Method and apparatus for communicating message signals in a load control system

• US 8,471,687 B2
• Filed: 10/11/2011
• Issued: 06/25/2013
• Est. Priority Date: 06/06/2005
• Status: Active Grant

• Current Assignee: Lutron Technology Company LLC
• Original Assignee: Lutron Electronics Company Incorporated (Lutron Electronics)
• Inventors: Steiner, James P., Dobbins, Aaron, Blair, Edward J.
• Primary Examiner(s): Mehmood, Jennifer
• Assistant Examiner(s): Jiang, Yong Hang
• Application Number:
  US13/270,704
• Publication Number:
  US 20120051444A1
• Time in Patent Office: 623 Days
• Field of Search: 340/533, 340/534, 340/538, 340/538.11, 340/538.12, 340/538.13, 340/538.16, 340/538.17, 340/12.31, 340/12.32, 340/12.33, 340/12.34, 340/12.35, 340/12.36, 340/12.37, 340/12.38, 340/12.39
• US Class Current: 340/12.32
• CPC Class Codes: H04B 2203/5412 by modofying wave form of the power source
• CPC Class Codes: H04B 2203/5416 by adding signals to the wave form of the power source
• CPC Class Codes: H04B 2203/5458 Monitor sensor; Alarm systems
• CPC Class Codes: H04B 3/54 Systems for transmission via power distribution lines
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data
• CPC Class Codes: H04L 1/1812 Hybrid protocols; Hybrid automatic repeat request [HARQ]
• CPC Class Codes: H04L 25/0266 Arrangements for providing Galvanic isolation, e.g. by means of magnetic or capacitive coupling
• CPC Class Codes: H04L 25/0282 Provision for current-mode coupling

Abstract

A system for independent control of electric motors and electric lights includes a plurality of two-wire wallstations coupled in series via power wires between an alternating-current (AC) source and a light/motor control unit. The light/motor control unit is preferably located in the same enclosure as an electric motor and an electric light and has two outputs for independent control of the motor and the light. The light/motor control unit and the wallstations each include a controller and a communication circuit that is coupled to the power wiring via a communication transformer and communicate with each other using a loop current carrier technique. The light/motor control unit and the wallstations utilize pseudo random orthogonal codes and a median filter in the communication process.

Claims

1. A load control system for controlling the power delivered from an AC voltage source to an electrical load, the system comprising:

a load control device adapted to be coupled to the electrical load for controlling the power delivered to the electrical load, such that a load current flows from the AC voltage source to the electrical load through the load control device, the load control device comprising a first current transformer having a primary winding adapted to be coupled in series electrical connection between the AC source and the electrical load, such that the primary winding of the first current transformer conducts the load current, the load control device further comprising a first communication circuit coupled to a secondary winding of the first current transformer for receiving message signals; and

a two-wire remote control device comprising a second current transformer having a primary winding adapted to be coupled in series electrical connection with the primary winding of the first current transformer between the AC source and the electrical load, such that the primary winding of the second current transformer conducts the load current, the remote control device further comprising a second communication circuit coupled to a secondary winding of the second current transformer for transmitting the message signals; and

wherein the primary windings of the first current transformer and the second current transformer are operable to conduct a communication loop current, the first communication circuit operable to receive and the second communication circuit operable to transmit the message signals via the communication loop current, further wherein the load control device comprises a first capacitor coupled in shunt electrical connection with the load, such that the first capacitor and the primary windings of the first and second current transformers are operable to conduct the communication loop current.

2. The load control system of claim 1, wherein the first communication circuit of the load control device and the second communication circuit of the remote control device are operable to both transmit and receive the message signals via the communication loop current.

3. The load control system of claim 2, wherein the first and second communication circuits each comprise a code generator operable to use Manchester encoding to generate an encoded signal from the message signal and a modulator operable to modulate the communication current loop with the encoded signal to produce a modulated signal.

4. The load control system of claim 3, wherein the first and second communication circuits each comprise a demodulator operable to demodulate the modulated signal to produce a detected encoded signal, and a median filter operable to remove impulsive noise signals from the detected encoded signal.

5. The load control system of claim 2, wherein the load control device is coupled to a plurality of electrical loads and is operable to individually control each of the plurality of electrical loads.

6. The load control system of claim 5, wherein the plurality of electrical loads comprises an electric motor and an electric light.

7. The load control system of claim 1, wherein the primary windings of the first and second current transformers are coupled to the AC voltage source, such that the AC voltage source and the primary windings of the first and second current transformers are operable to conduct the communication loop current.

8. The load control system of claim 1, further comprising a second capacitor coupled across the AC voltage source, such that the second capacitor and the primary windings of the first and second current transformers are operable to conduct the communication loop current.

18. The load control system of claim 1, wherein the load control device has a neutral terminal connected to the AC voltage source neutral line.

9. A load control device for a load control system for controlling the power delivered from an AC voltage source to an electrical load, the load control system comprising a remote control device adapted to be coupled in series between the AC voltage source and the electrical load, the load control device comprising:

a load control circuit adapted to be coupled to the electrical load for control of the load, such that a load current is operable to flow from the AC voltage source to the electrical load through the load control device;

a current transformer having a primary winding and a secondary winding, the primary winding adapted to be coupled in series electrical connection with the remote control device between the AC voltage source and the electrical load, such that the primary winding conducts the load current; and

a communication circuit coupled to the secondary winding of the current transformer for receiving message signals;

wherein the primary winding of the current transformer is adapted to be coupled in series electrical connection with a primary winding of a current transformer of the remote control device, such that the primary windings of the current transformers of the load control device and the remote control device are operable to conduct a communication loop current, and the load control device is operable to receive the message signals for controlling the electrical load from the remote control device via the communication loop current, further comprising a first capacitor adapted to be coupled in shunt electrical connection with the load, such that the first capacitor and the primary windings of the current transformers of the load control device and the remote control device are operable to conduct the communication loop current.

10. The load control device of claim 9, further comprising:

a second capacitor adapted to be coupled across the AC voltage source, such that the first and second capacitors and the primary windings of the current transformers of the load control device and the remote control device are operable to conduct the communication loop current.

11. The load control device of claim 9, wherein the electrical load comprises a lighting load and the load control circuit comprises a dimmer circuit for adjusting the intensity of the lighting load.

12. The load control device of claim 9, wherein the electrical load comprises a motor, and the load control circuit comprises a motor control circuit for adjusting the speed of the motor.

19. The load control device of claim 9, wherein the load control device has a neutral terminal connected to the AC voltage source neutral line.

13. A method for communicating between a first control circuit portion and a second control circuit portion over electrical power wiring of a building to control the operation of an electrical load, the first control circuit portion having a user actuable control for remotely controlling the load controlled by the second control circuit portion, the method comprising the steps of:

conducting a load current through the electrical load from an AC voltage source;

coupling a winding of a first current transformer of the first control circuit portion to the electrical power wiring, such that the winding of the first current transformer conducts the load current;

coupling a winding of a second current transformer of the second control circuit portion to the electrical power wiring in series electrical connection with the winding of the first current transformer and the AC voltage source, such that the winding of the second current transformer conducts the load current;

establishing a current signal loop in the electrical power wiring between the first and second current transformers;

providing a capacitor coupled in shunt electrical connection with the load, such that the capacitor and the primary windings of the first and second current transformers are operable to conduct the current loop signal;

transmitting control information over the electrical power wiring from the first control circuit portion to the second control circuit portion; and

receiving the control information at the second circuit portion for controlling the load.

14. The method of claim 13, wherein said step of transmitting comprises the steps of:

modulating a carrier signal with the control information; and

coupling the modulated carrier signal onto the signal loop through the current transformers.

15. The method of claim 14, wherein said step of receiving comprises the steps of:

demodulating the modulated carrier signal;

applying a median filter to remove impulsive noise; and

producing a detected signal containing the control information.

16. The method of claim 13, wherein the step of transmitting comprises the steps of:

encoding the control information;

modulating a carrier signal with the encoded control information; and

coupling the modulated carrier signal onto the signal loop through the current transformers.

17. The method of claim 16, wherein the step of receiving comprises the step of:

median filtering the demodulated carrier signal at the second control circuit portion to remove impulsive noise signals from said modulated carrier signal.

20. The method of claim 13, wherein the second circuit portion has a neutral terminal connected to the AC voltage source neutral line.