GB2409023A

GB2409023A - Wireless light system with master controller

Info

Publication number: GB2409023A
Application number: GB0328696A
Authority: GB
Inventors: Peter David Stokes; Dan Leach
Original assignee: Saf T Glo Ltd; STG Aerospace Ltd
Current assignee: Saf T Glo Ltd
Priority date: 2003-12-11
Filing date: 2003-12-11
Publication date: 2005-06-15
Anticipated expiration: 2023-12-11
Also published as: GB0328696D0; GB2409023B

Abstract

A lighting system comprises a network of devices arranged to communicate wirelessly with a master controller. One or more of the devices is provided with an LED light source. The LED is pulsed in order to reduce power consumption. Preferably, the LED is pulsed at a frequency invisible to the human eye. This frequency may be 100Hz. A variable load factor, which is proportional to the average illumination level, may be applied to the LED. The system may also be operable with a decreasing brightness reduce power consumption. The system may be used in a vehicle, such as an aircraft, as an emergency lighting system.

Description

IMPROVEMENTS IN OR RELATING TO ONBOARD EQUIPMENT

FOR AIRCRAFT AND THE LIKE

This invention concerns improvements in or relating to onboard equipment for aircraft and the like. The invention has particular, but not exclusive application to powered units employed for a variety of purposes, especially battery powered units such as may be used for lighting.

In our co-pending International patent application No. PCT/GB2003/003006 we describe a wireless communication system employing spread spectrum communication for controlling operation of networked communication devices such as battery powered light units for an emergency lighting system to assist evacuation of the aircraft in an emergency.

In our aforesaid application, the devices communicate wirelessly with a master controller and are arranged to cycle between an operable (awake) condition in which they can respond directly or indirectly to a signal transmitted by the master controller and an inoperable (sleep) condition in which they cannot respond to such a signal.

By arranging the devices to re-transmit any broadcast signal, not all the devices have to be within range of the master controller and synchronization of the wake/sleep cycle of the devices is not required. As a result, battery power is conserved and the effective life of the battery can be usefully extended without significantly affecting the overall response of the system to a signal transmitted by the master controller.

In the application to networked devices for emergency lighting, each light unit preferably employs light emitting diodes (LEDs). Typically an array of LEDs is employed requiring a low power consumption whereby the level and duration of light output can be achieved to comply with regulatory requirements using a small battery.

In our co-pending UK patent application No.0321959.9 we describe various improvements in and relating to onboard equipment employed in aircraft and the like especially wireless communication devices of the type described in our aforesaid International patent application.

In particular, we describe ways in which the battery life can be increased.

For example we describe a system for a vehicle such as an aircraft comprising a plurality of networked communication devices arranged to communicate wirelessly with a master controller wherein each device is arranged to cycle between an operable (awake) condition and an inoperable (sleep) condition in which the wake-up time is approximately 1 millisecond or less, preferably 0.5 millisecond or less and/or in which a multi-code generator is employed providing multiple switched outputs and spacing the switched outputs in the code space such that a search time for each device to detect a broadcast signal is reduced.

The present invention seeks to provide improvements to such systems whereby battery life may be further increased.

Thus according to one aspect of the present invention, we provide a system for a vehicle such as an aircraft comprising a plurality of networked communication devices arranged to communicate wirelessly with a master controller wherein one or more devices is provided with a light source comprising at least one LED wherein, in use, power consumption is reduced by pulsing said at least one LED.

Preferably, said at least one LED is pulsed at a frequency so that no pulsing is visible to the human eye. For example, we may employ a pulsing frequency of 100Hz.

Where the light source is employed as part of an emergency lighting system to indicate an escape route to the exit(s) of an aircraft, the current regulations require the system provide illumination for a minimum period of l 0 minutes in an emergency. However, many aircraft operators specify a longer minimum period, typically 20 minutes, so as to provide a safety margin to ensure the system will meet the minimum requirements at the time of use. In some cases, even longer periods of illumination in an emergency such as in the ETOPS [extended twin engined operations] scenario may be desirable.

Each device employs a battery to power the light source which requires the battery to have a minimum residual battery life sufficient to provide the necessary power for this period of illumination. Accordingly, extending the battery life by reducing power consumption through pulsing an LED light source may contribute to a reduction in system costs without compromising safety. In addition, the system may be capable of more than one "switch-on" without replacing the batteries such that the operational capability of the system is not compromised after an inadvertent " switchon " . According to a preferred feature of the invention we may employ pulsing of the light source with a variable load factor. The measured average illumination level is proportional to the load factor of the pulse and varying the load factor enables the light source to be effectively dimmed to produce a saving in power consumption and further extend battery life.

Thus, we may employ a variety of load factors between 10 and 100% of ON time according to the requirements of the system. The resulting

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savings in battery life are also proportional and an ON time operation for minutes at a pulsed load of 1 No is approximately equivalent to a standard ON time operation for 5 minutes full load.

The ability to dim the illumination has particular benefits when the system is employed to provide emergency lighting. Thus, we may operate the light source at full brightness for an initial period after switching on and then gradually reduce the brightness to a pre-determined minimum. In this way, the operation of the system can be matched to meet the ability of the human eye to dark adapt over time to a reduction in the level of illumination. As a result, power consumption is reduced at the time of use allowing the period of illumination to be increased providing additional safety margins, especially in the ETOPS scenario, while still meeting current rules and regulations.

Thus, according to another aspect of the present invention, we provide a system for a vehicle such as an aircraft comprising a plurality of networked communication devices arranged to communicate wirelessly with a master controller wherein one or more devices is provided with a light source comprising at least one LED wherein, in use, said at least one LED is capable of providing a variable illumination level.

Preferably, the level of illumination is controlled by pulsing the at least one LED with a variable load factor. For example, we may vary the load factor from 10 to looted ON time while pulsing the LED at a frequency that is not visible to the human eye, for example 100Hz, by means of an appropriate logic signal in the control system. In this way, the level of illumination can be varied according to requirements and power consumption can be reduced to provide extended illumination. Thus, when providing emergency lighting, we may gradually reduce the illumination level to match the dark adaptation of the human eye to lower illumination levels without compromising safety.

In the above-described aspects of the invention, each device may have a light source comprising one or more LEDs which may be white LEDs and/or coloured LEDs. A plurality of LEDs may be arranged in an array or take the form of flat panel diffuser as described in our aforementioned UK patent application.

Other features of the construction and operation of the networked communication devices and the systems employing such devices are not described further herein and the reader is directed to our co-pending UK patent application which should be read in conjunction with this application for such details.

Claims

1. A system for a vehicle such as an aircraft comprising a plurality of networked communication devices arranged to communicate wirelessly with a master controller wherein one or more devices is provided with a light source comprising at least one LED wherein, in use, power consumption is reduced by pulsing said at least one LED.

2. A system according to claim 1 wherein said at least one LED is pulsed at a frequency so that no pulsing is visible to the human eye.

3. A system according to claim 2 wherein said at least one LED is pulsed at a frequency of 100Hz.

4. A system according to any preceding claim wherein each device employs a battery to power the light source.

5. A system according to any preceding claim wherein the light source is pulsed with a variable load factor.

6. A system according to claim 5 wherein the load factor is variable between 10 and 100% of ON time

7. A system according to any preceding claim wherein the light source is operable at full brightness for an initial period after switching on and then gradually dimmed to reduce the brightness to a pre- determined minimum.

8. A system of networked communication devices substantially as hereinbefore described.