초록 ▼

A device for controlling a switching relay to deliver power to a load. The switching relay selectively couples a hot leg of a utility power supply to the load. The load is coupled to a neutral wire of the utility power supply. The device includes a sensor for detecting whether an area is occupied. I

A device for controlling a switching relay to deliver power to a load. The switching relay selectively couples a hot leg of a utility power supply to the load. The load is coupled to a neutral wire of the utility power supply. The device includes a sensor for detecting whether an area is occupied. If the sensor indicates that the area is occupied and the load is powered off, the device monitors the line voltage for a zero crossing. Upon detecting a zero crossing, an amount of time to a subsequent zero crossing is measured and stored. Then, the device waits the amount of time between zero crossings, less a delay time for closing the contacts of the relay, and initiates a closing of the contacts of the relay. Similarly, when the sensor detects that the area has not been occupied for a predetermined amount of time and the load is powered on, the line voltage is monitored for a zero crossing and a time to a subsequent zero crossing is measured and stored. Then, the device waits the amount of time between zero crossings, less a delay time for opening the contacts of the relay, and initiates an opening of the contacts of the relay. Accordingly, when the relay contacts actually close or open, the line voltage is at the ground level. Therefore, even if the load has a high in-rush current or high kick-back power, the relay contacts are not likely to be damaged.

대표청구항 ▼

[ What is claimed is:] [1.] An apparatus for selectively providing power to a load, the apparatus comprising:a. means for measuring an amount of time between a first zero crossing of an AC supply voltage and a second zero crossing of the AC supply voltage; andb. means for initiating a change in cond

[ What is claimed is:] [1.] An apparatus for selectively providing power to a load, the apparatus comprising:a. means for measuring an amount of time between a first zero crossing of an AC supply voltage and a second zero crossing of the AC supply voltage; andb. means for initiating a change in condition of a switching relay coupled to the means for measuring wherein, the means for initiating initiates a change in condition of the switching relay an amount of time after a third zero crossing wherein the amount of time after the third zero crossing is equal to the amount of time between the first zero crossing and the second zero crossing less a delay time for changing a condition of the switching relay.