Abstract:
A repeater in a power line control system includes a selective repeat feature. The repeater stores selected codes associated with a particular location. When a command is received on an input power line, the repeater repeats only those commands that have the selected codes. Implementations of the repeater include a test switch that, when activated, send command signals to activate and deactivate electrical devices in the power line communication system. A noise level indicator can be included to indicate a noise level on the input power line that can disable commands transmitted to an electrical device in the power line communication system.

Description:
[0001]     This application claims the benefit of the filing date of a provisional application having Ser. No. 60/568,548, which was filed on May 6, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention generally relates to power line communication systems.  
         [0004]     2. Description of the Related Art  
         [0005]     A power line communication system, such as a system based on the X10 standard, uses a power line as a carrier medium for communication between electrical devices. In a typical residential setting, such as a home, the power line can include an alternating current (AC) power source from a standard 60 Hz distribution line providing a domestic electric power source of 120V/240V at a maximum of 200 amperes for normal use. The power line in a home is derived from an AC power source at a step-down transformer provided by an electric utility company. The AC power source is shared with other homes in a neighborhood. Some neighborhoods with large homes may have fewer than 3 homes sharing the AC power source from the step-down transformer, whereas a condominium complex or a townhouse community may have upwards of 10 homes sharing the same transformer.  
         [0006]     Power line communication systems are bandwidth limited and susceptible to noise. To improve noise immunity, power line communication protocols tend to operate at a slow rate compared to radio-frequency (RF) or wired techniques. As power line communication systems increase in popularity and more homes share the AC power line, noise immunity and bandwidth may decrease further.  
         [0007]     In a power line communication system, each home may be assigned a unique code in a technique referred to as Coded Access. A master electrical device, such as a central controller, can send a command signal over a power line to a slave electrical device such as a wall switch connected to a lamp. The command signal can include an instruction to operate a slave device. For example, the instruction can cause a device to turn ON or OFF. Each command signal can include a unique code to identify a slave device and a home in which the slave device is installed. When a command signal with the unique code is sent over the power line of the home, only the slave device with a code that matches the unique code responds to the command signal. However, command signals that are not relevant to the home still travel over the home&#39;s power line. The bandwidth, which is a measure of the power line&#39;s ability to carry signals, can become congested with commands for neighbor&#39;s houses. That is, the power line of the house has a limited capacity to carry command signals and some of that capacity is occupied by extraneous commands.  
         [0008]     Various approaches may be employed to improve usage of the bandwidth. One solution includes installing an electrical device called a repeater at the service panel of a home. The repeater amplifies and repeats all command signals it receives including command signals from other homes that are not relevant. While this technique can improve the response of the system to weak signals, the bandwidth usage may not be improved. Another solution entails connecting a filter at the service panel of a home so to isolate the power line in that home from the power line of other homes in a neighborhood. However, these filters can be expensive and bulky to install.  
         [0009]     A typical slave device in a power line communication system is a switch device that responds to command signals for connecting power to a load such as an electronic ballast transformer in a lamp. Command signals have a frequency that is often substantially higher than the 60 Hz of the power applied to the load. When a particular switch is turned ON and power is applied to the electronic ballast, an attenuation of command signals may occur. As a result, a slave switch may not receive a command signal causing it to fail to operate.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention provides a repeater device that can receive command signals over a power line system at a step-down transformer and repeat the command signals having a code that matches selected codes to a second power line system at a home. The present invention also can provide a switch device having filtering capability to present a high impedance to command signals and prevent a load from attenuating the command signals.  
         [0011]     The repeater device can have a selective repeat feature that tends to block command signals that are not relevant to a selected home. As a result, the effective bandwidth of a power line communication system in a home may increase. However, this feature does allow a user to select command signals from another home such that the other home can control an electrical device in the user&#39;s home. In addition, the selective repeat feature of the repeater device may reduce the likelihood that noise present on the power line communication system (including random noise or noise from a neighbor&#39;s home) is interpreted as a command signal because only command signals having a code that matches a code selected by a user is repeated.  
         [0012]     An electrical switch device can include a filter circuit, such as an inductor, connected in series between a power source and load to reduce the possibility that a load, such as an electronic ballast, will attenuate a command signal. As a consequence, a switch device or other electrical device may be less likely to fail (e.g., not respond to a command) than without the filter circuit, increasing the reliability of the devices and of a power line communication system.  
         [0013]     Other objects and features of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principles of the invention, and the best mode, which is presently contemplated for carrying them out. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     Preferred embodiments of the present application are described herein with reference to the drawings in which similar elements are given similar reference characters, wherein:  
         [0015]      FIG. 1  is a block diagram of a repeater device for selectively repeating command signals in a power line communication system;  
         [0016]      FIG. 2  is a block diagram of a switch device with filtering capability for use in a power line communication system; and  
         [0017]      FIG. 3  is a block diagram of a method for selectively repeating command signals in a power line communication system. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]      FIG. 1  is a block diagram of a repeater device  12  with the capability to selectively repeat command signals in a power line communication system  10 . The repeater device  12  includes a selective repeater  14  to control the operation of electrical devices  26 ,  28  over an output power line  24  located in a home. The repeater device  12  can include a input port  30  to receive command signals  18  from a power line  38 . The selective repeater  14  is coupled to a memory  42  that can store selected device codes associated with electrical devices such as devices  26 ,  28 . The memory  42  is coupled to a code entry device  44  through which the selected device codes are provided to the memory  42 . The selective repeater  14  is coupled to an output port  32 . The output port  32  couples the output of the selective repeater  14 , which are commands having the selected location codes, to an output power line  24 . In an implementation, the repeater device  12  can include a test switch  34  for testing some functionality of the repeater device. An indicator  36  also may be coupled to the device to provide indicia of the operation of the repeater device or the communication line system.  
         [0019]     Command signals in a power line communications system are provided to an input power line  40 . The command signals can be used to control electrical devices in a location such as a house. The input power line may have command signals that are destined for more than one location. The input power line carrying the command signals is received at the service entrance panel  22  of a location. All of the command signals  18  that are on the input power line  40  are received by the service entrance panel  22 . However, not all of the received command signals may be associated with electrical devices at the home where the service entrance panel  22  is located. The command signals  18  can include a unique device code assigned to electrical devices  26 ,  28  and repeater device  12  as well as a location code, that identifies a specific home in which the devices are located. The command signals  18  also can include a command or instruction for controlling the electrical device. In an implementation, the repeater device  12  can include code entry circuitry  44  to enable a user to enter selected location codes that may be stored in memory  42 . Selective repeater  14  can retrieve the selected location codes from memory  42 . Only those received command signals having a location code that matches the selected codes are repeated through the output port  32  to the output power line  24 . Because only selected command signals  20  are repeated, the effective bandwidth of power line  24  is increased.  
         [0020]     In an implementation, an AC filter  16  may be included in the input port  30  to filter unwanted signals from power line  38  at service panel  22 . Output power line  24  can include, for example, a standard 50 Hz or 60 Hz distribution line providing a domestic electric power source of a nominal 120V/240V and may have a maximum of 200 amperes for normal use. Output power line  24  is derived from power at service panel  22 , which may be located in a home where electrical devices  26 ,  28  are installed.  
         [0021]     A switch  34 , such as a push-button switch, can be used to initiate one or more functionality tests of repeater device  12 . For example, a test can include having repeater device  12  transmit command signals to activate and deactivate electrical devices  26 ,  28  in power line communication system  10 . The repeater device  12  also can include an indicator  36 , such as a light emitting diode (LED), for providing an indication of the level of noise present in a power line communication system that can potentially disable electrical device  26 ,  28 .  
         [0022]      FIG. 2  is a block diagram of a switch device  52  with filtering capability for use in a power line communication system  50 . The switch device  52  is a type of electrical device  26 ,  28  illustrated in  FIG. 1 . The switch device  52  can receive power from an AC power line  70 . The switch device includes circuitry to receive command signals on the AC power line  70  and, in response, provide power to a load  58 . The switch device can include filter circuit  64 , such as an inductor, in series with the load  58 . The filter circuit  64  presents a high impedance to the command signals that have a higher frequency than the frequency of the AC power. Some loads, such as an electronic ballast that can generate a high frequency on the AC power line, can attenuate command signals and compromise the reliability if the command line system. The filter can help to prevent the load  58  from attenuating command signals. The switch device  52  includes control circuit  68  to receive command signals from the AC power line  70  and, in response to the command signals, activate a switch circuit  66 , such as a relay, so as to provide an electrical connection path between AC power line  70  and load  58 . The AC power line  70  can have phase  60  and neutral  62  conductors.  
         [0023]      FIG. 3  is a block diagram  300  of a method for repeating selected commands in a power line control system. Each location such as a home may be associated with a respective location code. Codes associated with a selected location may be stored, for example, in an electronic memory, box  302 . The selected location codes may be entered manually or electronically into the memory through a code entry device such as a keypad or electronic port. The memory is coupled to a repeater that can repeat received command signals. The location codes represent locations, such as a residence, that has addressable electric devices. A command signal can be received by the repeater from an input power line of the power line control system, box  304 . Each command can have an associated location code and instruction for an addressable electrical device. The repeater is responsive to repeat only the received command signals having the selected location codes stored in the memory, box  306 . Thus, while many command signals may be received, only those command signals that have the selected location code are repeated. The repeated command signals are transmitted to an output power line of the power line control system, box  308 . Addressable electrical devices are couple to the output power line. The electrical devices can receive and respond to the command signals repeated on the output power line.  
         [0024]     While there have been shown and described and pointed out the fundamental novel features of the invention as applied to the various embodiments, as is presently contemplated for carrying them out, it will be understood that various omissions and substitutions and changes of the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention.