Patent Publication Number: US-2013241699-A1

Title: Device tracking with lighting system

Description:
BACKGROUND 
     1. Technical Field 
     This application relates to tracking and, in particular, to device tracking. 
     2. Related Art 
     A modular equipment rack, such as a server rack, a server cabinet, a wallmount rack, a network rack, or a LAN (Large Area Network) rack, may be configured to receive rack-mount devices, such as computer servers, routers, network switches, blade servers, disk drive units, or any other rack-mountable device. A person may slide one or more such devices into the rack to install the device. The person may slide the device out of the rack to remove or replace. 
     SUMMARY 
     A system for tracking rack-mount devices may be provided that includes a light fixture and a communication module. The light fixture may include a radio frequency identification (RFID) reader and/or an antenna that is configured to read an RFID tag coupled to a device which is mountable in a modular equipment rack. The communication module may cause a device identifier to be transmitted to a power device that powers the light fixture. The device identifier may identify the device that is mounted in the modular equipment rack based on the RFID reader and/or the antenna reading the RFID tag. 
     A light fixture for tracking rack-mount devices may be provided. The light fixture may include a radio frequency identification (RFID) reader and/or an antenna. The light fixture may also include a processor. The RFID reader and/or the antenna may be positioned to read an RFID tag coupled to a device when the device is mounted in a modular equipment rack. The processor may provide a message comprising a device identifier to a lighting system. The message may indicate that the device identified by the device identifier is added to and/or removed from the modular equipment rack based on whether the RFID reader and/or the antenna detects the RFID tag. 
     A method of tracking rack-mount devices with a lighting system may be provided. A light fixture may be co-located with a modular equipment rack. A device identifier may be received from a communication module associated with the light fixture. The device identifier may identify a device determined to be mounted in the modular equipment rack based on a radio frequency identification (RFID) tag being read by a RFID reader, where the RFID tag is coupled to the device. The communication module may receive the device identifier from the RFID reader. A location of the device may be identified based on receipt of the device identifier from the communication module and on the light fixture, which is associated with the communication module, being co-located with the modular equipment rack. 
     In one interesting aspect, the light fixture may include multiple antennas arranged along a side of the modular equipment rack. Each one of the antennas may be positioned to be within range of the RFID tag when the device is mounted in a respective one of multiple mounting positions in the modular equipment rack. In a second interesting aspect, a card reader coupled to the modular equipment rack may read a user identifier from a card. The communication module may cause the user identifier to be transmitted to the power device, where an indication is stored that a person, who is identified by the user identifier, mounted the device in the modular equipment rack. 
     Further objects and advantages of the present invention will be apparent from the following description, reference being made to the accompanying drawings wherein embodiments of the present invention are shown. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments may be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like-referenced numerals designate corresponding parts throughout the different views. 
         FIG. 1  illustrates an example of a system for tracking rack-mount devices with a lighting system; 
         FIG. 2  illustrates an example of a light fixture that is in the form of a strip or an elongated rectangular cuboid that runs vertically along the rack; 
         FIG. 3A  illustrates an example of a light fixture in which a processor of the light fixture communicates with microcontrollers over a bus; 
         FIG. 3B  illustrates an example of a light fixture in which a processor of the light fixture communicates with the RFID readers over the bus; 
         FIG. 3C  illustrates an example of a light fixture in which a processor of the light fixture is selectively electrically coupled to antennas through a multiplexer; 
         FIG. 4  illustrates a flow diagram of a first example logic of a system for tracking rack-mount devices with a lighting system; 
         FIG. 5  illustrates a flow diagram of a second example logic of a system for tracking rack-mount devices with a lighting system; and 
         FIG. 6  illustrates an example of a light fixture adjacent to a rail of a modular equipment rack. 
     
    
    
     DETAILED DESCRIPTION 
     By way of an example, a light fixture for tracking rack-mount devices may be provided. The light fixture may be coupled to a modular equipment rack. The light fixture may include multiple RFID readers, where each one of the RFID readers is configured to read an RFID tag on a rack-mount device when the rack-mount device is mounted in a respective one of multiple mounting positions in the modular equipment rack. For example, the light fixture may be in the form of a strip having a height that is substantially the same as the height of the modular equipment rack. A communication module may transmit a message comprising a device identifier to a power device that powers the light fixture, where transmission of the message indicates that the rack-mount device identified by the device identifier is added to and/or removed from the modular equipment rack. A determination of whether the identified rack-mount device is added to and/or removed from the modular equipment rack may be based on whether the RFID tag is read by any of the RFID readers. The light fixture or the modular equipment rack may include the communication module in some examples. The power device may identify the location of the rack-mount device based on receipt of the message from the communication module and on the light fixture associated with the communication module being coupled to the modular equipment rack. 
     In a configuration in which multiple RFID readers and/or multiple antennas are included in the light fixture that runs the height of the modular equipment rack, an RFID tag on any rack-mount device may be read by any of the RFID readers regardless of which of the multiple mounting positions the rack-mount device is in. An existing lighting system may be used for tracking rack-mount devices instead of requiring an installation of an additional dedicated tracking system. 
       FIG. 1  illustrates an example of a system  100  for tracking rack-mount devices  110  with a lighting system  120 . The lighting system  120  may include one or more light fixtures  130  (individually designated “canister light” and “rack-mount light” in  FIG. 1 ), one or more communication modules  135 , and a power device  140 . The system  100  for tracking the rack-mount devices  110  may include the lighting system  120  or a subset of the elements of the lighting system  120 , such one or more of the light fixtures  130 . The system  100  for tracking the rack-mount devices  110  may include one or more radio frequency identification (RFID) readers  145  and one or more antennas  150  for the RFID readers  145 . Alternatively or in addition, the system  100  for tracking the rack-mount devices  110  may include one or more modular equipment racks  155  and/or one or more card readers  160 . 
     The modular equipment rack  155  may be any frame or enclosure for mounting equipment. Examples of the rack  155  may include a server rack, a server cabinet, a wall mount rack, a network rack, a LAN (Large Area Network) rack, or any other type of frame or enclosure configured to receive rack-mount devices  110 . The rack  155  may be a standardized rack, such as a 19-inch rack that conforms to a standardized system for mounting various electronic equipment, such as EIA (Electronic Industries Alliance) 310-D, IEC (International Electrotechnical Commission) 60297, or DIN (Deutsches Institut für Normung) 41494. 
     The rack-mount device  110  may be any device that is mountable in the modular equipment rack  155 . Examples of rack-mount devices  110  may include computer servers, routers, network switches, blade servers, disk drives, or any other device configured to mount in the modular equipment rack  155 . The rack-mount device  110  may include and/or be coupled to a radio frequency identification (RFID) tag  165 . For example, the RFID tag  165  may be included in, or attached to the outside of, the rack-mount device  110 . 
     Each light fixture  130  may be any electrical device or combination of devices that creates artificial light from electricity. The light fixture  130  may distribute, filter or transform the light from one or more lamps included or installed in the light fixture  130 . Alternatively or in addition, the light fixture  130  may include one or more lamps. The lamps may include incandescent bulbs, LEDs (Light Emitting Diodes), fluorescent tubes, any other device now known or later discovered that generates artificial light, or any combination thereof. Light generated by one or more of the light fixtures  130  may illuminate the rack  155  and/or any rack-mount devices  110  included in the rack  155 . Examples of the light fixture  130  include a luminaire, a rectangular bar light, a rack-mount light, a rack-mount gooseneck light, a compact fluorescent light, a task/wall bracket fixture, a linear fluorescent high-bay, a spot light, a recessed louver light, a desk lamp, a troffer, a canister light, or any other device that includes one or more lamps. 
     The light fixture  130  may include additional or fewer components. For example, the light fixture  130  may include the RFID reader  145 , the antenna  150 , and the communication module  135  or any combination thereof. The example rack-mount light illustrated in  FIG. 1  includes the RFID reader  145 , the antenna  150 , and the communication module  135 . 
     Each one of the light fixtures  130  may be located above the rack  155  (such as the canister light), in the rack  155  (such as the rack-mount light), on the rack  155 , or otherwise coupled to the rack  155 . If the RFID reader  145  is included in the light fixture  130 , then the light fixture  130  may be located in any position where the RFID reader  145  may read the RFID tag  165  coupled to the rack-mount device  110  when the rack-mount device  110  is mounted in the rack  155 . For example, the light fixture  130  may be a bar light elongated along an axis of the rack  155  and/or be generally parallel to an axis of the rack  155 . 
     The RFID tag  165  may be any device that wirelessly transmits an identifier. The identifier may be unique to that RFID tag  165 . As a result, each one of the rack-mount devices  110  that is tagged with a corresponding RFID tag  165  may be identified by the identifier transmitted by the corresponding RFID tag  165 . The RFID reader  145  may be any device that wirelessly reads the identifier transmitted by the RFID tag  165 . The RFID reader  145  and the RFID tag  165  may be implemented with any type of radio frequency identification technology now known or later discovered. For example, the RFID tag  165  may include an integrated circuit that encodes digital identification data and an antenna that communicates wirelessly to the RFID reader  145 . In one example, the RFID tag  165  may be a passive tag in which power to receive a query and to transmit identification data back to the RFID reader  145  in response to the query is provided wirelessly to the passive tag by the RFID reader  145 . In a second example, the RFID tag  165  may be an active tag that includes a local power source, such as a battery. The active tag may provide a higher power radio signal than the passive tag. The higher power radio signal may be read by the RFID reader  145  from a greater distance than the passive tag. 
     The RFID reader  145  may include a receiver circuit for example. The receiver circuit may be any circuit that receives the identifier from the RFID tag  165 . The RFID reader  145  may include a transmitter. Alternatively or in addition, the RFID reader  145  may include a transceiver. The RFID reader  145  may include the antenna  150  and/or be electrically coupled to the antenna  150 . In one example, the antenna  150  may extend the range of the RFID reader  145  so that RFID reader  145  may receive the identifier from the RFID tag  165  regardless of the position in the rack  155  of the rack-mount device  110  tagged with RFID tag  165 . The antenna  150  may be positioned in any number of ways and take on any number of shapes. In one example, the antenna  150  may include a spiral trace antenna. 
     The radio frequency identification technology may communicate using frequencies such as near 100 kHz, 10 MHz, various UHF frequencies (100s of MHz to a few GHz), or any other suitable frequency. The choice of frequencies may be determined in part by available radio bands not designated for other applications and in part by desired performance of particular applications. Alternatively or in addition, the choice of frequencies may be determined by the amount of conducting surfaces located near the RFID reader  145  and/or the RFID tag  165 . Each frequency band choice may provide different performance and price characteristics. 
     The card reader  160  may be any device that reads an identification card. For example, the card reader  160  may be a type of RFID reader. In a different example, the card reader  160  may read a magnetic strip in the identification card, such as a debit or a credit card. The identification card may be any card that identifies a person or organization, such as an employee badge or ID (identification) card. 
     The communication module  135  may be any hardware and/or software that communicates with the power device  140 . In one example, the communication module  135  may be included in a light adapter that is external to the light fixture  130 . In a second example, the communication module  135  may be included in the light fixture  130 , such as in the rack-mount light illustrated in  FIG. 1 . The light adapter and/or the communication module  135  may be included in a sensor pod that detects motion, temperature or any other physical property. The light adapter, the communication module  135  and/or the sensor pod and may be included in the rack  155 , coupled to the rack  155 , included in the light fixture  130 , located outside of the light fixture  130 , and/or located in any other suitable position. The communication module  135  may communicate wirelessly and/or over a wired connection with the power device  140 . The communication module  135  may, for example, transmit lighting related information to the power device  140 . Examples of lighting related information may include an amount of light detected in an area illuminated by the light fixture  130  and/or any other light sources, occupancy sensor information, temperature sensor information, identification of the light fixture  130 , and a module number of the light fixture  130 . 
     The power device  140  may be any device that provides power to the light fixtures  130 . The power device  140  may provide power to all of the light fixtures  130  or a subset of the light fixtures  130 . Alternatively or in addition, the power device  140  may provide power to one or more of the communication modules  135 . The power device  140  may include communication hardware and/or software that communicate with the communication modules  135 . 
     During operation of the systems  100  and  120 , a person may slide the rack-mount devices  110  into the racks  155  or otherwise add the rack-mount devices  110  to the racks  155 . Alternatively or in addition, the person may slide the rack-mount devices  110  out of the racks  155  or otherwise remove or replace the rack-mount devices  110 . Accordingly, the RFID tags  165  coupled to the rack-mount devices  110  may come in or out of range of the RFID readers  145  as the devices  110  are added to or removed from the racks  155 . 
     When one of the rack-mount devices  110  is added to one of the racks  155 , the RFID reader  145  associated with the light fixture  130  may receive the identifier from the RFID tag  165 . The RFID reader  145  may provide the identifier to the communication module  135 . The communication module  135  may transmit a device identifier to the power device  140  to indicate to the power device  140  that the rack-mount device  110  is mounted in the modular equipment rack  155 . The device identifier may be any identifier that identifies the rack-mount device  110  coupled to the RFID tag  165 . The device identifier may include the identifier received from the RFID tag  165 . Alternatively or in addition, the device identifier may be an identifier that is associated with the identifier received from the RFID tag  165 . For example, the device identifier may include a description of the rack-mount device  110  that is coupled to the RFID tag  165 . 
     The communication module  135  may, in some examples, transmit status information along with or included in the device identifier. The status information may indicate a detected status of the identified rack-mount device  110 . For example, the status information may indicate that the identified rack-mount device  110  is mounted in the modular equipment rack  155 . 
     Conversely, when one of the rack-mount devices  110  is removed from one of the racks  155 , the RFID reader  145  associated with the light fixture  130  may detect that the RFID reader  145  no longer receives the identifier from the RFID tag  165 . The RFID reader  145  may indicate to the communication module  135  that the RFID reader  145  no longer receives the identifier from the RFID tag  165 . The communication module  135  may transmit the device identifier to the power device  140  to indicate to the power device  140  that the rack-mount device  110  is not mounted in the modular equipment rack  155 . The communication module  135  may, in some examples, transmit the status information along with or included in the device identifier. For example, the status information may indicate that the identified rack-mount device  110  is not mounted in the modular equipment rack  155 . 
     The power device  140  may track the statuses of the rack-mount devices  110  as the rack-mount devices  110  are added to and removed from the racks  155  associated with the light fixtures  130 . In particular, the power device  140  may track the statuses of the rack-mount devices  110  based on messages received from the communication modules  135 . As described above, the messages may include the device identifiers and/or the status information. The power device  140  may determine whether each one of the rack-mount devices  110  is mounted in any of the modular equipment racks  155 . The power device  140  may store the device identifiers and the status information received in the messages from the communication modules  135  in a memory of the power device  140 . Accordingly, the power device  140  may look up the status of any of the rack-mount devices  110 . 
     Alternatively or in addition, the power device  140  may determine or identify locations of the rack-mount devices  110 . Each one of the modular equipment racks  155  may be associated or co-located with a corresponding one of the light fixtures  130 . The rack  155  may be co-located with the light fixture  130  if, for example, the rack  155  is within a predetermined distance of the light fixture  130  and/or the rack  155  is coupled to the light fixture  130 . The co-located or associated light fixture  130  may be installed above the rack  155 , coupled to the rack  155 , and/or mounted in the rack  155 , such as in the example of the rack-mount light illustrated in  FIG. 1 . 
     The communication module  135  may be associated with the light fixture  130 . The communication module  135  may be associated with the light fixture  130  by being electrically coupled to the RFID reader  145 . Alternatively or in addition, the communication module  135  may be associated with the light fixture  130  by being included in the light fixture  130 . Alternatively or in addition, the communication module  135  may be associated with the light fixture  130  by being wired to the light fixture  130 , such as in the example of the canister light illustrated in  FIG. 1 . Accordingly, the association of the rack  155  with the light fixture  130  also may form an association between the rack  155  and the communication module  135  that is associated with the light fixture  130 . The power device  140  may store an identification of the light fixture  130  and/or an identification of the communication module  135  from which the device identifiers are received in the memory of the power device  140  along with the device identifiers. 
     The power device  140  may determine that the rack-mount devices  110  identified by the device identifiers received from the communication module  135  are located with the light fixture  130  associated with the communication module  135 . More specifically, the power device  140  may determine that the rack-mount devices  110  identified by the device identifiers received from the communication module  135  are located in the rack  155  associated with the light fixture  130  that is associated with the communication module  135 . The power device  140  may include a database of locations of the light fixtures  130 . The power device  140  may, therefore, determine the location of the rack-mounted devices  110  from the location of the light fixture  130  associated with communication module  135  that transmitted the device identifiers of the rack-mounted devices  110 . 
     The locations of the rack-mount devices  110  that are determined by the power device  140  may be locations within a floor plan, global positioning coordinates, locations within the rack  155 , and/or any other type of location. Alternatively or in addition, the locations of the rack-mount devices  110  may be the identification of the light fixtures  130  that are associated with the racks  155  in which the rack-mount devices  110  are mounted. Alternatively or in addition, the locations of the rack-mount devices  110  may be the identification of the racks  155  in which the rack-mount devices  110  are mounted. 
     In one example, the power device  140  may cause a display of an indication of the location of the rack-mount device  110  in a floor plan. For example, the indication may be a highlighted rack depicted in a floor plan so that the relative position of the highlighted rack in the floor plan may be easily determined by a user. 
     In some embodiments, the power device  140  may determine who adds or removes the rack-mount device  110  to or from the rack  155 . A user who adds or removes the rack-mount device  110  may position the identification card of the user near, adjacent to, and/or through the card reader  160 . The card reader  160  may read a user identifier from the identification card. The user identifier may identify the user and/or the organization associated with the user. The card reader  160  may provide the user identifier to the communication module  135 . The communication module  135  may transmit the user identifier to the power device  140 . The power device  140  may determine that the user identified by the user identifier adds or removes the rack-mount device  110  to or from the rack  155 . The power device  140  may determine that any of the rack-mount devices  110  added or removed to or from the rack  155  during a predetermined time period after the user identifier is received, for example, was added or removed by the person or organization identified by the user identifier. 
     Alternatively or in addition, a door of the rack  155  may be unlocked by the card reader  160  when the user identifier is read from the identification card. When the door of the rack  155  is subsequently closed and/or locked, the card reader  160  or some other device may indicate to the communication module  135  that the door of the rack is closed. The communication module  135  may transmit information to the power device  140  indicating when the door opens and when the door closes. The power device  140  may determine that any of the rack-mount devices  110  added or removed in the time between when the door of the rack  155  opens and closes was added or removed by the person or organization identified by the user identifier. 
     In some embodiments, the power device  140  may record when each of the rack-mount devices  110  is added to or removed from any of the racks  155 . The power device  140  may therefore track when and where any of the rack-mount devices  110  were added to and/or removed from any of the racks  155 . 
     In one embodiment, the RFID reader  145  and/or the communication module  135  may limit how often a determination is made whether the rack-mount devices  110  are added to or removed from the rack  155  and/or how often changes of the rack-mount devices  110  in the rack  155  are recorded. A door of the rack  155  may be coupled to an RFID tag, such as the RFID tags  165  coupled to the rack-mount devices  110 . The RFID reader  145  or some other RFID reader may be able to read the RFID tag coupled to the door when the door is closed, but not when the door is open. Accordingly, the RFID reader  145  and/or the communication module  135  may be able to determine when the door is open or closed. The RFID reader  145  and/or the communication module  135  may determine whether the rack-mount devices  110  are added to or removed from the rack  155  when the door is open, but not when the door is closed. Alternatively or in addition, the RFID reader  145  and/or the communication module  135  may cause changes of the rack-mount devices  110  in the rack  155  to be recorded when the door is open, but not when the door is closed. 
     The lighting system  120  may include more, fewer, or different elements than are illustrated in  FIG. 1 . In one example, the lighting system  120  may include a display device and/or user input controls in communication with the power device  140 . In a second example, the lighting system  120  may include a computing device that performs one or more of the features that the power device  140  is described above as performing. In a third example, the lighting system  120  may include any number of the power devices  140 . 
     The system  100  for tracking rack-mount devices  110  may include more, fewer, or different elements than are illustrated in  FIG. 1 . For example, the tracking system  100  may just include the power device  140 , the light fixtures  130  that include the RFID readers  145 , and the communication modules  135 . In another example, the tracking system  110  may include just the RFID readers  145 , the communication modules  135  and the power device  140 . In yet another example, the tracking system  110  may just include one of the light fixtures  130  comprising the RFID reader  145  and the communication module  135 . The tracking system  110  may include the antennas  150  and the racks  155  in some examples. 
     The devices in the systems  100  and  120  may be arranged in any number of configurations. In one example, multiple light fixtures  130  may be added to a single modular equipment rack  155 . In such a configuration, the power device  140  may track the locations of the rack-mount devices  110  in corresponding sections of the single modular equipment rack  155 . In a second example, the modular equipment racks  155  may be positioned throughout a building or a site. 
       FIG. 2  illustrates an example of the light fixture  130  that is in the form of a strip or an elongated rectangular cuboid positioned along an axis of the rack  155 , such as running vertically along the rack  155 . The light fixture  130  may be embedded in a rail of the rack  155 , coupled to the rail, or otherwise positioned in the rack  155 . The light fixture  130  may be embedded in the rail by, for example, including components of the light fixture  130  inside of the rail. The light fixture  130  may include a LED (Light Emitting Diode) light circuit board  220 . The LED light circuit board  220  may be a circuit that receives and/or includes Light Emitting Diodes (LEDs)  230 . The LEDs may generate the light produced by the light fixture  130  and may be positioned along the length of the light fixture  130 . In addition, the LED light circuit board  220  may include multiple RFID readers  145  and multiple antennas  150  positioned along the length of the light fixture  130 . The antennas  150  may be spiral trace antennas, for example, that are embedded in the LED light circuit board  220 . 
     The LEDs  230  positioned along the length of the light fixture  130  may provide light to any of the rack-mount devices  110  installed in the rack  155  regardless of where in the rack  155  the rack-mount device  110  is installed. In addition, at least one of the antennas  150  positioned along the length of the light fixture  130  may be near enough to any of the rack-mounted devices  110  installed in the rack  155  to read the RFID tag  165  coupled to the installed rack-mounted device  110 . 
     In one example, the LED light circuit board  220  may include a processor  235  and a multiplexer  240 . The processor  235  may selectively communicate with the RFID readers  145  through the multiplexer  240 . For example, the processor  235  may sequentially receive the device identifiers from each of the RFID readers  145 . In a second example, the LED light circuit board  220  may include multiple processors  235 , one for each RFID reader  145 . The processors  235  in the LED light circuit board may communicate with each other over a bus, such as I 2 C (Inter-Integrated Circuit) or over any other communication mechanism. Producing the LED light circuit board  220  to include the single processor  235  may be less expensive than producing the LED light circuit board  220  to include the multiple processors  235 . The processor  235  and/or the multiplexer  240  may be included in a circuit not on the LED light circuit board  220  in some examples. The light fixture  130  may be in communication with a light adapter  210 . The light adapter  210  may include a processor  245  and a memory  248 . The memory  248  may include the communication module  135 . Alternatively, the communication module  135  may be implemented as hardware or a combination of hardware and software. For example, the communication module  135  may include the processor  245  and the memory  248 . 
     The power device  140  may include a processor  250 , a memory  255 , a communication circuit  260 , and a power source  265 . The communication circuit  260  may be any circuit that communicates with the communication module  135  in the light adapter  210 . The power source  265  may be any component that provides power, such as an AC/DC (Alternating Current/Direct Current) converter. In one example, the power source  265  may provide power on a line over which the communication circuit  260  communicates. 
     The processor  235  of the light fixture  130 , the processor  245  of the light adapter  210 , and/or the processor  250  of the power device may be one or more devices operable to execute computer executable instructions or computer code embodied in memory such as the memory  248  or  255  of the light adapter  210  or the power device  140 . Each one of the processors  235 ,  245 , and  250  may be a general processor, a central processing unit, an application specific integrated circuit (ASIC), a digital signal processor, a microcontroller, a field programmable gate array (FPGA), a digital circuit, an analog circuit, any other type of processor or a combination thereof. The memory  248  and  255  may be a non-volatile and/or volatile memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), flash memory, any other type of memory now known or later discovered, or any combination thereof. In some examples, the memory  248  and/or  255  may include one or more storage devices, such as a flash drive, an optical storage device, a magnetic storage device (hard-drive) or any other form of data storage device. 
     The memory  248  or  255  may hold the programs and processes that implement the logic described above for execution by the processor  245  or  250 . For example, the memory  248  may store program logic that implements the features of the communication module  135 . 
     During operation of the systems  100  and  120 , the processor  235  or the processors  235  of the light fixture  130  may regularly check for any detection of the RFID tags  165 . For example, every  1  to  15  seconds, the processor  235  of the light fixture  130  may check whether any of the RFID tags are detectable by the RFID readers  145 . The light adapter  210  may receive the device identifiers associated with the detected RFID tags  165  from the RFID readers  145  in the light fixture  130  through the processor  235  of the light fixture  130 . For example, the processor  245  of the light adapter  210  may communicate with the processor  235  of the light fixture  130  over a bus, such as I 2 C (Inter-Integrated Circuit) or over any other communication mechanism. The processor  235  of the light fixture  130  may provide the processor  245  of the light adapter  210  and/or the communication module  135  with a message or messages that indicate the device  110  identified by the device identifier is added to and/or removed from the modular equipment rack  155 . 
     Alternatively, the processor  245  of the light adapter  210  may perform the features of the processor  235  of light fixture  130  so that the light fixture  130  does not include the processor  235 . For example, the processor  245  of the light adapter  210  may receive the device identifiers directly from the RFID readers  145  in the light fixture  130  instead of indirectly from the RFID readers  145 . 
     The communication module  135  of the light adapter  210  may transmit the device identifiers to the power device  140 . The communication circuit  260  of the power device  140  may receive the device identifiers from the communication module  135  of the light adapter  210 . One or more of the processors  235 ,  245 , and  250  may determine that the rack-mount device  110  is not in the rack  155  anymore when the previously detected device identifier is no longer detected by the RFID reader  145 . 
     The light adapter  210  may receive information from devices in addition to the light fixture  130 . For example, the light adapter  210  may receive sensor information from a motion detector  270  and a temperature sensor  275 . The communication module  135  of the light adapter  210  may transmit the sensor information to the power device  140 . The communication circuit  260  of the power device  140  may receive the sensor information from the communication module  135  of the light adapter  210 . Alternatively or in addition, the light adapter  210  may include input devices, such as the motion detector  270  and the temperature sensor  275 , and/or output devices, such as a speaker. 
     The multiple RFID readers  145  positioned along the light fixture  130  may identify the relative positions of the rack-mount devices  110  in the rack  155 . Each one of the RFID readers  145  may be located substantially adjacent to a position in the rack  155  at which the rack-mount device  110  may be added. In other words, each one of the RFID readers  145  may be located so as to read the RFID tag  165  on the device  110  when the device  110  is mounted in a corresponding one of multiple mounting positions in the rack  155 . The mounting positions may be the positions in the rack  155  where edges or ears protrude so as to facilitate the device  110  being fastened to the rack  155  with screws. Each one of the RFID readers  145  on the LED light circuit board  220  may have a unique address on a bus over which the RFID readers  145  communicate. In one example, the unique addresses may be predetermined and correspond to a predetermined position along the light fixture  130 . In a second example, the unique addresses may be dynamically assigned to a corresponding position along the light fixture  130 . Accordingly, the address of the RFID reader  145  that reads the RFID tag  165  may indicate where the rack-mount device  110  coupled to the RFID tag  165  is installed. 
     The power device  140  may store the device identifiers of the rack-mount devices  110  in the memory  255  of the power device  140 . For example, the power device  140  may store the device identifiers and other associated information in a database in the memory  255 . The power device  140  may store the device identifiers of the rack-mount devices  110  that are currently and/or previously detected in the racks  155  in the memory  255 . The power device  140  may store the position in the rack  155  at which each the one of the devices  110  identified by the device identifiers is detected. 
     The power device  140  may maintain a log of any changes to the installation of the rack-mount devices  110  in the racks  155 . The log may identify, for example: when each one of the rack-mount devices  110  was added to and/or removed from the rack  155 ; the user identifier that identifies who added or removed the rack-mount device  110 ; an identification of the rack  155  to or from which the rack-mount device  110  was added and/or removed; and/or an identification of a position in the rack  155  to or from which the rack-mount device  110  was added or removed. 
     In response to a user request to locate one of the rack-mount devices  110 , the power device  140  may cause the light fixture  130  associated with the rack  155  containing the rack-mount device  110  to flash, illuminate or generate any type of light pattern. Alternatively or in addition, the power device  140  may cause a speaker in or near the rack  155  to emit an audible signal. For example, the speaker may be included in the light adapter. To help a user to find the rack-mount device  110  among a group of the rack-mount devices  110  in the rack  155 , the power device  140  may cause one or more of the LEDs  230  positioned near where the rack-mount device  110  is installed to generate a light pattern different from the other LEDs  230  in the light fixture  130 . 
     The power device  140  may conserve power by turning on the light fixtures  130  that are in the racks  155  where the motion detectors  270  detect motion, but turning off the light fixtures  130  that are in the racks  155  where the motion detectors  270  detect no motion or no motion for a determined period of time. Alternatively or in addition, the power device  140  may limit which of the light fixtures  130  are turned on based on the amount of light detected by light sensors co-located with the racks  155 . 
     Each one of the components in the systems  100  and  120  may include more, fewer, or different elements. For example, the rack  155  may include the light adapter  210  and/or the communication module  135 . Alternatively or in addition, the rack  155  may include multiple antennas  150  and/or multiple light fixtures  130  oriented in a number of ways. As another example, the power device  140  may include a network adapter, such as an Ethernet card, for communication over a packet-switched network, such as an Internet Protocol (IP) network. Computing devices may communicate with the power device  140  over the packet-switched network. Multiple power devices  140  may communication with each other over the packet-switched network. The power devices  140  may pass data onto a centralized or distributed database and/or share data with each other. 
     The systems  100  and  120  may be implemented in many different ways. For example, although some features are shown stored in computer-readable memories (e.g., as logic implemented as computer-executable instructions or as data structures in memory), all or part of the systems  100  and  120  and the corresponding logic and data structures may be stored on, distributed across, or read from other machine-readable storage media. The media may include memories, hard disks, floppy disks, CD-ROMs, or any other type storage medium. 
     Components of the light fixture  130 , with or without the LED light circuit board  220 , may interoperate with the antennas  150  in any number of ways.  FIGS. 3A-3C  illustrate example embodiments of the light fixture  130  in which components, such as the processor  235 , interoperate with the antennas  150 . 
       FIG. 3A  illustrates an example of the light fixture  130  in which the processor  235  communicates with microcontrollers  310  or other type of processors over a bus  320 . Each one of the microcontrollers  310  may implement the features of the RFID reader  145  and, therefore, be coupled directly to a corresponding one of the antennas  150 . Alternatively, each one of the microcontrollers  310  may be coupled to a corresponding one of multiple RFID readers  145 , where each one of the RFID readers  145  is coupled to the corresponding one of the antennas  150 . The processor  235  may receive the device identifiers and, in some examples, additional information from the microcontrollers  310  over the bus  320 . The processor  235  may provide the device identifiers and, in some examples, the additional information to the processor  245  of the light adapter  210 . 
       FIG. 3B  illustrates an example of the light fixture  130  in which the processor  235  of the light fixture  130  communicates with the RFID readers  145  over the bus  320 . Each one of the RFID readers  145  may be coupled to a corresponding one of the antennas  150 . The processor  235  may receive the device identifiers and, in some examples, additional information from the RFID readers  145  over the bus  320 . The processor  235  of the light fixture  130  may provide the device identifiers and, in some examples, the additional information to the processor  245  of the light adapter  210 . 
       FIG. 3C  illustrates an example of the light fixture  130  in which the processor  235  of the light fixture  130  is selectively electrically coupled to the antennas  150  through the multiplexer  240 . The processor  235  may implement the features of the RFID reader  145 . The processor  235  may direct the multiplexer  240  to select one of the antennas  150 . The processor  235  may attempt to detect the RFID tag  165  of any of the rack-mount devices  110  through the antenna selected by the multiplexer  240 . The processor  235  may direct the multiplexer  240  to select a next one of the antennas  150 , and repeat, to determine whether the RFID tag  165  of any of the rack-mount devices  110  may be read by any of the antennas  150 . In addition, the processor  235  may determine which of the antennas  150  detected the RFID tag  165  based on which one of the antennas  150  is selected by the multiplexer  240 . Knowing which one of the antennas  150  detected the RFID tag  165  may indicate the location of the rack-mount device  110  tagged with the RFID tag  165 . 
     In an alternative to the example illustrated in  FIG. 3C , a single RFID reader  145  may be coupled to the output of the multiplexer  240  instead of the processor  235  implementing the features of the RFID reader  145 . The processor  235  may communicate with the RFID reader  145  and control, with the multiplexer  240 , which one of the antennas  150  the RFID reader  145  is electrically coupled to. The processor may receive any of the detected device identifiers from the RFID reader  145 . 
     The processing capability of the systems  100  and  120  may be distributed among multiple entities, such as among multiple processors and memories, optionally including multiple distributed processing systems. Parameters, databases, and other data structures may be separately stored and managed, may be incorporated into a single memory or database, may be logically and physically organized in many different ways, and may implemented with different types of data structures such as linked lists, hash tables, or implicit storage mechanisms. Logic, such as programs or circuitry, may be combined or split among multiple programs, distributed across several memories and processors, and may be implemented in a library, such as a shared library (e.g., a dynamic link library (DLL)). 
       FIG. 4  illustrates a flow diagram of example logic of the system  100  for tracking rack-mount devices. The logic may include additional, different, or fewer operations. The operations may be executed in a different order than illustrated in  FIG. 4 . 
     The operations may begin with the device identifier being received from the communication module  135  associated with the light fixture  130  that is co-located with the modular equipment rack  155  ( 410 ). The device identifier may identify the rack-mount device  110  determined to be mounted in the modular equipment rack  155  based on the RFID tag  165  being read by the RFID reader  145 , where the RFID tag  165  is coupled to the rack-mount device  110 . The communication module  135  may receive the device identifier from the RFID reader  145 . 
     The location of the rack-mount device  110  may be identified based on receipt of the device identifier from the communication module  135  and on the light fixture  130  associated with the communication module  135  being co-located with the modular equipment rack  155  ( 420 ). For example, the light fixture  130  that is co-located with the modular equipment rack  155  in which the rack-mount device  110  is mounted is caused to generate a light signal, such as a flashing signal. 
     The operations may end by, for example, listening for additional messages from the communication module  135 . The additional message may indicate, for example, whether the rack-mount device  110  is removed from the rack  155  and/or additional rack-mount devices  110  are added to the rack  155 . 
       FIG. 5  illustrates a flow diagram of example logic of the system  100  for tracking rack-mount devices  110 . The operations may be executed in a different order than illustrated in  FIG. 5 . 
     The operations may start by performing a scan with an n th  one of n max  scan elements ( 510 ). The scan element may include the antenna  150 , the corresponding RFID reader  145 , and/or the corresponding processor  235  or  245 . The total number of the scan elements in the rack  155  may be n max . In one example of performing the scan, the processor  235  in  FIG. 3C  may select the n th  antenna  150  with the multiplexer  240  and attempt to detect the RFID tag  165  with the n th  antenna  150 . 
     Next, a determination may be made whether a new device  110  has been added to the rack  155  ( 520 ). For example, the processor  235  or  245  of the light fixture  130  or the light adapter  210  may determine whether any device  110  was previously detected with the n th  scan element. If the currently detected rack-mount device  110  was not previously detected in the mounting position(s) monitored by the n th  scan element, then the processor  235  or  245  may determine that the device  110  was added. 
     If the rack-mount device  110  was added, then the addition of the device  110  may be reported to the lighting system  120  ( 530 ). For example, the processor  235  or  245  of the light fixture  130  or the light adapter  210  may transmit one or more messages identifying the newly added rack-mount device  110  to the power device  140 . 
     After the addition of the device  110  is reported, or if no new device  110  was added, then a determination may be made whether any rack-mount device  110  previously detected with the n th  scan element is missing ( 540 ). For example, the processor  235  or  245  of the light fixture  130  or the light adapter  210  may determine whether any device  110  was previously detected with the n th  scan element. If the device  110  was previously detected but is currently not detected with the n th  scan element, then the processor  235  or  245  may determine that the previously detected device  110  was removed or is missing from the mounting position(s) monitored by the n th  scan element. 
     If the rack-mount device  110  is missing, then a failure to detect the rack-mount device  110  may be reported to the lighting system  120  ( 550 ). For example, the processor  235  or  245  of the light fixture  130  or the light adapter  210  may transmit one or more messages identifying the missing rack-mount device  110  to the power device  140 . After the failure to detect the rack-mount device  110  is reported, or if no device  110  is missing, then the operations may proceed to an iteration operation. 
     In the iteration operation, the scan element index, n, may be incremented (or decremented). If the incremented (or decremented) index is out of range, then the index may be wrapped to remain in a proper range ( 560 ). For example, if n is incremented and exceeds n max , then n may be set to 1. The operations may return to performing a scan with the n th  scan element ( 510 ), where n is the incremented, decremented, or wrapped value. In an alternative example, if the scan element index is out of range in the iteration operation, then the operations may end by waiting for an event to restart the scanning. The event may be a timer expiring, for example. 
     The logic may include additional, different, or fewer operations than illustrated in  FIG. 5 . For example, a scan may be performed with each one of the n scan elements, locally recording the device identifiers detected during the scan. For example, the device identifiers may be recorded in the memory  248  of the light adapter  210 . After scanning with all of the scan elements, a comparison may be made of the list of recorded device identifiers with a list of device identifiers detected in a previous scan. If any device identifiers are newly detected that were not previously detected, then the newly detected device identifiers may transmitted to the power device  140  as identifying the devices  110  that were added to the rack  155 . If any device identifiers that were previously detected are no longer detected, then the missing device identifiers may be transmitted to the power device  140  as identifying the devices  110  that were removed from the rack  155 . 
       FIG. 6  illustrates an example of the light fixture  130  adjacent to a rail  610  of the rack. The antennas  150  in the light fixture  130  are positioned adjacent to mounting positions  620  of the rack  155 . Each one of the antennas  150  is adjacent to a corresponding subset of the mounting positions  620 . Accordingly, each one of the antennas  150  may detect the RFID tag  165  affixed to the rack-mount device  110  that is positioned in any of the corresponding subset of the mounting positions  620 . 
     All of the discussion, regardless of the particular implementation described, is exemplary in nature, rather than limiting. For example, although selected aspects, features, or components of the implementations are depicted as being stored in memories, all or part of systems and methods consistent with the innovations may be stored on, distributed across, or read from other computer-readable storage media, for example, secondary storage devices such as hard disks, floppy disks, and CD-ROMs; or other forms of ROM or RAM either currently known or later developed. The computer-readable storage media may be non-transitory computer-readable media, which includes CD-ROMs, volatile or non-volatile memory such as ROM and RAM, or any other suitable storage device. Moreover, the various modules and screen display functionality is but one example of such functionality and any other configurations encompassing similar functionality are possible. 
     Furthermore, although specific components of innovations were described, methods, systems, and articles of manufacture consistent with the innovation may include additional or different components. For example, a processor may be implemented as a microprocessor, microcontroller, application specific integrated circuit (ASIC), discrete logic, or a combination of other type of circuits or logic. Similarly, memories may be DRAM, SRAM, Flash or any other type of memory. Flags, data, databases, tables, entities, and other data structures may be separately stored and managed, may be incorporated into a single memory or database, may be distributed, or may be logically and physically organized in many different ways. The components may operate independently or be part of a same program. The components may be resident on separate hardware, such as separate removable circuit boards, or share common hardware, such as a same memory and processor for implementing instructions from the memory. Programs may be parts of a single program, separate programs, or distributed across several memories and processors. 
     The respective logic, software or instructions for implementing the processes, methods and/or techniques discussed above may be provided on computer-readable media or memories or other tangible media, such as a cache, buffer, RAM, removable media, hard drive, other computer readable storage media, or any other tangible media or any combination thereof. The tangible media include various types of volatile and nonvolatile storage media. The functions, acts or tasks illustrated in the figures or described herein may be executed in response to one or more sets of logic or instructions stored in or on computer readable media. The functions, acts or tasks are independent of the particular type of instructions set, storage media, processor or processing strategy and may be performed by software, hardware, integrated circuits, firmware, micro code and the like, operating alone or in combination. Likewise, processing strategies may include multiprocessing, multitasking, parallel processing and the like. In one embodiment, the instructions are stored on a removable media device for reading by local or remote systems. In other embodiments, the logic or instructions are stored in a remote location for transfer through a computer network or over telephone lines. In yet other embodiments, the logic or instructions are stored within a given computer, central processing unit (“CPU”), graphics processing unit (“GPU”), or system. 
     To clarify the use of and to hereby provide notice to the public, the phrases “at least one of &lt;A&gt;, &lt;B&gt;, . . . and &lt;N&gt;” or “at least one of &lt;A&gt;, &lt;B&gt;, . . . &lt;N&gt;, or combinations thereof” or “&lt;A&gt;, &lt;B&gt;, . . . and/or &lt;N&gt;” are defined by the Applicant in the broadest sense, superseding any other implied definitions herebefore or hereinafter unless expressly asserted by the Applicant to the contrary, to mean one or more elements selected from the group comprising A, B, . . . and N, that is to say, any combination of one or more of the elements A, B, . . . or N including any one element alone or in combination with one or more of the other elements which may also include, in combination, additional elements not listed. 
     While various embodiments of the innovation have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the innovation. Accordingly, the innovation is not to be restricted except in light of the attached claims and their equivalents.