Abstract:
A power monitor for an electrically powered device provides audible and/or visual alarms in the event of a power failure in a particular branch circuit. A timer records the duration of the power outage and reports the result on a built-in display. Optional performance sensors may monitor and report the condition of the electrically powered device being monitored. A representative embodiment is a monitor for a refrigerator/freezer. A temperature sensor in each of the two compartments triggers an alarm if pre-set temperature limits are exceeded. The power monitor comprises an internal, rechargeable battery which powers the device during a power outage.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    None 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    This invention relates to electrical equipment. More particularly, it relates to line power monitors and performance monitors for appliances such as refrigerators, freezers and the like. 
         [0005]    2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
         [0006]    A total electrical power failure in a home or other building is usually immediately apparent to the occupants—lights go out and all non-battery-powered electrical devices stop working. However, the failure of a single branch circuit may not be noticed so easily. 
         [0007]    Many homes, especially those built or rewired recently, have dedicated circuits for certain appliances such as refrigerators and freezers. Because of this, a homeowner may not immediately be alerted to a loss of power to the appliance. If, for example, the circuit breaker on a dedicated branch were to trip, it would not be immediately obvious since other circuits (and the devices powered by them) would not be effected. Loss of power to a refrigerator or freezer can result in the spoilage of the contents in a relatively short time. Accordingly, it is important that a homeowner be made promptly aware of a loss of power to such a device. Loss of power to many other electrically powered devices can have severe consequences—e.g., medical devices, freeze-protection equipment, sump pumps, security systems, pet or livestock feeders and heaters. Hence the need for alerting devices. 
         [0008]    Some devices which are normally powered by the electrical mains can benefit from having an alternative power supply. An uninterruptible power supply (also known as an uninterruptible power source, UPS or battery backup), is an electrical apparatus that provides emergency power to a load when the input power source, typically the utility mains, fails. A UPS differs from an auxiliary or emergency power system or standby generator in that it can provide instantaneous or near-instantaneous protection from input power interruptions by means of one or more attached batteries and associated electronic circuitry. The on-battery runtime of most uninterruptible power sources is relatively short—5 to 15 minutes being typical for smaller units—but sufficient to allow time to bring an auxiliary power source on line, or to properly shut down the protected equipment in an orderly fashion. 
         [0009]    However, devices which draw substantial power over a significant period of time (e.g., a refrigeration unit) cannot benefit from being connected to a conventional UPS. The cost and size of the batteries required to power a typical home refrigerator/freezer for even a couple of hours would be prohibitive for most homeowners. 
         [0010]    Another problem with power interruption to refrigerators and freezers is that a power loss can occur, the temperature can increase to the point of allowing food to spoil, the power can subsequently be restored and the unit cooled back down to its normal operating point all without the knowledge of the owner (who may have been away from home on vacation). 
         [0011]    What is needed is a device which can alert a user to a loss of utility power and report the duration of the power outage. 
       BRIEF SUMMARY OF THE INVENTION 
       [0012]    The invention is a power and performance monitor for home appliances—especially refrigerators and freezers. 
         [0013]    The monitor plugs into a wall electrical outlet and the appliance plugs into the monitor—i.e., the appliance is in series with the monitor. In some embodiments, the monitor has a “piggyback” style plug into which the appliance is plugged. 
         [0014]    The monitor includes alarms—audible (buzzer), visible (flashing light), or both—to signal a power interruption. The monitor has an internal, rechargeable battery that powers the alarms. The battery is kept charged by an internal battery charging circuit. 
         [0015]    The monitor also includes battery-powered circuitry which records the duration and/or time of the power interruption(s). This allows a homeowner to know when and how long the refrigerator or freezer was off. This information can be displayed on a built-in display and/or downloaded via a USB port or the like to a computer or memory stick. 
         [0016]    An optional feature is one or more sensors that monitor the performance of the appliance. For a refrigerator/freezer monitor, the sensor comprises a temperature probe(s). The monitor can be set with minimum and maximum values which will trigger the alarm if exceeded. Circuitry can also be provided to record the temperature versus time either continuously or following a power interruption. 
         [0017]    In certain embodiments, only the maximum temperature reached during a power interruption may be recorded. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0018]      FIG. 1  is a perspective view of an apparatus according to a first embodiment of the invention. 
           [0019]      FIG. 2  is a functional block diagram of the device illustrated in  FIG. 1 . 
           [0020]      FIG. 3  is a flowchart of one particular method of operation of an apparatus according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    A representative embodiment of the invention monitors the temperature in either or both the refrigerator and freezer compartments of a refrigeration unit. The device has a countdown clock that is activated by an elevation in temperature and lets the consumer know the duration the temperature of the compartment was out of range as well as the highest temperature reached. It monitors the temperature via a probe(s) placed in the freezer and/or the refrigerator compartments. The device can detect a power failure as well as an elevation in temperature due to the door being left ajar or a malfunction of the cooling unit. Warning may be given by audible means such as an audio buzzer and/or by visual means such as a blinking light. The device preferably includes a charging circuit and a rechargeable battery that allows the unit to provide a continued warning signal and time recording despite a power failure of the utility mains. A piggy-back style plug allows the power of the circuit to be monitored while not supporting the load of the refrigeration unit being monitored. Unlike a UPS, a device according to the invention need not provide battery back-up power for the appliance being monitored. 
         [0022]    An apparatus according to the invention may have a reset button to reset the unit and a test switch to allow an automated check of its circuitry. One particular preferred embodiment has a 6-foot power cord with the piggy-back style plug which allows the device to be plugged into a wall outlet and then set above or beside the unit to be monitored (which is plugged into the back of the piggyback plug so as to ensure that the monitor and the appliance being monitored share the same power supply). 
         [0023]    The invention may best be understood by reference to one particular illustrative embodiment which is shown in the drawing figures. 
         [0024]    Referring to  FIG. 1 , a refrigerator/freezer power and temperature monitor  10  is shown housed in chassis  12 . Extending from chassis  12  are power cord  14  (which terminates at plug  16 ) and signal cables  22  which connect to freezer temperature probe  18  and refrigerator temperature probe  20 . Plug  16  may be a “piggyback” type plug which permits the refrigerator/freezer being monitored to share the same power outlet as monitor  10 . This arrangement ensures that monitor  10  is observing the very same power being supplied to the appliance being monitored. 
         [0025]    Freezer probe  18  and refrigerator probe  20  may be thermistors or any other temperature-sensing devices known in the art. Signal cables  22  may be ribbon cables which are particularly suited for routing between the cabinet of the refrigerator/freezer and the magnetic door seal commonly used on household refrigerators and freezers. 
         [0026]    Monitor  10  includes an audible warning device (such as warning buzzer  24 ) and chassis  12  may have slots or other openings to permit the sound to escape. Monitor  10  also includes a visual warning device such as warning lights  26  which may be flashing light emitting diodes (LEDs). 
         [0027]    Monitor  10  may comprise one or more display panels for displaying test results. In the embodiment illustrated in  FIG. 1 , monitor  10  includes separate digital displays  28  for the freezer and refrigerator temperatures and digital timer display  34 . The displays may be liquid crystal displays (LCDs), LED displays, vacuum fluorescent displays, mechanical drum counter displays or any suitable display known in the art. 
         [0028]    Controls  30 , which may be pushbutton switches, are provided for enabling/disabling the freezer temperature monitor and setting the threshold freezer temperature for the alarm. Controls  32  may perform the same functions for the refrigerator temperature monitor. 
         [0029]    Reset button  36  may be provided for re-initializing monitor  10  as described more fully, below. Ready light  40  may be provided on the front panel of monitor  10  to indicate that the unit is powered up and functioning normally. Test switch  42  may be provided to initiate a self-test function and/or activate the audible and visual alarms to ensure that they are fully functional. 
         [0030]    Power switch  38  may be provided disable monitor  10 . In one particular preferred embodiment, power switch  38  comprises a button which must be depressed and held for three seconds to power down monitor  10 . This arrangement helps to ensure that the monitor is not inadvertently shut off. It will be appreciated by those skilled in the art that piggyback-style plug  16  permits monitor  10  to be switched off without interrupting power to the refrigerator/freezer (or other appliance) to which it is connected. Piggyback-style plug  16  connects monitor  10  in parallel with whatever is plugged into the back (female outlet) of the plug. 
         [0031]    Referring now to  FIG. 2 , certain subsystems of monitor  10  are shown in block diagram form. Circuit board  44  may comprise one or more processors, memory devices and interface chip sets as well as temperature readouts  28  and timer display  34 . Connections may also be provided for buzzer  24 , LED warning flasher  26  and temperature probes  18  and  20 . Charging circuit board  46  may comprise one or more power supplies for providing power to circuit board  44  and charging current to rechargeable battery  50 . Under normal circumstances, charging board  46  receives AC electrical power from plug  16  (via power cord  14 ) and converts it to low-voltage DC to power the electrical components on circuit board  44  (via harness  48 ) and also provides a trickle charge to maintain battery  50  in a fully-charged state. In certain embodiments, charging board  46  may also include means for signaling circuit board  44  (via signal harness  48 ) that the AC power being supplied via plug  16  and power cord  10  has failed or is failing and that circuit board  44  should switch to battery  50  to supply its power needs. In similar fashion, charging board  46  may signal circuit board  44  when power is restored at plug  16 . In yet other embodiments, charging board  46  may comprise a rapid charger for quickly recharging battery  50  after power is restored. 
         [0032]    It will be appreciated by those skilled in the art that power supply  46  in combination with battery  50  comprises an uninterruptable power supply (UPS) for the circuits on circuit board  44 . A UPS designed for powering DC equipment is very similar to an online UPS, except that it does not need an output inverter, and the powered device may not need a power supply—i.e., a subsystem for converting high voltage AC into low voltage DC. Rather than converting AC to DC to charge batteries, then DC to AC to power the external device, and then back to DC inside the powered device, the equipment may accept DC power directly and thereby allow one or more conversion steps to be eliminated. 
         [0033]    One particular method for monitoring the power supplied to and the temperatures maintained by a refrigerator/freezer using the apparatus illustrated in  FIGS. 1 and 2  is shown in flowchart form in  FIG. 3 . In Figure, “Y” denotes a “yes” or positive test result and “N” indicates a “no” or negative test result. 
         [0034]    A power and temperature monitoring process according to the invention may begin at decision diamond  60  which is responsive to a test of the electrical supply. Test parameters may be pre-programmed into the device—e.g., minimum and maximum acceptable voltage levels, AC frequency limits, minimum power interruption interval (to avoid nuisance activations due to momentary power loss), etc. 
         [0035]    If the power is found to be within acceptable parameters, the process proceeds to step  72  for temperature monitoring. If, however, a fault in or complete failure of the power is detected, the system commands a switch to battery power (at box  62 ), activates the audible alarm (box  64 ) and starts a timer for the audible alarm (at box  66 ). The system may include a pre-programmed time limit for the audible alarm to extend the battery life and avoid unnecessary user aggravation. In certain embodiments, the system may include a “warning buzzer silence” button which deactivates the audible alarm when depressed. 
         [0036]    The system also activates the visual alarm (at  68 ) and, at box  70 , starts a timer which keeps track of the time duration of the power outage. 
         [0037]    At box  72 , the temperature of probe  20  (which may be positioned inside the refrigerator) is sampled and compared (at diamond  74 ) to a pre-set maximum acceptable temperature. If the temperature exceeds the pre-set limit (Y branch at  74 ), the audible and/or visual alarms may be activated (at  76 ) if they were not previously activated in response to a power failure (at  64  and  68 ). 
         [0038]    The system may store the maximum temperature reached within the refrigerator by storing the sampled temperature and comparing subsequent temperature measurements to the stored value. If the sampled temperature is greater than the previously stored temperature (Y branch at  78 ), the new maximum temperature is stored (at  80 ). 
         [0039]    At box  84 , the temperature of probe  18  (which may be positioned inside the freezer section) is sampled and compared (at diamond  84 ) to a pre-set maximum acceptable freezer temperature. If the temperature exceeds the pre-set limit (Y branch at  84 ), the audible and/or visual alarms may be activated (at  86 ) if they were not previously activated in response to a power failure (at  64  and  68 ) or by excessive temperature in the refrigerator section (at  76 ). 
         [0040]    The system may store the maximum temperature reached within the freezer by storing the sampled temperature and comparing subsequent temperature measurements to the stored value. If the sampled temperature is greater than the previously stored temperature (Y branch at  88 ), the new maximum temperature is stored (at  90 ). 
         [0041]    At diamond  92 , the system compares the current value of the alarm timer (which was started at  66 ) to the pre-set time-out value. If the time limit has expired (Y branch at  92 ) the audible alarm is silenced at step  94 . To further extend the battery life of the monitor, a test may be made (at  96 ) to determine whether the battery is nearly discharged. If so (Y branch at  96 ), all alarms may be deactivated (at  98 ) to further reduce the drain on the battery. 
         [0042]    At step  100 , a subsequent test is made of the power supply to determine whether utility power has been restored. In certain embodiments, this test may include a timer function so as to require the power to be continuously on for a certain period of time before it is deemed to be fully “restored” (Y branch at  100 ). If the power is still off (N branch at  100 ), the process repeats, starting at step  72 , with additional samples being taken of the temperatures within the refrigerator and freezer. 
         [0043]    However, if the power has been restored (Y branch at  100 ), the outage duration timer (which was started at  70 ) is stopped (at  102 ) and operation on battery power is discontinued (also at  102 ). At this point, a rapid charger (if so equipped) may be activated to quickly restore the capacity of the battery in the event that power is lost again within a short period of time. 
         [0044]    At  104 , the device displays (on temperature readouts  28  and timer display  34 ) the maximum temperatures reached in both the refrigerator and the freezer during the power outage as well as the total duration (e.g., in hours and minutes) of the power interruption. If not previously deactivated at  94  and/or  98 , the alarms are then shut off (at  106 ) and the alarm timer is reset (at  108 ). The process then repeats continuously with the power check at diamond  60 . 
         [0045]    In certain other embodiments, a plurality of timers may be provided to record a plurality of power outages which may occur between system resets. In still other embodiments, timers may be provided to record and report the length of time the refrigerator and/or freezer sections exceeded their pre-set temperature limits. In this way, a malfunction of the refrigerator/freezer could be detected and reported to a homeowner even if there were no power outage. 
         [0046]    In some embodiments, temperature and time values may be retained and displayed until the unit is manually reset by, for example, user activation of reset button  36 . Certain embodiments may be programmed to provide an automatic reset if one or more temperature limits are not exceeded during a power outage—i.e., a power outage of no consequence. 
         [0047]    It should be appreciated that the invention has been illustrated with reference to a particular embodiment optimized for use with a refrigerator/freezer. However, the invention may be used in power monitors intended for other electrically-powered devices. By way of example only, the monitor may be used with a sump pump and the temperature probes  18  and  20  of monitor  10  could be replaced with float switches that would alert a homeowner to rising water in his or her basement. In yet another example, the monitor may be used with an aquarium heater and the monitor equipped with a sensor responsive to the water temperature of the aquarium. Those skilled in the art will apply the method and apparatus of the invention to power monitors intended for other critical equipment either with or without auxiliary sensors. 
         [0048]    Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.