Occupancy sensor with active sensitivity adjustment based on ambient temperature

Patent metadata

Field	Value
Publication number	US-9930753-B2
Application number	US-201615387851-A
Country	US
Kind code	B2
Filing date	Dec 22, 2016
Priority date	Feb 25, 2013
Publication date	Mar 27, 2018
Grant date	Mar 27, 2018

Abstract

A system and method provide fail-safe operation of a lighting system. A lighting level detector is used to obtain a baseline lighting level for a low-intensity light. If the detector measures less than the baseline level when an occupancy sensor determines the space is unoccupied, a high-intensity light is energized and an indication is provided to a user that the low-intensity light has failed. A method provides daylighting operation of a lighting system. An occupancy sensor can have Wi-Fi functionality to enable remote configuration of the sensor. A line voltage occupancy sensor can include an interface with low voltage devices. An occupancy sensor can include an integral interface to enable an external control system to override the sensor's normal logic under emergency conditions. An occupancy sensor can include an active temperature compensation feature. An occupancy sensor can also incorporate an automatically adjustable coverage area.

First claim

What is claimed is:

1. An occupancy sensor, comprising:
a passive infrared (PIR) sensing element to sense a background infrared level of a monitored space, and a heat signature of an occupant or a moving object in the monitored space;
a temperature sensing element to sense an ambient temperature of the monitored space;
memory for storing the background infrared level; and
a processor communicatively coupled to the memory, the PIR sensing element and the temperature sensing element; the processor being programmed to:
determine a difference in temperature between the heat signature of the occupant or the moving object, and the background infrared level so that when the processor determines that the difference in temperature exceeds a sensing threshold, an occupied signal is generated; and
adjust the sensing threshold based on information representative of the ambient temperature in the monitored space;

wherein, when the processor determines that the ambient temperature of the monitored space has changed as compared to a stored value, the processor adjusts the sensing threshold so that a greater or lesser difference in temperature between the heat signature of the occupant or the moving object, and the background infrared level results in the occupied signal being generated.

2. The occupancy sensor of claim 1 , wherein, when the processor determines that the ambient temperature of the monitored space has increased as compared to a stored value, the processor reduces the sensing threshold so that a lesser difference in temperature between the heat signature of the occupant or the moving object, and the background infrared level results in the occupied signal to be generated.

3. The occupancy sensor of claim 1 , wherein the processor actively adjusts the sensing threshold by periodically receiving information representative of the ambient temperature in the monitored space from the temperature sensing element, and, based on the received information, adjust the sensing threshold.

4. The occupancy sensor of claim 1 , wherein the processor includes an algorithm to adjust the sensing threshold.

5. The occupancy sensor of claim 1 , wherein the memory includes a lookup table, the processor utilizing the lookup table to adjust the sensing threshold.

6. The occupancy sensor of claim 1 , wherein the sensing threshold is manually entered via a user input device.

7. The occupancy sensor of claim 1 , wherein the temperature sensing element is one of a thermocouple, a resistance temperature detector (RTD), or a thermistor.

8. An occupancy sensor, comprising:
a digital passive infrared (PIR) sensing element to sense an occupant or a moving object in a monitored space and to sense an ambient temperature of the monitored space; and
a processor communicatively coupled to the PIR sensing element, the processor being programmed to actively adjust a sensing threshold to account for changes in ambient temperatures in the monitored space;
wherein:
the PIR sensing element senses a background infrared level of the monitored space, the background infrared level being stored in memory associated with the processor;
the PIR sensing element senses a heat signature of the occupant or the moving object when in the monitored space;
when the difference in temperature between the heat signature of the occupant or the moving object, and the background infrared level exceeds the sensing threshold, an occupied signal is generated; and
the processor is programmed to actively adjust the sensing threshold by periodically determining the ambient temperature, and, based on the determined ambient temperature, adjust the sensing threshold.

9. The occupancy sensor of claim 8 , wherein, when the processor determines that the ambient temperature of the monitored space has changed as compared to a stored value, the processor adjusts the sensing threshold so that a greater or lesser difference in temperature between the heat signature of the occupant or the moving object, and the background infrared level results in the generation of the occupied signal.

10. The occupancy sensor of claim 8 , wherein, when the processor determines that the ambient temperature of the monitored space has increased as compared to the stored value, the processor reduces the sensing threshold so that a lesser difference in temperature between the heat signature of the occupant or the moving object, and the background infrared level results in the generation of the occupied signal.

11. A method for energizing a load; the method comprising the steps of:
sensing a background infrared level of a monitored space;
sensing an ambient temperature of the monitored space;
periodically sensing a heat signature of the monitored space;
determining whether the heat signature exceeds the background infrared level by a sensing threshold;
transmitting, when the sensing threshold has been met or exceeded, an occupied signal to a load control device, the occupied signal instructing the load control device to energize the load; and
actively adjusting the sensing threshold based on changes in the sensed ambient temperature of the monitored space via periodically determining the ambient temperature in the monitored space has increased or decreased; and, if a determination that the ambient temperature in the monitored space has increased, then decreasing the sensing threshold; and, if a determination that the ambient temperature in the monitored space has decreased, then increasing the sensing threshold.

Assignees

• Leviton Manufacturing Co

Inventors

• Balasubramanian Jaiganesh
• Morton Justin

Classifications

• H05B47/11 Primary

  by determining the brightness or colour temperature of ambient light · CPC title

• H05B47/10

  Controlling the light source · CPC title

• H05B47/19

  via wireless transmission · CPC title

• F21S8/006

  Solar simulators, e.g. for testing photovoltaic panels · CPC title

• H05B47/1965

  using handheld communication devices · CPC title