Method of communicating between control devices of a load control system

Abstract

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 . 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.