Abstract:
A method and apparatus for fire prevention in electronic equipment utilizes infrared imaging technology to monitor a substantial region of an enclosure within the electronic equipment. For example, a shelf within a computer cabinet may have a lens and thermal sensor array placed within to detect changes in temperature. A processor interprets the data from the thermal sensor array to determine whether to send an alert to an operator and/or to shut down a power supply.

Description:
FIELD OF THE INVENTION 
   The present invention generally relates to the field of safeguarding electronic equipment, and particularly to a method and apparatus for identifying thermal hot spots within an electronic equipment enclosure and taking corrective action. 
   BACKGROUND OF THE INVENTION 
   Presently, high power electronic equipment, especially over 200 W, is susceptible to fire damage caused by electrical shorts. Shorts occur across low voltage power planes and ground on the printed circuit cards within the computer cabinet and cause high currents to ignite the printed circuit boards. It has been observed that the electrical short circuits start as a localized hot spot before burning. Because the localized burning is not self-extinguishing, a fire may cause extensive damage to expensive equipment accompanied by a lengthy down time. 
   Therefore, it would be desirable to provide a system and a method for identifying hot spots within electronic equipment. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is directed to a method and a system for identifying hot spots within electronic equipment. 
   In a first aspect of the present invention, an apparatus for preventing fires in electronic equipment includes a radiation-collecting element for collecting infrared radiation generated within an enclosure of the electronic equipment. A sensor array is coupled to the radiation-collecting element for detecting intensity of the infrared radiation within the enclosure. The sensor array is formed of a plurality of pixels. Each of the pixels provides an electrical value (i.e., a voltage or a current) that is commensurate with the intensity of the infrared radiation received by the pixel. A signal processor detects changes in the intensity of the infrared radiation received by each pixel. A controller interprets the changes in the intensity of the infrared radiation received by each of the plurality of pixels and takes an action such as issuing an alert or shutting down power. A variant of the apparatus of the present invention includes the use of a single thermal sensor. Other variations include using a single lens, a lens array, a focusing mirror, or optical fibers with or without lenses. 
   In a second aspect of the present invention, a method for preventing fires in electronic equipment includes collecting spatially arranged infrared radiation from within an enclosure of the electronic equipment. A voltage or current is measured from each pixel of a sensor array. The electrical characteristic is processed to determine environmental changes in an enclosure of the electronic equipment. An action is performed as a result of the determination of environmental changes within the enclosure. 
   It is to be understood that both the forgoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the general description, serve to explain the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The numerous advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying figures in which: 
       FIG. 1  illustrates a functional block diagram of a preferred embodiment of an apparatus of the present invention; 
       FIG. 2  illustrates an embodiment of an apparatus of the first invention; 
       FIG. 3  illustrates a bundle of optical fibers of another embodiment of the present invention; 
       FIG. 4  illustrates placement of the ends of the optical fibers of  FIG. 3  in an exemplary embodiment of the apparatus of the present invention; 
       FIG. 5  illustrates an embodiment of a method of interpreting the thermal sensor array data of the present invention; 
       FIG. 6  illustrates an embodiment of a method of using the results of the interpretation of the thermal sensor array data; 
       FIG. 7  illustrates a block diagram of a redundant system employing the apparatus of the present invention; and 
       FIG. 8  illustrates a method for processing data from multiple apparatuses in the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. 
     FIG. 1  illustrates a preferred embodiment  100  of the present invention. A volume  40 , preferably an enclosed volume, is continually being measured by a radiation collecting system  10  for potentially detrimental changes in the physical environment. This enclosed volume may contain a heat-producing object, such as a shelf within an electronic equipment cabinet or rack, a motherboard, a printed circuit board, a collection of electronic boards, or the entire cabinet or rack. Examples of electronic equipment contained within the electronic equipment cabinet include servers, routers, hubs, network switches, mainframe electronics, radio frequency measurement equipment, storage devices, medical equipment, power supplies, and the like. The illustration of  FIG. 1  depicts the heat-producing object in volume  40  as a motherboard  50 . Preferably, the radiation collecting system  10  has a focusing element for directing radiation of a certain range of wavelengths onto a sensor array. A processor  20  then analyzes the detected radiation levels of each element of the sensor array A local sudden high temperature rise, progressive warming, or temperature exceeding a threshold is presumed to indicate a potentially dangerous condition. If a potentially dangerous condition is detected, the processor  20  may command the power supply  30  to shut off power to the electronic system, including the motherboard  50 . The present invention may be implemented using an infrared sensor array with a fish-eye lens located at the top of the inside of an electronic cabinet. The fish eye lens projects the thermal image of the inside of the electronic equipment, including printed circuit board(s) to the array of thermal sensors. Alternatively, a single infrared sensor may be used to sense the thermal energy of the entire enclosure, shelf, or cabinet. A microprocessor continually monitors the sensor array. If one or more cells of the array indicate a sudden temperature rise exceeding a preprogrammed value, the microprocessor initiates a power supply shutdown before the temperature can cause a fire. Thus, the equipment is protected from a fire outbreak. 
     FIG. 2  illustrates an embodiment of a system of the present invention. Radiation, especially thermal energy (i.e., infrared radiation), is being constantly emitted from the environment. The radiation may be passed through a notch filter  12  to isolate certain wavelengths, such as infrared radiation. Infrared radiation is especially useful because it is emitted by all objects above 0 degrees Kelvin (or −459.7 degrees Fahrenheit). Infrared radiation has a wavelength from 1 to 100 microns. The notch filter may pass all of or a portion of the infrared band. Limiting the passband to 1–5 or 1–10 microns in wavelength helps to sharpen the resolution of the detection system. The filter  12  is optional. If used, filter  12  may actually consist of several filter layers. Although filter  12  is shown as being shaped to conform to the shape of the lens  16 , different configurations are contemplated by the present invention, including a planar filter element. 
   Lens  16  is preferably a wide-angle lens. Possible wide-angle lenses useable with this invention include fish eye lenses, panoramic annular lenses, doughnut lenses, and cat&#39;s eye lenses. The lens  16  focuses the radiation onto a sensor array  14 , such as a thermal sensor array or thermopile array sensor. Multiple lenses, including lens arrays, may be used for redundancy and/or accuracy. Multiple individual sensors may also be used. Alternatively, another radiation collecting element such as an infrared mirror may be employed to focus and direct the radiation to the thermal sensor array. Infrared mirrors may be purchased at a low cost and lowers the overall cost of manufacturing the system additionally because the number of wires needed in the system are reduced. In the embodiment with an infrared mirror, the infrared mirror may be placed at the top of the enclosure to capture the radiation from the entire enclosure and the sensor array may be placed on the motherboard. Additionally, infrared mirrors may be employed with lenses to optimize the monitoring of potential hotspots. The radiation-collecting element may be placed at the top of the enclosed volume or as otherwise suitable, such as an enclosure wall. In an exemplary embodiment, a configuration of four individual sensors may have four lenses and four mirrors, each lens limited to focusing on ¼ of an enclosure or ¼ of a board being monitored. Other variations are envisioned by the present invention including using multiple lens and/or multiple mirrors per individual sensor or per individual pixel of a sensor array. Various optical elements may also be employed. For example, the background radiation may pass successively through an IR filter, a focusing lens, a collimator, and the sensor array. The use of a collimator would allow greater flexibility in the displacement between the lens and the sensor array. 
   The sensor array is preferably a two dimensional matrix of infrared radiation sensitive pixels that produce a voltage corresponding to the intensity of the radiation illuminating each individual pixel. The pixel data is sampled at a periodic rate through a multiplexer  22 . A signal processor analyzes the pixel data to detect hazardous conditions that have been sensed. This may be achieved through comparing individual pixel voltages against their individual preset voltages or simply against a standard voltage threshold. The pixels may also be monitored to detect progressive warming or other changes to provide an alert to potential troublespots in the environment  40 . The processed pixel data is converted from analog to digital form. Alternatively, the pixel data may be converted to a digital format before signal processing occurs. 
   A microprocessor  28  retrieves the processed data and determines through code whether to issue an alert or to shut down the power supply  30 . The microprocessor processor  28  sets the sample rate from the sensor array, such as by controlling the multiplexer  22 . The microprocessor  28  may be ported for remote monitoring or tracking of data in real-time or stored data. The power supply may also provide data to the microprocessor  28 . The power supply  30  may receive alternating current or direct current input and convert the provided power to direct current voltages and ground for the circuitry  50 ,  55 . 
     FIGS. 3 and 4  illustrate another embodiment  300 ,  400  of the present invention. Optical fibers  60  may be placed to optimize detection of radiant energy conditions with the environment  40 . The radiation receiving ends  65  of the individual optical fibers  60  may include filters and/or lenses and/or may be shaped so as to capture a wide angle of radiant energy. The opposite ends of the individual optical fibers may be placed in proximity to the sensor array, preferably in a one-to-one correspondence between sensor array element or pixel and an individual optical fiber. A separate lens or separate multiple lenses may be provided for all or a portion of the radiation receiving ends  65  of the individual optical fibers to collect a wider angle of radiation. Alternatively, the radiation receiving ends  65  may be flat and smooth to narrow the angle of radiation collected so as to carefully monitor the thermal characteristics of a defined region.  FIG. 4  shows the location of optical fiber ends  65  within an environment to be monitored. An advantage to optical fibers is the ability to place them around obstructions or shadow spots such as air baffles and standing boards. 
     FIG. 5  illustrates an embodiment of a method  500  of the present invention. Radiant energy is optionally filtered to remove non-infrared radiation  110 . The infrared radiation is then collected, such as through a lens or lens system  120 . The collected or focused infrared radiation falls onto a two-dimensional thermal sensor array, is sampled, and processed to determine a magnitude of the voltage. The magnitude of the pixel voltage is stored  125  in a memory, such as a first in, first out memory. The first pixel&#39;s voltage magnitude is processed to determine if the voltage magnitude exceeds a preset threshold for that pixel  135 . The threshold may be preset at the factory and may be programmable by the user. If the threshold is exceeded, then a flag, such as a “too hot” flag, is set. Further processing may include determining the amount or rate of change in the voltage readout magnitude between samples  145  and recording of this value in memory  150 . A history of the pixel changes may be used to determine if a region of the environment corresponding to the pixel is progressively warming up or otherwise changing  155 . If such a determination is made, a “heating up” flag may be set  160 . If the last pixel has been processed, the process may repeat after a sufficient passage of time  175 . This wait period may occur through a synchronizing means, such as a circuit or code. Otherwise, the next pixel data is processed  170 . Variations of the present method are contemplated such as providing an address of the pixel and only reporting pixels that have actually experienced a significant change or that have exceeded a threshold. 
     FIG. 6  illustrates an embodiment of a method for using the “too hot” and “heating up” flags. Pixel data may be successively accessed  210 ,  240 ,  245 . If the pixel is determined to represent a too hot region  215 , the power supply is cut off  220 ,  225 . Otherwise, if the pixel is becoming warmer  230 , an alert may be issued  235 . This alert may be a signal to another process and/or may involve the activation of an indicator, such as a light emitting diode. A remote operator may be informed of an alert condition as well as a power shut off condition and be provided with information concerning the status of the system. A graphical representation of conditions of the environment, including a temperature profile, over time may be displayed. 
     FIG. 7  illustrates an embodiment of the present invention employing redundancy. Two radiation collecting systems  10 ,  310  may concurrently monitor the conditions of an environment  40 . Alternatively, one radiation collecting system may serve as a backup for the other. Preferably, the radiation collecting systems  10 ,  310  operate in parallel. Each system may have a corresponding signal processor  20 ,  320  or may share a signal processor. A microprocessor  330  may control both processors  20 ,  320  and determine the reporting of alerts or automatically shutting down a power supply  30 . 
     FIG. 8  illustrates an embodiment of a method using the system of  FIG. 7 . If a first radiation collecting system determines a potential problem  415 , an alert may be issued  420  and stored  425 . A request may automatically be made to cancel the alert. If the second system also determines a potential problem  435 , a second alert may be issued  440 . If both radiation-collecting systems have issued alerts  445 , the power supply may be shut down  450 . Otherwise, processing continues  415 . If both radiation-collecting systems no longer determine a potential problem, the alert may be canceled  450 . 
   It is believed that the present invention and many of its attendant advantages will be understood by the forgoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely an explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.