count identifying that unit, a switch 25 is closed so that signals are passed to the ring 23 from a logic circuit 22 having inputs connected to detector 21 and a battery charging current sensor 45. A particular control signal applied to ring 23 by the central unit causes a test latch 47 to open a mains switch 48 to simulate mains failure. The lighting units may be divided into 28 groups, a different group being tested on each of the first 28 days in each month. <IMAGE>

Description

LIGHTING The present invention relates to an emergency lighting system having a plurality of lighting units, wherein each lighting unit has a light emitting means, and means for connecting said light emitting means to a storage type power supply on detecting a mains power supply failure.

In many situations in which mains connected lighting is provided, emergency lighting must also be provided such that, in situations of mains failure, the environment is still lit to some degree by the emergency back-up.

Such emergency lighting is particularly important in public places where the total failure of lighting may result in mass panic and injury.

In addition to legal requirements for providing emergency lighting, requirements also exist for testing that the lighting is functioning properly.

Systems are known in which the emergency lighting is configured in a number of zones and there is provision at each zone for detecting that a light has failed within that zone. It is then necessary for service personnel to manually investigate each lighting installation so as to isolate the exact position of the failure. In addition, more sophisticated systems are known which include means for detecting battery condition, given that, particularly when using lead-acid batteries, overcharging or excessive discharging may result in excessive battery wear.

It is an object of the present invention to provide an improved emergency lighting system.

According to a first aspect of the invention, there is provided an emergency lighting system of the aforesaid type, characterised in that each lighting unit has a light detecting means arranged to produce a first output signal and said system includes a central control unit arranged to sequentially examine the presence of a first output signal from each of said lighting units.

Thus, the light detecting means is arranged to detect any type of failure occurring at lighting units which results in light failure. The central control unit is then arranged to sequentially examine the lighting units, such that specific data may be obtained defining the exact unit that has failed.

Each lighting unit may have its own storage type power supply.

Alternatively or additionally there may be provided a common storage-type power supply. The or each power supply preferably has means for charging it.

In a preferred embodiment, each lighting unit has means for determining its position within the examination sequence. Thus, a preferred embodiment has the advantage that the sequential examination is not determined by physical location, allowing lights to be tested in any sequence.

During a test, the mains supply to a lighting unit is removed and the lighting unit will automatically switch over to its storage type power supply, preferably a nickel-cadmium battery. According to one particular requirement, the storage type power supply must supply power to the light emitting means for a total of three hours that is to say the mains voltage would be removed from the lighting unit for a total of three hours. In many situations, a particular region, such as a corridor or a room, may have a number of lighting units and, previously, all of the lighting units in this region were often tested at once. However, in a preferred embodiment, the lighting units are arranged in groups, wherein a particular region would contain lighting units belonging to different groups.In this way, lighting units may be tested in groups, such that1 if as a result of a test a lighting unit is made inoperative for a period of time, emergency lighting is still available in all regions, although some of the lighting units within that region may be inactive.

Preferably, a system may be divided into twenty eight groups, allowing a group test on each of the first twenty eight days in each month.

In a preferred embodiment, other conditions in addition to light being emitted, may be detected. For example, it may be possible to detect that the storage type power supply is being charged and to detect that the main lighting unit is correctly positioned within its mounting.

In a preferred embodiment, information is supplied from lighting units to said central control unit by means of a pulse and a plurality of bits may be supplied to said central units by modulating the amplitude of said pulse.

Preferably, said central unit includes means for generating an indication of the condition of each lighting unit. Furthermore, the central processing unit may include means for producing an indication that a number of failures have occurred, rather than printing an individual message for each failure.

The invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a lighting unit, including means for receiving data from and transmitting data to a central control unit; and, Figure 2 shows a central control unit connected to a plurality of lighting units of the type shown in Figure 1 and indicates the nature of data transmitted between the central control unit and the lighting units.

In the lighting unit shown in Figure 1, emergency lighting is provided by a light emitting means in the form of a conventional light bulb 15, although other suitable lighting means may be provided, such as a fluorescent tube etc.

Under normal conditions. that is to say when the electrical mains supply is available, power from said mains is supplied to a battery charger 16 via terminals 17. The battery charger 16 is arranged to charge a battery of nickelcadmium cells 18 and employs conventional circuit techniques for achieving this. A power fail detector 19 is arranged to detect failure of the mains supply and in doing so, said detector 19 closes a switch 20, thereby connecting the light bulb 15 to the battery 18 which, if all is well, will result in light being emitted by said bulb 15.

In order to test that the lighting unit is operating, a light sensing element 21 is provided which, on detecting light from said light bulb 15, supplies a signal to a combinational logic circuit 22. The lighting units are connected in cascade to a central processor via a data ring 23 and data, indicative of the condition of the output from the light sensing element is supplied to said data ring via a driving circuit 24 and a switch 25.

The central control unit is shown in Figure 2, connected to a plurality of lighting units L1, L2, L3....L254, L255, of the type shown in Figure 1.

In this embodiment, a total of two hundred and fifty five lighting units may be connected in cascade, thereby allowing the central control unit to identify a specific lighting unit by means of an eight bit number, although in practice any number of units could be connected in this way, given suitable programming of the central control unit.

The central control unit itself includes a microprocessor 30, which receives programs and data from memory devices 31. The memory devices 31 include read only memory devices 31a, for storing the operating program for the microprocessor 30, loaded on initialising the system. In addition, application specific programs are stored in an electrically erasable read only memory devices 31b such that, under normal operating conditions, said memory devices 3 lb cannot be erased accidentally although, after making the required connections, the devices may be erased so that new application specific software may be installed. Operational data, relating to the condition of lighting units at any specific time, is stored by random access memory devices 31c and transferred between the random access memory 31c and conventional computer peripherals, identified generally by reference 32, allowing hard copies of operational information to be produced.

New data may be manually supplied to the microprocessor 30 by means of a key pad 33 and fault conditions are displayed by means of indicators 34.

Indicators 34 may be sophisticated enough to identify the exact location and nature of a fault or, alternatively, said indicators may merely identify the presence of a fault thereby prompting an operator to consult the computer peripherals 32 for a complete breakdown.

A number of central units, with their associated loop of lighting units, may be connected together by means of a serial link 35 such that, for example, if a particular microprocessor encounters problems, it may receive back-up from another central unit or, for example, only one of said units may be connected to computer peripherals and information from other units may be received via said serial link.

The microprocessor 30 receives clock signals from a clock 36, which provides timing for signals supplied to the data ring 23. On initialisation, a pulse generator 37 supplies a reset timing signal to the data ring, in response to instructions from the microprocessor 30 derived from clock signals from the clock generator 36.TIle reset pulse generated by said pulse generator 37 is indicated at 38. The data ring is connected to an electrical supply of twenty four volts and a reset pulse consists of dropping the supply on ring 23 to nineteen volts for a period of twelve microsecond. Thereafter, clock pulses are supplied to said ring from said pulse generator of the type indicated by 39, consisting of nineteen volt pulses for two millisecond spaced eight millisecond apart.

Referring to Figure 1. the data ring includes a tap 40 arranged to supply timing pulses to a counter 41 and it should be noted that said timing pulses are received by counters present in each of said lighting units. On receiving a reset pulse, counter 41 is reset to zero and thereafter is incremented each time it receives a two millisecond timing pulse from the data ring 23. Each counter 41 is uniquely programmed with a number which identifies that particular lighting unit within the ring. As soon as the counter 41 has counted up to its programmed number, an output signal is supplied to switch 25, thereby dosing switch 25 and connecting the output from driver 24 to a line tap 42. The nature of pulses supplied to line tap 42 is illustrated by reference 43 in Figure 2.

After counting to its programmed value, the counter 41 is arranged to wait one millisecond before supplying a signal to switch 25, which allows a ring input circuit to sample a reference voltage from the ring, which is then subtracted from pulses received by circuit 44 so as to standardise said pulses by providing a nulling effect. Referring to Figure 1, logic circuit 22 receives an indication that light is being produced by bulb 15, by means of the light sensing element 21 and, in addition, a current sensing element 45 determines whether the battery 18 is receiving charge. Nickel-cadmium cells may receive a continuous trickle charge without causing damage, therefore current should always pass through element 45.In response to data from the logic circuit 22, the driving circuit 24 supplies a voltage to the switch 25 and said voltage may have one of four possible values. If light 15 is not on and element 45 is not detecting current, the voltage supplied to switch 25 is at a level one. A level two voltage is supplied if the light does not come on but the current sensing element 45 detects that the battery 18 is being charged. If, on the other hand, the light 15 does come on but battery 18 is not being charged, a level three output is produced indicating that the light 15 is receiving power from the mains and, when no faults at all exist, a level four output is produced, indicating that the light 15 is on and that the battery 18 is charging.

At the ring input circuit, pulses generated by lighting units are supplied to a plurality of comparators. which in turn supply signals to the microprocessor 30 indicating, firstly, whether or not a major fault exists, secondly, indicating as to whether the light bulb 15 is or is not emitting light and, thirdly, indicating as to whether or not the battery 18 is receiving charge.

Under normal operating conditions, a switch 45 connecting mains terminal 17 to the charging circuit 16 is closed, consequently switch 20 is open, no power is supplied to light 15 and charger 16 supplies current to the battery 18. Throughout normal operation, reset and timing pulses are supplied to the data ring 23 and return pulses are generating, indicating that the battery 18 is receiving charge. Obviously, in this condition, data relating to the condition of the light is disregarded given that said light is not receiving power. A test condition is initiated in response to supplying a signal from pulse generator 37 of the type indicated at 46 in Figure 1. As previously stated, counter 41 counts timing pulses which sequentially enable switch 25, so that after a one millisecond delay data may be supplied to the data ring via line tap 42.In addition to enabling switch 24, counter 41 also enables a test latch circuit 47, which is responsive to a timing signal of the type shown at 46.

On initiating a test. all lighting units within a particular group need to be placed into the test mode for a predetermined period. After a two millisecond timing pulse of the type shown at 39 in Figure 2, the timing signal would normally be placed in its high condition for eight millisecond.

Similarly, after receiving a reset pulse of twelve millisecond, as shown at 38 in Figure 2 and at 46 in Figure 1, the timing signal would again go high for eight millisecond, followed by a two millisecond timing pulse. To place a particular lighting unit into the test condition, the timing signal is placed in the high condition for eighteen millisecond, as shown at 46, after the counter of the selected timing unit has enabled both the switch 25 and the test latch 47.

Thus, the test latch 47 is arranged to detect a high level of eighteen millisecond and when enabled by the counter 41, the test latch supplies and maintains a signal to switch 48, placing said switch in its open condition and removing the main supply to the charging circuit 16. Thereafter, each time the lighting unit under test has its counter enabled, an eighteen millisecond high signal of the type shown at 46 is supplied to the data ring and said lighting unit remains in the test condition. The lighting unit is removed from the test condition by, instead of supplying an eighteen millisecond high signal to the data ring after enabling the counter 41, a normal eight millisecond pulse is supplied, which is again detected by the test latch circuit 47, resulting in switch 45 being placed in the closed condition.

When switch 48 is in its open condition, the removal of power to the battery charger 16 is detected by the power fail detector 19 and switch 20 is placed in its closed condition. If all components within the unit are working correctly, light 15 will receive power from the battery 18 and the light sensing element 21 will generate a signal to logic circuit 22 indicating that light is being produced. Thus, each time counter 41 enables the supply of data to line tap 42, a level two signal should be produced. Under test conditions the status of the light 15 is considered and, when a change of state occurs, and the change is detected for four consecutive cycles, an alarm is raised by the central processing system.

As previously stated, each counter 41 is programmed with a number unique to that specific lighting unit. Similarly, the central control unit is programmed with data relating counter numbers to the physical location of the lighting units Thus, the time at which a pulse is returned to the ring input circuit identifies to the central processing unit which of the lighting units L1, L2 etc is transmitting data and the amplitude of said pulse conveys the data itself. Under test, the emergency lighting may be required to supply light for a total of three hours and, after doing this, it may take a total of twenty four hours for the batteries 18 to be fully re-charged.To facilitate the laying of the data ring 23, a first set of lighting units may be in one specific region, the following set in another region and so on and it would be attractive to test lighting units on a region by region basis, thereby facilitating the manual detection of failures. However, the present system allows the accurate remote detection of failures, thereby avoiding the need for manual observation of the actual light emitting devices themselves. The lighting units are, therefore, grouped together in a total of twenty eight groups wherein, as far as possible, each region includes lighting units from as many groups as possible.Thus, in addition to retaining information relating to the actual location of a lighting unit within its region. the central control unit also includes information identifying the group to which each lighting unit belongs, therefore, on a particular day, the central unit includes information identifying which group and therefore which particular lighting units will be tested. Thus, on the basis of this information. it is able to accurately interpret data received from the data ring 23 so that the success or failure of a lighting unit may be compared accurately with a testing schedule. It is expected that, in a large installation, a total of twenty eight groups would be provided, thereby allowing a group test to be performed on each day of the month such that, assuming the emergency lighting is required, no regions should be totally without light, due to them having lighting units which have insufficient energy stored in their batteries, due to a test having been performed prior to the batteries having sufficient time to be re-charged.

The system has been described with a separate physical data ring for supplying timing signals to the lighting units and for receiving data from said units. Alternatively, the transmission of data between the central control unit and the remote lighting unit could be achieved using the mains wiring, optical fibre links, radio links or microwave links etc.

Claims (15)

1. An emergency lighting system having a plurality of lighting units, wherein each lighting unit has a light emitting means, and means for connecting said light emitting means to a storage type power supply on detecting a mains power supply failure, wherein each lighting unit has a light detecting means arranged to produce a first output signal and said system includes a central control unit arranged to sequentially examine the presence of a first output signal from each of said lighting units.

2. A system according to Claim 1 wherein each lighting unit has a storage type power supply.

3. A system according to Claim 2 wherein each lighting unit has means for charging the power supply.

4. A system according to Claim 1 wherein the storage type power supply is common to a plurality of the lighting units.

5. A system according to any of claims l to 4 wherein each lighting unit has means for determining its position within the examination sequence.

6. A system according to any of claims 1 to 5 wherein the lighting units are arranged in groups such that a particular region to be lit contains lighting units belonging to different groups.

7. A system according to Claim 6 wherein the system is divided into 28 groups such that, in use, a different group is arranged to be tested on each of the first 28 days in each month.

8. A system according to any of the preceding claims wherein a condition other than the emission of light is arranged to be detected.

9. A system according to Claim 8 wherein the electrical charging of the storage type power supply is arranged to be detected.

10. A system according to Claim 8 or claim 9 wherein the positioning of the lighting unit within a mounting is arranged to be detected.

11. A system according to any of the preceding claims wherein information is supplied from lighting units to said central control unit by means of an electrical pulse.

12. A system according to Claim 11 wherein a plurality of data bits are arranged to be supplied to said central unit by modulating the amplitude of said electrical pulse.

13. A system according to any of the preceding claims wherein said central unit includes means for generating an indication of the condition of each lighting unit.

14. A system according to any of the preceding claims wherein the central unit includes means for producing an indication that a number of failures have occurred.

15. A system substantially as herein described with reference the accompanying drawings.