Method of communicating between control devices of a load control system
A load control system for controlling the amount of power delivered to an electrical load from an AC power source includes a load control device and a remote control device. The load control device is operable to control the amount of power delivered to the electrical load in response to control signals transmitted by the remote control device. The remote control device may transmit the control signals to the load control device via current carrier control signals, radio-frequency control signals, or infrared control signals, which may be corrupted by noise during transmission. The received control signals are sampled and filtered by a multi-pass median filter, which substantially eliminates the noise corruption. Specifically, the multi-pass median filter repeatedly examines a set of N sequential samples of the received message signal, determines the median of the N sequential samples, and provides the median as an output sample.
1. Related Applications
This application is a continuation-in-part of co-pending commonly-assigned U.S. patent application Ser. No. 11/447,431, filed Jun. 6, 2006, entitled SYSTEM FOR CONTROL OF LIGHTS AND MOTORS, which claims priority from commonly-assigned U.S. Provisional Application Ser. No. 60/687,689, filed Jun. 6, 2005, also entitled SYSTEM FOR CONTROL OF LIGHTS AND MOTORS. The entire disclosures of both applications are hereby incorporated by reference.
2. Field of the Invention
The present invention relates to a method of communicating between control devices of a load control system for controlling the amount of power delivered to an electrical load from an alternating-current (AC) power supply, and more specifically, to a median filter for removing noise from a message signal transmitted by a remote control and received by a load control device.
3. Description of the Related Art
It is often desirable to include a lamp and a fan motor in a single enclosure. Since the lamp and the fan motor are often wired in parallel, the lamp and the fan motor are generally controlled together from a switch located remotely from the lamp and the motor.
There are also various schemes for independent control of a fan motor as well as a lighting load from a remote location such as a wallstation.
However, the dual light and fan speed control 22 requires two separate wires to be connected between the lamp and the fan motor. If these two connections are not provided between the wallbox and the enclosure containing the lamp and the fan motor, independent control of the lighting load 18 and the fan motor 16 will not be possible. Further, in the control system 20 of
However, existing power-line carrier systems have some limitations. For example, all devices in a PLC system require a neutral connection. Also, since the X10 protocol utilizes voltage carrier technology, communication messages are transmitted throughout the power system and it is difficult to isolate the communication signals from other devices connected to the power system. Finally, the X10 protocol is not a “reliable” communication scheme since no acknowledgements are sent to a transmitting device when a receiving device has received a valid message.
Thus, it is desirable to provide a reliable means to independently control from a remote location a fan motor and a lighting load that are located in the same enclosure. Since a consumer may wish to locate the fan motor and the attached lamp in a position previously occupied by only a lamp controlled by a standard single-pole single-throw (SPST) wall switch, it is desirable to be able to control a fan motor as well as an attached lamp independently, using a two-wire control device. A two-wire device is a control device that has only two electrical connections, i.e., one for the AC source voltage and one for the fan/lamp, and does not have a neutral line connection. As shown in
Prior art systems to accomplish this are known which provide a coding/communication scheme to independently control the fan motor and the lamp. However, many of these systems are unreliable, provide erratic, noisy operation, and require a neutral connection. It is desirable to provide a simple, reliable communication scheme for independently controlling the fan motor and lamp without a neutral connection.
SUMMARY OF THE INVENTIONThe present invention provides a method of communicating a message signal from a first control device to a second control device. The method comprises the steps of: (1) transmitting the message signal from the first control device; (2) receiving the message signal at the second control device; (3) sampling the received message signal; (4) producing a set of N sequential samples; (5) determining the median of the N sequential samples; (6) providing the median as an output sample; and (7) repeating the steps of sampling the received message signal, examining the set of N sequential samples, determining the median, and providing the median.
According to another aspect of the present invention, a method of filtering a received message signal having a sequence of samples comprises the steps of: (1) examining a set of N sequential samples of the received message signal; (2) determining the median of the N sequential samples; (3) providing the median as an output sample; and (4) repeating the steps of examining a set of N sequential samples, determining the median, and providing the median.
In addition, the present invention provides a control device for use in a load control system for controlling the amount of power delivered to an electrical load from an AC power source. The control device comprises a receiver operable to receive a message signal, and a controller coupled to the receiver. The controller is operable to sample the received message signal to produce a sampled signal, execute a median filter on the sampled signal to produce a median-filtered output signal, and process the median-filtered output signal.
The present invention further provides a load control system for controlling the amount of power delivered to an electrical load from an AC power source. The control device comprises first and second control devices. The first control device includes a transmitter operable to transmit a message signal. The second control device includes a receiver operable to receive a message signal and a controller coupled to the receiver. The controller is operable to sample the received message signal to produce a sampled signal, execute a median filter on the sampled signal to produce a median-filtered output signal, and process the median-filtered output signal.
Other features and advantages of the present invention will become apparent from the following description of the invention, which refers to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGSThe invention will now be describe in greater detail in the following detailed description with reference to the drawings in which:
The foregoing summary, as well as the following detailed description of the preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purposes of illustrating the invention, there is shown in the drawings an embodiment that is presently preferred, in which like numerals represent similar parts throughout the several views of the drawings, it being understood, however, that the invention is not limited to the specific methods and instrumentalities disclosed.
As is well known, a lamp and a fan motor are typically packaged in the same housing. It is desirable to be able to control the lamp and fan motor independently from the same remote location, by, for example, a wallstation. However, the two circuits to control the lamp and the fan motor are typically different. The lamp may be controlled by a series switch, typically a phase-angle dimmer. The fan motor may be controlled by a shunt switch in parallel with the fan motor, such as is disclosed in co-pending commonly-assigned U.S. patent application Ser. No. 11/447,728, filed on Jun. 6, 2006, entitled METHOD AND APPARATUS FOR QUIET VARIABLE MOTOR SPEED CONTROL, the entire disclosure of which is hereby incorporated by reference.
A block diagram of a system 100 for independent control of lights and fan motors according to the present invention is shown in
In the system 100 of
A simplified block diagram of the wallstation 104 is shown in
The controller 112 is preferably implemented as a microcontroller, but may be any suitable processing device, such as a programmable logic device (PLD), a microprocessor, or an application specific integrated circuit (ASIC). A user interface 114 includes a plurality of buttons for receiving inputs from a user and a plurality of light emitting diodes (LEDs) for providing visual feedback to the user. The controller 112 accepts control inputs from the buttons of the user interface 114 and controls the operation of the LEDs. The operation of the LEDs is described in greater detail in co-pending commonly-assigned U.S. patent application Ser. No. 11/191,780, filed Jul. 28, 2005, entitled APPARATUS AND METHOD FOR DISPLAYING OPERATING CHARACTERISTICS ON STATUS INDICATORS, the entire disclosure of which is hereby incorporated by reference.
The controller 112 is coupled to the communication circuit 116 for transmitting and receiving control information to and from the light/motor control unit 105 and the other wallstations 104 of system 100. The communication circuit 116 transmits and receives the control information via a communication transformer 118 over the electrical power wiring coupled from the AC voltage source 102 to the wallstations 104 and the light/motor control unit 105. The communication transformer 118 has a primary winding 11 8A that is connected in series electrical connection with the terminals H1, H2 of the wallstation 104 and a secondary winding 118B that is coupled to the communication circuit 116.
The wallstation 104 further includes an air-gap switch 117 in series with the power supply 110. When the air-gap switch 117 is opened, power is removed from all devices of the system 100 since the devices are coupled in a power loop. To provide safety when servicing the loads, i.e., changing a light bulb canopy, the wallstations 104 are preferably coupled to the hot line of the electrical power wiring such that the hot line is not provided in the canopy when the air-gap switch 117 is open. However, the wallstations 104 may also be coupled to the neutral line.
A simplified block diagram of the light/motor control unit 105 is shown in
A motor voltage detect circuit 156 determines the zero-crossings of the motor voltage across the fan motor 106 and provides a control signal to the controller 154, which operates the fan motor control circuit 152 accordingly. A zero-crossing of the motor voltage is defined as the time at which the motor voltage transitions from positive to negative polarity, or from negative to positive polarity, at the beginning of each half-cycle of the motor voltage. The operation of the fan motor control circuit 152 with the motor voltage detect circuit 156 is described in greater detail in previously-mentioned U.S. patent application Ser. No. 11/447,728.
The controller 154 is coupled to a communication circuit 158 (i.e., a transceiver), which transmits and receives control information over the electrical power wiring via a communication transformer 160. The communication transformer 160 is a current transformer that has a primary winding 160A that is connected in series with a hot terminal H of the motor/light control unit 105 and a secondary winding 160B that is coupled to the communication circuit 158.
A power supply 162 is coupled to the load-side of the communication transformer 160 and generates a DC voltage VCC to power the controller 154 and the other low-voltage circuitry. Two diodes 164A, 164B are provided such that the power supply is operable to charge only during the positive half cycles. The power supply 162 preferably comprises a capacitor (not shown) having a capacitance of approximately 680 μF. A capacitor 165 is coupled between the cathode of the diode 164A and the neutral terminal N and preferably has a capacitance of 2.2 μF.
A capacitor 166 is connected in parallel with the power supply 162 between the load-side of the communication transformer 160 and the cathode of the diode 164A. The capacitor 166 completes a communication loop with the wallstations 104 and isolates the communication transformer 160 from the high impedance of the fan motor 106, particularly when the fan motor 106 is off. The capacitor 166 is sized to pass the loop current carrier signal modulated with the control information, while blocking the 50/60 cycle power of the AC voltage source 102. A preferred value for the capacitor 161 is 10 nF.
A zero-cross detect circuit 168 is coupled between the load-side of the communication transformer 160 and the neutral terminal N for providing a signal representative of the zero-crossings of the AC voltage source 102 to the controller 154. A zero-crossing of the AC voltage is defined as the time at which the AC voltage transitions from positive to negative polarity, or from negative to positive polarity, at the beginning of each half-cycle of the AC voltage source 102. The controller 154 determines when to turn on or off the semiconductor switch of the dimmer circuit 150 each half-cycle by timing from each zero-crossing of the AC supply voltage.
The control system 100 preferably uses a current-carrier technique to communicate between the wallstations 104 and the light/motor control unit 105.
After the controller 112 has received user-actuated control information from the actuator buttons of the user interface 114 (
The message information may be modulated onto the hot line by any suitable modulation means, for example, amplitude modulation (AM), frequency modulation (FM), frequency shift keying (FSK), or binary phase shift keying (BPSK).
According to
In a preferred embodiment, the coded signal is thereafter encoded at a Manchester encoder 212. With Manchester encoding, a bit of data is signified by a transition from a high state to a low state, or vice versa, to represent a logic-zero bit or a logic-one bit, respectively, as is well known in the art. Although Manchester encoding is shown, other digital encoding schemes could be employed. The encoded signal is then modulated on a carrier signal by a modulator 214 using, for example, AM, FM, or BPSK modulation. After amplification by a power amplifier 218, the modulated signal is coupled to the tuned filter (comprising the capacitor 202 and the transformer 160) and is transmitted on to the hot line as a current signal. While the communication circuit 158 of the motor/light control unit 105 is described above and shown in
The original Manchester encoded stream 250 may be corrupted by noise during transmission such that a noisy Manchester encoded stream 252 shown in
Most types of interference only cause momentary excursions across the detection threshold. The resulting signal is much like digital shot noise and statistically is similar to the “random telegrapher's waveform”. As such, it is very impulsive in nature and can be modeled to a first order as a Poisson point process.
The multi-pass median filter 220 is used to substantially eliminate the noise corruption to generate the filtered Manchester encoded stream 254 shown in
N=2·M+1. (Equation 1)
Accordingly, the multi-pass median filter 220 examines N samples of the noisy Manchester encoded stream 252 at a time. For a 3rd order median filter, seven samples are examined since
N(M=3)=2·M+1=7. (Equation 2)
Each time the controller samples the noisy Manchester encoded stream 252 at step 219 and executes the multi-pass median filter 220, the window of the multi-pass median filter shifts by one sample, such that the multi-pass median filter examines a new set of N sequential samples.
The multi-pass median filter 220 preserves any “root signal” passing through the window. A root signal is defined as any signal that has a constant region M+1 points or greater with monotonic increasing or decreasing boundaries. By definition, root signals cannot contain any impulses or oscillations, i.e., signals with a width less than M+1. When a corrupted binary signal is passed through the median filter, the filter removes the impulses in the regions where the signal should be a binary zero or binary one.
The multi-pass median filter 220 repeatedly executes a single-pass median filter 220A, which is shown in
Specifically, the single-pass median filter 220A is executed a first time on the noisy Manchester encoded stream 252, which is sampled in step 219 of the receiver routine 208. The newest sample of the noisy Manchester encoded stream 252 is added to an initial pipeline (or sequence) of sampled data, i.e., a sampled signal. Accordingly, the newest sample of the Manchester encoded stream 252 is provided as the input sample 264 for the first execution of the single-pass median filter 220A. The single-pass median filter 220A is then executed a first time on N sequential samples of the initial pipeline of samples. The output sample of the first execution of the single-pass median filter 220A is added to the end of a first filtered-sample pipeline, i.e., a first sequence of filtered samples.
Then, the single-pass median filter 220A is executed a second time on N sequential samples of the first filtered-sample pipeline. In other words, the output sample 274 (of the first execution of the single-pass median filter 220A) is provided as the input sample 264 for the second execution of the single-pass median filter. The output sample 274 of the second execution of the single-pass median filter 220A is provided to the end of a second filtered-sample pipeline, which is the median-filtered output signal of the multi-pass median filter 220.
-
- 0 1 1 0 0 1 1,
the single-pass median filter 220A drops the Nth sample, i.e., 7th sample, and shifts the samples to the right to form the sequence - x 0 1 1 0 0 1,
where x represents the first sample, which is available to receive the new sample. The single-pass median filter 220A then receives the new input sample 264 and shifts the sample into the first position of the sequence of N samples at step 266. If the new input sample 264 is one (1) in the above example, the resulting new set of N sequential samples is - 1 0 1 1 0 0 1.
The new input sample 264 comprises the next sample from the noisy Manchester encoded stream 252 the first time the single-pass median filter 220A is executed. The second timer the single-pass median filter 220A is executed, the new input sample 264 comprises the output sample 272 from the first execution of the single-pass median filter 220A.
- 0 1 1 0 0 1 1,
Next, the single-pass median filter 220A determines the median of the present N sequential samples of the sliding window. According to a first embodiment of the present invention (as shown in
-
- 1 0 1 1 0 0 1,
the median filter 220A groups the zeros and the ones at step 286 to form a sorted sample stream - 0 0 0 1 1 1 1.
Since the middle value of the sorted sample stream is one, the median of the present N sequential samples of the sliding window is one at step 270. As step 272, the single-pass median filter 220A provides the chosen median as the output sample 274.
- 1 0 1 1 0 0 1,
Thus, the multi-pass median filter 220 provides the output sample 272 of the second execution of the single-pass median filter 220A to generate the median-filtered output signal, i.e., the filtered Manchester encoded stream 254 shown in
M+1=(N+1)/2, (Equation 3)
at step 282, the median is one is at step 284. Otherwise, the median is zero at step 286. Thus, for a 3rd order median filter 220B, if there are four ones in the N samples, the median is equal to one. Accordingly, the width W of the median filter 220B must always be an odd number, i.e., 2M+1.
After passing through the multi-pass median filter 220, the median-filtered output signal passes through a Manchester decoder 222 to produce a digital bit stream from the Manchester-encoded bit stream that is received. The decoded signal and a pseudo random orthogonal synchronization code 224 are fed to a cross correlator 226. The output of the cross correlator 226 is integrated by an integrator 228 and provided to a threshold detector 230. This processing occurs in real time with the output of the receiver routine 208 updated at the bit rate of the sequence.
At the cross correlator 226, the bit stream from the Manchester decoder 222 and the pseudo random orthogonal synchronization code 224 are input to an exclusive NOR (XNOR) logic gate. The number of ones in the output of the XNOR gate is counted to perform the integration at the integrator 228. A lookup table is utilized to count the ones during the integration. Since the codes are orthogonal, the correlation is small unless the codes match. The match does not have to be exact, merely close, for example a 75% match.
If the synchronization code is detected at step 232, the next M decoded bits (i.e., the message code 198) from the Manchester decoder 222 are saved at step 234. The forward error correction message codes 236 are then compared to the M decoded bits to find the best match, which determines the command at step 238 and the command is executed at step 240. This step is known as maximum likelihood decoding and is well known in the art. At step 232, if the synchronization code is not detected, the data is discarded and the process exits.
After receiving a decoded message, the controller transmits an acknowledgement (ACK) to the device that transmitted the received message. Transmitting the ACK allows for a reliable communication scheme.
The devices of the system 100 for independent control of lights and fan motors all communicate using a system address. In order to establish a system address to use, the wallstations 104 and the light/motor control unit 105 execute an automatic addressing algorithm upon power up.
Since the devices of system 100 are connected in a loop topology, it is possible to cause all devices to power up at one time by toggling (i.e., opening, then closing) the air-gap switch 117 of one of the wallstations 104. Upon power-up at step 300, the devices in the system 100 enters an addressing mode at step 302, meaning that the device is eligible to participate in the addressing algorithm and communicates with other devices of the system using a broadcast system address 0. In addressing mode, devices use a random back-off time when transmitting to minimize the probability of a collision since there could be many unaddressed devices in the system. After a suitable timeout period, e.g., 20 seconds, the devices leave the addressing mode.
First, the present device determines if all of the devices in the system have a system address at step 304. Specifically, upon power-up, all devices that do not have a system address transmit an address initiation request. At step 304, the device waits for a predetermined amount of time to determine if any address initiation requests are transmitted. If the device determines that all devices in the system have the system address at step 304, the device transmits the system address to all devices at step 306.
If all devices in the system do not have a system address at step 304, the present device transmits a query message to each device at step 308. The devices of the system respond to the query message by transmitting the system address and their device type, (i.e., a wallstation 104 or a light/motor control unit 105). At step 310, the present device determines if the system 100 is a “valid” system. A valid system includes at least one wallstation 104 and at least one light/motor control unit 105 and does not have more than one system address, i.e., no two devices of the system have differing system addresses. If the system is a valid system at step 310, the present device then determines if any of the devices of the system 100 have a system address at step 312. If at least one device has a system address, the present device saves the received address as the system address at step 314 and transmits the received address at step 316.
If the no devices have a system address at step 312, the present device attempts to select a new system address. At step 318, the device chooses a random address M, i.e., a random selection from the allowable address choices, as the system address candidate. For example, there may be 15 possible system addresses, i.e., 1-15. Since there may be neighboring systems already having address M assigned, the device transmits a “ping”, i.e., a query message, using address M at step 320 to verify the availability of the address. If any devices respond to the ping, i.e., the address M is already assigned, at step 322, the device begins to step through all of the available system addresses. If all available system addresses have not been attempted at step 324, the device selects the next available address (e.g., by incrementing the system address candidate) at step 326, and transmits another ping at step 320. Otherwise, the process simply exits. Once a suitable address M has been verified as being available, i.e., no devices respond at step 322, the present device sets the system address candidate as the system address at step 328, and transmits address M on the broadcast channel 0 at step 316. Accordingly, all unaddressed devices in addressing mode then save address M as the system address. The process then exits.
If the system 100 is not a valid system at step 310, then all system devices that presently have the system address exit the addressing mode at step 330. If the addressing assignment has only been attempted once at step 332, then the device transmits another query message at step 308. Otherwise, the process simply exits.
As a recovery method, an address reset is included that re-addresses all devices in the system 100. After power-up, i.e., when all the devices in the system are in addressing mode, a special key sequence may be entered by a user at the user interface 114 of the wallstation 104. Upon receipt of this input from the user interface 114, the controller 112 of the wallstation 104 transmits a message signal containing a “reset address” command over the power wiring to all devices. When a device in the addressing mode receives the reset address command, the device sets itself to the unaddressed state, i.e., the device is only responsive to messages transmitted with the broadcast system address 0 while in the addressing mode. The address assignment algorithm then proceeds as if all devices in the system 100 do not have a system address.
The remote control 420 comprises a plurality of actuators: an on button 422, a preset button 424, and an off button 426. The remote control 420 transmits messages via RF signals 406 to the dimmer switch 410 in response to actuations of the on button 422, the preset button 424, and the off button 426. Preferably, a message transmitted by the remote control 420 includes a serial number associated with the remote control and a command (e.g., on, off, or preset). During a setup procedure of the RF lighting control system 400, the dimmer switch 410 is associated with one or more remote controls 420. The dimmer switch 410 is then responsive to messages containing the serial number of the remote control 420 to which the dimmer switch is associated. The dimmer switch 410 is operable to turn on and to turn off the lighting load 404 in response to an actuation of the on button 422 and the off button 426, respectively. The dimmer switch 410 is operable to control the lighting load 404 to a preset intensity level in response to an actuation of the preset button 424.
The drive circuit 512 provides control inputs to the controllably conductive device 510 in response to command signals from a controller 514. The controller 514 is preferably implemented as a microcontroller, but may be any suitable processing device, such as a programmable logic device (PLD), a microprocessor, or an application specific integrated circuit (ASIC). The controller 514 receives inputs from the toggle actuator 414 and the intensity adjustment actuator 416 and controls the status indicators 418. The controller 514 is also coupled to a memory 516 for storage of the preset intensity of lighting load 404 and the serial number of the remote control 420 to which the dimmer switch 410 is associated. A power supply 518 generates a direct-current (DC) voltage VCC for powering the controller 514, the memory 516, and other low-voltage circuitry of the dimmer switch 410.
A zero-crossing detector 520 determines the zero-crossings of the input AC waveform from the AC power supply 402. A zero-crossing is defined as the time at which the AC supply voltage transitions from positive to negative polarity, or from negative to positive polarity, at the beginning of each half-cycle. The zero-crossing information is provided as an input to controller 514. The controller 514 provides the control inputs to the drive circuit 512 to operate the controllably conductive device 510 (i.e., to provide voltage from the AC power supply 402 to the lighting load 404) at predetermined times relative to the zero-crossing points of the AC waveform.
The dimmer switch 410 further comprises an RF receiver 522 and an antenna 524 for receiving the RF signals 406 from the remote control 420. The controller 514 is operable to control the controllably conductive device 510 in response to the messages received via the RF signals 406. Examples of the antenna 524 for wall-mounted dimmer switches, such as the dimmer switch 410, are described in greater detail in U.S. Pat. No. 5,982,103, issued Nov. 9, 1999, and U.S. patent application Ser. No. 10/873,033, filed Jun. 21, 2006, both entitled COMPACT RADIO FREQUENCY TRANSMITTING AND RECEIVING ANTENNA AND CONTROL DEVICE EMPLOYING SAME. The entire disclosures of both are hereby incorporated by reference.
The remote control 420 further includes an RF transmitter 536 coupled to the controller 530 and an antenna 538, which may comprise, for example, a loop antenna. In response to an actuation of one of the on button 422, the preset button 424, and the off button 426, the controller 530 causes the RF transmitter 536 to transmit a message to the dimmer switch 410 via the RF signals 406. Each transmitted message comprises the serial number of the remote control 420, which is stored in the memory 532, and a command indicative as to which of the three buttons was pressed (i.e., on, off, or preset).
The lighting control system 400 provides a simple one-step configuration procedure for associating the remote control 420 with the dimmer switch 410. A user simultaneously presses and holds the on button 422 on the remote control 420 and the toggle button 414 on the dimmer switch 410 to link the remote control 420 and the dimmer switch 410. The user may simultaneously press and hold the off button 426 on the remote control 420 and the toggle button 414 on the dimmer switch 410 to unassociate the remote control 420 with the dimmer switch 410. Further, the user may simultaneously press and hold the preset button 424 on the remote control 420 and the toggle button 414 on the dimmer switch 410 to store the present intensity of the lighting load 404 as the preset intensity level. The configuration procedure of the RF lighting control system 400 is described in greater detail in co-pending commonly-assigned U.S. patent application Ser. No. 11/559,166, filed Nov. 13, 2006, entitled RADIO-FREQUENCY LIGHTING CONTROL SYSTEM, the entire disclosure of which is hereby incorporated by reference.
At step 708, the controller 514 stores the output sample of the second median filter 706B in the memory 516, i.e., to form a median-filtered output signal. Next, the controller 514 decodes the samples that are stored in the memory 516 (i.e., the median-filtered output signal) to determine if the samples represent a bit of data at step 710. For example, if the received signal is encoded using Manchester encoding, the controller determines at step 708 whether the received signal is transitioning from a high state to a low state, or vice versa, to represent a logic-zero bit or a logic-one bit, respectively. Any bits determined at step 708 are stored in the memory 516 at step 712. A determination is made at step 714 as to whether the controller 514 has collected K bits, i.e., the number of bits corresponding to a complete message. If the controller 514 has not collected K bits (e.g., 74 bits), the procedure 700 simply exits at step 730.
If the controller 514 has received a complete message of K bits at step 714, but the serial number contained in the received message is not stored in the memory 532 at step 716, the procedure 700 exits at step 730. If the serial number contained in the received message is stored in the memory 532 at step 716, a determination is made as to what type of command has been received at steps 718, 722, and 726. If an on message is received at step 718, the lighting load 404 is turned on to full intensity at step 720 and the procedure 700 exits at step 730. If a preset message is received at step 722, the lighting load 404 is turned on to the preset intensity level at step 724 and the procedure 700 exits at step 730. If an off message is received at step 726, the lighting load 404 is turned off at step 728 and the procedure 700 exits at step 730.
Use of the multi-pass median filter 706 by the controller 514 of the dimmer switch 410 of the RF lighting control system 400 has resulted in an increased performance over prior art RF lighting control systems that have not included the median filter. Specifically, the dimmer switch 410 using the multi-pass median filter 706 has been determined to have a 3 dB increase in the conducted RF sensitivity in comparison to a prior art dimmer switch not using the median filter.
The conducted RF sensitivity of the dimmer switch 410 and a prior art dimmer switch was measured using a test setup 440 as shown in
The IR dimmer switch 810 implements the multi-pass median filter 706 in an IR signal procedure (not shown) in a similar fashion as the RF signal procedure 700 shown in
Although the words “device” and “unit” have been used to describe the elements of the systems for control of lights and fan motors of the present invention, it should be noted that each “device” and “unit” described herein need not be fully contained in a single enclosure or structure. For example, the light/motor control unit 105 may comprise a controller in a wall-mounted device and fan motor control circuit in a separate location, e.g., in the canopy of the fan motor and the lamp. Also, one “device” may be contained in another “device”.
Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. Therefore, the present invention should be limited not by the specific disclosure herein, but only by the appended claims.
Claims
1. A method of communicating a message signal from a first control device to a second control device, the method comprising the steps of:
- transmitting the message signal from the first control device;
- receiving the message signal at the second control device;
- sampling the received message signal;
- producing a set of N sequential samples;
- determining the median of the N sequential samples; and
- providing the median as an output sample.
2. The method of claim 1, wherein the step of sampling the received message signal further comprises the steps of:
- producing a sample of one if the received message signal is at a high state; and
- producing a sample of zero if the received message signal is at a low state.
3. The method of claim 2, wherein the step of determining the median of the N sequential samples further comprises steps of:
- grouping the one-samples and the zero-samples to form a sorted sample stream; and
- selecting the middle sample of the sorted sample stream as the median of the N sequential samples.
4. The method of claim 2, wherein the step of determining the median of the N sequential samples further comprise steps of:
- counting the number of one-samples in the set of N sequential samples.
- determining if the number of one-samples is greater than or equal to (N+1)/2;
- setting the median of the N sequential samples as one if the number of one-samples is greater than or equal to (N+1)/2; and
- setting the median of the N sequential samples as zero if the number of one-samples is no greater than or equal to (N+1)/2.
5. The method of claim 2, wherein the step of determining the median of the N sequential samples further comprises step of:
- determining the median of the N sequential samples from a lookup table.
6. The method of claim 1, wherein the step of sampling the received message signal further comprises the step of sampling the received message signal to produce a new input sample.
7. The method of claim 6, wherein the step of producing a set of N sequential samples comprises the steps of:
- discarding one of the set of N sequential samples;
- shifting the N sequential samples; and
- adding the new input sample to the set of N sequential samples to produce a new set of N sequential samples.
8. The method of claim 1, further comprising the step of:
- repeating the steps of sampling the received message signal, producing a set of N sequential samples, determining the median, and providing the median.
9. The method of claim 8, wherein the producing a set of N sequential samples comprises the steps of:
- discarding one of the set of N sequential samples;
- shifting the N sequential samples; and
- adding the output sample to the set of N sequential samples to produce a new set of N sequential samples.
10. The method of claim 1, wherein the message signal comprises a current-carrier signal.
11. The method of claim 1, wherein the message signal comprises a radio-frequency signal.
12. The method of claim 1, wherein the message signal comprises an infrared signal.
13. A method of filtering a received message signal comprising a sequence of samples, the method comprising the steps of:
- examining a set of N sequential samples of the received message signal;
- determining the median of the N sequential samples;
- providing the median as an output sample; and
- repeating the steps of examining a set of N sequential samples, determining the median, and providing the median.
14. The method of claim 13, further wherein the step of repeating further comprises examining a new set of N sequential samples of the received message signal;
- wherein the new set of N sequential samples is determined by discarding the Nth sample of the N sequential samples and shifting the sequence of samples of the received message signal.
15. A control device for use in a load control system for controlling the amount of power delivered to an electrical load from an AC power source, the control device comprising:
- a receiver operable to receive a message signal;
- a controller coupled to the receiver, the controller operable to: sample the received message signal to produce a sampled signal; execute a median filter on the sampled signal to produce a median-filtered output signal; and process the median-filtered output signal.
16. The control device of claim 15, wherein the median filter comprises a multi-pass median filter.
17. The control device of claim 16, wherein the multi-pass median filter comprises two single-pass median filters.
18. The control device of claim 15, wherein the controller is operable to repeatedly:
- sample the received message signal to produce a sampled signal;
- examine a set of N sequential samples of the sampled signal; and
- determine the median of the N sequential samples.
19. The control device of claim 15, further comprising:
- a memory coupled to the controller;
- wherein the controller is operable to store the median of the N sequential samples in the memory prior to processing the received message signal.
20. The control device of claim 15, further comprising:
- a controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load for controlling the amount of power delivered to the electrical load, the controllably conductive device comprising a control input coupled to the controller;
- wherein the controller is operable to control the controllably conductive device in response to the received message signal.
21. The control device of claim 15, wherein the receiver comprises an RF receiver operable to receive an RF message signal.
22. The control device of claim 15, wherein the receiver comprises an IR receiver operable to receive an IR message signal.
23. The control device of claim 15, further comprising:
- a current responsive element coupled in series electrical connection between the AC source and the electrical load, the current responsive element coupled to the receiver, such that the receiver is operable to receive a current-carrier signal.
24. The control device of claim 15, wherein the receiver comprises a transceiver for transmitting and receiving message signals.
25. A load control system for controlling the amount of power delivered to an electrical load from an AC power source, the control device comprising:
- a first control device including a transmitter operable to transmit a message signal; and
- a second control device including a receiver operable to receive a message signal and a controller coupled to the receiver, the controller operable to sample the received message signal to produce a sampled signal, execute a median filter on the sampled signal to produce a median-filtered output signal, and process the median-filtered output signal.
26. The load control system of claim 25, wherein the median filter comprises a multi-pass median filter.
27. The load control system of claim 25, wherein the controller is operable to repeatedly sample the received message signal, examine a set of N sequential samples of the received message signal, determine the median of the N sequential samples, and process the received message signal using the median.
28. The load control system of claim 25, wherein the second load control device further comprises a controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load for controlling the amount of power delivered to the electrical load, the controller operable to control the controllably conductive device.
Type: Application
Filed: Dec 22, 2006
Publication Date: May 17, 2007
Inventor: James Steiner (Royersford, PA)
Application Number: 11/644,652
International Classification: H04L 27/06 (20060101);