Abstract:
An energy efficient, easily manufacturable, multi-sensor detector incorporates a smoke sensor and a thermal sensor. A single die programmed processor with integrally formed storage circuits for programs and parameters senses sensor signals, from different types of sensors, during a common activation cycle and processes those signals during the same cycle. The processor can also monitor the condition of an energy supplying battery and provide modulation signals to an audible output device. Other detector functions can be interleaved between output device modulation signals to minimize the cost of the programmed processor and thereby provide the required functionality very cost effectively.

Description:
[0001]    This application claims the benefit of the earlier filed Provisional Application Ser. No. 60/196,685, filed Apr. 12, 2000. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The invention pertains to wireless detectors usable in alarm systems. More particularly, the invention pertains to such detectors which incorporate single die, multi-function, programmed processors configured for energy efficient battery powered operation.  
         BACKGROUND OF THE INVENTION  
         [0003]    Wireless ambient condition detectors are known. Such detectors, most conveniently, have been battery powered so that they may easily be mounted in a variety of locations without any need for power or communications cables. Known wireless detectors, while effective, have used energy at a rate which did not provide as long a battery life as desirable.  
           [0004]    Known detectors have used separate integrated circuits to interface with different types of sensors such as smoke sensors and heat sensors. Signal processing has in turn required other circuits.  
           [0005]    One type of circuit which has been used in detectors which incorporate smoke sensors have been application specific integrated circuits (ASIC). ASIC can be very inexpensive and cost effective in high volume, long run products. They are, however, expensive to develop, have long production lead times, and provide little or no flexibility. In addition, conventional ASIC contribute to higher than desirable power requirements.  
           [0006]    Known detectors have used a different ASIC for communications and low battery detection. Since the ASIC coupled to the respective smoke sensor and the communications ASIC operate autonomously, they create irregular and unpredictable current draw profiles. In known detectors, this irregular and unpredictable current draw profile impedes accurate battery voltage measurements. As a result of these unpredictable current draws, low battery trouble, voltage thresholds have had to be set higher than desirable. This also contributes to shorter battery life.  
           [0007]    Other known prior art detectors use an ASIC to couple electrical energy from the battery to an audible alarm indicating device in the detector. This produces a need for yet another, separate, circuit which must be interconnected with the rest of the circuitry of the detector and which contributes to further current draw.  
           [0008]    Additionally, sensitivity compensation, to take into account dust and aging of a sensing chamber, has in some known systems been carried out at a system control panel. Smaller, less expensive control panels may not have the processing capability to implement this function.  
           [0009]    One known type of detector based compensation provides a maximum incremental change which can take place in the detector during each compensation cycle. While this process does provide compensation over a period of time, the greater the extent of the required compensation, the longer is the time interval that is required to achieve a desired sensitivity.  
           [0010]    Some known detectors which incorporate heat sensors have recognized that heat sensors can be susceptible to nuisance conditions such as electrical noise from static electricity, power surges, radio-frequency interference, as well as thermal noise both from turning the sensor on and off as well as thermal variations from the ambient environment. It has been known to use reference heat sensors to compensate for temperature changes. Such reference heat sensors not only add additional cost to the respective detector but are limited in the thermal noise which can be rejected.  
           [0011]    It would be desirable therefore to provide highly energy efficient, multiple sensor detectors which require fewer integrated circuits. Preferably, such detectors could be implemented in a way so as to provide on-going flexibility to designers as product needs evolve, while at the same time extending battery life and providing enhanced rejection of nuisance signals.  
         SUMMARY OF THE INVENTION  
         [0012]    A wireless detector incorporates a single chip, or die, integrated control element. The element includes an integrally formed processor, read-write, reprogrammable read only memory or one time programmable read only memory. Different memory types can be formed on the same die. The same chip can include programmable timers, and I/O ports for both analog and digital inputs or outputs.  
           [0013]    In one aspect, the detector includes a photoelectric smoke sensor and at least one heat sensor. Executable instructions implement a common sensing cycle for both types of sensors. Two heat sensors can be incorporated into a disclosed embodiment.  
           [0014]    In another aspect, a battery used to power the detector provides an output voltage in a predetermined monitorable range which will support successful operation. A voltage multiplier circuit, coupled to the battery, provides a higher voltage to drive an audible output device in accordance with processor supplied modulation.  
           [0015]    In yet another aspect, the detector conserves energy, and extends battery life, by performing sensor sampling and signal processing functions for that sample interval during a single active interval. Then, the circuitry enters a low power, inactive state until the next activate interrupt arrives.  
           [0016]    A disclosed embodiment combines different types of sensors, some of which have longer stabilization intervals then others. Different types of sensors can be activated simultaneously. Those with relatively short stabilization intervals can be sampled and the respective signal, or signals, processed, at least in part, during longer stabilization and processing intervals for other types of sensors. This overlap contributes to minimal over-all energy usage during each active interval. 
       
    
    
       [0017]    Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is a system in accordance with the present invention;  
         [0019]    [0019]FIG. 2 is a block diagram of an electrical unit usable in the system of FIG. 1;  
         [0020]    [0020]FIG. 3 is a timing diagram illustrating various aspects of the operation of the unit of FIG. 2;  
         [0021]    [0021]FIG. 4 is a timing diagram illustrating other aspects of the operation of the unit of FIG. 2;  
         [0022]    [0022]FIG. 5 is a block diagram illustrating a method of processing signals from a smoke sensor carried by the unit of FIG. 2; and  
         [0023]    [0023]FIG. 6 is a flow diagram illustrating processing of signals associated with one or more heat sensors carried by the electrical unit of FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    While this invention is susceptible of embodiment in many different forms, there are shown in the drawing and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated.  
         [0025]    [0025]FIG. 1 illustrates a monitoring system  10  in accordance with the present invention. The system  10  incorporates a system control element  12  which could incorporate one or more programmed processors and pre-stored executable instructions. It will be understood that the exact details of the control element  12  are not a limitation of the present invention.  
         [0026]    The control element  12  is coupled to a wireless antenna  12   a  wherein the system  10  has been implemented using RF-type wireless transmissions. Other forms of wireless transmission come within the spirit and scope of the present invention.  
         [0027]    The members of a plurality of electrical units  16  are wirelessly coupled to control element  12 . The members of the plurality  16 , for example electrical unit  16   i , could be implemented as battery powered units having one or more ambient condition sensors for purposes of monitoring a region. The sensors could be responsive to smoke, gas, position, flow, intrusion, movement or the like all without limitation of the present invention. The electrical units  16  via respective antennas, such as antenna  16   i - 1  communicate status information and information pertaining to the condition being monitored to the control element  12 . Various levels of processing of the signals from the respective sensor or sensors at the unit  16   i  can be carried out locally and the results thereof transmitted via antennae  16   i - 1  and  12   a  to control element  12 .  
         [0028]    It will also be understood that system  10  can incorporate one or more wired communication links, representatively illustrated as link  18 , coupled to control element  12 . Members of a plurality of electrical units  20  can be coupled to link  18  for communication with control element  12 . Those of skill in the art will understand that the members of the plurality  20  could incorporate detectors of ambient conditions as well as output or control devices all without limitation of the present invention.  
         [0029]    [0029]FIG. 2 illustrates more details of a representative member  16   i  of the plurality  16 . The electrical unit  16   i  is carried in a housing  16   i - 2 . The housing  16   i - 2  can be mounted to a selected surface.  
         [0030]    The unit  16   i  includes a single die, programmed, control element  30 . The element  30  includes a processor  30   a , read/write memory  30   b , and non-volatile memory  30   c . The read/write memory  30   b  can be implemented using a variety of random access or quasi random access technologies as would be understood by those of skill in the art within the spirit and scope of the present invention.  
         [0031]    The non-volatile memory  30   c  can be implemented with a variety of non-volatile technologies including OPT, flash memory, EEPROM or PROM storage circuitry or combinations thereof. It will be understood that executable instructions and calibration parameters can be stored in one or more types of non-volatile memory all on the same die. By use of EEPROM or other types of reprogrammable storage, parameters and/or executable instructions can be up-dated wirelessly from time to time as a result of commands and files received from the control element  12 . In addition, when the unit  16   i  is being manufactured, executable instructions can be written therein, executed and/or modified without having to be delayed by expensive revisions to mask sets.  
         [0032]    The control element  30  includes, integrated on the same die, interrupt and I/O ports  30   d . Circuitry  30   a ,  30   b ,  30   c  and  30   d  are all interconnected on the single die resulting in a single chip element which also promotes manufacturability.  
         [0033]    Storing the executable instructions and calibration parameters in the same type of non-volatile memory, or in different types of non-volatile memory, but all on the same die, eliminates any need for separate integrated circuitry and associated interfaces, interconnections and the like. As will be understood by those of skill in the art, and discussed in more detail subsequently, sensor control and processing as well as other local functions and communications with control element  12  are implemented, in part, via the executable constructions in the non-volatile memory  30   c  in combination with local hardware.  
         [0034]    The unit  16   i  also includes a wireless interface  34  coupled to the I/O ports  30   d  and antenna  16   i - 1 . As those of skill in the art will understand, a variety of wireless interfaces can be used in the unit  16   i  without departing from the spirit and scope of the present invention so long as the interfaces enable the respective units, such as the unit  16   i  to communicate with the control element  12  wirelessly. Preferably, communication will be bidirectional although unidirectional communication from the respective electrical units  16  comes within the spirit and scope of the present invention.  
         [0035]    The illustrated electrical unit  16   i  also includes a smoke chamber  36   a . Chamber  36   a  is configured to permit an inflow and outflow of smoke carrying ambient atmosphere in the vicinity of the unit  16   i . Mounted within or adjacent to the chamber  36   a  are a radiant energy source  36   b , and, a radiant energy receiver  36   c . The radiator  36   b , which could be a laser diode or a light emitting diode, and the receiver  36   c  which could be a photo diode or a photo transistor. They are configured, in chamber  36   a , to provide a smoke sensing function, commonly referred to as a photo electric smoke sensor, as would be understood by those of skill in the art.  
         [0036]    Drive circuits  38   a  coupled to I/O port  30   d  and emitter  36   b  provide electrical energy to emitter  36   b  under control of instructions being executed by processor  38 . Similarly, photo amp  38   b  coupled between I/O ports  30   d  and sensor  36   c  via an activate line  38   b - 1  and an amplified sensor output line  38   b - 2  make it possible to drive emitter  36   b  via instructions being executed in processor  30   a , activate sensing amplifier  38   b  and receive an analog signal therefrom via line  38   b - 2 . The analog signal on line  38   b - 2  can be converted in an analog-to-digital converter integral to I/O ports  30   d . The resulting digitized value can be processed via instructions executed by processor  30   a . It will be understood that the photo-amp  38   b  can be eliminated where the analog-to-digital converter has sufficient resolution.  
         [0037]    Representative first and second thermal or heat sensors  40   a  and  40   b  are coupled via one or more sensor activate lines  40   a - 1  and  40   b - 1  to I/O ports  30   d . It will be understood that one or more than two thermal sensors could be used without departing from the spirit and scope of the present invention. Analog output signals from sensors  40   a ,  40   b  can be coupled via one or more output lines  40   a - 2  and  40   b - 2  to I/O ports  30   d . It will be understood that either a common activate line or a common feedback line or multiple activate or multiple feedback lines can be used to control or receive signals from the thermal sensors  40   a ,  40   b  without departing from the spirit and scope of the present invention.  
         [0038]    The processor  30   a  can periodically and autonomously activate sensors  40   a ,  40   b  via respective lines  40   a - 1 ,  40   b - 1 . This in turn provides analog signals, indicative of ambient adjacent thermal conditions on output lines  40   a - 2 ,  40   b - 2 . These signals can then be digitized and processed by processor  30   a.    
         [0039]    As described in more detail subsequently, with respect to FIG. 3, the processor  30   a , to minimize average energy requirements, can be activated only during intermittent spaced apart time intervals. Both smoke sensing and thermal sensing takes place during a common activation interval. Processing of the received signals from the respective sensors also takes place during the same activation interval.  
         [0040]    The unit  16   i  is preferably energized by a replaceable battery B. A battery condition measuring circuit  42  is coupled to I/O ports  30   d  via an activation line  42 - 1  and a battery parameter feedback line, indicative of battery voltage,  42 - 2 . The condition of the battery B can be periodically evaluated by processor  30   a  by activating measurement circuitry  42 . The condition of the battery B can then be monitored in real-time by processor  30   a  with a known current profile. For monitoring purposes, the value received from measuring circuit  42 , on line  42 - 2  can be compared to a factory programmed threshold value. If the sensed voltage of the battery B is below the preset threshold, the processor  30   a  can carry out a prestored low battery voltage routine.  
         [0041]    Voltage incrementing circuit  44  is coupled to battery B and enabling line  44 - 1 , for example a voltage multiplying circuit, can be used to generate an audible device output driving voltage on line  44 - 2 . This driving voltage substantially exceeds the value of the voltage of the battery B. The applied high voltage on the line  44 - 2  can be modulated via processor  30   a  and output line  44 - 3  to drive audible output device  48 . This device could be implemented as an audible sounder or piezo-electric device without limitation.  
         [0042]    As discussed in more detail subsequently with respect to FIG. 4, processor  30   a  directly drives battery voltage incrementing circuit  44  to produce an output voltage on line  44 - 2  sufficiently high to operate the sounder. The sounder via line  44 - 3  can be modulated in accordance with one or more pre-stored output patterns. For example, an ANSI S 3.41 output pattern can be stored and audibly output via device  48  where the units  16  are marketed in the United States. Alternately, a Canadian Standards Association, CSA, output pattern can be stored and output for electrical units installed in Canadian markets.  
         [0043]    When processor  30   a  is generating an audible output pattern, use is made of the silent intervals between tone bursts to carry on a non-tonal processing such as reading sensor values, processing sensor values, reading battery values processing battery output values and executing communication sequences. By multiplexing these operations, only the single processor  30   a  need be used. Using this same multiplexing approach, a low battery audible indicator can also be produced as appropriate.  
         [0044]    The timing diagrams of FIG. 3 illustrate the energy efficient operation of the electrical unit  16   i . Graph  100  illustrates one of a plurality of spaced apart active intervals for the control circuits  30 . During this interval, the resources of the processor  30   a  can be devoted to sensor sampling and signal processing. For example and without limitation, graph  102  illustrates a stabilization and sensing interval of photo amplifier  38   b , activated via line  38   b - 1 . As illustrated in graph  104 , the emitter  36   b  is activated via drive circuits  38   a , line  38   a - 1  near the end of the stabilization interval. This in turn produces radiant energy R in sample chamber  36   a , a portion of which, indicative of smoke, is converted to an electrical signal output via photo amp  38   b . This signal is sampled, graph  106 , and converted to a digital value at the end of the emitter activate interval.  
         [0045]    During the photo amplifier stabilization interval, graph  102 , one of the thermal sensors such as  40   a , can be activated for a predetermined period of time, graph  108 . An analog output therefrom, line  40   a - 2  can be sampled and digitized at the I/O port  30   d , signal  110   a.    
         [0046]    A second heat or thermal sensor, such as sensor  40   b  can be subsequently activated, graph  112 . An analog output therefrom, line  40   b - 2 , can be sampled and digitized at the end of the activation interval  112 , waveform  110   b . Subsequently, graph  114 , the acquired values from the smoke sensor and the thermal sensors can be processed.  
         [0047]    [0047]FIG. 4 illustrates a set of timing diagrams wherein a modulation signal, graph  120 , is presented via line  44 - 3  to an audible output device or sounder. During the time interval wherein the sounder ON signal is being provided, graph  120 , processor  30   a  via line  44 - 1  and voltage increasing circuit for example voltage multiplier circuit  44  can be driven thereby producing on the output line  44 - 2  a high enough output voltage to properly drive the sounder  48 . During sounder OFF intervals, for example between internal tonal groups, such as  120   a ,  120   b  and  120   c , sensor activation and signal processing, as illustrated in FIG. 3 can be carried out. Additionally, low battery testing, discussed above as well as any supervisory signal generation can be carried out and implemented in any of intervals  120   a ,  120   b  or  120   c.    
         [0048]    As noted above, sensor signal processing can be carried out in the same activate cycle as the signal has been acquired, graph  114 , FIG. 3. FIG. 5 is a flow diagram of processing in accordance herewith.  
         [0049]    With respect to FIG. 5, on a periodic basis and autonomously, the processor  30   a  samples the photo sensor  36   c , step  140 . This sensor output is processed and filtered to produce an adjusted value, for example Min 3  processing as described in Tice U.S. Pat. No. 5,736,928, step  142 . The value of Min 3 _smoke is updated with every photo sample.  
         [0050]    On every thirtieth photo sample, step  144 , the updated Min 3 _smoke value is used to calculate a running average, Avg step  146 . The running average is calculated using, for example, a sample size of 256. It will be understood that other numbers of samples could be used without departing from the spirit and scope of the present invention.  
         [0051]    Another value, Smooth, which represents the short-term increase in Min 3 _smoke, is computed, step  148 , by averaging the last two differences between Min 3 _smoke and corresponding Avg. Smooth is greater than zero when Min 3 _smoke is increasing. Smooth declines to zero when Min 3 _smoke remains constant or decreases.  
         [0052]    The most recent value of Smooth is compared with a predetermined value, step  150 . When exceeded, an alarm signal is transmitted and an indication is given at the detector step  152 . The above described steps not only filter out sensor noise, minimizing false alarms, they also carry out sensitivity compensation.  
         [0053]    With respect to FIG. 6, on a periodic basis and autonomously, the processor  30   a  samples the reading of a heat sensor, such as sensor  40   a , graph  108 , step  160 . A value, Avg_temp, representing the running average of the last 256 consecutive Inst_temp. including the most recent sample, is calculated, step  162 , and stored in memory, step  164 . Another value, Delta, representing the difference between the most recent Inst_temp and the most recent Avg_temp is calculated step  166   a . A third value, Avg_delta is calculated step  166   b  by taking the running average of the last 12 consecutive Deltas and then stored, step  168 .  
         [0054]    The current reading is compared to 22 degrees C., step  170 . If above 22 degrees C. and if Avg_delta is greater than or equal to 4, step  172 , then the flag ROR is set step  174 .  
         [0055]    If ROR is set, step  176   i  the fixed heat alarm threshold is set to a value that is higher than the most recent Inst_temp by an amount equal to 25% of the difference between the most recent Inst_temp and the predetermined fixed heat alarm threshold step  178 . This makes the detector more sensitive by allowing the detector to alarm at a temperature lower than the predetermined fixed heat alarm threshold.  
         [0056]    If Avg_delta is less than 4, then the fixed heat alarm threshold will not be reduced. The detector in this case will respond at the predetermined fixed heat alarm threshold step  180 . This process is repeated for the second heat sensor  40   b.    
         [0057]    By setting the heat alarm threshold above the current Inst_temp by a percentage of the difference between the current Inst_temp and the predetermined fix heat alarm threshold, a single adjustment would not be able to cause a valid alarm condition to occur. This reduces the chance of false alarms.  
         [0058]    Where more than one heat sensor is employed, when Avg_delta becomes greater or equal to 4 for one heat sensor, the fixed heat alarm thresholds for all heat sensors are adjusted. The adjustment to heat alarm threshold is only made if the temperature is above 22° C., i.e. room temperature, step  170 . The Avg_temp, and Avg_delta values for each heat sensor are stored individually. Inst_temp is also compared to the predetermined heat alarm threshold step  180 . When exceeded, an alarm signal is transmitted and an indication is given at the detector, step  182 . Inst_temp is also compared to a second heat threshold. When exceeded, a trouble signal, different from an alarm signal, is transmitted and an indication is given at the detector.  
         [0059]    It will be understood that smoke sensor output signals and thermal sensor output signals can be processed using a variety of methods without departing from the spirit and scope of the present invention. Similarly, other types of sensors can be incorporated into unit  16   i  without departing from the spirit and scope of the present invention.  
         [0060]    From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.