Abstract:
Systems and methods for protecting electrical wire connections from overheating are provided. In some embodiments, methods for protecting electrical wire connections from overheating are provided, the methods comprising: detecting a signal responsive to a temperature of an electrical wire connection using a temperature sensor; comparing the signal to a threshold; and disconnecting power to a circuit when the comparison indicates that the temperature is over a given value. In some embodiments, systems for protecting electrical wire connections from overheating are provided, the systems comprising: a temperature sensor that detects a signal responsive to a temperature of an electrical wire connection using a temperature sensor; an operational amplifier that compares the signal to a threshold; and a relay that disconnects power to a circuit when the comparison indicates that the temperature is over a given value.

Description:
BACKGROUND 
       [0001]    A major source of electrical fires is arcing and/or resistance in wiring connections. Arcing in a wiring connection can occur when electrical current flows through poor electrical connections, such as due to loose screws, loose wire nuts, bad crimps, damaged wire insulation, corrosion, etc. Resistance in a wiring connection can also be caused by poor electrical connections, such as due to loose screws, loose wire nuts, bad crimps, damaged wire insulation, corrosion, damage to a wire due to arcing, etc. 
         [0002]    Arcing in connections and high current flowing through resistive connections can create large localized heat sources. Such heat sources can degrade insulation which can increase arcing and result in heat sufficient to start a fire. 
       SUMMARY 
       [0003]    Systems and methods for protecting electrical wire connections from overheating are provided. In some embodiments, methods for protecting electrical wire connections from overheating are provided, the methods comprising: detecting a signal responsive to a temperature of an electrical wire connection using a temperature sensor; comparing the signal to a threshold; and disconnecting power to a circuit when the comparison indicates that the temperature is over a given value. In some embodiments, systems for protecting electrical wire connections from overheating are provided, the systems comprising: a temperature sensor that detects a signal responsive to a temperature of an electrical wire connection using a temperature sensor; an operational amplifier that compares the signal to a threshold; and a relay that disconnects power to a circuit when the comparison indicates that the temperature is over a given value. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a drawing of an example of a twist-on wire connector in accordance with the prior art; 
           [0005]      FIG. 2  shows examples of drawings of temperature sensors in accordance with the prior art; 
           [0006]      FIGS. 3-5  are cross-sectional views of twist-on wire connectors with temperature sensors embedded therein in accordance with some embodiments of the present invention; 
           [0007]      FIG. 6  shows examples of drawings of circuit interrupter devices in accordance with the prior art; 
           [0008]      FIGS. 7-10  shows examples of lighting fixture wire leads with temperature sensors and circuit interrupting devices incorporated therein in accordance with some embodiments; 
           [0009]      FIGS. 11 and 12  illustrate lighting fixture connections to cables at a junction box in accordance with some embodiments; and 
           [0010]      FIGS. 13-15  are schematic diagrams of control circuits that can be used to detect temperature conditions and perform actions in response thereto in accordance with some embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Systems and methods for protecting electrical wire connections from overheating are provided. In some embodiments, mechanisms are provided for interrupting electrical power to an electric appliance (such as a light) in response to an increase in temperature. 
         [0012]    More particularly, in some embodiments, these mechanisms can include an electrical interface between a power source (e.g., cables in a ceiling outlet junction box) and a lighting fixture that interrupts electrical power to the lighting fixture in the event that the temperature at one or more electrical connections reaches a given value. In some embodiments, such an interface can use one or more temperature sensors each embedded in a twist-on wire connector (or any other suitable type of electrical connector, such as a crimp connector, a lug connector, etc.) or in a wire for monitoring the temperature of one or more electrical connections. 
         [0013]      FIG. 1  is an illustration of an example of a typical twist-on wire connector used to join together two or more electrical wires as known in the art. When wires are joined in such a twist-on wire connector, the wire connector simultaneously forms an electrical wire junction and electrically insulates the wire junction from the wire&#39;s surroundings. 
         [0014]    Typically, a twist-on electrical connector includes a dome shaped electrically insulating housing  10  (which can be made of plastic, for example) for grasping by a user and an internal member, such as spiral metal coil  11 , for twistingly engaging bare ends of electrical wires to form an electrical connection therebetween as the bare ends of the wires are twisted into electrical engagement with each other through a twisting action on the wire connector with respect to the electrical wires. 
         [0015]    Any suitable temperature sensors can be used in some embodiments. For example, various commercially available temperature sensors as shown in  FIG. 2  may be suitable for embedding in a twist-on connector housing. For example, as illustrated, a miniature thermistor 21 made from Quality Thermistor, Inc. of Boise, Id., a Pico Bead, Type R Thermistor 22 from Redfish Sensors of Meridian, Id., a Thermistor Glass Probe RBGP-103M 23 from Redfish Sensors, a miniature microchip LM26NV 24 (which is a complete thermostat and can directly control an external transistor using only three wires: 5V, Ground and Vout) from National Semiconductor Corporation of Santa Clara, Calif., and/or any other suitable temperature sensor can be used in some embodiments. 
         [0016]      FIG. 3  is a cross-sectional view of a twist-on wire connector with a temperature sensor  31  embedded on the side of the connector&#39;s spiral coil in a chamber  33  of the connector&#39;s housing in accordance with some embodiments. This chamber can also contain a silicone paste  32  to improve thermal conductivity between the housing, spiral coil, and/or wires and the temperature sensor in some embodiments. Insulated sensor leads  34  can exit the housing through the top and terminate in 2-pin connector  35  in some embodiments. 
         [0017]      FIG. 4  is a cross sectional view of a twist-on wire connector with a temperature sensor  41  embedded at the tip of the spiral coil in a chamber  43  of the connector&#39;s housing in accordance with some embodiments. This chamber can also contain a silicone paste  42  to improve thermal conductivity between the housing, spiral coil, and/or wires and the temperature sensor in some embodiments. Insulated sensor leads  44  can exit the housing through the top and terminate in 2-pin connector  45  in some embodiments. 
         [0018]      FIG. 5  is a cross-sectional view of a twist-on wire connector with a temperature sensor  51  embedded in a chamber  53  of the connector&#39;s housing in accordance with some embodiments. This chamber  53  can also contain a silicone paste  52  to improve thermal conductivity between the housing, spiral coil, and/or wires and the temperature sensor in some embodiments. Insulated sensor leads  54  can exit the housing through the top and terminate in 2-pin connector  55  in some embodiments. 
         [0019]    In some embodiments, additional temperature sensors and/or circuit interrupting devices can be incorporated into lighting fixture leads. These sensors and/or devices can provide redundancy and backup protection in some embodiments. For example, line-voltage, snap-action, self-resettable circuit interrupters such as those shown in  FIG. 6  can be used in some embodiments. More particularly, a Klixon 3BT thermostat  61 , available from Sensata Technologies, Inc. of Attleboro, Mass., good for interrupting up to 1 Amp at 120V AC, a Klixon Model 9700 motor protector  62 , available from Sensata Technologies, Inc., good for up to 3 Amps at 250VAC, a CD-79F Thermal Protector  63  available from Calco Electric Corp. of Canton, Ohio, good for 15 Amps at 120V AC, a TB02 thermal protector  64 , available from Calco Electric Corp., good for 3 Amps current at 120V AC, a JUC 31 disc thermostat  65 , available from Calco Electric Corp., good for 1 Amp at 250V AC, and/or any other suitable interrupter can be used in some embodiments. 
         [0020]      FIG. 7  shows portion of a lighting fixture wire lead  75  with a temperature sensor  71  incorporated under the wire insulation  74  without disturbing the strand(s)  76 . Any suitable temperature sensor, such as a miniature thermistor or glass thermistor probe, can be used as temperature sensor  71  in some embodiments. Bare section  77  can be used to connect the lead to a ceiling outlet junction using a twist-on wire connector described above in connection with  FIGS. 3-5 . Leads  72  of temperature sensor  71  can terminate in a 2-pin connector  73  so that the sensor can be coupled to a controller board as described, for example, below in connection with  FIGS. 11 and 12 . In some embodiments, leads  72  can be positioned between strand(s)  76  and insulation  78 , which may be integrated with, or separate from, insulation  74 . 
         [0021]    In some embodiments, the distance between bare section  77  and temperature sensor  71  may be less than 2″ to improve heat transfer from a junction including bare section  77  to the temperature sensor. In some embodiments, the distance between bare section  77  and temperature sensor  71  may be more than 1″ to lessen the likelihood of difficulties with attaching a twist-on wire connector to bare section  77 . 
         [0022]      FIG. 8  shows portion of a lighting fixture wire lead  85  having a multi-strand wire with a temperature sensor  81  incorporated under its wire insulation  84 . Any suitable temperature sensor, such as a miniature thermistor or glass thermistor probe, can be used as temperature sensor  81  in some embodiments. As illustrated, wire strands  86  of lead  85  may be slightly untwisted to accommodate the temperature sensor between the strands. 
         [0023]    Bare section  87  can be used to connect the lead to a ceiling outlet junction using a twist-on wire connector described above in connection with  FIGS. 3-5 . 
         [0024]    Leads  82  of temperature sensor  81  can terminate in a 2-pin connector  83  so that the sensor can be coupled to a controller board as described, for example, below in connection with  FIGS. 11 and 12 . In some embodiments, leads  82  can be positioned between strand(s)  86  and insulation  88 , which may be integrated with, or separate from, insulation  84 . 
         [0025]    In some embodiments, the distance between bare section  87  and temperature sensor  81  may be less than 2″ to improve heat transfer from a junction including bare section  87  to the temperature sensor. In some embodiments, the distance between bare section  87  and temperature sensor  81  may be more than 1″ to lessen the likelihood of difficulties with attaching a twist-on wire connector to bare section  87 . 
         [0026]      FIG. 9  shows an example of a lighting fixture wire lead  95  with a circuit interrupting device  91  connected in series. Any suitable circuit interrupting device, such as a Klixon 3BT thermostat, can be used as circuit interrupting device  91  in some embodiments. 
         [0027]    In order to manufacture such a lead  95  in accordance with some embodiments, lead  95  can be cut, wire insulation can be removed from the two portions of lead  95  adjacent to the point of the cut, first wire strands from the portion of the lead proximal to a bare end  97  can be spread around the body of the circuit interrupting device (in the case in which the body is a terminal of the device) to improve heat transfer, the first wire strands can be soldered (or otherwise coupled) to a terminal  92  of device  91 , second wire strands from the portion of the lead distal to bare end  97  can be soldered (or otherwise coupled) to a terminal  93  of device  91 , and heat shrink type insulation  94  can be applied over the temperature sensor, first wire strands, and second wire strands. 
         [0028]    If temperature on the first strands exceeds a given threshold as a result of, for example, of arcing and/or resistance at bare end  97  of lead  95 , the circuit interrupting device may then interrupt the current through the wire lead. In some embodiments, this may cut power to a lighting fixture, which may then indicate the loss of power via any suitable mechanism, such as an audible or visual alert. In some embodiments, the threshold may be set at a temperature higher than that associated with a temperature sensor implanted in a twist-on wire connector so that the circuit interrupter device can provide back-up protection for the temperature sensor. 
         [0029]    In some embodiments, the distance between bare section  97  and circuit interrupter device  91  may be less than 2″ to improve heat transfer from a junction including bare section  97  to the temperature sensor. In some embodiments, the distance between bare section  97  and the circuit interrupter device may be more than 1″ to lessen the likelihood of difficulties with attaching a twist-on wire connector to bare section  97 . 
         [0030]      FIG. 10  shows another example of a lighting fixture wire lead  105  with a circuit interrupting device  101  connected in series. Any suitable circuit interrupting device, such as a CD-79F Thermal Protector, can be used as circuit interrupting device  101  in some embodiments. 
         [0031]    In order to manufacture such a lead  105  in accordance with some embodiments, lead  105  can be cut, wire insulation can be removed from the two portions of lead  105  adjacent to the point of the cut, first wire strands from the portion of the lead proximal to a bare end  107  can be spread around the body of the circuit interrupting device (in the case in which the body is a terminal of the device) to improve heat transfer, the first wire strands can be soldered (or otherwise coupled) to a terminal  102  of device  101 , second wire strands from the portion of the lead distal to bare end  107  can be soldered (or otherwise coupled) to a terminal  103  of device  101 , and heat shrink type insulation  104  can be applied over the temperature sensor, first wire strands, and second wire strands. 
         [0032]    If temperature on the first strands exceeds a given threshold as a result of, for example, of a glowing junction at bare end  107  of lead  105 , the circuit interrupting device may then interrupt the current through the wire lead. In some embodiments, this may cut power to a lighting fixture, which may then indicate the loss of power via any suitable mechanism, such as an audible or visual alert. In some embodiments, the threshold may be set at a temperature higher than that associated with a temperature sensor implanted in a twist-on wire connector so that the circuit interrupter device can provide back-up protection for the temperature sensor. 
         [0033]    In some embodiments, the distance between bare section  107  and circuit interrupter device  101  may be less than 2″ to improve heat transfer from a junction including bare section  107  to the temperature sensor. In some embodiments, the distance between bare section  107  and the circuit interrupter device may be more than 1″ to lessen the likelihood of difficulties with attaching a twist-on wire connector to bare section  107 . 
         [0034]      FIG. 11  shows an example of a lighting fixture  1115  connected to cables from a junction box  1100  in accordance with some embodiments. 
         [0035]    As illustrated, a ceiling outlet junction box  1100  can house three two-wire cables  1101 ,  1102 , and  1103 . Cable  1101  can be a cable that is connected to two poles of a switch. Cable  1102  can be a cable that is connected to a source of un-switched power, such as a line from a circuit breaker panel. Cable  1103  can be a cable that provides power to other components. Although three two-wire cables are illustrated in  FIG. 11 , any suitable number of cables and any suitable types of cables can be used in some embodiments. Although three twist-on type junctions are illustrated in  FIG. 11 , any suitable number of junctions and any suitable types of junctions can be used in some embodiments. 
         [0036]    As can be seen, there are three wire junctions in junction box  1100  that are formed using twist-on connectors  1104 ,  1105  and  1106 . Each one of these connectors can contain one or more temperature sensors placed in any suitable area(s) of the wire connector housings. For example, sensor  1107  can be placed at the tip of connector  1104  adjacent to its spiral metal coil, sensor  1108  can be placed in the plastic housing body of connector  1105 , and sensor  1109  can, be placed in the middle of the housing of connector  1106  in close proximity to its spiral coil. As shown, for example, a temperature sensor  1110  can additionally or alternatively be embedded in a lighting fixture neutral wire lead  1111  in some embodiments. A circuit interrupter device  1112  can additionally or alternatively be embedded in an un-switched power lead  1113 . 
         [0037]    In some embodiments, a control circuit  1114  can be located in lighting fixture housing  1115 . Control circuit  1114  can detect temperature conditions in lighting fixture  1115  and/or junction box  1100  and take any suitable action. For example, circuit  1114  can cut power to light bulbs  1118 , generate an audible or visual alarm, and/or perform any other suitable function. 
         [0038]    Circuit  1114  can be coupled to leads from the temperature sensors in twist-on wire connectors  1104 ,  1105 , and  1106 . Any suitable number, and any suitable type, of temperature sensors can be coupled to circuit  1114  in some embodiments. Extra connectors  1116   a  to  1116   n  can also be provided to circuit  1114  to accommodate any additional temperature sensors that may be desired or needed in an application in some embodiments. 
         [0039]      FIG. 12  shows another example of a lighting fixture  1215  connected to cables  1101 ,  1102 , and  1103  from a junction box  1100  in accordance with some embodiments. As shown, two power wires  1201  and  1202  are provided to fixture  1215  instead of three wires as shown connected to fixture  1115  of  FIG. 11 . This may be the case when only switched voltage is available at junction box  1100 . 
         [0040]      FIG. 13  illustrates an example of a schematic diagram of a control circuit  1300  that can be used to detect temperature conditions and perform an action in response thereto in accordance with some embodiments. Circuit  1300  can be used as circuit  1114  in some embodiments. 
         [0041]    Circuit  1300  may be provided with switched power from a power source and a light switch  1318 . 
         [0042]    As shown, circuit  1300  may include thermistors  1301   a  to  1301   n  as temperature sensors in some embodiments. Any suitable number, including only one, of thermistors can be used in some embodiments. Any suitable type or types of thermistor(s), such as Negative Temperature Coefficient) thermistors, can be used in some embodiments. 
         [0043]    These thermistors can be used as temperature sensors and positioned in a lighting fixture and/or junction box as described herein. For example, these thermistors can be placed in lighting fixture junction twist-on connectors as shown on  FIGS. 3-5  or in lighting fixture wire leads using one of the methods shown in  FIGS. 7-8 . 
         [0044]    Thermistors  1301   a - 1301   n  may be connected in parallel, and have one side connected to ground and another side connected to a non-inverting input of an operational amplifier  1304 . Any suitable operation amplifier, such as a LM741 operational amplifier available from National Semiconductor Corporation, can be used in some embodiments. 
         [0045]    In operation, as the resistance of the parallel thermistors drops under a given level due to increased temperature at one or more of the thermistors, the operational amplifier drives a transistor  1305 , which drives a relay winding  1306  of a relay. In response to the winding being driven, a normally closed switch  1307  of the relay opens and thereby disconnects power to one or more light bulbs  1308  of the lighting fixture. A normally open switch  1309  of the relay may also close in response to the winding being driven and thereby activate an audible alarm  1310  and/or a visual alarm  1311 . Another normally open switch  1312  of the relay may also be provided and wired in parallel to transistor  1305  to latch the relay winding in the energized state once the relay winding is energized. In this way, power can remain disconnected from the one or more light bulbs  1308  of the lighting fixture even after the temperature at the thermistors has dropped (e.g., due to the junction cooling off). A normally closed momentary switch  1313  can be provided in series with switch  1312  to allow an operator to release the latched state of the relay winding and thereby restore power to the light bulbs  1308 . 
         [0046]    In some embodiments, temperature sensitive circuit interrupter devices  1314  and  1315  can be included in circuit  1300 . Any suitable type(s) and number of circuit interrupter devices can be used, and these devices can be installed in any suitable location (e.g., such as in lighting fixture lead wires as shown in  FIGS. 9-10 ). An activation of any one of devices  1314  and/or  1315  may cause an interruption of a line voltage supply to circuit  1300 . In some embodiments, the circuit interrupter devices can be selected and/or configured to disconnect power at a temperature that is higher than the temperature at which relay winding  1306  is energized so that devices  1314  and  1315  act as back-up temperature sensors. 
         [0047]    In some embodiments, a battery  1316  and/or a battery charging circuit  1317  can be provided. Any suitable battery  1316  and battery charging circuit  1317  can be used in some embodiments. When line power is available to circuit  1300 , battery charging circuit  1317  can regulate the voltage from a rectifier, provide a DC supply voltage, and charge battery  1316 . When line power is not available, circuit  1317  can provide power from battery  1316  as the DC supply voltage. 
         [0048]    A potentiometer  1319  can also be provided in circuit  1300  as part of a voltage divider that sets the reference voltage at the inverting input of operational amplifier  1304  in some embodiments. This reference voltage can be used to adjust the temperature point at which relay winding  1306  is energized. In some embodiments, a potentiometer  1320  can be provided and used to set a hysteresis between the temperature at which the relay winding is driven by transistor  1305  and the temperature at which the transistor no longer drives the relay winding (although, the winding may still be driven by switches  1312  and  1313 ). 
         [0049]      FIG. 14  illustrates an example of a schematic diagram of a control circuit  1400  that can be used to detect temperature conditions and perform an action in response thereto in accordance with some embodiments. Circuit  1400  can be used as circuit  1114  in some embodiments. 
         [0050]    Circuit  1400  may be provided with un-switched power from a power source and used in instances in which no wall light switch is used and, instead, a light switch  1409  is provided on the lighting fixture (e.g., a “pull chain” type switch). 
         [0051]    As shown, circuit  1400  may include a relay having a relay winding  1401 , a normally closed switch  1402 , and a normally open switch  1407 . When power is received at circuit  1400  via circuit interrupting devices  1403  and  1404  and a momentary switch  1410  is manually closed, relay winding  1401  is energized which causes switch  1402  to open. However, when power to the relay winding is removed, such as because one of devices  1403  and/or  1404  has opened due to an over-temperature condition, switch  1402  closes causing an alarm to be generated. 
         [0052]      FIG. 15  illustrates an example of a schematic diagram of a control circuit  1500  that can be used to detect temperature conditions and perform an action in response thereto in accordance with some embodiments. Circuit  1500  can be used as circuit  1114  in some embodiments. 
         [0053]    Circuit  1500  may be provided when both switched power and un-switched power are available via lines  1501  and  1502 , respectively. As shown, a wall mounted light switch  1503  can be used to interrupt the circuit of light bulbs  1504 . 
         [0054]    Although the invention has been described and illustrated in the foregoing illustrative embodiments, it is understood that the present disclosure has been made only by way of example, and that numerous changes in the details of implementation of the invention can be made without departing from the spirit and scope of the invention, which is only limited by the claims which follow. Features of the disclosed embodiments can be combined and rearranged in various ways.