GB2218506A

GB2218506A - Automatic lighting system

Info

Publication number: GB2218506A
Application number: GB8811151A
Authority: GB
Inventors: Graham Wild
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-05-11
Filing date: 1988-05-11
Publication date: 1989-11-15
Anticipated expiration: 2008-05-11
Also published as: GB2218506B; GB8811151D0

Abstract

The system has a lamp 2 controlled by a control circuit. The control circuit includes a radiation detector (10 Fig 2, not shown) and is arranged to switch the lamp on when the detector receives infra-red radiation from a person. During daylight hours the operation of the lamp is inhibited by a daylight sensing device (16). The system further includes an auxiliary indicator 6 which is switched on during daylight hours, in response to the actuation of the radiation detector (10), when the lamp connection is disrupted. In this way, failure of the lamp can be detected, and by disconnection of the lamp the system can be walk tested, during daylight hours. <IMAGE>

Description

AUTOMATIC LIGHTING SYSTEM This invention relates to an automatic lighting system of the kind comprising a lamp, and a control circuit which includes a radiation detector, the control circuit being operable to switch on the lamp when the detector is actuated by received radiation. Automatic lighting systems of this kind are used to provide courtesy lighting, or to deter intruders, outside buildings, the arrangement being such that the lamp is switched on when abody, such as person or a motor vehicle enters a detection zone and transmits infra-red radiation from a local source on to the detector.

With known systems the control circuit includes a light sensor which inhibits switching on of the lamp in daylight, this being provided to avoid unnecessary or spurious actuation of the detector. However, this gives rise to the problem that the operation of the control circuit, and the proper functioning of the lamp, cannot readily be checked during daylight hours.

An object of the present invention is to overcome or at least minimise the above problem.

According to the invention therefore there is provided an automatic lighting system of the kind comprising a lamp, a control circuit which includes a radiation detector, said control circuit being operable to switch on the lamp when the lamp is connected as a load to the control circuit and the optical detector is actuated by received radiation, and a daylight sensing device operable to inhibit said switching on of the lamp in response to sensing of daylight conditions by said device, characterised in that the system further includes an auxiliary indicator which is arranged to be switched on by the control circuit during said daylight conditions in response to said actuation of the radiation detector, when the loading of the control circuit by the lamp is disrupted.

With this arrangement, it is possible to detect when failure of the lamp has occurred in daylight in so far as the control circuit can respond to the actuation of the radiation detector to cause operation of the auxiliary indicator. Also, checking of the operation of the control circuit can be readily carried out in daylight by removing the lamp, or otherwise simulating disruption of the loading of the control circuit thereby, so that the operation of the auxiliary indicator can be monitored as the detector is actuated.

The auxiliary indicator may comprise an audible and/or visual indicator, preferably an audible indicator such as a buzzer or the like.

The detector is preferably an optical (infra-red) detector which is arranged to be radiated by transmission from a body moving into a detection zone scanned by radiation from a local source. With this arrangement, the system can be conveniently 'walk tested' when the lamp is removed. That is, a person can monitor operation of the auxiliary indicator while moving within the scanned zone. Similarly, indication of failure of the lamp can be conveniently given to a person moving into the scanned zone during daylight, as a consequence of unexpected operation of the auxiliary indicator.

In accordance with usual practice the control circuit may include a timer which is operable to hold the lamp switched on for a predetermined period of time after termination of actuation of the detector. In this case, the timer may be by-passed or inhibited during operation of the auxiliary indicator so that, conveniently, the operation of the indicator is only maintained for a relatively short duration, if at all after termination of actuation of the detector.

Detection of daylight conditions may be affected in any suitable manner, for example using a light-sensitive resistor or other optically sensitive component.

The invention will now be described further by way of example only and with reference to the accompanying drawings in which Figure 1 is a diagrammatic representation of one form of a lighting system according to the invention; Figure 2 is a block circuit diagram of the lighting system; and Figure 3 is a more detailed circuit diagram.

The lighting system comprises a control circuit within a waterproof housed unit 1 arranged to be mounted for example at an elevated position on an outside wall of a house. The control circuit is connected to mains supply via a cable, and a filament lamp 2 is connected to the circuit and mounted on or adjacent the housed unit 1 so as to be capable of illuminating an area in the vicinity of the house.

On the exterior of the housed unit there is a lens 3 which collects infra-red radiation from a detection zone adjacent the house and focuses such collected radiation on to an infra-red detector forming part of the control circuit within the housed unit 1. The housed unit 1 also has a transparent region 4 through which a light-sensitive resistor of the control circuit can be exposed to ambient light; there is an infra-red source 5 arranged to direct infra-red radiation into the detection zone; and there is a piezo buzzer 6 mounted in or on the housed unit as to to be clearly audible to a person within the detection zone.

The control circuit comprises a power supply 7, a voltage regulator 8, an infra-red detection circuit 9 including the abovementioned detector 10, an amplifier 11 for amplifying the output of the detection circuit 9, a comparator 12 for comparing the amplifier output with a reference voltage from a potential divider 13, a timer 14 controlled by a gate 15 which is connected to the output of the comparator 12 and to the abovementioned light-sensitive resistor 16, a switching circuit 17 connected to the timer 14 and arranged in series with the abovementioned filament lamp 2, and a drive circuit 18 for the abovementioned piezo buzzer 6 connected to the output of the comparator 12.

During night time, the normal operation of the circuit is as follows.

When a body moves into the detection zone, infra-red radiation is transmitted to the detector 9. The output from the amplifier 11 exceeds the reference voltage and the comparator 12 produces an output which triggers the timer 14 via the gate 15, the gate 15 being enabled, and a gate 19 for the buzzer drive circuit 18 being disabled by a potential derived from a series circuit 20 connected to the lamp filament. The timer 14 activates an SCR of the switch circuit 17 which switches on the lamp 2 for a period of time determined by the setting of the timer 14. At the end of this time the lamp 2 is switched off and the timer 14 is re-set ready to be actuated again.

During daylight, the operation is as follows.

The gate 18 of the drive circuit is disabled, and the gate 15 of the timer 14 is enabled by the potential derived from the series circuit 20 connected to the lamp filament, but the comparator 12 cannot act to switch on the timer 14 because the output of the comparator 12 is earthed through the activated light-sensitive resistor 16.

If, however, the lamp 2 becomes open circuit due to removal of the lamp 2 or due to breaking of the filament, the gate 19 of the drive circuit 18 for the buzzer 6 is enabled and the buzzer 6 is operated whenever the comparator 12 produces an output. After removal of the comparator output the buzzer operation is sustained for only a very short period of time, determined by the time constants of the drive circuitry 18.

With this arrangement, in the event that the bulb blows, a person walking through the detection zone during daylight will be alerted to the failure of the bulb by actuation of the buzzer 6. When the system is installed, the sensitivity and orientation of the detection zone can be checked in daylight by removing the lamp 2 and then listening to the buzzer 6 while walking through the zone.

It is of course to be understood that the invention is not intended to be restricted to the above details which are described by way of example only.

Claims

1. An automatic lighting system of the kind comprising a lamp, a control circuit which includes a radition detctor said control circuit being operable to switch on the lamp when the lamp is connected as a load to the control circuit and the optical detector is actuated by received radiation, and a daylight sensing device operable to inhibit said switching on of the lamp in response to sensing of daylight conditions by said device, characterised in that the system further includes an auxiliary indicator which is arranged to be switched on by the control circuit during said daylight conditions in response to said actuation of the radiation detector, when the loading of the control circuit by the lamp is disrupted.

2. An automatic lighting system according to claim 1 wherein said auxiliary indicator comprises an audible indicator.

3. An automatic lighting system according to claim 1 or 2 wherein said auxiliary indicator comprises a visual indicator.

4. An automatic lighting system according to any one of claims 1 to 3 wherein said auxiliary indicator comprises a buzzer.

5. An automatic lighting system according to any one of claims 1 to 4 wherein said detector is an optical (infra red) detector which is arranged to be radiated by transmission from a body moving into a detection zone scanned by radiation from a local source.

6. An automatic lighting system according to any one of claims 1 to 5 wherein said control circuit includes a timer to hold the lamp switched on for a predetermined period of time after termination of actuation of the detector.

7. An automatic lighting system according to claim 6 wherein said timer is arranged to be by-passed or inhibited during operation of the auxiliary indicator.

8. An automatic lighting system according to any one of claims 1 to 7 wherein said control system includes an optically sensitive component to detect daylight conditions.

9. An automatic lighting system according to claim 8 wherein said optically sensitive component is a light-sensitive resistor.

10. An automatic lighting system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.