1. Field of the Invention
The present invention generally relates to power line communication systems.
2. Description of the Related Art
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.
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.
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's power line. The bandwidth, which is a measure of the power line's ability to carry signals, can become congested with commands for neighbor'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.
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.
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.
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.
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'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'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.
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.
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.
Preferred embodiments of the present application are described herein with reference to the drawings in which similar elements are given similar reference characters, wherein:
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.
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.
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.
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.
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.
Number | Date | Country | |
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60568548 | May 2004 | US |