Abstract:
A transmitting controller is connected to a powerline and on command places a reference signal and a series of signal pulses in the powerline at a series of signal timing positions related to zero voltage crossing points so that the signals pulses are substantially in the powerline temporal quiet zone near zero crossing. The signal pulses are produced from a pair of capacitors and switches which are each sequentially charged a first polarity from the powerline and is discharged in the powerline at the opposite polarity so that the powerline voltage at the time of the pulse is additive to the pulse voltage. The receiving controller is connected to the powerline and has a filter circuit therein which filters away the powerline AC signal and noise to leave the reference and signal pulses. The signal pulses are compared to the position of starting reference pulses to determine in which signal timing position the pulses have occurred.

Description:
CROSS-REFERENCE 
     This invention is related to my prior applications, entitled “ZERO CROSSING BASED POWERLINE PULSE POSITION MODULATED COMMUNICATION SYSTEM”, application Ser. No. 09/656,160, filed Sep. 6, 2000, now U.S. Pat. No. 6,734,784, granted May 11, 2004; and “SYNCHRONIZATION REFERENCE PULSE BASED POWERLINE PULSE POSITION MODULATED COMMUNICATION SYSTEM,” filed Jun. 6, 2001, application Ser. No. 09/879,874, now U.S. Pat. No. 6,784.790, granted Aug. 31, 2004. This application relies for priority upon my prior Provisional Application 60/564,499 entitled “POWERLINE PULSE POSITION MODULATED TRANSMITTER APPARATUS AND METHOD,” filed Apr. 22, 2004. 
    
    
     FIELD OF THE INVENTION 
     This invention is directed to an apparatus which enables the transmission of digital communication between two or more devices wherein the devices are connected to the same powerline and use the same powerline to receive power and as a physical channel for electronic intercommunication. 
     BACKGROUND OF THE INVENTION 
     There are devices which are more conveniently used if they can be remotely controlled. In a household, such devices are mostly appliances and lighting loads. The appliances and lighting loads may be remotely controlled for a number of different reasons. For example, for night security, some lights may be controlled by a timer. 
     In other cases, different lighting intensity and different lighting distribution may be desirable in a single room, depending upon its use. The room may be used for reading, conversation or watching displays, such as television. Each suggest a different lighting level and different lighting distribution. Normally, people do not make such changes because it is inconvenient to do so. Therefore, it is desirable to have a convenient, reliable way to remotely control lighting systems. 
     In addition to lighting systems, other devices can be conveniently remotely controlled. For example, powered gates and garage doors can be remotely controlled. An electric coffee pot may be turned on at an appropriate morning hour. Powered draperies may be opened and closed, depending upon sun altitude. 
     As electronic technology has advanced, inventors have produced a variety of control systems capable of controlling lighting and other electric loads. In order to be useful as a whole-house lighting control system, there are certain requirements that must be met. A system must permit both small and large groups of lights to be controlled on command. The problem is the connection between the controller and the lighting load. Such connection may be hard-wired, but such is complex and very expensive to retrofit into an existing home. Another connection system may operate at radio frequency, but this has proven difficult to implement because the FCC requires low signal levels which are subject to interference and because the transmission and receiving circuitry is complex and expensive. 
     It must be noted that both the controller and the load to be controlled are connected to the same powerline. It would be useful to use the powerline as the communication-connecting channel. Prior powerline communication schemes have had difficulties employing the powerline as a communication channel because the communication signals after being attenuated by the powerline circuitry are very small compared to the background noise. It is impossible to avoid the fact that between certain locations in a residence there will be very high attenuation of any transmitted signals. It has been difficult to reliably separate the highly attenuated communication signals from the background noise on the powerline. 
     The situation is further aggravated and complicated by the fact that the noise and attenuation parameters are constantly and unpredictably changing as loads are connected and disconnected both inside the primary residence and inside any of the many neighboring residences attached to the same mains power transformer. In reality the powerline circuit used for communication in a residence includes all the residences attached to the mains power transformer. There is no practical way to avoid the complications caused by this fact. 
     SUMMARY OF THE INVENTION 
     In order to aid in the understanding of this invention, it can be stated in essentially summary form that it is directed a specialized transmitter circuit and method to enable powerline pulse position modulated communication. The transmitting device senses the zero voltage crossing point in the powerline and transmits a series of signal pulses at a set of specified positions, the position of the data pulse relative to either the zero crossing time or the position of the starting reference pulses representing digital data in the form of a digital number. The set of all possible relative positions is in the quiet zone adjacent, but spaced from the main voltage zero crossing point. The energy needed to produce the signal pulses are stored in the capacitor. When the pulses are released to become a data pulse, they are released in the opposite half cycle from which they are charged. Thus, the amplitude of the pulse with respect to the zero crossing is the voltage of the power wave at the time of the pulse with respect to zero crossing, plus the voltage of the pulse with respect to zero crossing. The receiving circuit also senses the voltage zero crossing point and can reliably detect the signal pulse in the background powerline noise because of the knowledge of where the signal pulse is expected in the quiet zone adjacent, but away from the zero crossing point and because of the high magnitude of the very robust signal pulse even after significant residential attenuation. Since the data pulse is a voltage spike equal to the line voltage at the pulse point plus the discharge of the capacitor, the pulse can be more readily detected. After determining in which one of the possible relative positions the signal pulse was located, the associated digital data in the form of a digital number is easily determined. Thus digital data is communicated from one device through the powerline to another device using this method of powerline pulse position modulation. This patent describes a specific configuration of transmitting circuit and operation of that circuit to derive transmission signals that are much more effective that the previously described transmitter circuits. This transmitter circuit uses transmission components that are triggered in such a manner as to produce communication pulses in the next half cycle after the charging half cycle so that at the time the transmission pulse is produced the pulse voltage is additive to the line voltage with respect to zero which produces the most robust pulse possible that is derived directly from line voltage. 
     It is a purpose and advantage of this invention to provide a method and apparatus for reliable transmission of digital data over the powerline by means of a powerline pulse position modulation communication method utilizing a novel dual capacitor, dual switch circuit to provide much more robust data pulses when compared to our previous powerline pulse position modulation communication method that have only one available capacitor and switch to produce the necessary series of pulses. 
     It is a further purpose and advantage of this invention to provide a method and apparatus for powerline pulse transmission wherein the voltage zero crossing is sensed and the communication signal pulse is transmitted and sensed in a receiver based on the signal position relative to either the zero crossing point or the position of one or more of the previous transmitted pulses. 
     It is a further purpose and advantage of this invention to provide a method and apparatus by a powerline pulse position modulation transmission method for the purpose of remote electrical load control. 
     It is a further purpose and advantage of this invention to provide a method and apparatus wherein the voltage zero crossing is sensed, and digital pulse windows are defined with respect to the zero voltage crossing, but spaced from the zero voltage crossing so as not to interfere with other equipment using the zero voltage crossing time for various purposes. 
     It is a further purpose and advantage of this invention to provide a method and apparatus by a powerline pulse position modulation communication method for the purpose of remotely retrieving operational data from residential appliances. 
     It is a further purpose and advantage of this invention to provide a method and apparatus by a powerline pulse position modulation communication method for the purpose of remotely controlling residential loads for utility company energy management. 
     It is another purpose and advantage of this invention to provide a powerline pulse position modulated communication apparatus and method which complies with FCC regulations relating to apparatus which is connected to and communicating on the powerline. 
     The features of this invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by reference to the following description, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic electrical diagram of the powerline pulse position modulated communication apparatus in accordance with this invention. 
         FIG. 2  is a schematic electrical diagram of how a plurality of such apparatus is used to control plural lighting loads in a room. 
         FIG. 3  is a schematic electrical diagram of how a plurality of such apparatus is used to control the lighting load in a plurality of rooms. 
         FIGS. 4A ,  4 B,  4 C and  4 D show the powerline waveforms containing the communication signals therein as utilized by the previous methods and in my previous applications. 
         FIGS. 5A ,  5 B, and  5 C are powerline waveform diagrams showing the transmission positions employed by the apparatus of this invention for the half of the transmission circuit charging on the positive half cycles and discharging on the negative half cycles. 
         FIGS. 6A ,  6 B, and  6 C are powerline waveform diagrams showing the transmission positions employed by the apparatus of this invention for the half of the transmission circuit charging on the negative half cycles and discharging on the positive half cycles. 
         FIGS. 7A ,  7 B,  7 C,  7 D and  7 E are powerline waveform diagrams showing the transmission positions employed by the apparatus of this invention for combination of both transmitter sections described in  FIG. 5  and  FIG. 6 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The purpose of the powerline pule position modulated communication transmitter apparatus of this invention as shown in  FIG. 1  is to enable the communication of digital data from one device to another by means of the powerline to which both devices are connected. A further purpose is to enable communication with appliances and to control lighting or other electrical loads in one or more rooms of a residence. 
     Application Example Lighting Control System 
     A lighting control system as shown in  FIG. 2  and  FIG. 3  will be used as an example of an application in this description of this invention. 
     In  FIG. 2 , transmitting controller  10  is supplied with conventional household electric power from circuit panel  12 . Circuit panel  12  is supplied from commercial powerline and has two or three outputs. In the present example, the circuit panel  12  has a neutral line  14  and powerlines  16  and  18 . Further, the powerlines  16  and  18  inside a domestic residence are derived from a center tapped 240 vac transformer and are each nominally at 120 rms volts with respect to neutral line  14 . The voltage waves in powerlines  16  and  18  are at a 180 degree phase angle with respect to each other. 
     Also connected to the powerline  18  and neutral  14  are lighting load receiving controllers  20 ,  22  and  24 . These receiving controllers are respectively connected to loads  26 ,  28  and  30 . The loads are electric lights, in this example, but may be heater or motor loads as described above. Furthermore, the receiving controllers  20 ,  22  and  24  are capable of receiving digital commands which change the supply of power to the loads and may supply different levels of power to the loads to control the brightness of the lighting load. The transmitting controller  10  emits its digital commands into the powerline  18  for transmission to the receiving controllers  20 ,  22  and  24  by pressing one or more of the command buttons  160 ,  34  and  36  on transmitting controller  10 . Thus, the receiving controllers  20 ,  22  and  24  receive digital commands from the transmitting controller  10  to control the loads  26 ,  28  and  30 , respectively. No separate wiring or radio frequency communication is required, but the transmitting controller places signals in the powerline  18 . Such transmitted signals are coded so that they can be detected by all of the receiving controllers. 
     A similar arrangement is seen in  FIG. 3  wherein a main circuit panel  12  supplies power to four different rooms. The lighting and other loads in the four different rooms can be separately controlled in each room or can be controlled by a master, whole-house controller  44 . Assuming room No.  1  in  FIG. 3  is the same as the room in  FIG. 2 , it is seen that room  2 , room  3  and room  4  are identical. Each room has a transmitting controller the same as controller  10  and three receiving controllers, the same as controllers  20 ,  22  and  24 . Each of the receiving controllers controls a load, the same as loads  26 ,  28  and  30 , respectively. Each of the transmitting controllers  38 ,  40  and  42  is identical to the transmitting controller  10 , and each places digital command signals into the powerline. However, the receiving controllers are programmed to act only on the relevant command data. The response of the receivers is determined by the preprogrammed address and command-interpreting program located within each receiver. Thus, the loads in four or more rooms may each be controlled by a transmitting controller. 
     In addition, transmitting master controller  44  is connected to the powerline. It is identical to the transmitting controllers  10 ,  38 ,  40  and  42 , but it is programmed differently to send out digital data signals which command receiving controllers to control their loads individually. The fact that transmitting controller  44  is connected only between powerline  18  and neutral  14  does not interfere with its ability and function to send signals to receiving controllers connected between powerline  16  and neutral  14 . 
     Transmission and Receiving Circuit Operation 
     The transmitting controllers  10  and the receiving controllers  20  are identical, in the sense that they contain the same transmitting and receiving circuitry. They are programmed differently so as to achieve the desired different results. The controller  10  is schematically illustrated in  FIG. 1 . It has a transmitting circuit  46 , which is connected to powerline  16  through line  48  and to neutral through line  49 . The transmitting circuits comprises a pair of identical circuits, the first circuit consisting of triac  50  which is connected in series with energy storage capacitor  52 . Inductor  54  is also in the series connection between line  48  and capacitor  52 . Capacitor  56  forms a low pass filter with inductor  54  to minimize high frequency emissions so that the transmitter meets the FCC requirements. Triac  50  is controlled by line  58  which is the output from digital control integrated circuit  60 . Hereinafter, the conventional abbreviation “IC” will be used in place of the term “integrated circuit.” When the digital control IC sends an appropriate firing signal on line  58 , the triac fires and puts a pulse in line  16  with respect to the neutral  14 . The second identical circuit consists of a second triac  51 , capacitor  53  and inductor  55 . The filter capacitor  56  is common to both transmission circuits. 
     Controller  10  also contains a receiver circuit  62 . The important components of the receiver circuit  62  form a band pass filter circuit. This includes capacitor  66 , capacitor  68 , capacitor  76 , inductor  70 , inductor  74  and inductor  64 . Resistor  72  limits the current through the circuit. Resistor  78  is connected in series to limit the current in signal line  80 . This circuit filters the signal pulse out of the powerline  60  cycle voltage and background noise. 
     Signal line  80  is connected into digital control IC  60  as its signal input. As a particular example, digital control IC  60  is a microprocessor Microchip model PIC16F87. The input signal line  80  is connected between two clipping diodes  82  and  84  to protect the digital control IC  60  from excessively high and low voltages. The signal input line  80  is connected to comparator  86  where the signal voltage is compared to internal voltage reference  88 . The voltage reference  88 , which is adjustable by the digital control IC  60  allows the digital control IC  60  to automatically adjust the receiving signal level to be set above the noise level. This is a form of automatic gain control which is essential so that the digital control IC  60  can discriminate between noise and real signal pulses. The comparator output  90  carries the received digital signal to the internal processing circuitry of the digital control IC. 
     There are additional inputs to the digital control IC  60 . Zero crossing detector  92  is connected to powerline  16  and neutral  14 . It has an output to the digital control IC  60 . Power supply  94  supplies power to the digital control IC and to the EEPROM memory  96 . There may be a plurality of the input switches, one of which is indicated at  98 , for causing the digital control IC  60  to perform some internal operation or to issue transmitted commands. The commands of switch  98  correspond to the command buttons  160 ,  34  and  36  seen in  FIG. 2 . It is desirable that there be some method of visual feedback to the user for a variety of programming and control uses. This is provided by indicator light  100 , which may be energized by the digital control IC  60 . When the controller  10  is acting as a receiver load controller, it has an output circuit which controls the load. This output device  102  is in the form of a relay, triac, or the like. It controls the flow of power from line  16  to the load  104 . 
     Pulse Position Modulation of Digital Data 
       FIG. 7E  shows a sine wave  104  which represents the powerline voltage in one of the lines  16  or  18  of  FIG. 2 , as compared to neutral. Eight half cycles are shown. For the purpose of this disclosure, the powerline frequency is 60 cycles per second, which is the modern domestic standard. The voltage shown is nominally 120 volts rms, with peaks at about 160 volts, plus and minus. These are examples, and the apparatus and method can be utilized with other voltages and frequencies. Taking 60 cycles per second as the preferred embodiment, each half cycle, which is each of the intervals T, in all figures, is 8.333 milliseconds. 
     Transmitter Operation 
     In  FIG. 7E , the voltage through the time periods T 1 , T 2 , and T 3  is a plain sine wave  104  with no communication pulses. During the next five half cycles, T 3  through T 8 , there is a superimposed pulse on the sine wave near to each of the positive and negative zero crossing points. One positive and one negative zero crossing point are indicated at  105  and  107  respectively. In  FIGS. 7A ,  7 B,  7 C and  7 D, the zero crossing point is represented as the transition from one time period to the next. These superimposed pulses are the means of communication. The transmitting device places these pulses on the powerline. Receiving devices detect these pulses on the powerline. 
     Each pulse can represent one transmitted data number. The number transmitted can range from 1 to N where N is the total number of possible positions of one pulse. In  FIGS. 5C and 6C  a sine wave is shown with the four positions highlighted in each half cycle. Positions number  0 , 1 , 2 , and  3  are identified on  FIG. 5 , half wave T 3  as  180 ,  182 ,  184 , and  186 , respectively and in  FIGS. 5C and 6C , half wave T 4  as  170 ,  172 ,  174 , and  176 , respectively. The current embodiment utilizes four positions located in the quiet zone spaced from, but just before zero crossing. If the total time allotted to the four positions is 400 uS then the spacing of each position relative to the next possible position will be 100 uS. This is shown in  FIGS. 5C and 6C . By placing a pulse in one of the possible four positions, one numeric digit, from 0 to 3, can be transmitted every half cycle. In binary, this is equal to two bits per half cycle. Up to 256 positions are possible with current microprocessor technology. In binary, a number with 256 possible states is equal to eight bits or one byte per half cycle. 
     When a powerline transmission consisting of a series of pulses is desired, the first need is to charge the capacitor  52  in  FIG. 1 . Before the initial charging the initial charge state of the capacitor  52  is unknown. The digital control IC puts an initial trigger pulse  170 , see  FIG. 5A , in line  58  to begin turning on triac  50  to begin charging capacitor  52 . The initiating pulse is preferably near a zero crossing but is not critical. This turns on the triac  50 , and the capacitor  52  begins charging.  FIG. 5B  shows the voltage across capacitor  52 , and the start of its charging is shown at point  105 . The curve in  FIG. 5B  after the point  105  is the traditional capacitor charging curve. This does not yet produce a pulse in the powerline. Once the triac  50  is conductive, another initiating trigger pulse for charging is not necessary. Once the triac is charged and discharged, it will continue to charge in the opposite polarity and will be ready to discharge in the next half cycle, as seen in  FIG. 5B . The triac turns off and the capacitor stops charging each time the charging current through the triac  50  reaches zero, which occurs at every peak of the mains sine wave, which is shown at  104  in  FIG. 5B . When it is desired that a signal pulse be placed on the powerline, digital control IC  60  places a trigger pulse in line  58  to fire triac  50 . These trigger pulses are shown at  172 ,  FIG. 5A . This pulse produces conduction in triac  50  to create the corresponding signal pulse  178 , in the powerline, as shown in  FIG. 5C . The waveform in  FIG. 5B  is shown as a reference of the voltage across transmitting capacitor  52  as it is charged and discharged. As it is discharged every other half cycle, which is shown in  FIG. 5C  in the negative half cycles, a pulse is produced in the powerline. 
     The fact that the capacitor charge voltage is so much greater if the capacitor is discharged in the following half cycle as opposed to the same half cycle in which the charging began is the fundamental reason the pulse strength in this method is so strong. In the half cycle following charging, the powerline voltage is opposite that of the capacitor voltage and thus the two are additive to produce a strong pulse signal. 
     In order to be compatible with the transmission circuits and methods of prior it is necessary to produce messages consisting of one pulse per half cycle. With the present method discussed above and shown in  FIGS. 5 ,  6  and  7  using only one capacitor in series with one switch, only one pulse can be produced on every other half cycle. Therefore two independent capacitor/switch circuits are required to combine their resulting pulse trains occurring on every other half cycle into one composite pulse train with one pulse on every half cycle. This composite pulse train with the two pulse trains of  FIG. 5  and  FIG. 6  combined is shown in  FIG. 7 . 
     The simple reason this method of producing transmission pulses is superior to the method using a single capacitor is shown clearly in  FIGS. 4B and 5B . In  FIG. 4B  the voltage across the capacitor at the time of discharge is approximately 120V. In  FIG. 5B  the voltage across the capacitor at the time of discharge is approximately 240V. The larger voltage difference in  FIG. 5B  at the time of discharge produces a much stronger pulse. The larger pulse in turn produces more reliable transmission and communication. It has been found that this stronger method of transmitting works in certain high attenuation applications where the single capacitor method is unreliable. The seemingly obvious method of increasing signal strength by increasing the size of the transmitting capacitor does not work. Increasing the size after a certain size produces no change in the signal strength. The novel method utilized by this invention produces a very large increase in signal strength. 
     The reason two separate capacitor, switch transmission circuits are needed is because that the time between charging and discharging of one capacitor is more than one half cycle therefore each capacitor can only produce one pulse on every other half cycle. 
     Since only one pulse can be transmitted per half cycle with this circuit design, one and only one number can be transmitted each half cycle. The reason this method of modulating data is named “pulse position modulation” herein is because the value of the data is encoded in the position of the pulse. 
     Because of attenuation, background noise, and other periodic and intermittent random noise pulses present on the powerline, these signal pulses would ordinarily be difficult to detect. However, in accordance with this invention, when the pulse is stronger or of greater magnitude it is easier to detect. 
     To summarize, there are four primary reasons the area from 1000 uS to 500 uS before zero crossing is selected for our transmission period. First, because a relatively large pulse is generated because the capacitor is charged to a large voltage. Second, because there is a relatively is charged to a large uniform voltage from the beginning of this period to the end of this period. Third, because there is little interference caused by the communication pulses to devices that utilize the powerline zero crossing for various purposes, such as clocks or light dimmers. Fourth, because there is very little noise from pulse producing devices, such as light dimmers, during this period. The novel design presented here is for a simple method of greatly increasing signal strength of each transmitted pulse to increase overall communication reliability. 
     The manner of operation of this receiving circuit  62  in  FIG. 1  has been discussed above. It is connected to the line and awaits the incoming pulse. The powerline frequency and noise are filtered out, but the signal pulse can readily be detected because it is within the 1000 microsecond quiet zone near the zero crossing point. When the pulse is sensed, the signal position in which it is located is determined by the Digital Control IC  60 . 
     In a message transmission on each half cycle one pulse is received. A pulse may be a reference pulse at the start of the message or a data pulse following one or more reference pulses. Each pulse will be in one of several possible temporal positions that may be referenced to zero crossing or a previous reference or data pulse. Each of the possible temporal positions will represent a different data number. If there are four positions, as in the current embodiment, then one of the numbers, 0,1,2 or 3 can be transmitted by one pulse in one half cycle. A string of these pulses and derived numbers are combined to make a complete message. 
     This is the fundamental method of transmitting and receiving numerical data. This series of numerical data is stored in the Digital control IC and processed according to the application program requirements. If the device is a lighting controller, the data would most likely represent lighting system addresses and command instructions. Other applications would have other meanings for the decoded data. Some application devices such as a powerline modem might use the invention for pure communication of data and may not have a specific application function. 
     This invention has been described in its presently contemplated best embodiment, and it is clear that it is susceptible to numerous modifications, modes and embodiments within the ability of those skilled in the art and without the exercise of the inventive faculty. Accordingly, the scope of this invention is defined by the scope of the following claims.