AUXILLARY SWITCH FOR MULTIPLEXED CONTROL AND GROUND SIGNAL FROM A THERMOSTAT

• US 20120248208A1
• Filed: 03/30/2011
• Published: 10/04/2012
• Est. Priority Date: 03/30/2011
• Status: Active Grant

• Current Assignee: Energate Incorporated (Tantalus Systems Corp)
• Original Assignee: Energate Incorporated (Tantalus Systems Corp)
• Inventors: Deligiannis, Jorge
• Granted Patent: US 9,141,116 B2
• Time in Patent Office: Days
• US Class Current: 236/51
• CPC Class Codes: G05D 23/1902 characterised by the use of a variable reference value

Abstract

An auxiliary switch is provided that allows a thermostat to use full wave rectification for power while still communicating control information to the auxiliary switch over a multiplexed ground-control line to control associated equipment.

Claims

1. An auxiliary switch for a thermostat employing full-wave rectification, the auxiliary switch comprising:

an alternating current (AC) power output terminal for coupling an AC signal to the thermostat;

a ground-control output terminal for providing a thermostat ground reference to the thermostat over a common ground line;

an adapter network connected between the ground-control output terminal and an auxiliary switch ground reference, the adapter network providing a maximum and minimum voltage drop between the auxiliary switch ground reference and the thermostat ground reference to provide a stable reference at an expected maximum current flow; and

a controller for determining voltage differences between a sensed voltage signal across the adapter network and an expected voltage signal at periodic time intervals and for de-multiplexing control information multiplexed onto the common ground line by the thermostat based on the determined voltage differences.

2. The auxiliary switch of claim 1 wherein the controller generates control signal outputs to control switches for controlling one or more heating ventilation and cooling (HVAC) components coupled to the auxiliary switch in accordance with the de-multiplexed control information.

3. The auxiliary switch of claim 2 further comprising an AC power input terminal for receiving the AC signal connection from one of the one or more HVAC components and a ground input terminal for providing a ground connection from the one of the one or more HVAC components, where a connection between the AC signal and ground line by the thermostat energizes the one of the one or more HVAC component.

4. The auxiliary switch of claim 3 wherein the AC signal is typically a 24 VAC signal.

5. The auxiliary switch of claim 1, wherein the adapter network comprises a small-value resistor.

6. The auxiliary switch of claim 1, wherein the adapter network comprises:

a voltage clamping circuit for clamping a voltage signal to the maximum and minimum voltage drops; and

a resistor connected in parallel with the voltage clamping circuit for providing the voltage drop across the adapter network when the voltage clamping circuit is not clamping the voltage signal.

7. The auxiliary switch of claim 1, wherein the adapter network comprises:

a pair of diode junctions connected in anti-parallel; and

a resistor connected in parallel with the pair of junction diodes.

8. The auxiliary switch of claim 7, wherein the pair of diode junctions are provided by one of a pair of diodes and a TRIAC controlled by the controller.

9. The auxiliary switch of claim 1, wherein the adapter network comprises a TRIAC and a resistor coupled in parallel, the firing of the TRIAC controlled by the controller.

10. The auxiliary switch of claim 9, wherein the controller changes the firing time of the TRIAC with respect to a phase of the AC signal at the AC power terminal to alter a voltage signal sensed by the thermostat to provide communication from the auxiliary switch to the thermostat.

11. The auxiliary switch of claim 1, further comprising a re-settable fuse in series between the adapter network and the ground-control terminal, the controller further monitoring a second voltage between the fuse and the ground-control terminal, the controller stopping firing of the TRIAC if the second voltage rises above a threshold allowing the auxiliary switch to function with a legacy two-wire thermostat.

12. The auxiliary switch of claim 2, wherein an isolated switch, receiving AC power independently of the auxiliary switch, is associated with a second HVAC component of the one or more HVAC components, wherein when the isolated switch is closed AC power is provided to the second HVAC component.

13. The auxiliary switch of claim 2 wherein at least a portion of the de-multiplexed control information is provided to a data connection to send control information to at least one of the one or more HVAC components.

14. A method of communicating between an auxiliary switch coupled to a thermostat employing full-wave rectification, the method at the auxiliary switch comprising repeatedly:

measuring a voltage across an adapter network of the auxiliary switch during a start portion and end portion of each half-cycle of an alternating current (AC) signal provided to the thermostat over an AC power line relative to a common ground line;

comparing the measured voltage to an expected voltage; and

determining a communicated bit based on if the measured voltage differs from the expected voltage for de-multiplexing control information multiplexed onto the common ground line by the thermostat.

15. The method of claim 14 further comprising generating one or more control signal outputs to one or more heating ventilation and cooling (HVAC) components coupled to the auxiliary switch based on the determined control information.

16. The method of claim 15, wherein the start portion of each half cycle begins after the AC signal crosses 0 and ends before the half-way point of the half cycle;

and

the end portion of each half cycle begins after the half-way point of the half cycle and ends before the AC signal crosses 0.

17. The method of claim 16, further comprising:

detecting a repeating heading bit in the communicated bits by detecting an oscillating bit value; and

determining control information multiplexed onto the ground-control line by the thermostat from the communicated bits in the determined bits between the repeating heading bits.

18. The method of claim 15, further comprising:

communicating from the auxiliary switch to the thermostat through varying a voltage across the AC power line and the ground-control line, the varying of the voltage controlled by the auxiliary switch by varying a timing of firing of a TRIAC connected in series between the ground-control line and a ground reference of the auxiliary switch.

19. The method of claim 15 wherein the AC signal and the ground line is between one of the one or more HVAC components where a connection between the AC signal and ground line by the thermostat energizes the one of the one or more HVAC components.

20. The method of claim 15, wherein the adapter network comprises a small-value resistor.

21. The method of claim 15, wherein the adapter network comprises:

a voltage clamping circuit for clamping a voltage signal to the maximum and minimum voltage drops; and

a resistor connected in parallel with the voltage clamping circuit for providing the voltage drop across the adapter network when the voltage clamping circuit is not clamping the voltage signal.

22. The method of claim 15, wherein the adapter network comprises:

a pair of diode junctions connected in anti-parallel; and

a resistor connected in parallel with the pair of junction diodes.

23. The method of claim 22, wherein the pair of diode junctions are provided by one of a pair of diodes and a TRIAC controlled by a controller.

24. The method of claim 15, wherein the adapter network comprises a TRIAC and a resistor coupled in parallel, the firing of the TRIAC controlled by a controller.

25. The method of claim 24, wherein the controller changes the firing time of the TRIAC with respect to a phase of the AC signal at the AC power terminal to alter a voltage signal sensed by the thermostat to provide communication from the auxiliary switch to the thermostat.

26. The method of claim 15, further comprising a re-settable fuse in series between the adapter network and a ground-control terminal connected to the common ground line, a controller further monitoring a second voltage between the fuse and the ground-control terminal, the controller stopping firing of the TRIAC if the second voltage rises above a threshold allowing the auxiliary switch to function with a legacy two-wire thermostat.

27. The method of claim 15, further comprising controlling an isolated switch, receiving AC power independently of the auxiliary switch, associated with a second HVAC component of the one or more HVAC components, wherein when the isolated switch is closed AC power is provided to the second HVAC component.

28. The method of claim 15 further comprising providing at least a portion of the de-multiplexed control information to a data connection to send control information to at least one of the one or more HVAC components.