Abstract:
The Robust Safe Switch and Control Device is an “Internet of Things” end effecter that provides a minimally dissipating, robust switch tightly integrated with circuit, life and property automated safety features. The device enables extended sensing and monitoring capabilities that enable the effective management of the “Internet of Things.”

Description:
BACKGROUND OF THE INVENTION 
       [0001]    From the beginning of controlled electrical switching, arc pitting and the wear of switch contact points has been a pervasive issue that actually created significant job opportunities over many decades. With the advent of alternating current, point wear was at least somewhat normalized between the two points. And with the development of more powerful electrical machines switching apparatus became remote to the actual user as the economies of smaller wire and small currents were used to remotely switch much larger electrically activated switches. 
         [0002]    For many decades, the salvation of remote switching of resistive and especially inductive loads was the mercury-wetted contact relay. The resurfacing of the contacts with every mechanical action provided a switching lifetime rated in the tens of millions of cycles; but recent environmental concerns have eliminated the use of mercury in routine industrial and commercial devices and more so in the household application of remote switching. 
         [0003]    Solid state technologies created an opportunity for low power electronics to monitor the alternating current waveforms and attempt to synchronize the switch action of the actual opening and closing with the zero crossing of the waveform. The device speed of emerging solid state devices such as the Silicon-Controlled Rectifier (SCR) or Triac enabled the ambition for a zero-crossing switch. But these devices, at best, have about a 1.5 Volt drop across the device when switched on. This voltage, times the load current, is the energy dissipated as heat. For a 20 Amp load, this is 30 Watts of loss. In today&#39;s environmentally sensitive market, 30 Watts per switch is a terrible waste. 
         [0004]    Mechanical relays on the other hand do not dissipate significant energy in the “on” state, but unlike SCRs and Triacs, which are easily switched at a zero crossing, the relatively slow mechanical relays form arcs as the contact points open or close while current flows and the resulting heat melts or pits a little of the contact points at every switch cycle. The contact points have to be specifically designed to be “self cleaning,” in which case they are designed to wear out but maintain a low “on” resistance; or they are dramatically over-built in anticipation of wear. In either case, mechanical relays have a significant wear rate. 
         [0005]    As of 2017 opportunities to extend useful functionality through the “Internet of Things” brings heightened sensitivity to the efficiencies of remote switching. Additionally over the last 20 years an increased awareness of the capability to provide life safety capabilities in circuit extension and switching devices has brought forth first Ground Fault Interrupter National Electric Code requirements for such devices. And in the last few years the requirement for Arc Fault Interrupter protection for property has become a reality. 
         [0006]    This invention is a logical extension of the history of robust switching, the technology of embedded control, the emerging needs of an Internet-based remote switching activity, and the evolving concern to provide circuit safety as well as safety for life and property in the immediate environment of the switching activity. 
         [0007]    Early inventions targeting more robust switching were focused on the monitoring and detection of the alternating current zero crossing as a switch point opportunity. Michael Sidman&#39;s U.S. Pat. No. 4,153,870 granted on May 8, 1979, revealed a method and apparatus to identify the zero crossing in a power circuit switched by a Triac or back-to-back SCRs. 
         [0008]    Of significant achievement was the disclosure by Rockwell International of a monolithic solid state power controller featuring zero crossing switching and programmable or configurable current limiting in U.S. Pat. No. 4,174,496 by inventors William McFall et al, granted on Nov. 13, 1979. 
         [0009]    A disclosure using lower-cost components for a zero-crossing switch was granted to inventor Raymond Robertson on Aug. 14, 1984, U.S. Pat. No. 4,466,038. In this invention a single unidirectional SCR is used to isolate and control circuit switching for half cycles, allowing for a near zero voltage switching opportunity to energize and close a mechanical switch. 
         [0010]    In U.S. Pat. No. 4,767,944 granted on Aug. 30, 1988, Hiroto Takeuchi and Masahiro Hishimura confirmed that analysis had shown switch contact points to be most affected by the operation of opening under a load, as the AC cycle was more than π/8 away from a zero-crossing point. Their method supported a novel apparatus which detects and measures the exact phase angle of the alternating current and drives a mechanical relay to only open when within π/8 of a zero crossing in the alternating current phase angle. Prior to this invention, the option of using a solid state switch in AC circuits was the most likely way to extend contact point life. But Takeuchi&#39;s invention significantly extended point life and did not generate the thermal loss and heat build up as did solid state switching. 
         [0011]    Another unique extension solution to the switch point wear issue was disclosed by Hiroyuki Nishi et al in their Oct. 1, 1991, U.S. Pat. No. 5,053,907 in which three sets of contact points are synchronized to the alternating current waveforms of three phases and operate in conjunction with three triacs for the control of three-phase motors and other equipment. This device also includes circuitry to suppress leakage current of the electronics. 
         [0012]    The true “hybrid” relay was first disclosed by Andrew Kadah in his Dec. 16, 1997, U.S. Pat. No. 5,699,218 which used a TRIAC as the solid state switching device and a mechanical relay to carry the load current. In this method the leakage current is minimized by capacitor coupling the gate drive to the TRIAC. 
         [0013]    John Dougherty in his U.S. Pat. No. 6,046,899 of Apr. 4, 2000, presents a method of simultaneous operation of both a solid state switch and a mechanical switch where actuation of the two devices is achieved by a common power feed. This method relies on the inherent speed of the solid state device to close or open the circuit before the mechanical components have physically connected or broken the circuit and had opportunity to arc the contact points. 
         [0014]    Gerard Blain and Luc Raffestin, in their U.S. Pat. No. 6,347,024 B1 of Feb. 12, 2002, revealed a method of simultaneously energizing the solid state switch and the mechanical relay on the same alternating current cycle. This method incorporates a programmable device that can be configured to sequence the solid state switch and the mechanical relay in response to the relative speed of a variety of solid state switches by adjusting the timing between control signals for each particular type of switch. 
         [0015]    Hervé Carton and Denis Flandlin, in their U.S. Pat. No. 6,643,112 B1 of Nov. 4, 2003, reveal a novel implementation of a single transistor used to eliminate the point arc of a mechanical relay. In this implementation the transistor is used in parallel with a mechanical relay to eliminate point arcing in DC circuits. And to detect the alternating current direction and only permits a mechanical switch closing or opening when the alternating current is flowing such that the transistor is forward biased and configured to initiate or terminate current flow at the next zero crossing. 
         [0016]    Sergio Orozco in his U.S. Pat. No. 8,089,735 B2 of Jan. 3, 2012 further evolved both the method and the apparatus by integrating the temperature measurement of the solid state switch into the control process and protectively disabling the switch as the temperature rises before the solid state device is damaged by excessive heat. 
         [0017]    Common to the significant evolutionary steps of robust switching is a relatively narrow focus towards maximizing the useful life of the switch and minimizing the operational thermal losses of the switching activity. The early Rockwell device (U.S. Pat. No. 4,174,496) stands out uniquely as an attempt to combine circuit protection with zero-crossing switching by implementing a configurable current limiting activity as an integrated functionality. 
         [0018]    Recent technology developments have enabled the monitoring of branch circuits to not only add protection for equipment but also provide precise monitoring and control to protect human and animal life from the dangers of electric shock or electrically ignited fire. These concerns are now addressed in Ground Fault Circuit Interrupters and ARC Fault Circuit Interrupters. 
         [0019]    The invention disclosed herein includes not only the features of a robust switch and a configurable means for circuit protection, but also includes the features of life safety (Ground Fault Interruption) and property safety (Arc Fault Interruption). This collection of features fills an important need when confronted with the opportunities of the “Internet of Things” and the intended applications of remote switching where, because of their nature, the remote components of Internet implementations imply that the only observational opportunities will be built-in to the controller. 
         [0020]    Although the telepresence sensors are not required for a full implementation, this disclosure will illustrate that the basic apparatus configuration is constructed to provide extended environmental sensors as support to the effective management of the remote switch. Support sensing such as temperature, audio and ambient light measurement will greatly enhance the effective remote management of “Internet of Things.” 
         [0021]    This invention comprises both an apparatus which is an exceptionally robust, efficient, safe and reliable remote switching device for controlling AC-powered circuits and a method to operate said device. This device nearly eliminates the thermal dissipation common to all SCR (Silicon Controlled Rectifiers) and Triacs (Back-to-Back SCRs for full wave switching) and also nearly eliminates the wear caused by arcing of the contact points in a relay switching device. This invention includes an embedded microcomputer and sensing apparatus and a method which will schedule and control the interleaved switching action of an SCR or Triac electronic switching device and actuation of a mechanical relay creating a “Hybrid Relay,” while monitoring the load and return currents for life safety and circuit current waveforms for distortion caused by arcing: thus a “Robust Safe Switch.” 
         [0022]    Still this “Robust Safe Switch,” because of its intended support for the “Internet of Things” and such end effectors as motors, solenoids and other inductive loads, has the configurable ability to accommodate time-limited start-up current ramps that will exceed the normal operating current limits, while maintaining vigilant management of life safety and property safety issues. 
       BRIEF SUMMARY OF THE INVENTION 
       [0023]    The emergence of the “Internet of Things” has brought new emphasis on remote switching of both resistive and inductive loads. Not only is the switching remote from the user, but the process now includes computer-adaptive automated switching—whether the computer is embedded, tied in by a wired or wireless network or a cell phone doing “app” duty to regulate some “thing” in a user&#39;s physical world. 
         [0024]    Adaptive automated switching includes techniques that enable apparent proportional control by pulse-width modulating a simple remote on and off switch. The economy of the “Internet of Things” will depend to a large part on the useful life of the remote switch. 
         [0025]    What is missing from the current repertoire of components to enable the Internet of Things is a cost-effective switch that is both highly reliable and energy efficient with virtually no thermal losses. Yet because this switch is by definition “remote” it must incorporate provisions to ensure the safety of equipment, lives and property. 
         [0026]    The Hybrid Relay is a circuit that makes the best use of the Triac solid state device and the mechanical relay. The solid state electronic device is forced to work in harmony with the mechanical relay by an embedded microprocessor that also performs multiple integrated functions delivering “robust” characteristics. 
         [0027]    The microprocessor coordinates the timing of the Triac and the mechanical relay to optimize the combined action of both devices operating in parallel on the same current flow path. The Hybrid Relay uses a Triac to initially switch the load at a zero voltage crossing. As soon as the Triac has made the switch, the mechanical relay closes when the voltage across the Triac has settled to approximately 1.5 Volts max. This voltage is too low to significantly cause arcing to the mechanical points in the relay. But as soon as the mechanical relay is made, the thermal dissipation across the Triac is reduced to zero as the mechanical contacts of the relay present a very low resistance path to the current flow. Because the Hybrid Relay is operating in a fixed-frequency environment of either 50 or 60 cycles per second, the timing is a fixed period that more than encompasses the operating time of the mechanical relay. After the mechanical relay has had time to close, the drive voltage to the Triac gate can be removed by the microprocessor and applied again prior to the opening of the mechanical relay. 
         [0028]    Additionally, the microprocessor enables “Robust” characteristics by monitoring the total current that is passing through the switch. If the current draw becomes excessive compared to a configurable reference, then the microprocessor will command the Hybrid Relay to open the circuit. 
         [0029]    Further, the microprocessor monitors the combined current of the load and the return legs of the circuit. If there is an imbalance of more than a few milliAmps (i.e., a Ground Fault), the circuit will open. Simultaneously, the microprocessor continuously monitors the circuit waveforms and frequency. Significant deviations from a smooth 60 cycle alternating current will be detected as an ARC Fault. 
         [0030]    And finally, the microprocessor provides visible status indication through the use of LEDs to indicate a fault condition of excessive current draw, a Ground Fault or an ARC Fault and the operational state of the Hybrid relay. If the Robust Safe Switch is configured with a network extension processor, the average and peak current flow, as well as the fault status, are also sent to the network processor. 
         [0031]    Although the Robust Safe Switch is configured to operate as a near direct replacement for a standard remote solid state or mechanical relay requiring only a wired AC or DC control voltage signal to enable operation, the device is also equipped with a two-wire network interface to operate as an extension of an embedded wired or wireless network control processor. 
         [0032]    When the Robust Safe Switch operates as an extension of a network control processor, the safety and power-saving features are extended to remote functionality, such as manual remote control or automated response control, such as turning off power when a smoke detector sounds. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0033]      FIG. 1  represents a typical electrical schematic of the functionality of the Robust Safe Switch incorporating the functionality of the Hybrid Relay, indicating the major functional components. 
           [0034]      FIG. 2  is an expansion of the Robust Safe Switch which makes use of the interprocessor bus connectivity to enable true remote wired or wireless features as well as the added functionality of many easily integrated hardware capabilities such as “Off Board Temperature,” temperature of the electronics, a microphone and/or a visible light detector. 
           [0035]      FIG. 3  is a functional flow chart of the logic of the embedded functionality within the Robust Safe Switch. 
       
    
    
       [0036]      
         [0000]    
       
         
               
               
             
           
               
                   
               
               
                 Reference 
                   
               
               
                 Signs 
                 Description 
               
               
                   
               
             
             
               
                 CN1 
                 External connector extending internal power and control to a network 
               
               
                   
                 interface processor 
               
               
                 CN2A 
                 DC input control signal connector 
               
               
                 CN2B 
                 AC line input control signal connector 
               
               
                 CN3 
                 Input Connector delivering AC Power from the line to the local “switch 
               
               
                   
                 mode power supply” 
               
               
                 CN4 
                 Connector delivering AC Line and Neutral Power out of the Robust 
               
               
                   
                 Switch 
               
               
                 CN5 
                 Connector delivering AC Line and Neutral Power in to the Robust Switch 
               
               
                 ISO-1 
                 Opto-isolated input open collector diode triggered by the presence of an 
               
               
                   
                 AC (Line) input at CN2B 
               
               
                 ISO-2 
                 Opto-isolated input open collector diode triggered by the presence of a DC 
               
               
                   
                 input at CN2A 
               
               
                 KC 
                 Mechanical Relay in parallel with TRIAC 1 carrying the AC LOAD in the 
               
               
                   
                 steady state 
               
               
                 LED1 
                 Status indicator LED 
               
               
                 LED2 
                 Status indicator LED 
               
               
                 OPTO TRIAC 1 
                 Optically isolated AC buffer switch between U11 and TRIAC 1 
               
               
                 OPTO TRIAC 2 
                 Optically isolated AC buffer switch between U11 and relay KC 
               
               
                 SH1 
                 Current shunt on the AC “Hot” or “LOAD” side 
               
               
                 SH2 
                 Current shunt of the AC Neutral side 
               
               
                 TRIAC 1 
                 Power TRIAC carrying the AC LOAD during all switching operations 
               
               
                 U1 and U3 
                 Differential amplifier pair providing isolation 
               
               
                 U2 
                 Differential amplifier 
               
               
                 U4 
                 Level shifting unity gain amplifier 
               
               
                 U5 and U9 
                 Differential amplifier pair providing isolation 
               
               
                 U6 
                 Differential amplifier 
               
               
                 U7 
                 Level shifting unity gain amplifier 
               
               
                 U8 
                 Summing amplifier, summing the detected current levels between the out- 
               
               
                   
                 of-phase AC “Hot” and AC “Neutral 
               
               
                 U10 
                 Hard limiting comparator, square wave frequency detector 
               
               
                 U11 
                 Programmable, highly integrated resource circuit featuring, Analog-to- 
               
               
                   
                 Digital Converters, Counters, Timers, digital outputs and communication 
               
               
                   
                 buses 
               
               
                 U12 
                 Differential shunt voltage pickup on the LOAD side of the AC 
               
               
                 U14 
                 Differential shunt voltage pickup on the Neutral side of the AC 
               
               
                 U15 
                 Switch Mode Power Supply integrated circuit controller 
               
               
                  1 
                 Network Extension Processor 
               
               
                  2 
                 System on a Chip (SOC) 
               
               
                  3 
                 Robust Safe Switch 
               
               
                  9 
                 Ambient Light Sensor of the network processor 
               
               
                 10 
                 DC trigger connector on network processor 
               
               
                 11 
                 Interprocessor bus connector on network processor 
               
               
                 12 
                 Barometric Pressure Sensor of the network processor 
               
               
                 13 
                 The ARM processor of the network processor 
               
               
                 14 
                 Ethernet connector to a physical Local Area Network 
               
               
                 15 
                 Microphone peripheral of the network processor 
               
               
                 16 
                 Humidity sensor of the network processor 
               
               
                 17 
                 Temperature sensor of the network processor 
               
               
                 18 
                 Projected Infrared temperature sensor measuring “off-board” temperature 
               
               
                 20 
                 WiFi radio of the network processor 
               
               
                 21 
                 BlueTooth radio of the network processor 
               
               
                 22 
                 ZigBee radio of the network processor 
               
               
                 23 
                 Physical antenna of the WiFi radio 
               
               
                 24 
                 Physical antenna of the ZigBee radio 
               
               
                 25 
                 Physical antenna of the BlueTooth radio 
               
               
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF THE INVENTION 
       [0037]    The Robust Safe Switch circuit performs several separate functions simultaneously using a hybrid mix of analog and digital circuitry. The following description is notional, or an example. The circuit could be implemented with a variety of circuit components able to provide the method functionality. 
         [0038]    ISO- 1  and ISO- 2  are open collector type opto-isolators that enable the circuit to be controlled by virtually any type of device that can source a minimum amount of current at a minimum voltage. The circuit can be configured on the inputs to connector CN 2 A to operate as driven by an AC/Neutral input or to be driven by a separate DC source CN 2 B. ISO- 1  and ISO- 2  completely isolate the circuit from the devices providing the driving current to CN 2 B and CN 2 A, respectively. 
         [0039]    U 15  is a highly efficient Switch Mode Power Supply (smps) providing DC power from the AC Line voltage, as presented in  FIG. 1  to be 120-240 Volts AC. Such an smps power supply could be created using an integrated circuit or created from discrete components. The power supply for this circuit need only be sufficient and is not a critical component of the functionality. 
         [0040]    CN 1  is the connector that links the Robust Safe Switch to a controller module that will support wired and wireless networking to enable the Robust Safe Switch to be the end effecter component of an Internet of Things system. The connector provides all of the inner process component controls to enable monitoring and augmented control of the Robust Safe Switch internal system, including an interprocessor bus. 
         [0041]    The Robust Safe Switch extension processor (see  FIG. 2 ) adds an integrated System on a Chip (SOC) with a central processing unit (a low power ARM processor) using an interprocessor bus interface to a programmable radio system, or separate radio systems such as Bluetooth, ZigBee or WiFi radio subsystems, or any combination thereof. 
         [0042]    The principal control circuitry presented in  FIG. 1  showing CPU (U 11 ) uses opto-isolated OPTO TRIAC  1  to initialize all AC switching operations. When the load is fully carried across the TRIAC  1 , then the CPU (U 11 ) will energize or de-energize mechanical relay (KC) by driving opto-isolated OPTO TRIAC  2  to power the relay (KC) or removing the drive from OPTO TRIAC  2  to de-energize relay (KC). After the load is fully carried across relay (KC) or fully removed from the relay (KC), the CPU (U 11 ) will release the drive on OPTO TRIAC  1 . (Note that this is not the only configuration, nor even the most optimal configuration, both OPTO TRIAC  1  and OPTO TRIAC  2  could be replaced by transistor or CMOS drives.) 
         [0043]    This action ensures that the voltage across the mechanical relay KC is never greater than the saturation voltage of the TRIAC  1  during a relay KC switching action. The TRIAC  1  is used to eliminate the arcing and contact wear in the relay KC. The use of the relay KC to carry the steady-state load eliminates the dissipation factor of the TRIAC  1  during a continuous duty operation. Thus a significant energy savings and a dramatically extended useful life expectancy of both TRIAC  1  and relay KC are maintained. 
         [0044]    Operational amplifiers U 1 , U 2 , U 3  and U 4  provide an isolation differential amplifier monitoring current shunt SH 1  interface U 12  which could be a zero-loss Hall Effect device. SH 1  accurately measures the current flowing through the “hot” side of the AC supply circuit which will be controlled and monitored to supply the “load” side of the hybrid relay. 
         [0045]    Operational amplifiers U 5 , U 6 , U 7  and U 9  provide a similar function on the neutral leg of the AC supply circuit. The outputs of both differential amplifier circuits are fed into summing and level-shifting amplifier U 8 . 
         [0046]    Both U 7  and U 4  have offset circuits that have been conditioned to set the measured current flow of the neutral shunt monitoring SH 2  through interface U 14  (which again could be a zero-loss Hall Effect device) and SH 1  through interface U 12 , representing the AC “hot” side current, to be precisely one half V cc  when the monitored current is zero respectively in each measured side of the AC circuit. 
         [0047]    The low-pass summing amplifier U 8  will sum the measured current in the neutral leg of the AC with the out-of-phase AC “hot” leg measured current and amplify the result. The amplified sum is detected by the Analog-to-Digital converter in U 11 , where the digital representation of the sum will be compared to a programmable leakage current limit. Excessive current will indicate a Ground Fault condition. 
         [0048]    Upon a Ground Fault Condition, the CPU U 11  will implement an immediate shutdown and issue an appropriate signal on LED 1  and LED 2  to indicate that a GROUND FAULT has occurred. 
         [0049]    Removing power from the Robust Safe Switch will reset the GROUND FAULT detection. 
         [0050]    Comparator U 10  is configured to compare the measured current of the AC “hot” leg as represented by the voltage across SH 1  to the approximated mid-scale of the voltage swing of the representative signal from SH 1  through interface U 12 . Comparator U 10  will hard limit and create a square wave representative of the frequency of the current signal monitored by SH 1 . This frequency representative signal will be fed into U 11  where a counter output will read by the CPU U 11 . Significant deviations from the expected frequency will be considered indications of ARC FAULT. An ARC FAULT will cause the CPU to issue the commands to open the AC circuit and send a notification signal pattern to LED 1  and LED 2 . 
         [0051]    Resetting the AC power will resent the ARC FAULT status. 
         [0052]    The well conditioned output of U 4  represents the current flowing to the load and it is fed to a high performance Analog-to-Digital Converter A/D. The output of the converter is used by the CPU (U 11 ) to compare the current flowing through the load to the expected (configured) limits. 
         [0053]    Acceptable current limits can be configured at manufacturing (or field configured with a network connector adapter and a cell phone “app” or through a connected network processor) to apply just to the configurable startup period of, for example, 2 seconds to follow one of several available motor startup curves. During the startup period, the circuit continues to monitor the current flow for indications of GROUND FAULT and ARC FAULT conditions. 
         [0054]    After the startup period, the CPU (U 11 ) compares the maximum permissible current to a normal or “run time” expected limit. Any current measurements that do not meet the expected values for startup or run situations will be considered faults and the hybrid relay will be commanded to shut off the flow of AC current and CPU (U 11 ) will issue the appropriate status signal patterns on signal LED 1  and LED 2 . 
         [0055]    During all operations, the CPU (U 11 ) is available through a two-wire bus available at connector CN 1 . This bus enables the use of the Robust Safe Switch as an effective and efficient end-effecter for a network centric controller and the extension of a wired or wirelessly connected network, including the Internet, to the low level of remote switching. 
         [0056]    The external connector CN 1  links the Robust Safe Switch to a network processor extension  1 , through interprocessor bus connector  11 , which will enable wired and wireless networking to enable the Robust Safe Switch  3  to be the end effecter component of an “Internet of Things” system. The connector  11  provides all of the inner process component controls to enable monitoring and augmented control of the Robust Safe Switch internal system through the interprocessor bus. 
         [0057]    It is possible that an adapter with a wireless connection could be temporarily connected to connector CN 1  on the Robust Safe Switch  3 , which would enable a smart phone “app” to field reconfigure the set points for the current limit or to read the current load on the circuit in real-time. 
         [0058]    The Network Extension Processor  1  (see  FIG. 2 ) adds an integrated System on a Chip (SOC)  2  with a central processing unit  13  (a low power ARM processor) using the interprocessor bus interface  11  to link the Robust Safe Switch  3  to the network processor subsystem  1  featuring a wired  14  or a wireless  20 ,  21 ,  22  network system. Wireless systems could be any or all of a low-power Bluetooth  21 , a ZigBee  22  and/or a WiFi  20  radio system. Each of these radio system could utilize an external antenna or integrated circuit-board antennas  23 ,  24 ,  25 . 
         [0059]    Currently many of these households do not have the ability to use a controlled network to assist them in the control and the operation of appliances. These people are outside of the Internet. But the Robust Safe Switch technology is extending the Network of Things to those without access to the Internet. 
         [0060]    The Robust Safe Switch with the Network Extension processor features could be configured with a BlueTooth  21  and a ZigBee radio system  22  delivering control and mesh networking. The ZigBee units  22  will automatically network together and enable a rural home owner without benefit of the Internet or WiFi to use his cell phone as an interface to control an impromptu Internet of Things network. Such a system could include heaters and other appliances like window-mounted air conditioners, lighting and gate controllers. As shown on  FIG. 2 , the SOC could include telepresence sensors to detect and report environmental parameters such as humidity  16 , device temperature  17 , projected temperature  18 , ambient light  9 , or barometric pressure  12 . Through Network Extension processor  1  and interface CN 1 , the homeowner can control the home environment and other appliances, through a computer or phone “app” or through an on-board microphone interface  15 . The embedded microcontroller U 11  could be configured to maintain schedules downloaded to each device and monitored through the ZigBee Mesh when the cell phone is within range of its BlueTooth signal. 
         [0061]    The apparatus described herein employing the method as described dramatically extends the capability to effectively and safely manage the “end effect” of the long reach of the “Internet of Things”. Although not currently required by code at all locations suitable for extension through the Internet of Things, the concern for circuit, life and property safety should be reasonably considered as the power of the Internet reaches to the practicalities of remote control to the masses. 
       Detailed Description of the Method Logic Flow Chart 
       [0062]    As shown in  FIG. 3 , at power up  100  the processor resets to read the input status pin  105  and then evaluates the status as changed to “off”  120  or “off” no change then loops back to read the pin again at  105 . If the pin reads “on,” control moves to  107  to test for persistence (i.e., still on)  115  or a change to “on”  110 . 
         [0063]    If the circuit is just turned on then sub-routine  110  operates the interleaving cycle of energizing TRIAC  1  for a zero crossing switching action to power the circuit, then energizing the mechanical relay KC after the TRIAC  1  has settled and the voltage to be switched is near a minimum 1.5 volts and then un-powering the TRIAC  1  after the mechanical relay KC has settled. 
         [0064]    If the circuit is still on, then routine  115  evaluates whether the process is still inside a preset or configurable motor startup current ramp. If it is, then control advances to process  116  where the program execution time is compared with the table stating the allowable current at that preset or configurable time window of control for the “motor start up” current control ramp (e.g. a current limit that varies as a function of time). If within the time window of startup current ramp then control is advanced to process  130  where the measured current is compared to the selected ramp profile. If the measured current is not within the profile then control advances to process  120 . At process  120 , TRIAC  1  is energized to pick up the load from the mechanical relay KC at the next zero voltage crossing. This action allows the mechanical relay KC to open at a minimal voltage across the relay contact points on KC. After the mechanical relay KC has settled into the open condition, TRIAC  1  is de-powered at the next zero crossing, again minimizing both switching arcing and thermal dissipation. Return from process  120  advances to the LED message display  117 , where the “Motor Startup Over Current” indication is displayed on signal LEDs LED 1 , LED 2 . After a preset or configurable presentation time, the Robust Safe Switch will halt and wait for a power cycle to reset  118 . 
         [0065]    If the measured current is within the stated measurement profile, then program control is advanced to process  155  where process  150  results for high frequency ARC fault test conditions are evaluated. If an ARC fault condition is detected, then control is advanced to process  120  for shutdown and upon return to process  156  “ARC FAULT” indications are flashed on the signal LEDs LED 1 , LED 2 . After a preset or configurable presentation time, the Robust Safe Switch will halt and wait for a power cycle to reset,  118 . 
         [0066]    If an ARC FAULT condition is not detected then control advances to  145  where the return values for process  160  are evaluated for indications of a GROUND FAULT condition of leakage current to ground. If the evaluation indicates that the GROUND FAULT conditions have existed for a time period to exceed the threshold, then control will shift to shut down procedure  120  to shut down power and upon return to  146  “GROUND FAULT” indications are flashed on the signal LEDs LED 1 , LED 2 . After a preset or configurable presentation time, the Robust Safe Switch will halt and wait for a power cycle to reset,  118 . 
         [0067]    If the “on time” exceeds the “motor start up ramp” timer then control moves to process  125  where the results from sub-routine  140  are evaluated and the preconfigured or configurable “normal runtime” current” limits are used to test the measured AC “hot” load current. If the measured current exceeds the limit then shutdown process  120  is called and upon return process  126  is called to flash “Run Over Current” on the signal LEDs LED 1 , LED 2 . After a preset or configurable presentation time, the Robust Safe Switch will halt and wait for a power cycle to reset,  118 . 
         [0068]    If the measured current does not exceed the limits of sub-routine  140 , then control is passed to process  155  where process  150  and then process  160  are called. If the results of  150  and then  160  are within limits, control is returned to process  105  and the control loop is repeated.