Abstract:
A method and apparatus for a cooking appliance having a built-in smoke detector is disclosed. The disclosed apparatus includes a housing with a heating cavity, a door, a heating element, a controller, and a detection module. The detection module includes an energy source directing energy toward a first direction, and in communication with the controller, a detector unit receiving energy from a second direction substantially perpendicular to the first direction, and in communication with the controller, and an aperture for allowing entrance of air into the detection module from the cooking appliance, wherein the detector unit detects a level of smoke in the air from the cavity of the cooking appliance based on an amount of energy scattered from the first direction toward the second direction, and an alarm condition is identified based on the level of smoke. The disclosed method includes the steps of obtaining detection readings at predetermined intervals of time corresponding to an amount of scattered light in a detection module, comparing the obtained detection reading to a first smoke detection threshold and a second smoke detection threshold, determining whether an alarm condition exists based on said comparisons, and decreasing said intervals of time if an obtained detection reading is between said first and said second smoke detection thresholds.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Technical Field  
           [0002]    The invention relates to cooking appliances, and more particularly, to a method and apparatus for identifying an alarm condition in an undercabinet cooking apparatus.  
           [0003]    2. Related Art  
           [0004]    Conventional cooking appliances such as ovens and toaster ovens, may present risk of smoke or fire if foods within the cooking cavities are overcooked. Such conditions may be more problematic in undercabinet cooking appliances due to their general placement in close proximity to wooden cabinets or other potentially flammable surfaces in a kitchen.  
           [0005]    Undercabinet cooking appliances are desirable because of their significant space saving characteristic. Thus, a system to increase the safety of such undercabinet cooking appliances is needed. One such safety feature that may be added is a smoke detection means which, when smoke is detected, would deactivate the heating elements of the appliance and would further render the door to the cooking cavity inoperable. Such a system is particularly useful in a device which includes a door to the cooking cavity which automatically opens. Once a door is opened, increased oxygen and access to the foods can increase fire and/or smoke exposure to surrounding surfaces. If a safety system can operate in conjunction with the automatic door, preventing it from opening in an emergency, the safety of the appliance would be increased.  
           [0006]    Photoelectric and ionization smoke detectors for the home are well known in the art and have been applied in cooking appliances in the past. However, these prior art devices have several disadvantages. First, many of these smoke detectors use light emitting diodes (LEDs) to illuminate smoke particles. LEDs provide energy having very precise characteristics such as wavelength and intensity. However, LEDs are expensive and require more power than other light sources, and often, the precise data LEDs may provide is not necessary. Further, certain foods which may be cooked in the cooking appliance emit acidic and/or greasy substances which may quickly corrode or otherwise damage or destroy the components in a conventional photoelectric or ionization smoke detector. This would substantially decrease the functional life of the smoke detection unit. Light-based prior art smoke detectors also experience diminished longevity due to stress put on their filaments when energized directly from a cooled, powered-off state to maximum intensity.  
           [0007]    Finally, prior art cooking appliances often use a separate independent fan (or natural air convention) to force smoke through a smoke detection device. This adds to the complexity and expense of the cooking appliances especially those that already utilize a convection fan for added cooking efficiency. To decrease such cost and complexity, and to increase overall efficiency, it would be desirable to design the device such that a single fan is used for convection and smoke detection.  
           [0008]    Thus, there is a need in the cooking art for an alarm system for use with cooking appliances to increase safety, while providing decreased complexity and cost, and lasting life.  
         SUMMARY  
         [0009]    These and other advances in the art are provided by the disclosed method and apparatus. The disclosed system may be embodied in various methods and apparatuses for a cooking appliance having a built-in smoke detector. A cooking appliance is disclosed comprising a housing with a heating cavity, a door, a heating element, a controller, and a detection module. The detection module includes an energy source directing energy toward a first direction, and in communication with the controller, a detector unit receiving energy from a second direction substantially perpendicular to the first direction, and in communication with the controller, and an aperture for allowing entrance of air into the detection module from the cooking appliance, wherein the detector unit detects a level of smoke in the air from the cavity of the cooking appliance based on an amount of energy scattered from the first direction toward the second direction, and an alarm condition is identified based on the level of smoke.  
           [0010]    A method of detecting an alarm condition in a cooking appliance is also disclosed. The method comprises obtaining detection readings at predetermined intervals of time corresponding to an amount of scattered light in a detection module, comparing the obtained detection reading to a first smoke detection threshold and a second smoke detection threshold, determining whether an alarm condition exists based on said comparisons, and decreasing said intervals of time if an obtained detection reading is between said first and said second smoke detection thresholds.  
           [0011]    Other systems, methods, features and advantages of the invention will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0012]    The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principals of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views.  
         [0013]    [0013]FIG. 1 illustrates a perspective view of a cooking appliance to be located underneath a cabinet.  
         [0014]    [0014]FIG. 2 illustrates a schematic diagram of a control system for the undercabinet cooking appliance of FIG. 1.  
         [0015]    [0015]FIG. 3 illustrates a detailed schematic internal view of one side of the smoke detection module shown in FIG. 2.  
         [0016]    [0016]FIG. 4 illustrates a complete smoke detection module with both sides of the module chamber securely sealed together to create a light-tight cavity within the smoke detection module.  
         [0017]    [0017]FIG. 5 illustrates a general method of operation of the undercabinet cooking appliance illustrated in FIG. 1.  
         [0018]    [0018]FIG. 6 illustrates a method of detecting smoke and alarm conditions in the undercabinet cooking appliance of FIG. 1.  
         [0019]    [0019]FIG. 7 illustrates a side cutaway view of the cooking appliance illustrated in FIG. 1.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    [0020]FIG. 1 illustrates a perspective view of the a cooking appliance  1  to be located underneath a cabinet  2  for space-saving purposes, also referred to as an “undercabinet” cooking appliance, in accordance with the invention. The illustrated appliance  1  allows a user to cook/heat a food item at a particular temperature or for a certain period of time, and includes a smoke detection module (“the smoke detection module” or “the module”) built into the controls of the cooking appliance  1 . The smoke detection module (not shown in FIG. 1) is illustrated in detail in FIG. 3. The undercabinet cooking appliance  1  further includes an automatic door  3  (operation discussed further below), a user interface control panel  4 , and a convection fan  5  inside the cooking cavity  6  for moving air within the cooking cavity  6  as well as from the cooking cavity  6  into the smoke detection module.  
         [0021]    [0021]FIG. 2 illustrates a schematic diagram of the undercabinet cooking appliance  1  of FIG. 1. The disclosed undercabinet cooking appliance  1  includes a microcontroller or microprocessor  200  which contains control programs and peripherals to operate the overall appliance  1 . The microcontroller may be, for example, a PIC16F73 chip manufactured by Microchip. A power supply  202 , which supplies power to all circuits in appliance  1 , is preferably a DC power supply which provides regulated DC power to the appliance  1 . The undercabinet cooking appliance further includes a door motor control circuit  204  which provides a door signal  206  to the door  3  of the appliance instructing the door to open or close based on the amount of voltage applied to the door mechanism. The voltage is determined by instructions from the microcontroller  200 . The door motor control circuit  204  further provides a door feedback signal  208  to the microcontroller  200  indicating the position of the door (e.g., open, closed) at any given time. This door position sensing task may be accomplished by position switches, optical sensors, or other means. The operation of the door  3  in accordance with the invention is described further with respect to FIGS. 5 and 6.  
         [0022]    The appliance  1  further includes a user interface  210  operably associated with the user interface control panel  4  (FIG. 1) which allows a user to select various modes of operation of the appliance, such as for example, cooking times or temperatures. In addition, an LCD display  7  and/or other visual indicators or input buttons  8  may be included in the device to allow the user to input data (e.g., temperature, time, mode) and/or to show the user various information such as, for example, the status of the appliance  1 , the cavity temperature, the current mode of operation, and/or an alarm condition (as described further herein). An audio transducer  214  (such as, for example, a PMK22 22 mm piezoelectric sounder from Panasonic) may also be included to indicate, for example, a button being pressed, a finished cooking cycle or an alarm condition.  
         [0023]    The undercabinet cooking appliance  1  of the present invention preferably includes a fan motor control circuit  216  for controlling a convection fan  5  which moves air around the cooking cavity  6  thus increasing cooking efficiency. The convection fan may be preferably combined with a cooling fan which moves ambient air inside the oven but outside the cooking cavity, effectively cooling the controls and exhausting smoke particles which may have exited the smoke detection module. The convection fan  5  is also preferably used to force sampled air  218  from the cooking cavity  6  into the smoke detection chamber  220  of the smoke detection module  226 . The smoke detection chamber  220  is preferably constructed such that no ambient light may enter the chamber  220 . This characteristic is referred to herein as “light-tight.” To increase the light-tight characteristic, the chamber  220  may be made of an opaque black thermoplastic material, an opaque thermoset material or a metal. The cooking appliance of the present invention may further include a heating element relay  222  to control the electric resistance heating elements which heat the cooking cavity  6 , as well as a temperature sensor  224  located within the cooking cavity  6 . The temperature sensor  224  senses the cavity temperature and provides that information to the microcontroller  200 . This temperature information may then be displayed on the LCD display  212  and/or used to complete one or more algorithms (for example, a temperature control algorithm) during operation of the appliance  1 . Other types of user interface may be used to signal the user besides an LCD display, such as an LED display, or indicator lamps.  
         [0024]    The undercabinet cooking appliance  1  in accordance with the invention includes a built-in smoke detection module  226 . The smoke detection module  226  includes an energy source  228  for transmitting visual light or infrared energy into the smoke detection chamber  220 , and a detector unit  230  with a corresponding detection circuit  232  for detecting any visual light or infrared energy which is scattered toward the detector unit  230 . The energy source  228  is preferably a standard, inexpensive incandescent bulb (for example, a CMD2182 14V long life bulb manufactured by Chicago Miniature Lamp Co.) which emits both visual light as well as infrared radiation. The detector unit  230  may be a standard semiconductor photodiode or phototransistor (for example, a QSD122 phototransistor from QT Optoelectronics or Fairchild Semiconductor).  
         [0025]    [0025]FIG. 3 shows a detailed schematic internal view of one side of the smoke detection module  226  of FIG. 2 in accordance with the invention. For purposes of reference only, the side of the smoke detection chamber  220  illustrated in FIG. 3 will be referred to as the right side. The opposing or left side of the chamber  220  is a substantial mirror image of the right side. As illustrated in FIG. 4, the left and right sides of the chamber  220  are securely sealed together to create a light-tight cavity within the chamber  220 . Each edge  402  of the chamber  220  may include baffled ridges  404 , which may further enhance the light-tight characteristic of the chamber  220 . The external portion of each side of the chamber  220  may include mounting brackets  406  for mounting the smoke detection module  226  at an appropriate location within the cooking appliance  1 .  
         [0026]    Returning to FIG. 3, the energy source  228  and the detector unit  230  are preferably located at two adjacent corners of the smoke detection chamber  220  in respective independent venting channels  300 ,  302  within the chamber  220 , and are respectively arranged to be directed at substantially right angles from each other. The energy source  228  is connected to the microcontroller  200 , and the detector  230  is connected to the detection circuit  232  which in turn communicates with the microcontroller  200 . As would be understood to those skilled in the art, a separate dedicated controller or control circuit could be used in place of microcontroller  200  to allow this device to be retrofitted into an existing kitchen appliance. In addition, an analog control circuit could be used to process alarm conditions and perform functions outlined herein. In order to more effectively exclude ambient light from the chamber  220  while allowing communication with the microcontroller  200  and the detection circuit  232 , the corners at which the energy source  228  and detector unit  230  are located may be sealed with light seals  306 . The light seals  306  include one or more apertures  308  through which wire connections may travel to allow communication with the microcontroller  200  and the detection circuit  232 , respectively.  
         [0027]    The venting channels  300 ,  302  are preferably arranged at right angles from each other, as illustrated, and intersect at a chamber cavity  304  substantially in the center of the chamber  220 . One venting channel  300  may include an exhaust exit and drain hole  310  at one end, and the other venting channel  302  may include a smaller drain hole  312 . In addition, one channel ends in an air aperature  316  for receiving air from the cooking cavity  6 . In one embodiment of the invention, the smoke detection module  226  is arranged such that the electronic components are on the upper side of the chamber  220 , and the drain holes  310 ,  312  are on the bottom side so that any moisture which may condense on the components inside the module  226  may escape from the drain holes  310 ,  312  with the help of gravity. Further, the module  226  itself is preferably located far enough away from the main circuit board (which typically contains the microcontroller and other circuitry) so as to prevent corrosive or other damaging liquids from dripping onto the board. The module  226  is also located so that exhausted smoke does not condense on the main circuit board, which could also result in damaging or corrosive deposits. A detailed method of operation of the smoke detection module  226  is described below with respect to FIG. 6.  
         [0028]    [0028]FIG. 7 illustrates a side cutaway view of the cooking appliance  1  illustrated in FIG. 1. In particular, FIG. 7 illustrates the relative location of various components of the control system of the appliance  1  in accordance with one embodiment of the invention. As illustrated, the user interface control panel  4  is located at the front of the appliance  1  so that a user may easily view and access the LCD display, and the visual indicators and interface buttons or controls  8 . The fan  5  may be located on one side of the appliance  1  and functions to both create a convection air current within the cooking cavity  6  of the appliance  1 , as well as to draw out air from inside the cooking cavity  6  and force it into the detection module  226 . Additionally, this fan may have an extra set of fan blades (not shown) that draws ambient room air into the controls cavity of the oven, cooling it and removing exhausted smoke from said cavity. Air from the cooking cavity  6  may be forced into the module  226  through a smoke tube  704  connected to the detection module  226  via the air aperture  316 . As further illustrated in FIG. 7 (and briefly explained above), the detection module  226  is located off of the main circuit board  706  (on which most of the other control components are located) so as to prevent corrosive or other damaging liquids from dripping onto the board, and connected to appropriate components on the main circuit board  706 .  
         [0029]    [0029]FIG. 5 illustrates a general method of operation of an undercabinet cooking appliance  1  as illustrated in FIG. 1. When the appliance  1  is powered off, the energy source  228  remains energized at a low “standby” level (for example, 5% of maximum). This increases the lifetime of the source  228  by keeping it warm and thus reducing stress on the filament when the intensity of the source  228  increases. To use the appliance  1 , a user turns on the appliance  1  and the door  3  is opened (step  502 ). In one embodiment, the user instructs the automatic door  3  to open via the user interface control panel  4  (for example, the user may press a key called “door open/close” to open the door). In another embodiment, the door  3  may open automatically when the device is turned on. In a preferred embodiment, there is no handle to allow a user to manually open the door  3 . This is advantageous from a safety standpoint, as it prevents a user from accidentally or unintentionally opening the door  3  in an alarm or emergency condition. A door locking mechanism could be used, but is not needed in the preferred embodiment because the door motor will not allow the door to be opened manually. An alarm or emergency condition is typically a situation when either smoke or fire has been detected within the cooking cavity  6 . Alarm tasks associated with an alarm or emergency condition are discussed in detail below.  
         [0030]    Once the door  3  is open, the user places a food item into the cooking cavity  6  and closes the door  3  (step  504 ). Similar to opening the door, the door may be closed by an instruction from the user via the user interface control panel  4 . Alternatively, the door may be manually closed by the user. Then, a user may input one or more selectable settings into the user interface control panel  4 , and then instruct the appliance  4  (via, for example, a “Start Cooking” button on the control panel  4 ) to beginning cooking. The selectable settings may include, for example, temperatures, time and/or cooking mode. Once cooking begins, the smoke detector module carries out a continuous smoke detection process (step  508 ) as described in detail with respect to FIG. 5. Alternatively, the smoke detection process may occur immediately upon powering on the appliance (step  502 ), and continue until the appliance is completely powered off.  
         [0031]    [0031]FIG. 6 illustrates a method of detecting the presence of smoke in the cooking appliance  1  of FIG. 1 in accordance with the invention. Generally, the smoke detection module  226  receives air  218  from inside the cooking cavity  6  at regular intervals, either by being forced by a convection fan  5  or by natural convection. As explained further below, the module  226  generally operates by periodically illuminating or energizing the energy source  228  and obtaining one or more measurements from the detector unit  230  to determine the level (if any) of smoke present in the chamber cavity  304  of the chamber  220 . When the energy source is energized, a beam of light shines into the light-tight chamber. As explained, the chamber is arranged such that air from the cooking cavity  6  (and thus smoke if present) enters the chamber and exits through a series of bends and elbows, (shown by, for example, the venting channels  300 ,  302  of FIG. 3), in the module that lock out excess ambient light. The beam of light and the reception angle of the detector unit  230  are at right angles from each other, such that normally almost no light is sensed by detector unit  230 . If smoke is introduced into the chamber cavity  304 , however, the beam of light reflects off of the smoke particles and some of the reflected light will fall on the detector unit  230 , indicating a relative level of smoke in the cooking chamber  220 .  
         [0032]    The undercabinet cooking appliance  1  generally has four predetermined threshold values—three smoke detection thresholds (low, mid and high thresholds) and a faulty source threshold. These thresholds, which may be measured in units of “volts,” specifically indicate the level of reflectivity of energy (e.g., light, heat) in the chamber cavity  304 . Because this reflectivity is proportional to the smoke levels detected, the thresholds (as well as the detection readings, which are discussed further below) will be identified in terms of smoke levels. Of course, more or less than four predetermined detection thresholds could be used in an alternative embodiment.  
         [0033]    With respect to the faulty source threshold, either when the system is first turned on, when cooking begins, or on a continuous basis, the detector unit  230  obtains an initial detection reading (as described below) of scattered light. Even with no smoke at all, there still exists a minimal amount of scattering that may be detected by the detector unit  230 . Thus, if the amount of light detected is less than the faulty source threshold when the unit is turned on or cooking just begins, then either the bulb has failed or become occluded with soot or cooking products. In either case, the microcontroller  200  shuts down operation of the toaster and alerts the user that there is a problem.  
         [0034]    As illustrated in FIG. 6, the intensity level of the energy source  228  is first slowly increased from the low-level standby intensity (for example, 5%) to maximum (i.e., 100%) intensity (step  602 ). This increase may occur, for example, over the course of 230 milliseconds. Alternatively, the intensity could be immediately increased from a low level to maximum. Then, at the start of cooking (or, in the alternative, when the appliance  1  is powered on), the system determines whether the energy source is faulty (step  604 ) by obtaining a detection reading. In one embodiment, a detection reading may be obtained by taking a predetermined number of measurements of energy detected by the detector unit  230  (for example, seven measurements) at predetermined time intervals (e.g., every 2300 microseconds), and calculating either the median or the average of these seven measurements. One reason for taking multiple measurements is to filter out unwanted noise. Alternatively, an analog or digital filter may be used to filter noise components and process the measurements. This median or average calculation is referred to herein as a “detection reading” by the detector unit. At the end of each detection reading, the energy level of the source  228  may be slowly reduced from 100% to some lower level (for example, 5%) to conserve longevity of the source  228 , until the next detection reading, at which time the intensity level is again slowly increased to 100%. If the detection reading indicates a detection of energy less than the faulty source threshold, this indicates a faulty source. If a faulty source is detected, an alarm condition is identified (step  606 ), and one or more alarm tasks (as discussed below) are carried out.  
         [0035]    In one embodiment, once it is determined that the energy source is not faulty (step  604 ), it may be determined whether the appliance  1  is in a cooking mode (step  608 ). If not (for example, cooking is complete or the user turned off the heating elements), the appliance  1  may provide some message to the user such as “Cooking Complete” or “Cooking terminated,” and may slowly reduce the intensity level of the energy source back to the standby level (e.g., 5%) (step  612 ). This determination of whether the appliance is in a cooking mode (step  608 ) may occur continually in the background of the detection process, or may only occur at designated times.  
         [0036]    After a faulty source determination is made (step  604 ), smoke detection takes place by obtaining detection readings at various predetermined time intervals. Initially, a detection reading may be obtained once every 20 seconds (step  614 ). At each of these intervals, the system determines whether the current calculated detection reading is below the low threshold (step  616 ). For example, the low threshold may be 1.27 volts. If the detection reading is below 1.27 volts, then the next detection reading is taken 20 seconds later.  
         [0037]    If the detection reading is neither less than 1.27 volts nor between the low threshold (1.27 volts) and the high threshold (for example, 1.76 volts) (step  618 ), this means the detection reading is above the high threshold, which indicates a likely problem. In this case, an alarm condition is identified (step  620 ), and one or more alarm tasks (as discussed below) are carried out. However, if the detection reading is between the low and high thresholds (referred to as the “mid-level detection range”), a warning flag is set to indicate that the smoke level is in this mid-level detection range, and a warning timer is set to zero (step  622 ). For purposes of this discussion, a value of “ 1 ” for the warning flag indicates smoke levels in the mid-level detection range, and a value of “0” indicates smoke levels above or below the mid-level detection range.  
         [0038]    Setting of the warning flag to “ 1 ” triggers the smoke detector to be read more often, such as every 6 seconds rather than every 20 seconds (step  624 ). In many circumstances where the most recent detection reading is greater than the low threshold, but not as high as the high threshold, an alarm condition may not actually exist. Thus, the increased frequency in detection readings is first done in this mid-level detection range to more closely monitor the situation and be ready to indicate an alarm condition should the situation turn into one. For example, through testing, the inventor has determined that when most foods product smoke levels of 1.27 volts or greater, they are generally already too burnt to be edible, but have not produced dangerous amounts of flame or smoke. Performance of the increased frequency of detection readings in the mid-level detection range as described herein makes the device less sensitive to quick puffs of smoke (such as may occur, for example, if juices from the cooking food drip onto a heating element), and more sensitive to a sustained stream of smoke which may be of a somewhat lower-level than an immediate alarm condition, but that may nevertheless indicate a problem. Thus, the step of increasing the detection interval (step  624 ) reduces the occurrence of a false alarm condition or a missed alarm condition.  
         [0039]    While the smoke level is between the mid-level detection range (which is, as explained above, when the smoke level is between the low threshold and the high threshold, and thus the warning flag=1), the step of determining whether the appliance  1  is still in a cooking mode (step  608 ) may occur again as explained above (step  608 ). As explained, while the warning flag=1, the system obtains a detection reading every 6 seconds. For each detection reading taken while the warning flag=1, it is determined whether the smoke level for that detection reading is greater than the low threshold (e.g., greater than 1.27 volts). If not, the warning flag is reset to “0” (step  610 ), and thus the detection reading interval returns to one detection reading every 20 seconds. However, if the detection reading indicates a smoke level greater than the low threshold, it is determined if the detection reading is less than the mid threshold (for example, 1.57 volts) (step  628 ). If the smoke level is between the low and mid thresholds, the warning flag remains set at 1 and the warning timer is reset to zero (or remains zero if the timer was never started) (step  622 ). However, if the smoke level is greater than the mid threshold, it is determined whether the level is less than the high threshold (step  630 ).  
         [0040]    If the smoke level is not less than the high threshold (i.e., it is greater than the high threshold), an alarm condition is identified (step  632 ), and one or more alarm tasks (as discussed below) are carried out. However, if it is determined that the smoke level is less than the high threshold (and thus between the mid and high thresholds), it is determined if the warning timer is equal to 0 (step  634 ). If it is, the warning timer begins to run, and a new detection reading is taken six seconds after the prior detection reading (step  624 ). If the warning timer is not equal to zero, then it is determined if the warning timer is greater than or equal to a predetermined time (for example, 12 seconds). If the timer is not greater than or equal to 12 seconds, the next detection reading is taken six seconds after the prior detection reading (step  624 ). However, if the warning timer is greater than or equal to 12 seconds, this indicates that the smoke level has remained above the mid level (but below the high level) for at least 12 seconds, and thus an alarm condition is identified (step  640 ), and one or more alarm tasks (as discussed below) are carried out.  
         [0041]    In the flow chart illustrated in FIG. 6, it is noted that with respect to the detection reading steps (step  614  and  624 ), the process preferably continues to the steps following these detection reading steps automatically and continuously, even if a new detection reading has not been taken, so that the timing determinations (for example, step  638 ) are made in a timely fashion.  
         [0042]    When an alarm condition is identified (for example, steps  606 ,  620 ,  632  and  640 ), this generally means that either smoke or a fire has been detected within the cooking cavity  6 , and thus one or more alarm tasks associated with the alarm condition should be carried out to contain the smoke and/or fire, and to otherwise maintain the safety of the user as well as the surfaces surrounding the appliance  1 . The alarm tasks may include automatically closing the electronic door  3  and rendering it inoperable, thus containing the smoke and/or fire within the cooking chamber. This is a helpful safety feature of the system because it is highly unlikely that a smoking or ignited food item in the heating cavity  6  will ignite any surrounding surfaces through the metal walls of the cooking appliance  1 .  
         [0043]    The alarm tasks may also include shutting off or de-energizing the heating elements of the cooking appliance  1 . If the cooking chamber is kept closed in combination with the heating elements being de-energized, there is little to no chance for flame to escape the cooking cavity  6  and cause damage to outside surfaces. The alarm tasks may further include activation of an aural or visual indication (or some other message) to alert the user that there is a problem. This indication may further include a text message indicating exactly what the problem is which has occurred.  
         [0044]    [0044]FIG. 8 illustrates an alternative method of detecting smoke and alarm conditions in the undercabinet cooking appliance of FIG. 1. As many of the steps are similar to those described with respect to FIG. 6, the alternative method of FIG. 8 will only be briefly described herein. First it is determined whether the appliance  1  is in a cooking mode (step  802 ). If it is not, then an appropriate message is provided to the user via, for example, an audio tone, a visual indicator or a text message (on the LCD) (step  804 ). The appliance  1  then waits for a user input to initiate cooking (step  806 ). If the appliance  1  is in a cooking mode, then a warning flag is checked to determine if it is set to 1 or 0 (step  808 ). It is noted that the warning flag and warning timer are initially, upon powering on the appliance, set to zero. If the warning flag is set to 0, then detection readings are taken every 20 seconds (or some other predetermined interval of time) (step  810 ). If the warning flag is set to 1, then detection readings are taken every 6 seconds (or some other predetermined interval of time which is less than the interval of time for detection readings when the warning flag is set to 0) (step  812 ). It is understood by one of skill in the art that the warning flag values may be reversed.  
         [0045]    For each detection reading the energy source is slowly increased from a less than maximum intensity level (for example, 5%) to maximum intensity (step  814 ). A detection reading is obtained (step  816 ) and a determination is made as to whether the energy source is faulty (step  818 ). If the energy source is faulty, an alarm condition is identified (step  820 ), and one or more alarm tasks (as discussed above) are carried out. If the energy source is not faulty, then it is determined whether the obtained detection reading is at a value less than the low threshold (step  822 ), and if it is, the warning flag and warning timer are reset to 0 (step  824 ). However, if the obtained detection reading is not less than the low threshold, it is determined whether the obtained detection reading is at a value between the low and high thresholds (step  828 ). If the obtained detection reading is not between the low and high thresholds (and also not less than the low threshold as determined at step  822 ), then it is above the high threshold. Thus, an alarm condition is identified (step  830 ), and one or more alarm tasks (as discussed above) are carried out.  
         [0046]    If the detection reading is between the low and high thresholds as determined at step  828 , then the warning flag is set to 1 and the warning timer begins to run (or continues to run if the warning flag was already previously set to 1). In one embodiment, the warning timer is only reset to zero when the warning flag is reset to zero. Next, it is determined whether the warning timer is greater than or equal to 12 seconds (or some other predetermined time period), and if it is, an alarm condition is identified (step  836 ), and one or more alarm tasks (as discussed above) are carried out. If the warning timer is less than 12 seconds, the intensity of the energy source is slowly reduced and the controls wait for the next detection reading (based on the value of the warning flag) (step  826 ).  
         [0047]    While various embodiments of the application have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of this invention. For example, one of ordinary skill in the art would understand that the scope of this invention includes an independent smoke detection module which may be retrofitted into an existing or stand alone cooking appliance as a separate component therefor. Such an independent smoke detection module may include its own power supply, controller, audio transducer and/or visual transducer or display, and may be used to detect smoke in a cooking appliance while operating independently of most or all controls of the cooking appliance. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.