Methods and apparatus for detecting refrigerator door openings

1. A method for detecting an open door of a refrigerator, the refrigerator including at least one door including a first door, at least one switch including a first switch configured to be activated by opening of said first door, and at least one detection circuit including at least one phase shift circuit coupled to an opto-coupler and a processor, said method comprising the steps of:

receiving a signal from said first switch when said first switch is activated;

phase-shifting the signal;

feeding the phase-shifted signal to the opto-coupler;

isolating the phase-shifted signal in the opto-coupler;

monitoring an output signal from the processor; and

comparing said output signal with a line signal to determine whether the first door is open.

2. A method in accordance with claim 1 wherein said step of phase-shifting the signal comprises the steps of:

rectifying the signal; and

phase-shifting the rectified signal.

3. A method in accordance with claim 2 wherein said step of rectifying the signal comprises the step of half-wave rectifying the signal.

4. A method in accordance with claim 2 wherein said step of phase-shifting the rectified signal comprises the step of producing a shifted voltage leading a line voltage.

5. A method in accordance with claim 4 wherein the shifted voltage leads the line voltage by a lead value between zero degrees and 90 degrees.

6. A method in accordance with claim 2 wherein said step of phase-shifting the rectified signal comprises the step of producing a shifted voltage lagging a line voltage.

7. A method in accordance with claim 6 wherein the shifted voltage lags the line voltage by a lag value between zero degrees and −90 degrees.

8. A method in accordance with claim 1 wherein the refrigerator includes a plurality of doors included within the at least one door and includes corresponding switches included within the at least one switch, said method further comprising the steps of:

receiving a plurality of signals from the switches when the switches are activated;

phase-shifting the-signals from the switches;

mixing the phase-shifted signals for the switches; and

supplying the mixed signal to a processor.

9. A method in accordance with claim 8 wherein said step of mixing the phase-shifted signals comprises mixing the phase-shifted signals using an opto-coupler.

10. A method in accordance with claim 8 wherein further comprising the steps of:

converting a value in degrees of phase shifting of the mixed signal to a time value; and

determining which of the doors is open using the time value.

11. A method in accordance with claim 8 further comprising the step of shifting a phase of a signal output by one activated switch to a degree different in magnitude from a degree of shift of another switch signal output.

12. A method in accordance with claim 8 wherein said steps of phase shifting the signals from the switches and mixing the phase-shifted signals are performed using a single component.

13. An apparatus for detecting refrigerator door openings, the refrigerator including at least one switch configured to be activated by a door opening, said apparatus configured to:

phase-shift a signal output by an activated switch;

isolate the phase-shifted signal using an opto-coupler;

determine whether a door is open using the shifted signal; and

provide the shifted signal to a microcontroller.

14. An apparatus in accordance with claim 13 wherein said apparatus is further configured to rectify the signal; and phase-shift the rectified signal.

15. An apparatus in accordance with claim 14 further configured to half-wave rectify the signal.

16. An apparatus in accordance with claim 14 further configured to produce a shifted voltage leading a line voltage.

17. An apparatus in accordance with claim 16 further configured to produce a shifted voltage leading the line voltage by a lead value between zero degrees and 90 degrees.

18. An apparatus in accordance with claim 14 further configured to produce a shifted voltage lagging a line voltage.

19. An apparatus in accordance with claim 18 further configured to produce a shifted voltage lagging the line voltage by a lag value between zero degrees and −90 degrees.

20. An apparatus for detecting refrigerator door openings of a refrigerator, the refrigerator including a plurality of doors and corresponding switches configured to be activated by the refrigerator door openings, said apparatus configured to:

phase-shift signals output by activated switches;

determine whether the doors are open by using the phase-shifted signals;

mix the phase-shifted signals output by the activated switches to generate a mixed signal;

isolate the mixed signals using an opto-coupler; and

supply the mixed signal to a processor.

21. An apparatus in accordance with claim 20 further configured to:

convert a value in degrees of phase shifting of the mixed signal to a time value; and

determine which of the doors is open using the time value.

22. An apparatus in accordance with claim 20 further configured to shift a phase of a signal output by one activated switch to a degree different in magnitude from a degree of shift of another switch signal output.

23. An apparatus in accordance with claim 20 further comprising a single component configured to phase shift and mix the phase-shifted signals.