Patent Publication Number: US-2005128067-A1

Title: Automatic sensitivity adjustment on motion detectors in security system

Description:
BACKGROUND OF THE INVENTION  
      1. Field of Invention  
      The invention relates generally to a motion detector for use in a security system and, more particularly, to a motion detector with an adjustable sensitivity.  
      2. Description of Related Art  
      Motion sensors are commonly used in security system to detect the presence of an intruder in the home or other building. These sensors commonly use passive infrared (PIR) sensors that detect the body heat of the intruder. Active sensors such as microwave sensors are also used, which transmit a microwave signal and observe the reflected signal. A change in the reflected signal indicates the presence of the intruder. Furthermore, so-called “pet immune” motion sensors have been developed which are desensitized to the presence of a pet such as a dog or cat near the floor of the building. For example, a wall-mounted motion sensor may have one detecting element that receives infrared radiation from different lens portions that are arranged to detect heat from different elevations in a room. The lens portions for the lower elevations are less transmissive to the infrared radiation so that the heat from the pet is not sufficient to trip the gain threshold of the sensor.  
      In some cases, the motion sensor can be set to adjust the number of pulse counts that are required to trigger an alarm, such as by manual adjustment of a dual inline pole (DIP) switch. However, the adjustments are normally made manually to components that are within a housing of the sensor. Once the housing is closed and the sensor is installed, no further adjustments can be made. Moreover, a trained technician is needed to make the adjustments. This can cause difficulties if the sensitivity needs to be adjusted at a later time. For example, the setting made by the technician may not be optimal. If the sensitivity is too great, the pet will trigger an alarm, and if the sensitivity is too low, a human intruder may not trigger the alarm. Moreover, variations in sensitivity can occur as the sensor ages, or due to environmental factors such as dust. Furthermore, the homeowner may acquire a larger pet, which requires the sensitivity to be reduced. Additionally, the conventional installation procedure is inconvenient.  
      Accordingly, a solution is need that addresses the above and other issues.  
     BRIEF SUMMARY OF THE INVENTION  
      To overcome these and other deficiencies in the prior art, the present invention provides a motion detector whose sensitivity can be adjusted as needed.  
      In one aspect of the invention, an apparatus for adjusting the sensitivity of a motion detector includes a transmitter, and a control for controlling the transmitter to transmit a signal for adjusting the sensitivity of the motion detector.  
      In another aspect of the invention, a motion detector includes a component for sensing electromagnetic radiation that is indicative of the presence of a living being such as a person or pet, a control responsive to the component for determining, in accordance with the sensed electromagnetic radiation, whether to trigger a signal indicating that the living being has been detected, and a receiver for receiving a remotely-generated signal for adjusting a sensitivity of the component. The control is responsive to the remotely-generated signal for adjusting a sensitivity with which the component senses the electromagnetic radiation.  
      In yet another aspect of the invention, a motion detector includes a component for sensing electromagnetic radiation that is indicative of the presence of a living being, a control responsive to the component for determining, in accordance with the sensed electromagnetic radiation and a decision parameter, whether to trigger a signal indicating that the living being has been detected, and a receiver for receiving a remotely-generated signal for adjusting a sensitivity of the motion detector. The control is responsive to the remotely-generated signal for adjusting the decision parameter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These and other features, benefits and advantages of the present invention will become apparent by reference to the following text and figures, with like reference numbers referring to like structures across the views, wherein:  
       FIG. 1  illustrates an overview of a security system, according to the invention;  
       FIG. 2  illustrates a remote transmitter, according to the invention;  
       FIG. 3  illustrates a pet collar with a remote transmitter, according to the invention;  
       FIG. 4  illustrates a motion sensor with adjustable sensitivity, according to the invention;  
       FIG. 5  illustrates voltage pulses, and a detection threshold, according to the invention;  
       FIG. 6  illustrates a circuit for adjusting a detection threshold, according to the invention; and  
       FIG. 7  illustrates a user interface device for remotely adjusting the sensitivity of a motion sensor, according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Many buildings today, such as homes and places of businesses, are equipped with security systems to deter burglaries and detect fires and other hazards such as carbon monoxide.  FIG. 1  illustrates an overview of a security system  100  according to the invention, which includes a central control panel  110  that communicates with a number of sensors via wired and/or wireless paths. For example, the control panel  110  may receive signals from one or more motion sensors  125  that detect when a person enters a room. Signals received from fire sensors  130 , such as smoke or heat sensors, indicate that a fire has been detected. Signals received from window and door sensors  135  indicate that a window or door has been opened.  
      Signals received from a peripheral user interface device  140 , e.g., including a keypad and display, may arm and disarm the system, as well as trip an alarm via a panic button feature. The user interface device  140  may be the primary interface between the human user and the security system  100 . The user interface device  140  typically includes components that are analogous to the control panel  110 , including a control, memory and power source. Optionally, the user interface device  140  includes a transceiver. The user interface device  140  is commonly provided as a wireless device to allow it to be installed in the home without running wire, such as by affixing it to a wall or placing it on a table, for instance. The control panel  110  generally is a larger component that may be installed in an unobtrusive location in the home, such as a closet or basement. However, it is not necessary for the user interface device  140  to be separate from the control panel  110  as the user interface device  140  may be integrated into the control panel  110 .  
      Various other components may communicate with the control panel  110 , such as a wireless key fob  123  that is used to trip an alarm. The control panel  110  may also transmit signals to components of the security system  100 . For example, signals may be transmitted to a siren  120  to activate the siren when an alarm condition is detected. Signals may be sent to the user interface device  140  to display status information to the user, such as whether the system is armed or disarmed, or whether a specific door or window has been opened. The control panel  110  may also have the ability to notify a monitoring service of an alarm condition via a communication interface  122 , which may be a telephone dialer or interface to a computer network, for instance. The interface  122  may also allow the security system  100  to send and receive data for other purposes. For example, settings in the control panel  110  may be configured or changed remotely over a phone line or computer network connection. These settings include adjustments to the motion sensor&#39;s sensitivity. For example, if a motion sensor has a continuous false alarm tripping problem, the remote monitoring service may lower the sensitivity of the motion sensor from its remote location. An example of remote configuring software is the Ademco Compass software. The interface  122  may receive instructions from a remote device that is configured appropriately for communicating with the control panel  110 . Such a remote device may have a control, memory and transmitter or transceiver. The interface  122  provides the instructions to the control panel  110 , which in turn communicates with the motion sensor  125  to adjust its sensitivity.  
      The components of the security system  100  may communicate via wires routed through walls, ceilings and the like, and/or via wireless signals. One wireless system uses RF signals at 345 MHz to provide a nominal indoor range of 200 feet. The motion sensors  125 , fire sensors  130 , and window and door sensors  135  typically only transmit back to the control panel  110  when they are tripped, while the siren  120  only receives a signal from the control panel  110  when the control panel  110  detects an alarm condition based on a signal received from one of the sensors. However, in accordance with the invention, the motion sensor  125  has a receive capability, described further below, to allow remote adjustment of its sensitivity. The user interface device  140  may have both transmit and receive capabilities to communicate with the control panel  110 . Different manufacturers may use different proprietary schemes for communicating data, such as different coding and modulation techniques may be used. Components provided by Honeywell Corp. may advantageously be used.  
      The control panel  110  includes a transceiver (transmitter and receiver)  112  for transmitting and receiving wired and/or wireless signals. The control  114  may include a microprocessor that executes software, firmware, micro-code or the like to implement logic to control the security system  100 . The control panel  110  may include a non-volatile memory  115  and other additional memory  116  as required. A memory resource used for storing software or other instructions that are executed by the control  114  to achieve the functionality described herein may be considered a program storage device. A dedicated chip such as an ASIC may also be used. Generally, each wireless component of the security system must be “learned” by the control  114 . In the learning process, data is stored in the non-volatile memory  115  that identifies the characteristics of each sensor, including the sensor type, serial number or other identifier, and what type of action to take based on signals received from each sensor. For example, the action may be to provide a status message to the user, store data for subsequent maintenance purposes, or trip an alarm. A power source  118  provides power to the control panel  110  and typically includes a battery backup to AC power.  
      As mentioned above, the motion sensor  125  has a receive capability to allow remote adjustment of its sensitivity. For example, the user interface  140  may transmit a signal to the motion sensor  125  to adjust its sensitivity. This signal can be communicated directly from the user interface device  140  or via the transceiver  112 , via a wired or wireless path. Furthermore, a remote transmitter  200  may transmit an adjustment signal to the motion sensor  125 , either directly or via the transceiver  112 . Also, as mentioned, the communication interface/telephone dialer  122  may receive instructions via a telephone or computer network for adjusting the sensitivity of the motion sensor  125 . The instructions are processed by the control panel  110 , for example, and a signal is sent by the control panel  110  to the motion sensor  125  for adjusting its sensitivity accordingly.  
       FIG. 2  illustrates a remote transmitter according to the invention. The remote transmitter  200  may include a transmitter  210  for transmitting wireless signals for instructing the motion sensor  125  to adjust its sensitivity, a control  220  with memory  225  for controlling the transmitter  210 , and a power source  230  such as a battery for powering the control  220  and the transmitter  210 . The control  220  may include a microprocessor that executes software, firmware, micro-code or the like to implement logic to control the remote transmitter  200 . A memory resource  225  used for storing software or other instructions that are executed by the control  220  to achieve the functionality described herein may be considered a program storage device. A dedicated chip such as an ASIC may also be used.  
       FIG. 3  illustrates a pet collar with a remote transmitter according to the invention. In one possible scenario, the remote transmitter  200  is carried by a pet in the home, such as in a portable housing  310  attached to a loop  305  of a collar  300  ( FIG. 3 ). The housing  310  can be of any design. The housing may open to allow a battery to be replaced, and may have an on-off switch which allows it to be turned off when not in use. The remote transmitter transmits a signal to the motion sensor  125  to lower its sensitivity so that an alarm is not triggered when the pet moves around in a room in which the motion sensor  125  is installed. The signal of the remote transmitter  200  should have a sufficient range and power so it can be received by the motion sensor. Moreover, the remote transmitter  200  should transmit either continuously or frequently enough so that the motion sensor  125  receives the signal before informing the control panel  110  that an intrusion has been detected. For example, if the motion sensor  125  takes three seconds to decide whether an intruder is present, the remote transmitter may transmit every second or so to allow a sufficient safety margin to avoid a false alarm, while also reducing power consumption in the remote transmitter  200 .  
      It is also possible for a remote transceiver to be used in place of the remote transmitter  200 , which receives a challenge signal from the motion sensor  125  when the intruder, e.g., a living being such as a pet or a human, is detected. If the remote transceiver responds back to the motion sensor  125  with an appropriate code, and within a specified time limit, no alarm is triggered. If the motion sensor  125  receives no response, an alarm is triggered.  
       FIG. 4  illustrates a motion sensor with adjustable sensitivity according to the invention. The motion sensor  125  is shown as a passive infrared (PIR) sensor. However, other types of sensors may be used as well, including active sensors and dual mode sensors that include both passive and active components. The example motion sensor  125  receives infrared electromagnetic (EM) radiation via one or more lenses  440  and one or more sensing components  430 , such as an infrared photo detector. The sensing component  430  converts the sensed EM radiation into an electrical signal that is processed by a control  410  with working memory  415 . The control  410  determines whether to send a signal to the control panel  110  via the transceiver  400  to trigger an alarm based on the sensed radiation. The transceiver  400  allows the motion sensor  125  to receive commands for adjusting its sensitivity, e.g., from the remote transmitter  200  or the user interface device  140 .  
      The motion sensor  125  includes a power source  420  such as a battery or a connection to the AC power in a building for powering the control  410  and the transceiver  400 . The control  220  may include a microprocessor that executes software, firmware, micro-code or the like to implement logic to control the motion sensor  125 . The memory resource  415  is a program storage device that may be used for storing software or other instructions that are executed by the control  410  to achieve the functionality described herein. A dedicated chip such as an ASIC may also be used.  
      There are a number of different ways for the motion sensor  125  to adjust its sensitivity in response to a remotely-transmitted signal. One way is by adjusting the pulse count. A sensitive PIR sensor will trigger an alarm on one pulse count. To lower the sensitivity, the control  410  can be configured so that the pulse count is increased, e.g., to require two or more pulses before triggering an alarm. A pulse is generated when an intruder passes through a sensitive zone. Specifically, the optical element, e.g., the sensing component  430 , of a PIR motion sensor typically includes two sensing elements connected in a voltage-bucking configuration to cancel signals caused by vibration, temperature changes and sunlight. One of the sensing elements outputs a positive voltage pulse when a radiation source such as a living being passes in front of it, while the other sensing element outputs a negative voltage pulse when a living being passes in front of it. The sensing elements may be arranged on a horizontal plane so that they are sequentially exposed to the radiation source as the living being moves across a room, for example.  
      The positive and negative sensing elements are projected out of the motion sensor through lenses  440 . Although very small internally, they become larger (as does the gap between them) as one moves a greater distance away from the motion sensor. A pulse count of one requires someone to cross in front of only one of the sensing elements (either positive or negative). A pulse count of two requires someone to cross in front of either a positive or a negative band, then through a dead spot between the bands, and then through the second band. A pulse count of three requires a person to cross in front of either a positive or negative band, then through the dead spot, then through the second band, then through another dead spot, and then through any other band of either polarity.  
      For example,  FIG. 5  illustrates voltage pulses, and a detection threshold, according to the invention. Pulses  510  and  550  are positive voltage pulses corresponding to detection of a human, while pulse  530  is a related negative voltage pulse. Pulses  520  and  560  are positive voltage pulses corresponding to the detection of a pet, while pulse  530  is a related negative voltage pulse. The pulse count thus is a decision parameter that can be updated in the control  410 , e.g., according to a signal received from the remote transmitter  200  or the remote user interface device  140 . The remote adjustment of the pulse count used by the control  410  can be achieved using any type of communication and control algorithm.  
      Another way to lower a motion sensor&#39;s sensitivity is to lower the gain/threshold, which defines the electrical sensitivity. This can be accomplished, e.g., by adjusting the level at which the motion sensor  125  detects a pulse. For example, the control  410  may apply a detection threshold as a detection parameter to a signal from an analog to digital converter input that is being detected. The detection threshold can be adjusted internally within the motion sensor to be higher or lower. For example, the threshold  580  is relatively low since it detects the lower amplitude pulse  520  caused by detection of the pet. The threshold  570  is relatively high since it is higher than the lower amplitude pulse  520  from the pet, but it still results in the detection of the higher amplitude pulse  510  from the human. Thus, by raising the threshold, the sensitivity of the motion detector  125  can be decreased, e.g., so that it does not trigger an alarm when a pet is present. It may also be desirable to lower the sensitivity of the motion detector if it is detecting movement in an area of a home where detection is not desired, such as in an adjacent room or hallway. Similarly, by lowering the threshold, the sensitivity of the motion detector  125  is increased.  
       FIG. 6  illustrates a circuit  600  for adjusting a detection threshold, according to the invention. The circuit may be used for adjusting the pulse detection level as discussed above in connection with  FIG. 5 . For example, the circuit may be an external ladder network with resistors R 1  and R 2  that set the detection level. A transistor  610  may be used to remove or add resistors to change the detection level. Specifically, when the transistor  610  is controlled to pass current, the resistor R 2  will be bypassed. Otherwise, the resistor R 2  is not bypassed. The control  410  may provide a voltage on line  615  that controls the transistor  610  accordingly.  
      One can also adjust the sensitivity of the motion sensor  125  by adjusting the optical gain, e.g., by varying the area of the optical elements. A reduced area results in less sensitivity. Or, a filter can be moved into a position in front of the radiation detection element so it becomes less sensitive. Various techniques for implementing this feature are believed to be within the purview of a person skilled in the art. It may also be possible to adjust the sensitivity of one or more different detection bands of a motion sensor, depending on the configuration of the motion sensor.  
       FIG. 7  illustrates a user interface device for remotely adjusting the sensitivity of a motion sensor, according to the invention. As mentioned, the user interface device  140  can be provided, e.g., as a peripheral to, or a part of, the main control panel  110 . The exact arrangement of components is transparent to the user. Thus, the functionality that is described herein as being provided by a user interface device may be provided wholly locally to the device  140 , or partially remotely, such as at the associated control panel  110 . The user interface device  140  may include a user input component such as a keypad  720  and/or microphone  740  for speech recognition in a voice-activated system, and a user output component such as a display  710  and/or speaker  730 . The display  710  may be a multi-line, multi-character LCD display, for instance. The display  710  can provide a graphic device such as a cursor or other highlight to allow the user to select a particular motion sensor or a room in a house or other building where one or more motion sensors are installed, using a “select” key to obtain additional information or options. In the example shown, the display  710  indicates that a first motion sensor has a sensitivity level of 5, e.g., on a scale of one through ten, and that a second motion sensor is configured in a “pet immune on” mode, which means the sensitivity of the motion sensor  125  is reduced to avoid triggering an alarm when a pet is present.  
      Advantageously, the user interface device  140  may be of the type that is used for controlling a home security system so no re-design, e.g., to provide additional keys on the keypad  420  is necessary. In particular, functions can be assigned to existing keys to accommodate the functionality of the present invention. Each key can have more than one function as well by employing double function or soft keys. In one possible example, the “off” key has the additional function of “escape”, the “away” key has the additional function of “status”, the “stay” key has the additional function of “adjust”, and the “aux” or auxiliary key has the additional function of “select”. Each of the additional functions can be accessed by pressing a “shift” or “function” key or the like, or by simply entering a specific mode. Optionally, dedicated keys can be provided for adjusting and monitoring the sensitivity level of the motion sensors.  
      Control logic associated with the user interface device  140  allows it to control both the conventional home or other building security system components, while also communicating with the motion sensor  125  of the invention to send commands to the motion sensor, such as to change the sensitivity, and receive status information from the motion sensor, such as the current sensitivity setting. Any appropriate menu display scheme and logic may be used. In one possible scenario, a technician or other user remotely adjusts the sensitivity of the motion sensor to an optimal level while carrying the portable user interface device  140  around a room. This makes the installation procedure much more convenient. If the user interface device  140  is not portable, a second person may be used to walk in front of the motion sensor while the first person adjusts the sensitivity to the optimal level. The user interface device  140  may also be used to set a schedule for varying the sensitivity of one or more motion sensors. For example, for homeowners who keep their pets outside the home during the daytime, and in the home at night, the sensitivity may automatically adjust so that it is less sensitive, or pet immune, at night.  
      The invention has been described herein with reference to particular exemplary embodiments. Certain alterations and modifications may be apparent to those skilled in the art, without departing from the scope of the invention. The exemplary embodiments are meant to be illustrative, not limiting of the scope of the invention, which is defined by the appended claims.