Patent Publication Number: US-6215398-B1

Title: Occupancy sensors for long-range sensing within a narrow field of view

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This claims the benefit of United States Provisional Application Ser. No. 60/068,012, filed Dec. 18, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to occupancy sensors. More particularly, this invention relates to occupancy sensors that provide long-range occupancy sensing within a narrow field of view. 
     Occupancy sensors typically sense the presence of one or more persons within a designated area and generate occupancy signals indicative of that presence. These signals activate or deactivate one or more electrical appliances, such as, for example, a lighting unit or a heating, ventilating, and air conditioning system. Occupancy sensors help reduce maintenance and electrical energy costs by indicating when these appliances can be turned off. 
     Conventional occupancy sensors sense occupancy by projecting a detecting beam, (active sensing) or defining a detection zone (passive sensing), through a curved lens that provides the sensor with a wide field of view. This field of view typically ranges from about 160° for wall-mounted sensors to about 360° for ceiling-mounting sensors. Occupancy os sensed, for example, when the the heat differential between the background heat of the designated area and that of a person entering the area is sensed. 
     Such conventional occupancy sensors, however, are typically inefficient when used in environments requiring long-range, narrow field of view sensing, such as in warehouse environments. Warehouse environments typically have long aisles between high storage areas. Accordingly, much of the energy used to generate detecting beams or define detection zones in wide fields of view is wasted, rendering conventional sensors inefficient. Moreover, the curved lenses used to provide the wide fields of view limit the sensing range of conventional sensors. Thus, each aisle may typically require several conventional occupancy sensors to provide adequate coverage. This alone may render conventional occupancy sensors impractical in large warehouse environments having hundreds of thousands of square feet. 
     Furthermore, warehouse environments typically have high ceilings (e.g., 30 feet). To provide the proper angles for optimum sensing performance, occupancy sensors should preferably be mounted on walls near the top. Scissor lifts are usually required to install occupancy sensors at that height. The occupancy sensors are thus not easily accessible. Adjustments and final alignments can therefore be very difficult and time consuming. For example, it is often difficult to determine if a conventional sensor is positioned properly for sensing occupancy down a long aisle. The light emitting diode commonly used in conventional sensors to signal occupancy cannot normally be seen when attempting to locate the long-range sensing limit of the sensor. 
     Warehouse environments frequently contain dust and other airborne particles that can adversely affect the operation of conventional occupancy sensors, which generally are not adequately protected from such conditions. The large curved lens areas of conventional sensors require regular periodic cleaning, and the sensor electronics often become contaminated requiring cleaning or replacement. Conventional occupancy sensors are thus subject to increased maintenance, which is made more difficult because of their high mount location. 
     Also, warehouse environments commonly use high intensity discharge (HID) lighting. This type of lighting typically operates at two settings: high intensity and low intensity. When power is first applied, HID lamps usually require a warm-up period at high intensity of about 15 to 20 minutes. Thus, these lamps are not regularly turned off. When used with occupancy sensors, an HID lamp operates at high intensity when a signal indicating occupancy is received and at low intensity when a signal indicating non-occupancy is received. Furthermore, when HID lamps are first installed, they require operation at high intensity for about 100 hours or more (i.e., a burn-in period) in order to reach their true color rendition. Conventional occupancy sensors are not well-suited for HID lighting. 
     Conventional occupancy sensors typically do not automatically operate in occupancy mode (i.e., the sensor outputs a signal indicating occupancy) for a fixed period of time when the sensor first powers-up. Some occupancy sensors do however have a manual override switch that sets the sensor in occupancy mode. Thus, to operate HID lamps at high intensity for the warm-up period when first powered-up, conventional occupancy sensors have to be manually set in occupancy mode for the warm-up period, and then manually reset to normal operation. In a warehouse environment with hundreds or thousands of HID lamps, such a manual effort is impractical at best and prohibitively time consuming and costly at worst. 
     Similarly, to provide a burn-in period for newly installed HID lamps, conventional occupancy sensors should also be manually set to occupancy mode, and then manually reset to normal operation after the burn-in period. Again, such a manual effort is impractical at best and prohibitively time consuming and costly at worst. 
     In view of the foregoing, it would be desirable to provide an occupancy sensor that provides more efficient long-range occupancy sensing within a narrow field of view. 
     It would also be desirable to provide an occupancy sensor that can be easily adjusted and aligned to sense occupancy within a designated area. 
     It would further be desirable to provide an occupancy sensor that can be set in occupancy mode for a predetermined time period, after which the sensor automatically returns to normal operation. 
     It would still further be desirable to provide an occupancy sensor that upon power-up automatically operates in occupancy mode for a predetermined warm-up period, after which the sensor automatically returns to normal operation. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide an occupancy sensor that provides more efficient long-range occupancy sensing within a narrow field of view. 
     It is also an object of this invention to provide an occupancy sensor that can be easily adjusted and aligned to sense occupancy within a designated area. 
     It is a further object of this invention to provide an occupancy sensor that can be set in occupancy mode for a predetermined time period, after which the sensor automatically returns to normal operation. 
     It is still a further object of this invention to provide an occupancy sensor that upon power-up automatically operates in occupancy mode for a predetermined warm-up period, after which the sensor automatically returns to normal operation. 
     In accordance with this invention, an occupancy sensor for more efficient long-range sensing within a narrow field of view is provided. The occupancy sensor includes sensor circuitry operable to sense occupancy and generate occupancy signals, a voltage input terminal coupled to the sensor circuitry for receiving an input voltage, and an output terminal coupled to the sensor circuitry for outputting occupancy signals. The output terminal preferably includes a relay contact. The sensor circuitry includes a sensing circuit that generates a detecting beam. Alternatively, the sensing circuit passively defines a detection zone (accordingly, “detecting beam” alternatively means “detection zone”). The occupancy sensor also includes a rigid housing disposed about the sensor circuitry, the rigid housing having an opening over the sensing circuit. A flat lens is mounted on the rigid housing over the opening. The sensing circuit is positioned such that the detecting beam is substantially perpendicular to the flat lens. The occupancy sensor provides long-range sensing up to preferably about 100 feet within a field of view ranging from preferably about 15° to preferably about 25°. 
     The flat lens is preferably a Fresnel lens, and preferably has a plurality of lens segments that enable the flat lens to provide the occupancy sensor with long, intermediate, and short range occupancy sensing. 
     To facilitate positioning of the sensor, the occupancy sensor preferably includes a plurality of indicators that indicate when occupancy is sensed. One indicator preferably indicates when long-range occupancy is sensed, and another preferably indicates when short range occupancy is sensed. The indicators preferably include light emitting diodes (LEDs) that illuminate and are visible through the flat lens when occupancy is sensed. One LED appears to illuminate more brightly than the other LEDs when viewed from within a long-range field of view, and another LED appears to illuminate more brightly than the other LEDs when viewed from within a short-range field of view. 
     The sensor circuitry preferably includes an override timer circuit that when activated causes the sensor circuitry to output an occupancy signal indicating occupancy for a predetermined time period. The predetermined time period is adjustable. For example, the predetermined time period can be set to about 100 hours. The occupancy sensor automatically returns to normal operation substantially upon elapse of the predetermined time period. 
     The sensor circuitry also preferably includes a warm-up timer circuit that causes the sensor circuitry to output an occupancy signal indicating occupancy for a predetermined warm-up period when power is initially applied to the occupancy sensor. The predetermined warm-up period is adjustable. The occupancy sensor automatically returns to normal operation substantially upon elapse of the predetermined warm-up period. 
     The rigid housing of the occupancy sensor preferably includes an access door that permits access to adjustment controls when open and protects the controls and sensor circuitry from airborne particles when closed. The access door remains attached to the rigid housing when the door is open to prevent loss of the door while sensor adjustments are being made. 
     The present invention also includes an occupancy sensor system. The occupancy sensor system includes an occupancy sensor having a flat lens, and mounting hardware attached to the sensor. The mounting hardware permits the sensor to be positioned after the hardware is mounted to a structure, such as a wall or ceiling, such that the sensing range and field of view of the sensor can be aligned in accordance with a designated area. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and advantages of the invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
     FIG. 1 is an perspective view of an exemplary embodiment of an occupancy sensor according to the present invention; 
     FIG. 2 is a cross-sectional view of the occupancy sensor of FIG. 1 according to the present invention, taken from line  2 — 2  of FIG. 1; 
     FIG. 3 is a plan view of the field of view of the occupancy sensor of FIG. 1 according to the present invention; 
     FIG. 4 is a front elevational view of an exemplary embodiment of the flat lens of the occupancy sensor of FIG. 1 according to the present invention; 
     FIG. 5 is a side elevational view of the sensing ranges provided by the flat lens of FIG. 4 according to the present invention; 
     FIG. 6 is a front elevational view of the occupancy sensor of FIG. 1 indicating the positions of LED indicators according to the present invention; 
     FIG. 7 is a cross-sectional view of the occupancy sensor of FIG. 6 indicating the positions of LED indicators according to the present invention, taken from line  7 — 7  of FIG.  6 . 
     FIG. 8 is a front elevational view of an exemplary embodiment of an access door of the occupancy sensor of FIG. 1 according to the present invention; 
     FIG. 9 is a circuit diagram of an exemplary embodiment of the sensor circuitry of the occupancy sensor of FIG. 1 according to the present invention; 
     FIG. 10 is a circuit diagram of an exemplary embodiment of the override timer circuit of the sensor circuitry of FIG. 9 according to the present invention; and 
     FIG. 11 is a side elevational view of an occupancy sensor system according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides occupancy sensors that more efficiently sense long-range occupancy within a narrow field of view. The present invention is well-suited for environments with long aisles, high ceilings, and high intensity discharge lighting. 
     FIGS. 1 and 2 show an exemplary embodiment of occupancy sensor  100  constructed in accordance with the present invention. Occupancy sensor  100  includes a rigid housing  102 , which is preferably fabricated in plastic, disposed about circuit board  104 . Circuit board  104  has sensor circuitry  106  mounted thereon. Sensor circuitry  106  includes sensing circuit  108  that generates a detecting beam, which is preferably an infrared detecting beam. Alternatively, sensing circuit  108  can be passive, as described below with respect to the embodiment shown in FIG.  9 . Accordingly, phrases such as “generating a detecting beam” are alternatively understood to mean “defining a detection zone.” Similarly, phrases such as “detecting beam” are alternatively understood to mean “detection zone.” Rigid housing  102  has an open area  110  above sensing circuit  108 . Mounted on rigid housing  102  over open area  110  is flat lens  112 . Flat lens  112  is preferably a Fresnel lens. 
     Flat lens  112  provides more efficient longer range sensing within a narrower field of view than conventional curved lenses. Flat lens  112  causes the parallel rays of the detecting beam generated from sensing circuit  108  to diverge less than if they had been passed through a conventional curved lens. This results in less beam distortion, increasing the sensitivity and range of occupancy sensor  100 . Thus, flat lens  112  enables occupancy sensor  100  to provide more efficient sensing by focusing the detecting beam into a narrower longer range beam. To provide the longest range, sensing circuit  108  is preferably positioned such that the detecting beam is substantially flat lens  112 . Furthermore, because the resulting detecting beam is narrow the area of flat lens  112  can be substantially less than that of a curved lens. This advantageously reduces the cost of occupancy sensor  100 . 
     Occupancy sensor  100  optionally includes manual override switches  114  and  116 . When actuated, switch  114  sets sensor  100  in occupancy mode (i.e., sensor  100  outputs a signal indicating occupancy), and switch  116  sets sensor  100  in stand-by mode (i.e., sensor  100  outputs a signal indicating non-occupancy). If both switches are actuated, sensor  100  is preferably set in stand-by mode. 
     Occupancy sensor  100  preferably includes manual override timer switch  115  that when activated sets sensor  100  in occupancy mode for a predetermined time period. Substantially upon elapse of the predetermined time period, sensor  100  automatically returns to normal operation. 
     Occupancy sensor  100  also preferably includes access door  118 . Access door  118  provides access to adjustment controls (described below with respect to FIGS. 8 and 9) and protects the controls and sensor circuitry  106  from dust and other airborne particles. 
     FIG. 3 shows detecting beam  302  of occupancy sensor  100 . Occupancy sensor  100  is mounted preferably high on wall  303 . Detecting beam  302  is directed down aisle  304  between storage areas  306  and  308 . Detecting beam  302  has a maximum range  310  of preferably about 100 feet and a field of view  312  that can range from preferably about 15° to preferably about 25°. Alternatively, ranges less than maximum range  310  can be provided by sensor  100  by positioning sensor  100  such that detecting beam  302  is directed at a point down aisle  304  between sensor  100  and maximum range  310 . 
     FIG. 4 shows an exemplary embodiment of flat lens  112  constructed in accordance with the present invention. Flat lens  112  includes lens segments  402 ,  404 ,  406 , and  408 . Lens segment  402  provides occupancy sensor  100  with long-range sensing. Lens segments  404  and  406  provide sensor  100  with two intermediate ranges of sensing, and lens segment  408  provides sensor  100  with short-range sensing. The four ranges of occupancy sensing provided by lens segments  402 ,  404 ,  406 , and  408  are within field of view  312 . Alternatively, other numbers of lens segments and lens segment geometries and configurations can be provided, as is known in the art. 
     FIG. 5 shows the projection of detecting beams  502 ,  504 ,  506 , and  508  resulting respectively from lens segments  402 ,  404 ,  406 , and  408  of flat lens  112  of FIG.  4 . 
     To facilitate the positioning of occupancy sensor  100 , sensor circuitry  106  includes light emitting diodes (LEDs)  602  and  604 , as shown in FIGS. 6 and 7. LEDs  602  and  604  illuminate when occupancy is sensed. LED  602  is preferably positioned on circuit board  104  such that it is centered under lens segment  404  at its upper border with lens segment  402 . Most of the light rays of LED  602  parallel long-range detecting beam  502  of lens segment  402 . LED  602  therefore appears to illuminate more brightly than LED  604  when viewed from within the long-range field of view. Thus by viewing from the area designated for occupancy sensing when LED  602  appears to illuminate more brightly than LED  604 , the location of the lower limit of the long-range field of view can be determined. By viewing from the designated area when LED  602  first illuminates, the location of the upper limit of the long-range field of view can be determined. Positional adjustments of sensor  100  can then be made accordingly. 
     LED  604  is preferably positioned on circuit board  104  such that it is centered under lens segment  406  at its lower border with lens segment  408 . Most of the light rays of LED  604  parallel short-range detecting beam  508  of lens segment  408 . LED  604  therefore appears to illuminate more brightly than LED  602  when viewed from within the short-range field of view. Thus, by viewing from the designated area when LED  604  appears to illuminate more brightly than LED  602 , the location of the upper limit of the short-range field of view can be determined. By viewing from the designated area when LED  604  first illuminates, the location of the lower limit of the short-range field of view can be determined. Positional adjustments of sensor  100  can then be made accordingly. 
     When occupancy sensor  100  is viewed from within the fields of view of intermediate-range detecting beams  504  and  506 , neither LED  602  nor LED  604  appears to illuminate more brightly than the other. 
     Alternatively, other types of indicators can be used with occupancy sensor  100  to indicate when occupancy is sensed within the various sensing ranges of field of view  312 . For example, sound transmitting devices that transmit different sound signals to a receiver can be used to indicate the upper and lower limits of the various ranges. 
     FIG. 8 shows an exemplary embodiment of access door  118  constructed in accordance with the present invention. Access door  118  is preferably a sliding door that slides in the directions of arrow  802 . Access door  118  permits access to adjustment controls  804  and  806  when open (as shown in FIG. 8) and protects adjustment controls  804  and  806  and sensor circuitry  106  from airborne particles when closed. Access door  118  preferably remains attached to rigid housing  102  preferably with tabs  808  and  810 . Tabs  808  and  810  slide along the inside edges of rigid housing  102  in preferably integrally molded tracks that stop tabs  808  and  810  when access door  118  is fully open. This prevents the loss of access door  118  when sensor adjustments are being made, particularly when occupancy sensor  100  is located high on a wall or on a ceiling where retrieval of an accidentally dropped access door is unlikely. Alternatively, other known techniques can be used to retain sliding door  118  to rigid housing  102 . Moreover, access door  118  alternatively can be other types of doors, such as, for example, a hinged door that preferably remains in an open position while adjustments are being made. 
     FIG. 9 shows an exemplary embodiment of sensor circuitry  106  constructed in accordance with the present invention. Sensor circuitry  106  includes sensing circuit  108 , which is preferably a passive infrared detecting circuit that preferably includes piezoelectric chip  902 . Detected changes in temperature are focused by flat lens  112  on chip  902 , which generates a small voltage in response. The small voltage is then processed through sensor circuitry  106  to generate an occupancy signal indicating occupancy. 
     Sensor circuitry  106  also includes input voltage terminal  906  for coupling to an input voltage, ground terminal  908  for coupling to ground or neutral, and output terminal  904  for providing occupancy signals to one or more electrical appliances, such as, for example, high intensity discharge (HID) lighting. Output terminal  904  is preferably a relay contact whose output signal is determined by the position of switch  910  (e.g., open position indicates non occupancy, while closed position indicates occupancy). The position of switch  910  is controlled by relay coil  926 , which responds accordingly when sensor circuitry  106  goes from stand-by mode to occupancy mode and vice versa. Optionally, sensor circuitry  106  includes auxiliary output relay contacts  966 . 
     Voltage regulation circuit  911  provides two internal voltages. The first internal voltage is preferably about 6.8 volts set by Zener diode  912  at node  913 , and the second internal voltage is preferably about 30 volts set by Zener diode  928  at node  927 . 
     Sensor circuitry  106  further includes NPN Darlington pairs  930 ,  932 ,  940 ,  942 ,  944 , and  954 ; NPN transistors  914 ,  922 ,  924 ,  934 ,  946 ,  948 ,  950 ,  958 , and  960 ; PNP transistors  916 ,  918 ,  920 ,  962 , and  964 ; manually actuated switches  114 ,  115 , and  116 ; and LEDs  602  and  604 . All capacitors are preferably in the microfarad range. 
     Sensor circuitry  106  includes delay timer circuit  937 , which includes capacitor  936  and potentiometer  938 . When occupancy is sensed, capacitor  936  charges up. When occupancy is no longer sensed, sensor circuitry  106  continues to output a signal indicating occupancy until capacitor  936  discharges through resistor  939  and potentiometer  938 . This delay time prevents lighting or other electrical appliances from abruptly turning off when a person momentarily leaves the sensor&#39;s field of view. The time delay can preferably be adjusted from about 15 seconds to about 30 minutes by varying potentiometer  938  via adjustment control  804 . 
     Sensor circuitry  106  preferably includes warm-up timer circuit  955 , which sets occupancy sensor  100  in occupancy mode for a predetermined warm-up period when power is first applied to sensor  100 . Sensor  100  is thus well-suited for HID lighting, provided that both are coupled to the same input voltage source, because HID lamps require a warm-up period at high intensity when first powered-up. 
     Warm-up timer circuit  955  includes capacitor  952  and potentiometer  956 . When input voltage is first applied to sensor circuitry  106 , node  913  quickly rises to about 6.8 volts DC. Capacitor  952 , which is initially discharged, first acts like a short circuit, permitting Darlington pair  954  to turn ON. This provides an activating signal (i.e., a logical “1” signal) at node  957 , which causes sensor  100  to output a signal indicating occupancy regardless of whether occupancy is actually sensed. Until capacitor  952  charges up, sensor circuitry  106  continues to output a signal indicating occupancy. Once capacitor  952  is charged up, it acts like an open circuit, causing voltage at node  953  to go low, turning OFF Darlington pair  954 . This returns sensor circuitry  106  to normal operation. When sensor  100  powers-down, capacitor  952  discharges through NPN transistor  914 . 
     The warm-up period is thus substantially the charge-up time of capacitor  952 , which is determined by the values of capacitor  952  and potentiometer  956 . Accordingly, the warm-up time can be adjusted by varying potentiometer  956  via adjustment control  806 , and preferably ranges from about 15 to 30 minutes. 
     Sensor circuitry  106  preferably also includes override timer circuit  1000 . Override timer circuit  1000  sets occupancy sensor  100  in occupancy mode for a predetermined time period when activated by switch  115 . The predetermined time period can be adjusted up to several hundred hours. Occupancy sensor  100  is again well-suited for HID lighting, because HID lamps require a burn-in period of about 100 to 200 hours at high intensity when first installed. 
     Override timer circuit  1000  is coupled to node  913  to receive input voltage. The output of override timer circuit  1000  is coupled to node  957 . When activated by switch  115 , override timer circuit  1000  outputs a logical “1” signal causing sensor  100  to output a signal indicating occupancy regardless of whether occupancy is actually sensed. Override timer  1000  can be other known circuits that when activated output a logical “1” signal for an adjustable time period of up to several hundred hours. 
     FIG. 10 shows an exemplary embodiment of override timer circuit  1000  constructed in accordance with the present invention. Override timer circuit  1000  includes timer chip  1002 , which can be an MC14536 programmable timer chip, manufactured by Motorola, Inc, of Austin, Tex. Pin connections for timer chip  1002  are as shown in FIG.  10 . Override timer circuit  1000  also includes resistors  1004  and  1008 , capacitor  1006 , diode  1012 , and potentiometer  1010 . Potentiometer  1010  is preset such that the resultant oscillator frequency preferably is about 23.3 Hz. At that frequency, timer chip  1002  outputs a logical “1” signal for about 100 hours, after which the output signal goes low, returning occupancy sensor  100  to normal operation. 
     FIG. 11 shows an exemplary embodiment of occupancy sensor system  1100  constructed in accordance with the present invention. System  1100  includes occupancy sensor  100  mounted to electrical enclosure  1102  with mounting screws  1104  through threaded holes  1105 . Electrical enclosure  1102  fastens to electrical connector  1106  with mounting screws  1108  and threaded holes  1109 . Note that any other suitable manner of fastening sensor  100  to enclosure  1102  and of fastening enclosure  1102  to connector  1106  can be used. Further note that enclosure  1102  and connector  1106  can be integrally constructed (e.g., stamped or welded) to form a single unit. 
     The assembly of sensor  100 , enclosure  1102 , and connector  1106  (i.e., occupancy sensor system  1100 ) can be mounted with mounting screws  1112  to structure  1110 , which may be a wall, ceiling, support beam, or any other structure capable of supporting system  1100 . Note that system  1100  can be mounted in any other suitable manner. 
     Electrical connector  1106  is preferably hollow to permit electrical wiring (not shown) to pass through from structure  1110  to electrical enclosure  1102 . Electrical connections to sensor  100  can accordingly be made in enclosure  1102 . Preferably, connector  1106  includes rotatable portion  1114  that rotates about fixed portion  1116 . This permits occupancy sensor  100  to be angled horizontally and vertically with respect to structure  1110 , thus permitting final sensing alignments of sensor  100  to be made. 
     Alternatively, occupancy sensor system  1100  can include occupancy sensor  100  fastened to any known swivel type bracket or other similar mounting hardware that permits sensor  100  to be angled horizontally and vertically with respect to structure  1110 . 
     Thus it is seen that occupancy sensors providing long-range occupancy sensing within a narrow field of view are provided. One skilled in the art will appreciate that the present invention can be practiced by other than the described embodiments, which are presented for purposes of illustration and not of limitation, and the present invention is limited only by the claims which follow.