Abstract:
An LED street lamp including a PLC modem and a control circuit is disclosed. The LED street lamp is able to receive control commands from remote controller. It is also capable of doing self-control based on status information gathered by diagnostic circuit. A system for LED street lamp monitoring and control is also disclosed which includes a central controller, a distribution network and a plurality of LED street lamps. Based on the PLC technology, each LED street lamp can be centrally controlled by the central controller.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims benefit under 35 U.S.C. §119(e) of U.S. Provisional Application having Ser. No. 61/030,572 filed Feb. 22, 2008, which is hereby incorporated by reference herein in its entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates to an apparatus and system for monitoring and controlling street lighting. 
       BACKGROUND OF INVENTION 
       [0003]    The street lamp is an important public facility in the city. On top of providing lighting for pedestrians, it also prevents criminals from committing crimes in dark. 
         [0004]    Currently, the most commonly used street lamp is sodium vapor lamp, which has typical power consumption between 250 W and 400 W and a lifetime up to 5,000 hrs. It takes some delay to turn on or off the sodium vapor lamp. Another type of street lamp being used is mercury vapor lamp, which not only is detrimental to the environment but also requires a longer delay in turning on or off—as much as five minutes. There is therefore a need to continue to improve street lighting systems to make them more efficient and environmentally friendly. 
       SUMMARY OF INVENTION 
       [0005]    In the light of the foregoing background, provided is an alternative device and system for street illumination. 
         [0006]    Accordingly, the present invention, in one aspect is a lighting apparatus for street illumination, which includes an LED light source, a control circuit which is connected to said LED light source, a power supply connected to power line and supplying electrical power to the LED light source and the control circuit, and a PLC transceiver electrically coupled to the control circuit and the power line. The control circuit controls electrical power supplied to the LED light source. 
         [0007]    In one aspect of the present invention, a street lighting system includes a plurality of LED street lamps, each said LED street lamp contains an LED light source, a control circuit connected to said LED light source, and a PLC transceiver connected to the control circuit. Each LED street lamp is assigned with a unique identification code; and an electrical distribution network is electrically connected to and supplies electrical power to each LED street lamp. A central controller is connected to the electrical distribution network via a second PLC transceiver. The central controller controls and monitors the operation of each LED street lamp connected to the electrical distribution network by sending control commands to each street lamp and receives status information therefrom via the second PLC transceiver. 
         [0008]    There are many advantages to the present invention, one of which is that the luminance of the LED street lamp can be adjusted or the LED street lamp can be switched on or off according to the ambient light. This is due to the intelligent control by the control circuit inside the LED street lamp, which can control the LED light according to information feedback from various sensors. The control circuit can also protect the LED light by reducing the current supplied to the LED light when there is an overheating situation detected by the diagnostic circuit inside the LED street lamp. 
         [0009]    Another advantage provided by the present invention is the ability of centralized controlling of multiple LED street lamps via a PLC network. In one embodiment, all the LED street lamps are connected to the electrical distribution network via a PLC modem. A central controller which is also equipped with a PLC modem can then send various control commands to every LED street lamp via the electrical distribution network. This configuration provides huge convenience and saves lots of manpower for controlling and monitoring street lamps scattered over a large geographical area. The PLC network also enables additional functions such as security surveillance. 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0010]      FIG. 1  is a block diagram of the apparatus of an LED street lamp in one embodiment. 
           [0011]      FIG. 2  is a block diagram of the apparatus of an LED street lamp in another embodiment. 
           [0012]      FIG. 3  is a structural diagram of an LED street lamp system in one embodiment. 
           [0013]      FIG. 4  is a structural diagram of an LED street lamp system utilizing Internet in one embodiment. 
           [0014]      FIG. 5  is a structural diagram of an LED street lamp system utilizing wireless communication in one embodiment. 
           [0015]      FIG. 6  shows the use of an LED street lamp with cameras as a part of a surveillance system. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    It is therefore an object of the present invention to provide an alternate street lamp monitoring and control system. 
         [0017]    Recent advance in technology has produced high-power light emitted diode (LED) that is suitable for street lamps. An LED street lamp consumes only a quarter of the power of a traditional sodium vapor lamp. Moreover, it can last much longer—at least 50,000 hours. This reduces substantial amount of maintenance work in lamp replacement. Also, the time to turn on or off an LED lamp is significantly shorter than that of the sodium vapor lamp, not to mention the on/off delay of the mercury vapor lamp. The current invention recognizes that not only LED lamps are more energy efficient, but also their electronic mode of operation results in the ability to control lighting systems down to the individual lamp, resulting in much better control and efficiency if the necessary components are incorporated into the system as described below. 
         [0018]    Referring now to  FIG. 1 , the first embodiment of the present invention is an LED street lamp with a self-diagnosis function and remote access capability. The LED street lamp comprises an LED light source  50 , a control circuit  20 , a power supply  24 , a Power Line Communication (PLC) modem  22 , a lamp socket  23  and a diagnostic circuit  26 . The control circuit  20  connects to the other parts in the apparatus as a central control unit. The control circuit  20  comprises a microcontroller  32 , a Read Only Memory (ROM)  34 , a Random Access Memory (RAM)  36 , and external ports  38 , whose functions will be introduced later. The power supply  24  provides both the constant current for the LED light source  50 , and the working voltage for the control circuit  20 . Each street lamp is provided with a unique identification code so that it can be uniquely identified by a remote, central controller. In one embodiment, the unique identification code is stored in the ROM  34 . 
         [0019]    The PLC modem  22 , which is a type of transceiver, enables the control circuit to connect to the PLC network. PLC is a data communication technology whereby the data is modulated onto the Alternative Current (AC) wave of the electrical power system. Hence, the power line not only supplies power to the equipments such as street lamp but also serves as a carrier for data transmission. The PLC modem  22  is the device that extracts from or injects data to the power line. 
         [0020]    In the exemplary embodiment as shown in  FIG. 1 , both the electricity power and the data communication are linked to the distribution network via the lamp socket  23  when the LED street lamp  21  is mounted on a lamp pole. The diagnostic circuit  26 , which comprises a current sensor  28  and a temperature sensor  30 , monitors the operation of the LED light source  50  and provides a warning signal if an unusual condition is detected. 
         [0021]    Now turning to the operation of the device described above. When the PLC modem  22  receives an incoming data packet sent by the central controller via the PLC network, the PLC modem  22  will first demodulate the data signal from the power line and send the information to the control circuit  20 . In one embodiment, the data packet comprises at least one unique identification code of the street lamps, a command for the street lamp to execute, and optionally some parameters associated with that command. The control circuit  20  then examines the unique identification code. If this matches that of the street lamp, the control circuit  20  then executes the command. The command may be either to switch on the street lamp, to switch it off, or to modify its luminance to a value specified by the parameters. The control circuit  20  then controls the power supply  24  that supplies power to the LED light source  50 . Meanwhile, the control circuit  20  of an individual street lamp  21  can also send status information together with its unique identification code via the PLC modem  22  back to the central controller, so that the central controller can monitor the well-being of each individual street lamp  21 . In one embodiment, all the components, including the electronic parts mentioned above, of the LED light source  50  can be made to the same dimension of a conventional street lamp so that it can fit to the existing street lamp socket and housing. As such, by replacing existing street lamps with the LED street lamps  21 , and by adding the computer server and the corresponding PLC modem at the server end, an operator can instantly control and monitor each individual street lamp within the network. 
         [0022]    The power supply  24  provides electrical power to both the LED light source  50  and other circuits in the apparatus. In one embodiment, a Pulse Width Modulation (PWM) current source is used within the power supply  24  to provide PWM current to the LED. A special driving circuit that includes an inductor is also designed so that the driving current needs not drop to zero. By adjusting the pulse width in the PWM, the luminance of the LED lamp can vary accordingly. This arrangement saves significant power consumption compared to a pure DC power supply. It is found that even when the pulse width reduces greatly, the luminance only drops a small percentage. Moreover, the color change due to PWM power reduction can be contained in an acceptable range by properly controlling the PWM parameter. As the PWM driving circuit is embedded in each street lamp, each LED lamp can independently adjust its brightness. In an exemplary embodiment, the control circuit  20  adjusts the luminance by sending out control signal to the power supply  24  to adjust the pulse width of the supply current. The control circuit  20  can be programmed to do it independently, or it does so upon receiving a command from a central controller. This is a substantial advantage over existing street lamp system whereby an expensive and bulky controller is needed to install along the roadside to control a group of street lamps. 
         [0023]    The diagnostic circuit  26  in the LED street lamp  21  monitors the operation of the LED light source  50 , as well as other circuits/modules in the street lamp  21 . In one embodiment, the diagnostic circuit  26  contains a luminance sensor  27 , a current sensor  28  and a temperature sensor  30 . The sensors in the diagnostic circuit  26  are used to detect the state element of the LED street lamp  21 . Such state elements include but not limited to luminance, current or temperature. The luminance sensor  27  is a direct means for monitoring the luminance of the environment as well as the LED light source  50 . The current sensor  28  monitors the current sent to the LED light source  50  to prevent it from over-supplying and burning the LED light source  50 . The temperature sensor  30 , on the other hand, monitors the overall temperature within the enclosure of the LED street lamp  21  and specifically the temperature of the LED light source  50 . For example, when an LED street lamp  21  is accidentally covered by a blanket or similar material, the temperature sensor  30  in the diagnostic circuit  26  will detect that the temperature of the LED street lamp  21  is irregularly high. The diagnostic circuit  26  will then send a warning signal to the control circuit  20 , which then send control signal to the power supply  24  to reduce the PWM current so as to protect the LED lamp from overheating. In this way, the street lamp itself can adjust the LED immediately without the intervention of a remote central controller. Thus, a potential failure can be discovered and avoided at the earliest time. The control circuit  20  may also report the abnormality to the central server so that a maintenance crew can be deployed to investigate. This self-diagnosis, self-rectifying and self-reporting feature can greatly relieve the burden of the maintenance unit and at the same time reduce the failure rate of the street lamps. 
         [0024]    In one embodiment as shown in  FIG. 2 , the LED street lamp  21  further comprises various peripheral devices, which can communicate with external parties through the PLC network. For example, one or more cameras  40  may be installed on street lamp poles to monitor the real-time traffic on the road and send the captured information to a central system via the power line for further use. In addition, many types of environmental sensors  42  detecting atmosphere information such as sunlight radiation, temperature, humidity, air pressure, wind speed, wind direction, air quality, etc, may be installed in the LED street lamp  21  to provide environmental sensing ability to the street lamps. The sensor data can then be transmitted via the power line to a central server for further analysis. 
         [0025]    Turning now to  FIG. 3 , each LED street lamp  21  within the PLC network is connected to the electrical distribution network  66  which supplies electricity to street lamps. The structure of the PLC network is thus the same as the electrical distribution network  66 . As mentioned earlier, each LED street lamp  21  is assigned with a unique identification code, which can be identified and individually communicated by the central controller  60 . Using the PLC network, the central controller  60  is able to activate and control the luminance of each LED street lamp  21 , or control multiple LED street lamps  21  at the same time. With this arrangement, street lamps along a street need not be turned on or off at the same time, but the brightness of each of them can be individually controlled to balance between sufficient luminance on the street and overall power saving. Furthermore, this embodiment takes an advantage of the power line infrastructure as the media for supplying power and transmitting data. There is no need to add additional hardware to the existing street lamp poles. Thus, the cost of establishing a centralized monitoring and control network is kept to minimum—a computer server that acts as a central controller and a PLC modem at the server end that serves as a bridge for data communication to individual street lamp  21 . Yet the benefit of such a network is fully realized. 
         [0026]    In an alternative embodiment, the LED street lamp  21  is able to operate in a stand-alone mode without the need of the central controller. In one embodiment, the LED street lamp  21  that is equipped with the luminance sensor  27  can switch itself on when the sensor detects that the ambient light is below a pre-determined threshold. Likewise, it can adjust its luminance according to the environment. For example, when the luminance sensor  27  detects that the ambient light is higher than another pre-determined threshold, the control circuit will set the LED street lamp  21  to dimming mode by adjusting the current supplied to the LED street lamp  21 . This will save electrical power. In a further embodiment, while the street lamps  21  are networked together as mentioned before, each individual street lamp  21  can also operate on its own. Under normal circumstances, the street lamps  21  are under the control of the central controller. However, when the central controller  60  fails to operate, the individual street lamp  21  takes control to switch itself on or off, or adjust its luminance. This prevents the undesirable scenario that a single failure at the central controller or control point may cause the entire group of street lamps to become in-operative. 
         [0027]    The street lamp system in the present invention has overcome the shortcoming of existing street lamp system, which is based upon manual inspection and replacement of individual street lamp. This manual procedure is labor intensive, time consuming and costly. For example, one approach to reduce the failure rate is to replace the street lamps before their life-expectance runs out. Though this premature replacement can reduce the failure rate, it leads to suboptimal use of street lamp resources. In the present invention, signs of potential failure in each street lamp can be individually detected, which reduces the need of the premature replacement procedure. 
         [0028]    In one embodiment as shown in  FIG. 4 , each LED street lamp  21  is further connected to a PLC Internet gateway  62  while the central controller  60  is coupled to the Internet  52 . The PLC Internet gateway  62  serves as a data communication bridge between the central controller  60  and the street lamps  21 . This enables the central controller  60  to monitor and control street lamps across a wide metropolitan area, or even across different cities. The administration of street lamps can thus be focused and centralized by the aid of the Internet  52 . 
         [0029]    In another embodiment as shown in  FIG. 5 , one or more LED street lamps  21  are further connected to a wireless-to-PLC access point  68 . Then, all the communications between the street lamps  21  and the central controller  60  will be carried on a wireless channel over the air. This configuration utilizes the wireless communication in lieu of the Internet  52 . In yet another embodiment, each street lamp is equipped with a wireless module that can communicate to the central controller  60  either directly or through a public wireless network. The wireless technology can be, but not limited to, dedicated wireless radio, cellular network, Wireless Local Area Network (WLAN), or Bluetooth, ultra wide band (UWB), Zigbee, or WiMAX technologies. 
         [0030]    In the specific example shown in  FIG. 6 , a typical LED street lamp  21  in a residential area is equipped with at least one camera  40  which captures the snap-shot images or continuous video of the vehicles  80  and pedestrians  82  on the street. This configuration saves tremendous effort and costs in deploying separate cameras in the area to monitor traffic or a high secure zone where surveillance is needed. The captured image or video can be instantly sent to a remote control center via the PLC network. Likewise, a speed radar gun can also be installed on the street lamp pole to capture vehicles on a road that travel at a speed exceeding a pre-defined threshold, and then send relevant information to the police station via the PLC network. 
         [0031]    The exemplary embodiments of the present invention are thus fully described. Although the description referred to particular embodiments, it will be clear to one skilled in the art that the present invention may be practiced with variation of these specific details. Hence this invention should not be construed as limited to the embodiments set forth herein. 
         [0032]    Although it is mentioned that the control circuit  20  comprises a microcontroller  32  with ROM  34  and RAM  36 , it is clear to those skilled in the art that other technologies, such as an application-specific integrated circuit (ASIC) may be used instead. Moreover, the diagnostic circuit  26  may include not only the current sensor or temperature sensor but also circuitries to perform other diagnostic functions. 
         [0033]    Though LEDs are used in the aforementioned embodiments to illustrate the inventive idea, other light-emitting technologies may also be used. For different lighting technologies, some or all components as shown in  FIGS. 1 and 2  may need to be modified to adapt to the specific characteristics of that technology. Nonetheless, the inventive ideas mentioned in this disclosure can easily be extended to accommodate different lighting technologies by those skilled in the art, and hence they also fall in the scope of this disclosure.