Powerline communicated load control
A system for transmitting communication signals, the system comprising an injector circuit connected to a powered circuit conductor and configured to modulate a power signal with a direct current voltage offset, the direct current voltage offset being within a range that causes approximately 1 percent or less total harmonic distortion of the power signal; and a decoder connected to the powered circuit conductor and a load, the decoder configured to demodulate the direct current voltage offset to control the load. A method for transmitting communication signals, the method comprising modulating a power signal on a powered circuit conductor with a direct current voltage offset, the direct current voltage offset being within a range that causes approximately 1 percent or less total harmonic distortion of the power signal; and demodulating the direct current voltage offset to control a load.
1. A system for transmitting communication signals, the system comprising:
an injector circuit connected, in series, between a powered circuit conductor and a decoder, the injector circuit configured to modulate, in series, an AC power signal with a time sequence of instantaneous DC voltage offsets over at least a portion of a voltage phase to produce one or more bits to be transmitted on the powered circuit conductor, wherein the one or more bits form a command, wherein the AC power signal is modulated with respect to ground/neutral used by AC voltage, and wherein modulating the AC power signal includes varying one or more properties of a periodic waveform by subtracting a magnitude of the DC voltage offsets from a magnitude of the AC voltage; and
the decoder connected to the powered circuit conductor and configured to be connected to a load, the decoder further configured to demodulate the instantaneous DC voltage offsets to extract the command to control the load based on a selected control scheme.
2. The system of claim 1 , wherein the instantaneous DC voltage offset is within the range of approximately 1 to 5 volts.
3. The system of claim 1 , further comprising a system control module in communication with the injector circuit, the system control module configured to open a short across the injector circuit to allow the injector circuit to modulate the AC power signal by subtracting the magnitude of the DC voltage offsets from the magnitude of the AC voltage, and further configured to short across the injector circuit in the powered circuit conductor while modulation does not occur.
4. The system of claim 3 , wherein the system control module is wirelessly connected to the injector circuit.
5. The system of claim 3 , wherein the modulation scheme is a two-state scheme.
6. The system of claim 3 , wherein the modulation scheme is a multi-level scheme.
7. The system of claim 1 , wherein the injector circuit is an asymmetrical network.
8. The system of claim 7 , wherein the asymmetrical network modulates the AC power signal with the instantaneous DC voltage offset, the instantaneous DC voltage offset having a first voltage offset for modulating a first polarity of the AC power signal and a second voltage offset for modulating a second polarity of the AC power signal, the first voltage offset being different than the second voltage offset.
9. The system of claim 8 , wherein the asymmetrical network comprises a transistor configured to produce the first voltage offset in the first polarity; and a diode configured to produce the second voltage offset in the second polarity.
10. The system of claim 8 , wherein the asymmetrical network comprises a rectifier circuit configured to produce the first voltage offset in the first polarity; and a diode configured to produce the second voltage offset in the second polarity.
11. The system of claim 1 , wherein the injector circuit includes a first asymmetrical network and a second asymmetrical network.
12. The system of claim 1 , further comprising an isolation interface configured to provide galvanic isolation between the powered circuit conductor and the decoder.
13. The system of claim 1 , wherein the decoder includes a microprocessor configured to demodulate the DC voltage offset to control the load.
14. The system of claim 13 , wherein the microprocessor is configured to demodulate the instantaneous DC voltage offset on the powered circuit conductor by calculating an average instantaneous DC voltage offset of the AC power signal, measuring an instantaneous DC voltage offset of the AC power signal, comparing the instantaneous DC voltage offset of the AC power signal to the average instantaneous DC voltage offset of the AC power signal, and converting the instantaneous DC voltage offset of the AC power signal to a control signal for controlling the load when the instantaneous DC voltage offset of the AC power signal is greater than the average instantaneous DC voltage offset of the AC power signal.
15. A method for transmitting communication signals, the method comprising:
modulating, in series, an AC power signal on a powered circuit conductor with a time sequence of instantaneous DC voltage offsets over at least a portion of a voltage phase to produce one or more bits to be transmitted on the powered circuit conductor, wherein the one or more bits form a command, wherein the AC power signal is modulated with respect to ground/neutral used by AC voltage, and wherein modulating the AC power signal includes varying one or more properties of a periodic waveform by subtracting a magnitude of the DC voltage offsets from a magnitude of the AC voltage; and
demodulating the instantaneous DC voltage offsets to extract the command to control a load.
16. The method of claim 15 , wherein the instantaneous DC voltage offset is within the range of approximately 1 to 5 volts.
17. The method of claim 15 , further comprising modulating the AC power signal in a pulse pattern.
18. The method of claim 15 , further comprising opening a short to allow modulation of the AC power signal, and shorting across the powered circuit conductor while modulation does not occur.
19. The method of claim 18 , wherein the modulation scheme is a two-state scheme.
20. The method of claim 18 , wherein the modulation scheme is a multi-level scheme.
21. The method of claim 15 , further comprising providing galvanic isolation from the powered circuit conductor.
22. The method of claim 15 , wherein demodulating the instantaneous DC voltage offsets to control the load comprises:
calculating an average instantaneous DC voltage offset of the AC power signal;
measuring an instantaneous DC voltage offset of the AC power signal;
comparing the instantaneous DC voltage offset of the AC power signal to the average instantaneous DC voltage offset of the AC power signal; and
converting the instantaneous DC voltage offset of the AC power signal to a control signal for controlling the load when the instantaneous DC voltage offset of the AC power signal is greater than the average instantaneous DC voltage offset of the AC power signal.