GB2453540A

GB2453540A - Wirelessly controlled light unit for use as part of a multi-light unit array

Info

Publication number: GB2453540A
Application number: GB0719593A
Authority: GB
Inventors: Geoffrey Lunn
Original assignee: ART LED BV; VML TECHNOLOGIES BV
Current assignee: ART LED BV; VML TECHNOLOGIES BV
Priority date: 2007-10-08
Filing date: 2007-10-08
Publication date: 2009-04-15
Also published as: GB0719593D0

Abstract

A light unit for use with other light units to form a multi-light unit array includes a control circuit 13 for controlling the energisation of at least one light source 11, such as an LED, provided on the light unit and having a receiver 16 for wirelessly receiving a control signal 17 from an external transmitter 18. There is also provided an energy source 12 for powering the at least one light source 11 and the control circuit 13. The energy source 12 includes at least one solar cell 14 adapted to convert solar energy into electrical energy and may also include an electrical energy storage device 15, such as a rechargeable battery, a super-capacitor or a wind turbine, adapted to store electrical energy generated by the at least one solar cell 14. The control circuit 13 may include a RFID tag to communicate the identity of the light unit to a remote system.

Description

-1-2453540

LIGHT UNIT

The present invention relates to a light unit intended for mounting in an array with other similar light units and adapted to be controlled remotely.

Large visual displays for presenting still and moving images are well known and are commonly provided at large public events such as concerts and sports events. Increasingly, such displays are also being used in architectural applications in city centres, either standalone or integrated in to the facades of buildings. Such displays comprise a plurality of light units arranged in an array, where each light unit represents a pixel of the image to be presented and includes one or more light sources adapted to emit light of a particular colour.

Typically, a display may be up to 320 pixels wide and 240 pixels high, requiring a total of 76,800 light units. Furthermore, the size of the display can vary considerably depending on the size of the individual light units and the spacing between them, but some displays can be of the order of 25 metres long and 20 metres high. Each light unit includes at least one light source and is wired to an electricity supply to power the light source and a control circuit to control the energisation of the light source, and so in view of the number of light units and the spacing between those light units a complex network of cables is required.

An advantage of such displays is that they can be dismantled and transported to other venues as and when required. A disadvantage of such displays is that the cabling can be cumbersome and also time consuming to install and dismantle. In addition, faulty connections can be very troublesome and are often the most unreliable part of the display. Furthermore, though light sources such as LEDs are becoming far more energy efficient than incandescent bulbs, collectively they consume a large amount of electricity and a large display may consume many kilowatts of electricity.

As well as image and video displays, light unit arrays have many other applications including vehicle signalling on roads, runways and so forth. Quite often such systems are installed in remote locations where the provision of power and data feeds is not readily available, thereby making installation somewhat difficult and costly.

Furthermore, arrays of light units are sometimes used to illuminate public places such as precincts, roads and walkways. Sometimes the light units are to be retrofitted and in which case the provision of power and data feeds can be unsightly, difficult and costly.

It is an object of the present invention to overcome the above disadvantages of conventional displays and lighting installations by providing a light unit which does not need to be wired to a data source or a power source, thereby reducing installation times and costs. It is a further object of the present invention to provide a light unit that includes means to generate its own electricity.

Accordingly, there is provided a light unit for use with other light units to form a multi-light unit array, which unit comprises: -at least one light source; -a control circuit for controlling the energisation of the at least one light source and which includes a receiver for wirelessly receiving a control signal from an external transmitter; and -an energy source for powering the at least one light source and the control circuit which energy source includes a solar cell adapted to convert solar energy into electrical energy.

Preferably, the energy source includes an electrical energy storage device adapted to store electrical energy generated by the solar cell. Most preferably the electrical energy storage device comprises a rechargeable battery, though it could comprise a super capacitor. Different kinds of solar cells are available for converting solar energy into electrical energy, but the most suitable are those that are small while still generating sufficient electrical energy to energise the at least one light source. A preferred type of solar cell is a single silicon crystal cell. Since certain types of light sources, including LEDs are driven by direct current electricity and the solar cells convert solar energy into direct current electricity, there is no requirement for a rectifier or inverter to convert mains AC electricity into DC, or vice-versa.

Furthermore, the energy source may also include a wind turbine for converting wind energy into electrical energy for powering the light sources and control circuit.

The control signal, which is transmitted by the external transmitter to the receiver, contains data relating to the brightness and colour of light to be emitted from all light units forming the multi- light unit array. The light unit is accorded an identity associated with its location in the array and which identity may be included in the control signal to ensure that the data is received by the light unit for which it was intended. For this purpose, the control circuit may include means for defining a unique identity for the light unit. It is preferable for the light unit to be configured so that its identity is representative of its location within the multi-light unit array. To facilitate this, the control circuit may include a programmable device having manually operable switches by which the identity of the light unit may be changed. Conveniently, the address of the light unit within the array may be used as the light units identity and which could be defined by the light unit's column and row number within the array.

Alternatively the identity of the light unit may be preset and a separate programmable device may be provided to communicate with the control circuit to register the light unit's identity with its position within an array. Preferably, the control circuit includes a radio frequency identification tag to communicate the identity of the light unit to the programmable device. Otherwise, it may be necessary to enter the identity of each light unit into the programmable device which may give rise to the entry of erroneous identities or physically connect the programmable device to the light unit to enable the identity to be sent to the programmable device.

In an alternative arrangement, the control circuit may include a positioning system such as a global positioning system (GPS) receiver to determine data relating to the location of the light unit, which data then forms part of the identity. For example, the identity could include co-ordinates relating to the location of the light unit.

The control signal is transmitted to each light unit in the array by an external transmission system, using a radio transmission standard which has sufficient capacity and bandwidth to accommodate the amount of data needed to describe the brightness level of each light unit in the array, and to refresh such data as may be required in order to facilitate the display of moving images. Typically, each light source within a light unit will require a minimum of eight bits of data to describe its brightness at any time, and in order to facilitate smooth motion graphics, such data must be refreshed at least thirty times per second. Accordingly, the transmission system should be selected on the basis of the amount of data to be transmitted to the multi-light unit array in order to ensure that sufficient bandwidth is available.

There are several transmission standards available which might be suitable for this application, including, but not limited to, WiFi, Bluetooth, Zigbee and the 2.4GHz ISM (Industrial, Scientific and Medical) and SRD (Short Range Device) standards.

Preferably, the light unit comprises a plurality of light sources collectively to emit more light, but the maximum number of light sources is governed by the maximum brightness required) and the amount of available electrical power since more light sources require more power. Most preferably) the light unit includes light sources of different colours, including for example red) blue and green light sources. Thus, the light unit should be capable of emitting any colour of light merely by adjusting the brightness of the individual red) blue and green light sources.

Most preferably, the light sources comprise light emitting diodes (LED) or organic light emitting diodes (OLED), featuring high efficiency, saturated colours and the energisation of which light sources may be controlled using digital pulse width modulation (PWM).

In a further arrangement the control circuit includes a transmitter adapted to relay information relating to the operational status of the at least one light source to one or more of the other light units in the multi-light unit array.

Each light unit in the array may then respond to this information in a predetermined way by varying the brightness and colour of light emitted from its light sources. Alternatively or additionally, the transmitter may be adapted to relay that information to an external control unit, which may monitor whether the light unit is emitting light of the intended brightness and colour.

Advantageously, the transmitter may be adapted to relay information relating to the operational status of the solar cell and electrical storage device to an external control unit. The external control unit can then monitor the charge rate and charge level of the storage device for diagnostic purposes.

Preferably, the light unit includes a proximity detector, such as a passive infrared detector (PIR), a motion sensor, or a light sensor for detecting the presence of a person1 animal or inanimate object in the vicinity thereof. The control circuit may be adapted to energise the light source in response to the detection of a person, animal or inanimate object by the proximity detector.

The proximity detector may also be linked to the transmitter so that the detection of a person, animal or inanimate object can be communicated to other light units in the multi-light unit array. Thus, the light unit may emit light when a proximity detector of another light unit in the multi-light unit array senses the presence of a person or object. Thus, a light source need only emit light in the event that an object or person is in or about to enter the vicinity of the light unit, thereby preserving the electrical energy stored in the storage device. The control circuit may be adapted to predict if a person or object is about to enter the vicinity of its light unit by analysing the operational status of other light units in the multi-light unit array. The detector could also determine the magnitude of the ambient light and adjust the brightness of the light emitted from the light unit accordingly. This arrangement would be particularly useful in public places, such as in a Street or in a car park.

The light unit may be particularly well suited to security lighting applications, in which it could be arranged in an array with other light units also having proximity detectors and transmitters. The proximity detector of the light unit could detect the presence of a person and in response the control circuit could adjust the brightness of the light emitted from the light source.

Furthermore, the transmitter may communicate with an external receiver which could be configured to elicit an alarm and or activate cameras in the vicinity of the person.

Advantageously, the light unit has a housing having a front face on which the solar cell and at least one light source are provided and an interior in which the electrical storage device and control circuit, including the receiver are mounted. The solar cells may be provided on any exterior face of the housing and preferably arranged for receiving direct sunlight. The shape of the housing may vary considerably depending on many factors, including manufacturing limitations and the applications for which the light unit is to be used.

In an alternative embodiment the light unit includes a body defining a void in which the light source and solar cell are mounted, the body being made from a material which is at least partially translucent, particularly in the region surrounding the void so that light emitted from the light source may pass therethrough. Preferably the body is transparent and the material from which it is made is glass or a like material. Most preferably the body is formed from two plates spaced apart to define the void in which the light unit is mounted, the periphery of the void being sealed by a frame or the like to prevent the entry of moisture and debris. The other components of the light unit could be hidden within the frame and connected to the light source and solar cell by wires made from Indium tin oxide or other suitable materials which appear transparent.

This arrangement would be particularly well suited for use on large building facades and light emitted from the light units could selectively be directed outwardly or inwardly so as to illuminate the exterior or the interior of the building respectively. Daylight could enter the building through the glass panels and charge the storage device and at night the light units could be energised to display patterns and images, including full motion video on the exterior of buildings.

In a further embodiment of the invention one or more arrays of light units may be disposed along roads, car parks and airfields to indicate a particular route to be taken by a vehicle. The external transmitter may send a control signal to all light units in the array and only light units located along the intended route would be energised and therefore emit light of the intended colour and brightness. The light units could be energised sequentially so as to show the direction to be followed and different colours could be used to display other important messages.

In a further aspect of the invention there is provided a display comprising a plurality of light units of this invention as described above and arranged in an array so that each light unit represents at least one pixel of an image to be presented on the display. Preferably the plurality of light units are mounted to a support structure such as a purpose built frame. Alternatively, the light units could be mounted on a floor, wall or ceiling. In yet a further arrangement, the light units could be integratecj into the fabric or material of a building or structure.

When the light unit represents a single pixel of the display some or all the light sources included in the light unit may be energised collectively to emit light of the required brightness and colour. Alternatively, the light unit may include multiple groups of red, blue and green light sources and each group may represent a single pixel of the image to be displayed. Most preferably, the groups of light sources are arranged in a grid so that each group of light sources aligns with groups on other light units provided in the array. Thus, the receiver may be adapted to receive multiple control signals relating to the brightness and colour of light to be emitted from multiple groups of light sources and the control circuit may be adapted to control the energisation of the light sources included in each of those groups Simultaneously.

In a yet further aspect of the invention, there is provided the combination of a display as described above and a transmitter adapted to transmit the control signal to the plurality of light units. The control signal may be digitally encoded and includes data relating to the energisation of the plurality of LEDs.

By way of example only, one embodiment of the present invention will now be described in detail, reference being made to the accompanying drawings in which: Figure 1 is a schematic view showing the various components of the light unit; Figure 2 is a perspective view of a light unit according to the invention; and Figure 3 is a schematic view of a display comprising a plurality of the light units shown in Figures 1 and 2.

Referring initially to Figures 1 and 2, there is shown a light unit generally indicated 10 and comprising nine LEDs 11, an energy source 12 and a control circuit 13 for controlling the energisation of the LEDs 11. Three of the nine LEDs emit red light when energised, three emit green light when energised and three emit blue light when energised.

The energy source 12 includes a solar cell 14 arranged to convert solar energy into electrical energy and a rechargeable battery 15 adapted to store the electrical energy converted by the solar cell and drive the control circuit and LEDs. The solar cell comprises a single silicon crystal cell, which is relatively inexpensive and is reasonably small while still providing sufficient power.

Though the solar cell does not require direct sunlight to generate electricity, more electricity is generated as more light falls on the solar cell and so the orientation of the light unit should be a consideration.

The control circuit 13 includes a receiver 16 for receiving a control signal 17 from an external transmitter 18, which control signal contains information concerning the energisation of each LED, in particular the brightness of the light to be emitted from each colour LED 11. The control circuit 13 is adapted to convert the control signal into a series of pulse width modulated (PWM) signals which are then applied to the correct LEDs 11 to achieve the desired brightness. The resulting colour of light collectively emitted from the nine LEDs ills determined by the brightness of the red, green and blue LEDs and so it is critical that the correct PWM signal is applied to each LED.

The control circuit also includes a transponder comprising a radio frequency identification device (hereinafter referred to as RFID device) 19 which is adapted selectively to emit a digitally encoded signal 20 when in receipt of an initiation signal 21. The light unit 10 has a unique identity which is encoded in the digitally encoded signal 20 and by which the light unit 10 can be identified. The RFID device 19 is a passive device which therefore draws no power from the rechargeable battery 15, but instead relies on the incoming initiation signal 21. Alternatively, the RFID could be a semi passive device that draws a small amount of power from the rechargeable battery to operate a microchip holding the identity, but the power for transmitting the digitally encoded signal 20 comes from the initiation signal 21.

The light unit 10 includes a generally rectangular case 30 having four side walls 31, a front face 32 and a rear face 33. The LEDs ii are mounted in the centre of the front face 32 and arranged in a 3x 3 matrix in which the red, green and blue LEDs are mixed to enable the red, green and blue lights to appear as a single colour light corresponding to that of the intended pixel. The LEDs 11 are bonded to the front face 32 by an adhesive and the legs (not shown) of the LEDs 11 extend through small holes (not shown) formed in the front face 32 and connect to the control circuit 13. The solar cell 14 is also bonded to the front face of the case 30 by a suitable adhesive, the solar cell being generally rectangular and having a rectangular cut-out 34 in its centre so as to locate around the periphery of the 3 by 3 matrix of LEDs. Four flanges 35 are provided or, the sidewalls of the case to enable the light unit to be secured to a supporting structure (not shown), each flange having a hole 36 through which a bolt or like fastener (not shown) may be secured.

Figure 3 shows the light unit 10 with a plurality of other similar light units to form a display generally indicated 40 on which an image may be presented, where each light unit 10 represents a pixel of the image. The display exemplified in Figure 3 has only 25 light units whereas a typical display having 320 by 240 pixels would require 76,800 light units. The size of the light units and the number of LEDs mounted in each light unit depends on the size of the display, the brightness required, and the available power. If the display is to be viewed from a relatively long distance it must be considerably larger than a display which is to be viewed from a relatively short distance and therefore larger light units having more LEDs may be used. Conversely, a display that is to be viewed from a relatively close distance might be considerably smaller than a display which is to be viewed from a relatively long distance and so smaller light units having fewer LEDs may be required. The spacing between adjacent light units can vary considerably depending on the particular application.

The display 40 is to be used in combination with the transmitter 18 and a transmitter control circuit 50 adapted to receive a video signal 51 containing data relating to the colour and brightness of each pixel of the image to be presented on the display 40. The data relating to each pixel is ordered sequentially, typically starting with data relating to the top left hand pixel Al of the image and finishing with the bottom right hand pixel of the image Y5, which is typical of most video signals. So that each light unit 10 receives data relating to the pixel it represents, the identity of each light unity must be encoded in the signal, whereby the data relating to a particular pixel is preceded by the identity of the corresponding light unit 10.

In order for the control signal 17 to include the identities of the light units the transmitter control circuit 50 must first learn the identity of the light units 10 and associate each identity with the pixel of the image that light unit represents.

This is achieved during installation of the display 40 by use of a portable transmitter receiver 55 that is presented to each light unit 10 in turn. When the portable transmitter receiver 55 is presented to a particular light unit 10 a button is pressed on the portable transmitter receiver 55 that causes the initiation signal 21 to be transmitted towards the RFID device 19 mounted in that light unit 10. The RFID device 19 then transmits its digitally encoded signal 20 containing its identity and the portable transmitter receiver 55 receives the digitally encoded signal 20 and stores the identity in its memory (not shown) against the particular pixel represented by that light unit 10. Once this process has been carried out for each light unit 10, the portable transmitter receiver 55 is connected to the transmitter control circuit 13 whereby the identities stored in the memory are registered.

The transmitter control circuit 50 includes means for receiving the video or other control signal 51 and sampling the data to determine a value relating to the colour and brightness of each pixel (hereinafter referred to as the pixel value). The pixel value contains information relating to the brightness of the light to be emitted from the red, blue and green LEDs 11 of the corresponding light unit 10 collectively to emit light of the required colour and brightness.

Thus, the control signal 17, which is transmitted by the transmitter 18 to the display 40, includes the identity of each light unit 10 and the pixel values to be applied to the red, green and blue LEDs 11 in each light unit.

In use, the transmitter control circuit 50 receives and samples the video signal 51 and then determines the magnitude of the pixel value for each pixel.

Each pixel value holds information relating to the brightness of light to be emitted from the red, green and blue LEDs 11 of the light unit representing that pixel. A data set is created for each pixel, which dataset comprises the identity of the light unit 10 representing a particular pixel and the magnitude of the pixel value corresponding to the LEDs 11 of that light unit. The data sets of the pixels making up an image are then assembled and formatted to form the control signal 17 which is transmitted to the display 40. The control signal 17 is received by all light units 10 which recognise their own identity encoded in the signal 17 and the pixel value which accompanies their identity. The control circuit of each light unit then responds by converting the pixel values into a PWM signal for energising the LEDs 11, thereby causing the desired colour of light to be emitted.

Claims

1. A light unit for use with other light units to form a multi-light unit array, which light unit comprises: -at least one light source; -a control circuit for controlling the energisation of the at least one light source and which includes a receiver for wirelessly receiving a control signal from an external transmitter; and -an energy source for powering the at least one light source and the control circuit which energy source includes at least one solar cell adapted to convert solar energy into electrical energy.

2. A light unit as claimed in claim 1, wherein the energy source includes an electrical energy storage device adapted to store electrical energy generated by the at least one solar cell.

3. A light unit as claimed in claim 2, wherein the electrical energy storage device includes at least one rechargeable battery.

4. A light unit as claimed in claim 2 or claim 3, wherein the electrical storage device includes at least one super-capacitor.

5. A light unit as claimed in any of the preceding claims, wherein the energy source includes a wind turbine.

6. A light unit as claimed in any of the preceding claims, wherein the control circuit includes means for defining a unique identity for the light unit.

7. A light unit as claimed in claim 6, wherein the control circuit includes a programmable device by which the identity of the light unit cart be changed.

8. A light unit as claimed in claim 6 or claim 7, wherein the control circuit includes a radio frequency identification tag to communicate the identity of the light unit to a remote system.

9. A light unit as claimed in claim 6, wherein the control circuit includes a positioning system to determine the location of the light unit and the identity of the light unit is defined by its location.

10. A light unit as claimed in any of the preceding claims, wherein the at least one light source comprises an LED.

11. A light unit as claimed in any of claims 1 to 9, wherein the at least one light source comprises an organic LED.

12. A light unit as claimed in any of the preceding claims, and further comprising a plurality of light sources.

13. A light unit as claimed in claim 12, wherein the plurality of light sources include light sources of different colours.

14. A light unit as claimed in claim 13, wherein the plurality of light sources include red, green and blue light sources.

15. A light unit as claimed in claim 12, wherein the plurality of light sources include white light sources.

16. A light unit as claimed in any of the preceding claims, wherein the control circuit includes a transmitter adapted to relay information relating to the operational status of the at least one light source to an external control unit or other light units in the array.

17. A light unit as claimed in any of the preceding claims and further comprising a proximity detector to sense the presence of a person, animal or inanimate object within a predefined range thereof.

18. A light unit as claimed in any of the preceding claims, wherein a housing is provided having an interior in which the control circuit is mounted and an exterior on which the at least one light source and solar cell are mounted.

19. A light unit as claimed in any of claims ito 17 and further comprising a body defining a void in which the light source is mounted, the body being made from a material which is at least partially transparent.

20. A light unit as claimed in claim 19, wherein the body is formed from two plates spaced apart to define the void in which the light unit is mounted, the periphery of the void being sealed to prevent the entry of moisture and debris.

21. A light unit as claimed in any of the preceding claims and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

22. A display comprising a plurality of light units as claimed in any of the preceding claims and arranged in an array so that each light unit represents at least one pixel of an image to be presented on the display.

23. A display as claimed in claim 22, wherein the plurality of light units are mounted to a support structure.

24. A combination of a display as claimed in claim 22 or claim 23, and the transmitter adapted to transmit the control signal to the plurality of light units.