Ultrasonic sensing system

Abstract

A low-cost, simple ultrasonic sensing system has an increased detection range. The ultrasonic sensing system may be implemented as part of a load control system for controlling the power delivered from an AC power source to an electrical load. The load control system may comprise a load control device for controlling the power delivered to the electrical load, an ultrasonic receiver for receiving ultrasonic waves characterized by an ultrasonic frequency, and an ultrasonic transmitter located remotely from the ultrasonic receiver. The load control device controls the power delivered to the electrical load in response to the ultrasonic waves received by the ultrasonic receiver. The load control device may include the ultrasonic receiver and may be a wall-mounted load control device. The ultrasonic receiver may be a wireless ultrasonic receiver for transmitting wireless signals to the load control device in response to the ultrasonic waves received by the ultrasonic receiver.

What is claimed is: 
     
       1. A load control system for controlling power delivered from a power source to an electrical load, the system comprising:
 a load control device configured to be coupled in series between the power source and the electrical load for controlling the power to the electrical load via a switching circuit, the load control device comprising a load control device communication circuit; 
 a remote ultrasonic transmitter configured to transmit ultrasonic waves characterized by an ultrasonic frequency and an amplitude, wherein the remote ultrasonic transmitter does not include a receiver for receiving ultrasonic waves transmitted by the remote ultrasonic transmitter; and 
 a sensor comprising:
 a sensor communication circuit; 
 a local ultrasonic transmitter configured to transmit ultrasonic waves at the ultrasonic frequency; 
 an ultrasonic receiver configured to receive attenuated ultrasonic waves from the remote ultrasonic transmitter and configured to: 
 receive reflections of the ultrasonic waves transmitted by the local ultrasonic transmitter; 
 convert a change in amplitude of the attenuated ultrasonic waves received from the remote ultrasonic transmitter and the change in frequency of the received reflected ultrasonic waves from the local transmitter to a voltage signal; and  
 
 a control circuit coupled to the sensor communication circuit and to the ultrasonic receiver, the control circuit configured to:
 receive, via the ultrasonic receiver, signals representing the attenuated ultrasonic waves and the reflected ultrasonic waves; 
 determine occupancy from the received signals based on at least one of (i) a change in amplitude between the attenuated ultrasonic waves and the characterized amplitude and (ii) a change in frequency between the reflected ultrasonic waves and the characterized ultrasonic frequency 
 determine whether the voltage signal is at least one of: greater than upper voltage threshold value or less than a lower voltage threshold value; 
 determine an occupancy condition exists responsive to at least one of: the voltage signal being greater than the upper voltage threshold value or the voltage signal being less than a lower voltage threshold value; and 
 transmit a command via the sensor communication circuit to the load control device based on the determination of occupancy; 
 
 
 wherein the load control device, the remote ultrasonic transmitter device, and the sensor are each separate devices; and 
 further wherein the load control device is configured to receive the command via the communication circuit of the load control device and to control the power delivered via the switching circuit to the electrical load in response to the command. 
 
     
     
       2. The system of  claim 1 , wherein the remote ultrasonic transmitter comprises an ultrasonic transmitting element, a drive circuit for energizing the ultrasonic transmitting element, and a low phase-noise oscillator circuit directly driving the drive circuit to cause the ultrasonic transmitting element to transmit ultrasonic waves at the ultrasonic frequency. 
     
     
       3. The system of  claim 2 , wherein the remote ultrasonic transmitter further comprises an internal power supply generating a supply voltage for powering the oscillator circuit and the drive circuit. 
     
     
       4. The system of  claim 3 , wherein the power supply of the remote ultrasonic transmitter is configured to generate the supply voltage from an AC line voltage of an AC power source. 
     
     
       5. The system of  claim 4 , wherein the remote ultrasonic transmitter is configured to be plugged into an electrical outlet. 
     
     
       6. The system of  claim 3 , further comprising:
 an external power supply configured to generate a DC voltage from an AC line voltage of an AC power source; 
 wherein the power supply of the remote ultrasonic transmitter is configured to generate the supply voltage from the DC voltage of the external power supply. 
 
     
     
       7. The system of  claim 2 , wherein the remote ultrasonic transmitter further comprises a battery configured to produce a battery voltage for powering the oscillator circuit and the drive circuit. 
     
     
       8. The system of  claim 2 , wherein the low phase-noise oscillator circuit comprises a Pierce oscillator circuit having a crystal. 
     
     
       9. The system of  claim 1 , wherein the load control device comprises a ceiling mounted load control device. 
     
     
       10. The system of  claim 1 , wherein the load control device is configured to turn the electrical load on and off in response to the ultrasonic waves received by the ultrasonic receiver. 
     
     
       11. The system of  claim 1 , wherein the ultrasonic frequency is 40 kHz±2 Hz. 
     
     
       12. The system of  claim 1 , wherein the electrical load comprises a lighting load. 
     
     
       13. The system of  claim 1 , wherein the remote ultrasonic transmitter and the local ultrasonic transmitter each continuously transmit the respective ultrasonic waves. 
     
     
       14. The system of  claim 1 , wherein the sensor is configured to be mounted to a ceiling. 
     
     
       15. The system of  claim 14 , wherein the sensor is a powered by a battery. 
     
     
       16. The system of  claim 1 , wherein the sensor communication circuit is a wireless communication circuit. 
     
     
       17. The system of  claim 1 , further comprising at least two remote ultrasonic transmitters. 
     
     
       18. The system of  claim 17 , wherein the at least two remote ultrasonic transmitters and the sensor each comprises an ultrasonic coverage pattern based on the transmission of the respective ultrasonic waves from the respective ultrasonic transmitter, and
 wherein the at least two remote ultrasonic transmitters and the sensor are placed in a room such that the respective ultrasonic coverage patterns of each of the at least two remote ultrasonic transmitters and the sensor overlap to substantially fill the room with ultrasonic waves. 
 
     
     
       19. The system of  claim 18 , wherein the at least two remote ultrasonic transmitters are configured to increase a range of occupancy detection within the room. 
     
     
       20. The system of  claim 19 , wherein the room comprises at least: 
 a first, wall including the sensor;  
 a second wall including at least one remote transmitter; and 
 a third wall, wherein each wall has at least one of: the at least two including at least one remote ultrasonic transmitters and the sensor transmitter. 
 
     
     
       21. The system of  claim 1 , wherein the remote ultrasonic transmitter is configured to be located on a first wall, and the sensor is configured to be located on a second wall, the first wall being different from the second wall. 
     
     
       22. A load control system for controlling the power delivered from a power source to an electrical load, the system comprising:
 a remote ultrasonic transmitter configured to transmit ultrasonic waves characterized by an ultrasonic frequency, wherein the remote ultrasonic transmitter does not include a receiver for receiving ultrasonic waves transmitted by the remote ultrasonic transmitter, and wherein the remote ultrasonic transmitter is configured to be plugged into an electrical outlet; and 
 a load control device that is a separate device from the remote ultrasonic transmitter and that is adapted to be coupled in series electrical connection between the power source and the electrical load for controlling the power delivered to the electrical load via a switching circuit, the load control device comprising a load control device communication circuit; and  
 a sensor comprising:
 a sensor communication circuit; 
 a local ultrasonic transmitter configured to transmit ultrasonic waves at the ultrasonic frequency; 
 an ultrasonic receiver configured to:  
 receive ultrasonic waves from the remote ultrasonic transmitter and to:  
 receive ultrasonic waves from the local ultrasonic transmitter; 
 convert a change in amplitude of the attenuated ultrasonic waves received from the remote ultrasonic transmitter and the change in frequency of the received reflected ultrasonic waves from the local transmitter to a voltage signal; and  
 a control circuit operatively coupled to the ultrasonic receiver, the control circuit configured to:
 (i) detect occupancy based on the received ultrasonic waves by at least one of:
 (a) detecting a period of amplitude modulation from the ultrasonic waves received from the remote ultrasonic transmitter, and   (b) detecting a Doppler shift of the ultrasonic frequency from the ultrasonic waves received from the local ultrasonic transmitter;   
 determine whether the voltage signal is at least one of: greater than upper voltage threshold value or less than a lower voltage threshold value; 
 determine an occupancy condition exists responsive to at least one of: the voltage signal being greater than the upper voltage threshold value or the voltage signal being less than a lower voltage threshold value; and 
 (ii) transmit a command via the sensor communication circuit to the load control device based on the determination of occupancy; 
 
 wherein the sensor is separate from the load control device and the remote ultrasonic transmitter device; 
 further wherein the load control device is configured to receive the command via the communication circuit of the load control device and to control the power delivered via the switching circuit to the electrical load in response to the command. 
 
 
     
     
       23. The system of  claim 22 , wherein the load control device further comprises a controllably conductive device comprising a relay. 
     
     
       24. The system of  claim 22 , wherein the remote ultrasonic transmitter is configured to be located on a first wall, and the load control device is configured to be located on a second wall, the first wall being different from the second wall. 
     
     
       25. A system comprising:
 a remote ultrasonic transmitter configured to transmit ultrasonic waves characterized by an ultrasonic frequency, wherein the remote ultrasonic transmitter does not include a receiver for receiving ultrasonic waves transmitted by the remote ultrasonic transmitter; and   a sensor comprising:
 a sensor communication circuit; 
 a local ultrasonic transmitter configured to transmit ultrasonic waves at the ultrasonic frequency; 
 an ultrasonic receiver configured to:
 receive ultrasonic waves, wherein the received ultrasonic waves comprise attenuated ultrasonic waves transmitted by the remote ultrasonic transmitter and reflected ultrasonic waves transmitted by the local ultrasonic transmitter; 
 convert a change in amplitude of the attenuated ultrasonic waves received from the remote ultrasonic transmitter and the change in frequency of the received reflected ultrasonic waves from the local transmitter to a voltage signal; 
 generate one or more ultrasonic sense signals in response to determining whether there are periods of frequency modulation in the received ultrasonic waves; and 
 
 a control circuit operatively coupled to the sensor communication circuit and the ultrasonic receiver, the control circuit configured to:
 receive the voltage signal generated by the ultrasonic receiver; 
 determine whether the voltage signal is at least one of: greater than upper voltage threshold value or less than a lower voltage threshold value; 
 determine an occupancy condition exists responsive to at least one of: the voltage signal being greater than the upper voltage threshold value or the voltage signal being less than a lower voltage threshold value; 
 transmit a command via the sensor communication circuit that indicates the space is occupied in response to the determination that an occupany condition exists within the space; 
 
 wherein the remote ultrasonic transmitter and the sensor are separate devices. 
   
     
     
       26. The system of claim 25, further comprising:
 wherein the remote ultrasonic transmitter comprises a first remote ultrasonic transmitter, the system further comprising a second remote ultrasonic transmitter configured to transmit ultrasonic waves characterized by the ultrasonic frequency; and   wherein the ultrasonic receiver is further configured to:
 receive ultrasonic waves transmitted by the local ultrasonic transmitter; and 
 determine whether there are periods of frequency modulation in the received ultrasonic waves transmitted by the local ultrasonic transmitter. 
   
     
     
       27. The system of claim 25,
 wherein each of the plurality of remote ultrasonic transmitters further comprises an ultrasonic transmitting element, a drive circuit configured to energize the ultrasonic transmitting element, and a low phase-noise oscillator circuit configured to directly drive the drive circuit to cause the ultrasonic transmitting element to transmit the ultrasonic waves at the ultrasonic frequency.   
     
     
       28. The system of claim 27,
 wherein each of the plurality of remote ultrasonic transmitters further comprises a power supply configured to generate a supply voltage for powering the low phase-noise oscillator circuit and the drive circuit.   
     
     
       29. The system of claim 28, wherein the power supply of each of the plurality of remote ultrasonic transmitters is further configured to generate the supply voltage from an AC line voltage of an AC power source. 
     
     
       30. The system of claim 27,
 wherein each of the plurality of remote ultrasonic transmitters is further configured to power the low phase-noise oscillator circuit and the drive circuit from a battery.   
     
     
       31. The system of claim 25, wherein the sensor is configured to be mounted to a ceiling. 
     
     
       32. A system comprising:
 a plurality of remote ultrasonic transmitters, each configured to transmit ultrasonic waves characterized by an ultrasonic frequency, wherein each of the plurality of remote ultrasonic transmitters does not include a receiver for receiving ultrasonic waves; and   a sensor comprising:
 a sensor communication circuit; 
 a local ultrasonic transmitter disposed proximate the ultrasonic receiver; 
 an ultrasonic receiver configured to:
 receive ultrasonic waves, wherein the received ultrasonic waves comprise attenuated ultrasonic waves transmitted by the plurality of remote ultrasonic transmitters and reflected ultrasonic waves from the local ultrasonic transmitter; and 
 convert at least one of: a change in amplitude of the attenuated ultrasonic waves received from the remote ultrasonic transmitter or the change in frequency of the received reflected ultrasonic waves from the local transmitter to a voltage signal; and 
 
 a control circuit operatively coupled to the sensor communication circuit and the ultrasonic receiver, the control circuit configured to:
 receive the voltage signal generated by the ultrasonic receiver; 
 determine whether the voltage signal is at least one of: greater than upper voltage threshold value or less than a lower voltage threshold value; 
 determine an occupancy condition exists responsive to at least one of: the voltage signal being greater than the upper voltage threshold value or the voltage signal being less than a lower voltage threshold value; 
 transmit a command via the sensor communication circuit that indicates the space is occupied in response to the determination that an occupancy condition exists within the space; 
 wherein each of the plurality of remote ultrasonic transmitters and the sensor are separate devices. 
 
   
     
     
       33. The system of claim 32,
 wherein each of the plurality of remote ultrasonic transmitters further comprises an ultrasonic transmitting element, a drive circuit configured to energize the ultrasonic transmitting element, and a low phase-noise oscillator circuit configured to directly drive the drive circuit to cause the ultrasonic transmitting element to transmit the ultrasonic waves at the ultrasonic frequency.   
     
     
       34. The system of claim 33,
 wherein each of the plurality of remote ultrasonic transmitters further comprises a power supply configured to generate a supply voltage for powering the low phase-noise oscillator circuit and the drive circuit.   
     
     
       35. The system of claim 34, wherein the power supply of each of the plurality of remote ultrasonic transmitters is further configured to generate the supply voltage from an AC line voltage of an AC power source. 
     
     
       36. The system of claim 33, wherein each of the plurality of remote ultrasonic transmitters is further configured to power the low phase-noise oscillator circuit and the drive circuit from a battery. 
     
     
       37. The system of claim 32, wherein the sensor is configured to be mounted to a ceiling.