WO2000017728A2

WO2000017728A2 - Computer controlled ac electrical terminations and network

Info

Publication number: WO2000017728A2
Application number: PCT/US1999/021669
Authority: WO
Inventors: Alexander J. Severinsky
Original assignee: U1, Inc.
Priority date: 1998-09-22
Filing date: 1999-09-20
Publication date: 2000-03-30
Also published as: WO2000017728A3; WO2000017728A9

Abstract

The computer controlled AC electrical termination of the present invention comprises a microcontroller unit (MCU) (14), a bistable relay (128), a power supply operated in a pulsed mode and at least one sensor. In one embodiment, the MCU (14) senses an electrical condition via the electrical sensor, and control the bistable relay (128) via the power supply operated in a pulsed mode. Voltage and current sensors (12) are input to the microcontroller (14), from which over-voltage, under-voltage, miswired neutral, lack of ground connection, ground fault currents and the like are detected by use of an algorithm stored in the microcontroller (14). Mechanical sensors (416, 418) are provided to sense the presence of inserted prongs (412), which is used by the microcontroller (14) to detect child tampering and shut off output power. The microcontroller (14) in each respective AC electrical termination is responsive to digital signals from the central control computer (654) to remotely control and monitor a variety of power functions.

Description

COMPUTER CONTROLLED AC ELECTRICAL TERMINATIONS AND NETWORK

Cross-reference to related applications

Applicant hereby claims the benefit of priority of U.S. patent application no. 60/101365, filed September 22, 1999.

Field of the invention

The present invention relates to the field of AC power control.

Background of the invention

Alternating Current (AC) power is the primary source of electrical energy for most electrical and electronic equipment. Electrically powered equipment is typically controlled in several ways. A basic power control function is to turn power on and off using a manually operated on/off switch between the power source and the load. More advanced power control functions include detection of fault conditions, and responses to fault condition detection by turning off AC power. Examples of fault conditions include input over- voltage, output current overload, input under-voltage, reversed connections for the neutral and ground conductors, lack of a ground connection, detection of ground fault currents and the like.

AC outlets with power control fault detection, as for example GFCI protection (ground fault circuit interruption) , currently use analog power components. For example, a relay is typically used to turn off the output power responsive to a detected fault condition. In addition, prior art AC outlet safety features are achieved using mechanical devices. For example, a typical GFI outlet has a mechanical push button to reset the AC outlet and restore output power after fault detection. As another example, prior art tamper resistant outlets (which sense a child inserting a pin into an outlet) use relatively complex mechanical interlocks to prevent insertion of a single object into one of the contact holes of an AC outlet.

Networked power control systems have been designed to control AC power using a variety of communication and control techniques . Industrial power control systems use a central computer to supervise energy distribution and save energy. For example, turning off lights when not in use, load leveling power consumption between major electrical appliances, adaptive dimming to utilize ambient light and similar power saving techniques require control over AC power delivery. In the industrial control area, LonWorks™, a widely supported industry standard, has been used for automating commercial lighting and heating, ventilation, air conditioning (HVAC) . LonWorks is a distributed control network using a flexible communications protocol for the distribution and use of AC power. However, such industrial power control systems have been prohibitively expensive, and far too complex for consumer use.

SUMMARY OF THE INVENTION

The computer controlled AC electrical termination of the present invention comprises a microcontroller unit (MCU) , a bistable relay, a power supply operated in a pulsed mode and at least one sensor. The sensor may be either electrical or mechanical. In one embodiment, the MCU senses an electrical condition via the electrical sensor, and controls the bistable relay via the power supply operated in a pulsed mode. All the components fit into a standard AC power receptacle. In particular, the invented computer controlled AC electrical termination fits within a volume of 1.625 inches wide, by 2.625 inches high, by 1.25 inches deep, which is the maximum usable volume of space available within a standard AC power receptacle.

The features of AC electrical termination of the present invention are determined by programming in the MCU. Use of a programmable digital architecture fitting within an AC power receptacle, results in a computer controlled AC electrical termination with more features and lower cost than the prior art AC outlets having mechanical and analog power components. While analog and mechanical power control components are mature components that have relatively stable prices, one chip microcontrollers have become less expensive, and, like other semiconductor devices, tend to become less and less expensive with time. Furthermore, since the operation of the computer controlled AC electrical termination of the present invention is based on a digital MCU and a programmable architecture, novel AC power control functions, normally not feasible with analog and mechanical power components, are added by programming and changed by re-programming.

By way of example, the microcontroller in the AC electrical termination of the present invention can monitor the AC current, compare it to a preset maximum. AC power is shut off when an AC over-current condition is detected. The level of preset maximum current is programmable. In such manner, the AC electrical termination of the present invention becomes a programmable resettable fuse. The same computer controlled AC electrical termination is used regardless of the desired fuse value, because the level at which the fuse interrupts the circuit is programmable.

Additional functionality is achieved due to the use of a programmable device. In particular, different levels of over-current for different time periods may be tolerated by programming in the microcontroller. For example, a preset current limit of 15 amperes may be tolerated for 1 second (before shutting off AC power), while 100 amperes may be tolerated for 0.1 second. In other words, the computer controlled AC electrical termination of the present invention is intelligent enough to react to a serious over-current condition faster than mild over-current condition. Additionally, the computer controlled AC electrical termination may test for removal of the fault that caused the over-current condition, and restore AC power automatically without the need for a mechanical reset switch.

For general power control, all basic AC power controls are implemented in software by the microcontroller. For example, voltage and current sensors are input to the microcontroller, from which over-voltage, under-voltage, miswired neutral, lack of ground connection, ground fault currents and the like, are detected by use of an algorithm stored in the microcontroller.

In another embodiment, mechanical safety functions (e.g., a childproof AC outlet) are also implemented in software using the computer controlled AC termination of the present invention. Normally, when a three-prong AC plug is inserted into a three-prong AC outlet, three contacts are made: line, neutral and ground. A child inserting a single object into one of the contact holes of an AC outlet causes an abnormal condition. In the prior art, relatively complex mechanical interlocks prevent a single object from being fully inserted into the AC outlet.

To detect child tampering, mechanical sensors are provided to sense the presence of each inserted prong of the AC plug. Pair of contacts forming a switch, which is input to the microcontroller, implements each mechanical sensor. The advancing prong shorts each contact pair. The presence of three switch closures is regarded as normal to which the microcontroller responds by turning on AC outlet power. The presence of only one out of three switch closures is regarded as a tamper condition, to which the microcontroller responds by preventing input AC power from being applied to the AC outlet output power.

When the tamper condition is removed, the microcontroller turns power back on again. As another example of safety programming, the computer controlled AC outlet of the present invention, may for example, be programmed to accept only grounded three prong plugs, and not accept ungrounded two prong plugs, (i.e., detect the presence of, and not supply power to, a two prong plug).

A plurality of computer controlled AC electrical terminations of the present invention is used in conjunction with a central computer to form a flexible power control network. The microcontroller in each respective AC electrical termination is responsive to digital signals from the central control computer to remotely monitor and control a variety of power functions. The network uses 3 types of programmable microcontroller based elements: 1) AC electrical termination switches (outlets, light fixtures etc), 2) AC electrical termination dimmers and 3) sensor control devices (manual switches, dimmer controls, temperature sensors etc) . A separate low voltage network power and control bus, using a standard communications protocol connects a plurality of such programmable microcontroller based AC electrical terminations to the central computer to form a complete AC power control network. Each of the programmable microcontroller based AC electrical terminations is assigned a unique address and the central computer remotely addresses each power control electrical termination individually .

As used herein, the following terms are defined as follows:

"Load Devices" are devices that consume power, and include for example, lights, home appliances, air conditioners, motors and the like.

"Load Actuators or Controlled Load Actuators or Actuators" are computer controlled AC electrical terminations of the present invention, including computer controlled AC outlets.

"Controlled Load Devices" are load devices coupled through a computer controlled AC electrical termination or outlet (through a controlled load actuator) to AC power.

A "Sensor Control Device" is a remote power control device, which is not directly connected to an AC power source. Sensor control devices include remote on/off switches, remote dimmer controls and remote temperature sensors, remote position indicators and any other sensor or control device that provides logic signals to control AC power to a load device through a load actuator. All sensor control devices are connected to a separate common bus for control signals and sensor DC power.

The connection between the sensor control devices and the load devices is indirectly controlled by software programming at the central computer. That is, the central computer defines connections between the load devices and the sensor control devices via each respective controlled load actuator. Since each controlled load actuator is a computer controlled AC electrical termination, full circuit protection including over-voltage, over-current, GFI and the like, is provided locally at each respective load device.

The power control network thus formed provides the framework for expansion of the AC power control network to include additional features. For example, the peak power output from an AC outlet may be monitored by the electric company for load leveling billing credits (i.e., discounts for not using electricity during peak periods of the day) . Room fans may be thermostatically controlled from a room temperature sensor. In the latter application, temperature information from the sensor is communicated to the microcontroller in the AC outlet via the central computer for the purpose of controlling the electric fan.

The computer controlled AC electrical termination of the present invention is applicable to a wide range of applications using a few standard configurations. The invented AC electrical termination is programmable to define its features, and, using suitable erasable memory is re-programmable to redefine its features.

Brief description of the drawings

Figure 1 is a schematic diagram, partially in block form, of a computer controlled AC electrical termination in accordance with the present invention.

Figure 2 is a block diagram of a computer controlled AC electrical termination in accordance with the present invention.

Figure 3A is a block diagram of a computer controlled AC electrical termination configured as light dimmer in accordance with the present invention.

Figure 3B is timing diagram illustrating the operation of the light dimmer of figure 3A embodying the present invention.

Figure 4 is a mechanical blade sensor configuration for use with a computer controlled AC electrical termination in accordance with the present invention.

Figure 5 is an alternate embodiment of a mechanical blade sensor configuration for use with a computer controlled AC electrical termination in accordance with the present invention.

Figure 6 is a block diagram of a power control network connecting a plurality of computer controlled AC electrical terminations, dimmers and sensor control devices in accordance with the present invention.

Figure 7 is a block diagram of a computer controlled AC electrical termination configured as light dimmer for use in a power control network in accordance with the present invention.

Figure 8 is block diagram of a sensor control device for controlling the computer controlled AC electrical termination of figure 7 configured as light dimmer in accordance with the present invention.

Figure 9 is a block diagram of signal and DC power distribution to sensor control devices in accordance with the present invention.

Detailed Description A computer controlled AC outlet is shown in figure 1. Single phase power input consists of line L, neutral N and ground G. The power output form is an AC outlet 16 consisting of L' , N' and G' .

The computer controlled AC outlet includes a microcontroller 14, a relay 128 with a separate relay driver 10, and a number of electrical sensors. In particular, there is a first sensor for detecting the voltage between line L and neutral N using a resistive voltage divider comprising resistors Rl and R2. There is a second sensor for detecting the voltage between neutral N and ground G, comprising a voltage divider formed by resistor R3 and resistor R4. A series capacitor Cl is included to block the high voltage DC that is normally applied between the neutral N and ground G terminals during manufacturing test. Another capacitor C3 is placed between line L and ground G terminals. Capacitor C3 is used by the microcontroller 14 to detect when ground G terminal is floating, i.e., not actually connected to ground.

Another sensor is the inductive common mode current sensor Tl for detecting any difference in current between line L and neutral N currents. The common mode current sensor Tl has an overlay winding L3, which is used by the microcontroller 14 to test and calibrate sensor Tl. Finally, there is an output voltage sensor 12 for detecting the voltage between output terminals L' (AC outlet line) and N' (AC output neutral) . The output sensor 12 provides information to MCU 14 as to whether the bistable relay 128 is open or closed.

Relay 128 is a double pole, single throw bistable relay comprising a first coil winding LI for activating a first switch SI, and a second coil winding L2 for activating a second switch S2. The first switch SI connects or disconnects the AC outlet line conductor L' from the input line L, while the second switch S2 connects or disconnects the AC outlet line conductor N' from the input neutral N. Coil windings LI and L2 are wired in series such that both switches SI, S2, operate together to couple or de-couple AC power (L and N) from the power input source to the AC outlet 16. Bistable relays do not need continuous current to be maintained in either an open or closed position. To operate a bistable relay, a pulse of current may be applied to a solenoid coil in one direction or the other to set or reset the relay respectively. Alternatively, there may be two coils operated with the same polarity current pulses - one for an open position and one for a closed position. There may also be only one relay coil with two sets of contacts, versus two relays with two sets of contacts. A 5-volt power supply for MCU 14 and relay driver 10 is formed by diode Dl, resistor R5, zener diode D2 and filter capacitor C2. AC input line L and neutral N power the 5-volt power supply.

POWER SUPPLY OPERATED IN A PULSED MODE

MCU 14 draws very little current from the 5-volt power supply, say 2 milliamperes (mA) . In such case, the value of resistor R5 is selected to provide 2 mA steady state current output (or 2 mA charging current to the power supply capacitor C2) . However, a much larger current capacity, e.g., 100 mA, may be required to operate the bistable relay 128. In order to operate a 100 mA bistable relay 128 from a 2 mA, 5-volt power supply, the value of capacitor C2 is selected to be large enough to supply 50 times the steady state current, i.e., a 100 mA current pulse for relay driver 10. In such manner a smaller power supply (less than 100 mA) may be used. The tradeoff for using a smaller power supply, is that the capacitor C2 requires time to recharge between current pulses to relay 128. In particular, if a 6 millisecond, 100 mA current pulse is required to operate the relay 128, the power supply will need 300 milliseconds (50 times the 6 millisecond operation) to recover, thereby allowing capacitor C2 to recharge back to 5 volts through resistor R5.

During the current pulse operate the bistable relay 128, the power supply output voltage will fall below 5 volts. However, the MCU 14 will continue to operate on as little as 3 volts while capacitor C2 provides a current pulse for relay driver 10. MCU 14 is programmed to allow sufficient time between relay operations for the power supply capacitor C2 to recharge. In addition, when input AC power is removed (power loss) , MCU 14 will continue to operate for a sufficient time to carry out power down functions, such as operating the bistable relay to remove AC output power. When AC input power is later restored, the computer controlled AC electrical termination is initialized in a safe state i.e., disconnected from the load.

In operation, the computer controlled AC outlet of figure 1 turns off outlet output voltage as a function of the following: a) Input voltage between power carrying conductors, L and N, being above a selected value (prevent over-voltage on the load) ; b) Input voltage between power carrying conductors, L and N, being below a second selected value (prevent under-voltage on the load) ; c) Voltage between the power carrying neutral conductor N (grounded at the electrical distribution panel) , and a grounding conductor G, being above a selected value (detect a miswired neutral) ; d) Grounding conductor not being connected to ground; and e) Common mode current being above set values as a function of time (the same type fault condition that is detected by ground fault current interrupters or GFCI) .

Over-voltage and Under-voltage tests:

Microcontroller 14 monitors input voltage via voltage divider Rl, R2. If the input voltage (line L to neutral N) is within a predetermined range of acceptable values, MCU 14 closes the bistable relay 128 (unless sensor 12 indicated that it was already closed) , thereby activating power to the AC outlet 16. If the input voltage is (or later becomes) greater or less than the predetermined range of acceptable values, MCU 14 opens the bistable relay 128 (unless sensor 12 indicated that it was already opened) , thereby removing power from the AC outlet 16. Thus, the AC outlet 16 is protected against over-voltage and under voltage input conditions . As indicated, relay 128 is bistable, i.e., it can be latched in either an open or closed condition without requiring power, and can be pulsed to latch in the opposite position. Relay driver 10 provides bidirectional current through coil windings LI and L2 under the control of microcontroller 14 to latch relay 128 in either an open or closed state.

Normally, neutral N is tied to ground at the electrical distribution box where the fuses or circuit breakers are located. When the neutral line is carrying normal load current, there will be a small voltage drop between neutral and ground at the AC outlet. The MCU 14 senses the voltage drop between neutral and ground via voltage divider formed by resistors Rl and R2. If the voltage is above a predetermined value, then the neutral and ground conductors have been miswired. Microcontroller 14 responds to detection of a miswired neutral by activating an alert condition (at LED indicator D3) and/or by removing power from the AC outlet 16 by opening the bistable relay 128.

Microcontroller 14 converts sensed AC analog values to digital form (A/D) for voltage and current sensing. A low cost method of A/D conversion is to use a programmable reference and analog comparator internal to the microcontroller 14. The microcontroller 14 sets the programmable reference as one input to the comparator, the unknown analog input to the other input to the comparator, and then senses the comparator output. When the comparator switches output states, the microcontroller senses that the analog input is equal to the value of programmable reference. The comparator method of measuring analog AC signals includes measuring peak AC value by adjusting the level of the programmable reference voltage just to the point where the comparator does not switch states (i.e., no output pulses result when the reference voltage is set above the highest input analog voltage) . The microcontroller also measures AC values by setting the programmable reference to less than the peak AC value and measuring the duration (width) of the resulting pulses (measurement pulses) at the output of the comparator.

Grounding test :

Capacitor C3 permits MCU 14 to detect when the input ground G terminal is not actually connected to ground. If the ground terminal G is properly grounded, then the circuit node at the connection between capacitor Cl and capacitor C3 is at ground potential. Since the voltage on neutral conductor N is typically small, the voltage at the connection between resistor R3 and resistor R4 is also very small. However, if the ground G terminal is not grounded, the circuit node at the connection between capacitor Cl and capacitor C3 floats. The connection of capacitor C3 to line L pulls the voltage at the voltage divider R3/R4 up high towards line L voltage. The MCU 14 senses the substantially increased voltage and interprets the condition as lack of a ground connection.

Ground fault test:

The computer controlled AC outlet of figure 1 is also a ground fault circuit interrupter (GFCI) which detects and responds to ground faults. A ground fault condition occurs when some or all of the current provided by input line L is diverted to ground by an accidental short circuit. Normally, the current drawn from line L is the same as that returned to line N. A ground fault sensor Tl detects the difference in currents between lines L and N. When the current from line L is the same current as that returned to line N (a normal condition), a ground fault sensor Tl has zero output. When the current from line L is not the same as that returned to line N (a ground fault condition), ground fault sensor Tl has a non-zero output. In response to a predetermined non-zero output level (a ground fault indication) from sensor Tl, MCU 14 activates relay driver 10 to latch bistable relay 128 in an open state, thereby removing power from the AC outlet 16. Self-tests :

The microcontroller 14 is able to self-test portions of the computer controlled AC outlet. For example, the MCU 14 is programmed to periodically test the sensitivity of the GFCI sensor Tl via overlay coil L3. If the sensor Tl test indicates that the GFCI is not working, then the AC outlet 16 is unprotected against ground faults. In such case, microcontroller 14 may open relay 128 as a safety feature.

Microcontroller 14 also tests the operability of the relay 128 via output sensor 12. If the relay 128 is inoperable, then AC outlet 16 is unprotected. In addition to self-test features, the MCU 14 reports on its internal state via LED D3. For example, short LED flashes may indicate over-voltage, long LED flashes may indicate a ground fault while a dark LED may indicate a no fault condition.

As used herein, a microcontroller is a composed of a general-purpose microprocessor with programmable memory, either read only memory (ROM) , random access memory (RAM) or a combination of both ROM and RAM. Generally, RAM may be any type of memory that can be electrically programmed and reprogrammed. A suitable microcontroller, which may be used as MCU 14, is a single chip part, model PIC16C622A microcontroller, made by Microchip Technology, Chandler Arizona, USA. Programmability of MCU 14 gives the computer controlled AC electrical termination of the present invention substantial functional flexibility, both in the original configuration as released from manufacture and in the ability to adapt to changing electrical and environmental circumstances.

The following is a summary of the AC outlet programming sequence:

1. On power up, turn off power to AC outlet 16 (turn off relay 128) and begin test measurements.

2. Test L-N voltage and N-G voltage. If both OK, turn on power to AC outlet 16.

3. Monitoring sequence for L-N and N-G voltage measurements (Make all 3 measurements consecutively within 20 ms each) : Measurement 1 - Set reference voltage on the L-N comparator at a level corresponding to no measurement pulse at 132 VRMS and some measurement pulse at 127 VRMS, around 3.25 VDC. If any measurement pulse is detected, turn off relay 128 and blink LED (over-voltage) . Measurement 2 - If no measurement pulse is detected in measurement 1, set reference voltage on the L-N comparator at the level corresponding to a measurement pulse at 95 VRMS but no measurement pulse at 103 VRMS, around 2.5 VDC. If no measurement pulse is detected, turn of relay 128 and blink LED (under-voltage) . Measurement 3 - If no over-voltage or under-voltage, then set reference voltage for the N-G test corresponding to 30 VRMS, below 1 VDC. If there is any measurement pulse, turn off relay 128 and blink LED (neutral or ground is incorrect) .

4. Test for over-current condition. Turn off relay 128 if over-current detected. If no over-current is detected, proceed to GFCI test.

5. GFCI test. Calibrate common mode current transformer (Microcontroller 14 keeps a long-term counter and performs a self-test calibration sequence once per month) . If outside of 10% tolerance band, turn relay 128 off and blink LED indicator. If calibration ok, turn relay 128 on.

6. Monitor common mode current, and turn relay 128 off if ground fault current detected. Periodically turn relay 128 on and measure common mode current. Turn relay 128 off again if ground fault current detected. The monitoring value is a function of fault duration as specified by performance standards, such as those issued by Underwriters Laboratories, for example.

7. If no ground fault current detected, turn on relay 128.

8. At regular intervals (e.g. one month), the microcontroller 14 runs a self test of the bistable relay 128 and a re-calibration L3 of the common mode current detector Tl. Test for zero load current (that AC outlet 16 is not in use) . If AC outlet 16 is not being used, turn off relay 128, and test for lack of voltage at AC outlet 16. If relay 128 can be turned off ok, then turn on relay 128. If relay 128 cannot be turned off, set alert indication. 9. On power down, (L-N under-voltage) turn off power to AC outlet 16.

GENERAL CASE

The general case of a computer controlled AC electrical termination is shown in figure 2. Power input is shown as single phase AC consisting of line L, neutral N and ground G to terminals 218, 212, 214 respectively, but may be multi-phase AC power as well. A power output to a load device is generalized as any type of AC receptacle 232 for coupling power to such load device. The computer controlled AC electrical termination comprises a microcontroller 234, a power supply 224, a power output control device 228, and a number of electrical sensors. In particular, there is a first sensor 218 for detecting the voltage between line L and neutral N. There is a second sensor 220 for detecting voltage or voltage changes between neutral N and ground G. A third sensor 222 detects line current. There is also a common mode current sensor 226 for detecting ground fault currents, and an output voltage sensor 230 for detecting the voltage between output terminals L' and N' , which provides information to MCU 234 as to the state of the output power control device 228. Finally, there are three sensors, Ml, M2 and M3 respectively, which detect the mechanical presence of a corresponding conductor (pin or blade of a plug) to receive power from output terminals L' , N' and G' , respectively.

All components and interconnections fit within the limited space of the type of AC power receptacle 232 normally used to couple AC power the load device. For a two-phase AC outlet, the computer controlled AC electrical termination fits in a standard two-phase AC receptacle. As indicated, the usable space in a two-phase AC receptacle is about 1.625 by 2.625 by 1.25 inches. For a lighting fixture, the computer controlled AC electrical termination fits in a standard AC receptacle to which such lighting fixture is normally attached. Similarly, for a three-phase motor, the computer controlled AC electrical termination fits in a standard receptacle that holds a three phase electrical socket or three-phase wiring termination.

In addition, microcontroller 234 receives two types of control inputs. There is a local control input 216. A local control input is a control input on or within the same electrical termination as the microcontroller 234. There is also a remote control input, i.e., a network control signal terminal 217A which is coupled to microcontroller 234 via an appropriate network control interface 219. A remote control input is a control input that is external to the AC electrical termination containing the microcontroller 234, i.e., a control input from elsewhere on a network of sensors, actuators and load devices.

It is understood that a typical computer controlled AC electric termination will not have all of the sensors, input controls and test features as shown in the general case in figure 2 and the specific case of figure 1. For example, mechanical blade sensors are relevant mainly for childproof AC outlets. In any given case, for a given application, only some of the sensors, input controls and test features will be included. For example, an under-voltage test is important for a load device such as a motor (under- voltage can damage an AC motor), but is not desirable for a light bulb. An over-voltage test is important for a bulb because over-voltage will damage a light bulb, while under-voltage will still permit a light bulb to operate during a brownout. Furthermore, since many features of the AC electrical termination share the same sensors and other components, the addition of such features is a function of programming additional memory in the microcontroller 234. For example, the over-voltage sensor 218 used for load device protection, can also be used as the sensor for a dimmer control functionality.

In operation, MCU 234 monitors input sensors, such as load current from sensor 222, L-N voltage from sensor 218, N-G voltage from sensor 220, plug blade sensors L' , N' and G' from sensors Ml, M2 and M3 respectively and common mode current from sensor 226. In response to sensed conditions, MCU 234 operates output power control 228 to apply or remove AC power to the load device 232. If sensed conditions from the sensors indicate output power should be removed, MCU 234 causes output power control device 228 to remove or disconnect output power from the load device 232. After power is removed, MCU 234 continues to monitor the electrical and mechanical sensors. If sensed conditions from the sensors indicate output power should be restored (a programmed reset function) , MCU 234 causes output power control device 228 to reconnect output power to the load device 232.

Also, MCU 234 provides output indications of its internal state to a power status indicator 236. Power status indicator 236 may be an indicator light such as an LED, an audible alarm (beeper) or a speaker for playing synthesized voice output from MCU 234.

MECHANICAL SENSOR EMBODIMENTS

An embodiment of a mechanical means for detecting the presence of an inserted plug blade or prong 412 of an AC plug 410 is shown in figure 4. The plug blade 412 passes through a hole in the receptacle wall 414. The advancing plug blade 412 first contacts the power carrying spring socket 416. Then, as the plug blade 412 is further advanced into the AC outlet, the plug blade 412 contacts an additional spring contact 418. The pair of spring contacts 416 and 418 and the plug blade 412 function as a mechanical presence switch with two output wires 420, 422. The mechanical presence switch is coupled to the microcontroller through an appropriate interface to block any AC line voltage.

An alternate embodiment of a mechanical presence switch is shown in figure 5. The plug blade 516 passes through a hole in the receptacle wall as before. As the advancing plug blade nears the end of its travel, it contacts a flexible lever 526, which in turn depresses a microswitch 524. The use of microswitch avoids the need to isolate the microcontroller from the higher voltage AC line. The wires from the microswitch 520, 522 are coupled to the microcontroller to indicate the mechanical presence of the corresponding plug blade.

1: Child tamper shutoff

The microcontroller normally initializes an AC outlet by turning off power to the AC outlet when no plug blade is present. The introduction of only one plug blade (sensor Ml, M2 or M3 in figure 2) indicates a tamper condition, such as when a child is attempting to insert a pin or other object into the AC outlet. In such case, the microcontroller keeps power off. If for some reason the power was previously on, the microcontroller turns power off. Once a tamper condition is detected, the mechanical blade sensors must indicate to the microcontroller substantially simultaneous plug blade insertions before the microcontroller will turn on power to the AC outlet.

2: Ground pin lacking

If the mechanical presence sensors indicate to the microcontroller that two plug blades are inserted into the respective line L' and the neutral N' contacts, but not the ground contact G' , then there are two possible options. In one case, the microcontroller may turn on AC power without the mechanical presence of a ground G plug blade (or pin) . Thus the AC outlet may be used with both grounded and ungrounded electrical appliances and AC plugs. In other cases, such as AC outlets for appliances and fixtures that must have a grounded plug or chassis, it may be desirable to disable power unless a mechanical ground connection is made. Thus as an added safety precaution where only grounded appliances are expected, the computer controlled AC electrical termination of the present invention may be programmed to not turn on AC power unless a properly grounded AC plug is inserted into the AC outlet.

ELECTRICAL SENSOR EMBODIMENTS 1: Over-voltage, Line to Neutral. If the voltage between line L and neutral N exceeds a prescribed level, output power is removed. The prescribed level is a fixed constant or a function of some other variable, such as time or temperature. In particular, the MCU is programmed to respond slowly to a slight over-voltage while responding rapidly to a large over-voltage. At lower ambient temperature (detected by an internal or external temperature sensor) , higher over-voltage conditions are tolerated. That is, the prescribed over-voltage level is raised. At higher temperatures, the prescribed L-N (line to neutral) over-voltage level that will trigger a power shutoff is lowered.

2: Over-voltage, Neutral to Ground. If the voltage between neutral N and ground G exceeds a prescribed level, output power is removed. A neutral to ground voltage is an indication of a reversed connection of line and neutral, or other faults in electrical distribution like a break or a grounding conductor. The prescribed level is a fixed constant or a function of some other variable, such as time or temperature.

3: Under-voltage, Line to Neutral. If the voltage between line L and neutral N falls below a prescribed level, output power is removed. The prescribed level is a fixed constant or a function of some other variable, such as time or temperature.

4: Ground Fault Circuit Interrupter (GFCI). If the common mode current through a ground fault current transformer exceeds a prescribed value, output power is removed. The prescribed value is a fixed constant or a function of some other variable, such as time or temperature. A ground fault indication will also result from miswired connections, reversing the connections for the neutral and ground conductors.

5: Output load over-current. If the load current through a current load transformer exceeds a prescribed level, output power is removed. The prescribed level is a fixed constant or a function of some other variable, such as time or temperature.

The computer controlled AC electrical termination of the present invention is thus programmed to become a circuit breaker. As a circuit breaker, the response to an over-current condition is fully programmable. For example, instead of simply switching off power whenever load current exceeds a given level, the response of the circuit breaker is programmed to accommodate common temporary over-current conditions without switching power off. In particular in response to a 30% over-current level, the time for the circuit breaker to turn power off is set to 1 hour. However, in response to a 300% over-current level, the time for the circuit breaker to turn power off is set to 50 milliseconds. In such manner, a brief (less than 1 hour), mild over-current condition (less than 30%) is ignored, while a large over- current condition (300%) is acted upon almost immediately to avoid substantial damage as a result of the large over-current condition.

6: Sensor self test.

The ground fault detection circuit includes a test coil by which the MCU 234 periodically tests the sensor. Other sensors may include self-test capability that can be monitored by the MCU 234. Sensor failure is an unsafe condition that may warrant removal of output power because, without sensors, the MCU 234 cannot detect and respond to unsafe conditions. In the alternative, rather than shut off power, the MCU 234 may alert the user to the unsafe condition (the failure of the sensor and the corresponding lack of functionality) via the power status indicator 236 that replacement or repair is necessary.

The current load transformer (over-current sensor 222) is tested by the MCU 234 by sending a calibration signal to the current load transformer. The MCU 234 senses the result of the over-current sensor output to the calibration signal. Failure of the load current sensor 222 is an unsafe condition that may warrant removal of output power because, without a current overload sensor 222, the MCU 234 cannot detect and respond to unsafe conditions. In the alternative, the MCU 234 may alert the user to the unsafe condition (failure of the over-current sensor) via the power status indicator 236 that replacement or repair is necessary. Self-test features are applicable to any sensor (e.g., line to neutral over-voltage) allowing the MCU 234 to test any sensor and respond accordingly.

7: Output power control self test

The output power control device 228 is tested by the MCU 234 by turning off the output power control device 228 (e.g., a relay), and testing for the absence of output voltage. Failure of the output power control device 228 is an unsafe condition because the MCU 234 cannot respond to unsafe electrical conditions by turning off output power. In the event of failure of the output power control device 228, the MCU 234 alerts 236 the user to repair or replace the computer controlled AC electrical termination.

8: Reset from fault conditions:

Whenever a fault condition occurs, the MCU 234 turns off output power in accordance with its programming. However the AC electrical termination of the present invention further tests for removal of the fault condition, and turns on output power whenever the fault condition no longer exists, also in accordance with its programming. For example, after an over-voltage fault condition and subsequent power shutoff, the MCU 234 tests at regular intervals, e.g., 1, 5 or 10 minutes, for removal of the over-voltage fault condition. When the over-voltage condition returns to normal, the MCU 234 turns on output power. Other fault conditions such as ground fault, or load current, the MCU 234 tests the fault condition over a short interval, such as over several cycles of the AC line voltage. If the condition persists, the MCU 234 turns off power. The fault condition is periodically performed over longer intervals. DIMMERS

A computer controlled AC electrical termination programmed as a dimmer is shown in figure 3A. A voltage sensor 318 (which also functions as an over- voltage sensor) is connected between line L coupled to terminal 310 and neutral N coupled to terminal 312. A triac 328 couples the load device, an incandescent bulb 329, to line L and neutral N. Microcontroller 334, which receives 5-volt DC power from a power supply 324, is coupled to voltage sensor 318, and to a local dimmer control 316. Sensor 318 provides microcontroller 334 with a measure of line to neutral voltage as shown by the waveform 340 in figure 3B. Local dimmer control 316 is typically a variable resistor or other positional sensor by which the brightness of the lamp 329 is controllable.

To control brightness, microcontroller 334 senses zero crossings 341, 342 of the AC input voltage as shown in figure 3B. A firing pulse 343 (figure 3B) is generated by the microcontroller 334 to the input control terminal of the triac (328 in figure 3A) . The delay 344 of firing pulse 343 controls the brightness of lamp 329. The microcontroller 334 uses the input signal from the local dimmer control 316 to set the delay 344. Since the microcontroller 334 is programmable, any non-linearity in the sensor 318, triac 328, bulb 329 or local dimmer control 316 may be corrected by programming, such as by using a lookup table. If desired, the user may set customized levels of brightness versus position of dimmer control 316. Further, the microcontroller 334 is programmable to receive an external brightness control signal over a communications network. Figure 7 shows a network dimmer actuator similar to the stand-alone dimmer in figure 3A, except that in figure 3A, the dimmer control 316 signal is local, while in figure 7, the dimmer control signal is received over a network control bus 717A, 717B. The network control bus 717A, 717B provides signals to the microcontroller 734 to remotely control the brightness of the incandescent lamp 744.

It should be understood that the dimmer function of figure 3A might typically be combined with one or more additional AC power control functions. In particular, since the dimmer of figure 3A has an input line L to neutral N voltage sensor 318, over-voltage test functionality can be achieved by additional programming. That is, in addition to the dimming function, microcontroller 334 is programmed to monitor the voltage from sensor 318, and prevent triac 328 from becoming conductive if the line L to neutral voltage exceeds a predetermined level. As an alternative to using the triac 328 to turn off power to the load 329, a bistable relay can be added in series with the triac 328. A relay provides greater isolation for improved safety, as compared to a triac 328. Thus, an over-voltage test and a dimmer functionality are implemented in software using the shared sensors and electrical components.

NETWORK CONTROL

A plurality of computer controlled AC electrical terminations are programmed to form a network. In figure 6, a central computer 654 is used to bring all of the AC electrical power terminations together into a centrally controlled network. In addition to computer controlled AC electrical terminations ("load actuators" or "actuators") for powering load devices (lamps, appliances, etc.), the network includes a plurality of sensor control devices ("sensors") . Sensor control devices include both human controls and data inputs. Human controls consist of manually operated switches, dimmer controls and the like. Data inputs are thermal sensors, mechanical position sensors and the like.

Separate AC power and network control buses connect the sensors, actuators and loads into a network. The AC power bus consists of standard three-phase AC power lines 602, 604, 606, plus neutral 608, which AC power bus is supplied to all load actuators in accordance with the appropriate wiring specifications. Single-phase actuators receive just a single-phase line 606 plus neutral 608. The AC power bus is supplied only to actuators, and not to sensors. Instead, sensors are connected to the network by a network control bus 610, 612. The network control bus, which consists of a twisted wire pair 610, 612, is supplied to all load actuators and all sensor control devices. The network is further extended 656 to external networks to permit external control.

System actuators include a dimmer actuator 614 to control the brightness of lamp 618, a bulb actuator 620 to switch lamp 622 on and off, an appliance actuator 624 to control dryer 626 and a motor actuator 628 to control motor 630. System sensors include a switch sensor 636 to sense the state of switch 638, a position sensor 640 to sense the position of a variable resistor indicator 642 and a room temperature sensor 644 to measure the resistance of a thermal sensor 646.

The actuators 614, 620, 624, 628 shown in figure 6 are all wired on a common AC power bus. Each of actuators 614, 620, 624, 628 has an over-current sensor, and acts as its own circuit breaker. The computer controlled AC electrical termination of the present invention may be programmed as a circuit breaker actuator 632. In such case, the maximum current in a branch circuit 634 is limited to a maximum current. The circuit breaker 632 protects a branch circuit 634 containing other actuators.

The central computer 654 transmits and receives control signals to and from the network control bus 610, 612 via a high pass filter 652. Any one of a number of standard protocols such as USB (Universal Serial Bus), TCP/IP (Internet Protocol) , and the like, enables communication between system devices on the network control bus 610, 612. In the alternative, since communication between networked AC electrical termination devices may not require all features of a standard protocol, a simplified protocol or a subset of a standard protocol may be used. The network control bus carries both signal and DC power. DC power (e.g. 5-8 VDC) is supplied via DC power supply 650 is coupled to the twisted pair through a low pass filter 648. The central computer system controller 654 is coupled to the network control bus through a high pass filter 652. The high pass filter 652 and low pass filter 648 keep signal and sensor power separate.

Figure 9 illustrates how signal and DC power are separated at each sensor. The network control bus 917A, 917B is coupled to sensor 1 and sensor 2. In sensor 1, a high pass filter 910 consisting of a series capacitor 914 and parallel resistor 916 separate network control signals 917 from DC power on the signal bus 917A, 917B. At the same time, a low pass filter 912 consisting of series resistor 918 and parallel capacitor 920 separates DC power 919 from the network control bus 917A, 917B for sensor 1. In the alternative, for sensors having generally higher DC power requirements, a low pass filter 922 consisting of series inductor 924 and parallel capacitor 926 is used to separate DC power 925 from the network control bus 917A, 917B for sensor 2.

A block diagram of a sensor for a manually operated switch 838 and a position indicator 842 is shown in figure 8. The switch 838 and position indicator 842 are wired to microcontroller 834, which receives 5-volt power from a power supply 825, which in turn receives DC power from the network control bus 817A, 817B via a low pass filter 812. The microcontroller 834 also sends and receives network control signals 817 to and from the network control bus 817A, 817B via a high pass filter 810. The sensor in figure 8 is programmable as a dimmer control when position indicator 842 represents brightness, and switch 838 represents an on/off switch for the dimmer. The dimmer actuator in figure 7 is a companion actuator for the sensor in figure

SYSTEM OPERATION

In figure 6, each sensor and each actuator on the network has a unique address. Each sensor and actuator is addressable by the central computer 654 using the unique address of each sensor and actuator to send and receive network control signals. When the system is initially built, the electrician installer wires each actuator to both the AC power bus 602, 604, 606, 608 and the network control bus 610, 612. The installer wires each sensor only to the network control bus 610, 612. Since AC power does not run between sensors and actuators, much less AC power wiring is required. The installation of the AC power system is thus considerably simplified as compared to the installation of conventional AC wiring. Furthermore, an additional sensor or an additional actuator can be added to the network at an additional desired location just by extending the nearest available bus (AC power and/or network control) to the new desired location of the additional sensor or actuator. Safety is enhanced because all human-operated sensors use low voltage and are not connected to electric power lines.

The logical connections between sensors and actuators are defined by software in the central computer system controller 654. That is, after the system is wired, the installer defines which sensor is to control which actuator. A graphical user interface (GUI) at the central computer 654 presents a floor plan of the facility with the location of sensors and actuators noted on the floor plan. The installer clicks on each sensor and actuator, which brings up a dialog box or table by which the installer indicates the desired connections. For example, switch 638 is programmable to turn lamp 622 on and off. In the alternative, switch 638 may be programmed to turn dryer 626 on and off, or to turn air conditioner motor 630 on and off. Position indicator 642 is programmable to control the brightness of lamp 618. Thermal sensor 646 is programmable to report temperature values (at its local physical location) to air conditioner motor actuator 628. If an additional switch sensor is installed in an upstairs bedroom, the added sensor may be programmed to control a basement lamp without having to wire and rewire AC power lines between the bedroom and the basement. Control over a single lamp by two or three separately located switches is similarly defined by software.

In operation, the central computer system controller 654 periodically polls each sensor and actuator to report its status (e.g. the position of each manual switch, the current being supplied to each lamp, etc. ) If the status of any sensor changes, the central computer 654 looks up the appropriate actuator, and signals the designated actuator to take the action indicated. For example, when the sensor poll indicates to the central computer 654 that switch 638 is closed, the central computer 654 sends a signal over the network control bus 610, 612 to bulb actuator 620 to supply current to turn on lamp 618. In addition, actuators may report changes in status to the central computer 654 for the purpose of diagnosing system electrical problems. Furthermore, the network thus formed is extended via communication 656 to external networks. Such external networks may be reached over the Internet for the purpose of monitoring and control. The electric company may turn actuators on and off for the purpose of load leveling. For example, the actuator for the hot water heater may be turned off during periods of peak electric usage. As another example, the homeowner may remotely control any AC electrical termination.

A block diagram of a remote control dimmer actuator is shown in figure . A voltage sensor 718 is connected between line L coupled to terminal 710 and neutral N coupled to terminal 712. Voltage sensor 718 provides microcontroller 734 with a measure of line to neutral voltage. A triac 728 couples the load device, an incandescent bulb 729, to line L and neutral N. The firing of the triac 728 is controlled by an output signal from the microcontroller 734. Microcontroller 734, which receives 5-volt DC power from a power supply 724, is coupled to the network control bus 111 A, 717B through a high pass filter 741 (which consists of a series capacitor 739) and a transformer 742. The microcontroller 734 receives network control signals 717 over the network control bus 717A, 717B to remotely control the brightness of the incandescent lamp 744.

The sensor of figure 8 controls the dimmer actuator of figure 7 indirectly over the network. In figure 8, position indicator 824 (a variable resistor) is set to indicate a desired brightness level. The position indicator 842 may be replaced by keypad through which a digit is entered, or by a pair of buttons (one for increasing brightness, and another for decreasing brightness) , or a touch pad or any other suitable brightness control. Microcontroller 834 senses the position of the indicator 842, and, via a high pass filter 810, sends information representing position back to the central computer (654 in figure 6) over the network control bus 817A, 817B. The central computer 654 receives position information, looks up the address of the dimmer to be controlled by the sensor of figure 8, and forwards the position information received to the appropriate addressed actuator device. In figure 7, the received brightness (position) information is transferred from the network control bus 717A, 717B via high pass filter 741, and transformer 742 to form network control signals 717 to microcontroller 734. The microcontroller 734 uses the received network control signals, and the voltage sensor 718 output to determine the firing angle of the triac 728 (timing with respect to zero crossings of the AC power input) , which in turn controls the brightness of the incandescent lamp 744.

The dimmer actuator of figure 7 uses a separate 5-volt supply powered from the AC power terminals 710, 712. In general, for actuators such as shown in figure 6, 5-volt DC is derived from the AC power input. In the alternative, the microcontroller in all actuators may be powered from the same network control bus 817A 817B as the sensors. The advantage of powering all microcontrollers from the network control bus (instead of the AC power bus) is that in the event of a partial or full AC power loss, the microcontroller in each actuator will still continue to operate and report network system conditions to the central computer 654.

Claims

What is claimed is:

1. A programmable electrical termination device for use in an AC power receptacle, said programmable electrical termination device comprising:

first and second input power terminals for receiving input AC electrical power;

first and second output power terminals for providing output AC electrical power;

an output power control device having first and second input terminals, first and second output terminals and a power control terminal, said first and second input power terminals being connected to said first and second input terminals of said output power control device respectively; said first and second output terminals of said output power control device being connected to said first and second output power terminals respectively, said output power control device being responsive to a control signal on said power control terminal to connect AC electrical power, and disconnect AC electrical power, from said first and second input terminals, and said first and second output terminals respectively;

a sensor for measuring an electrical value; and

a microcontroller having at least one control input and one control output, said control input coupled to said sensor and said control output coupled to said power control terminal of said output power control device, said microcontroller being programmed to determine when said electrical value represents a detected fault condition, said microcontroller further being programmed to respond to said detected fault condition by causing said output power control device to disconnect AC power from said first and second power output terminals, wherein said output power control device, said microcontroller and said sensor are disposed within said AC power receptacle.

2. A programmable electrical termination device in accordance with claim 1, wherein said sensor is a voltage sensor connected to sense the voltage between said first and second input power terminals, and said microcontroller is programmed to detect an over-voltage condition between said first and second input power terminals as said fault condition.

3. A programmable electrical termination device in accordance with claim 1, further including an input ground terminal, wherein said sensor is a voltage sensor connected to sense the voltage between said second input power terminal and said input ground terminal, and said microcontroller is programmed to detect an over-voltage condition between said second input power terminal and said input ground terminal as said fault condition, wherein said fault condition is a reversed connection of said first and second input power terminals.

4. A programmable electrical termination device in accordance with claim 3, wherein said sensor is capacitively coupled to said input ground terminal.

5. A programmable electrical termination device in accordance with claim 4, further including a capacitor connected between said first power input terminal and said ground input terminal, wherein said sensor is programmed to detect an over-voltage condition as said fault condition, wherein said fault condition is a lack of ground connection to said input ground terminal .

6. A programmable electrical termination device in accordance with claim 1, wherein said sensor is a voltage sensor connected to sense the voltage between said first and second input power terminals, and said microcontroller is programmed to detect an under-voltage condition between said first and second input power terminals as said fault condition.

7. A programmable electrical termination device in accordance with claim 1, wherein said sensor is a common mode current sensor connected to sense the difference in current carried by conductors to and from said first and second input power terminals respectively, and said microcontroller is programmed to detect a given difference in current as said fault condition, wherein said fault condition is a ground fault condition between said first and second input power terminals .

8. A programmable electrical termination device in accordance with claim 1, wherein said sensor is a current sensor connected to sense the current at said first input power terminal, and said microcontroller is programmed to detect a given level of current as said fault condition, wherein said fault condition is an over current condition at said first input power terminal.

9. A programmable electrical termination device in accordance with claim 1, wherein said microcontroller is programmed to respond to said detected fault condition by causing said output power control device to disconnect AC power from said first and second power output terminals after a predetermined time interval.

10. A programmable electrical termination device in accordance with claim 1, wherein said sensor includes a self test input coupled to an output from said microcontroller, and said microcontroller is programmed to test said sensor.

11. A programmable electrical termination device in accordance with claim 10, further including a power status indicator coupled to said microcontroller, said microcontroller further being programmed to respond to a failure of said test of said sensor by activating said power status indicator.

12. A programmable electrical termination device in accordance with claim 10, wherein said microcontroller is further programmed to respond to a failure of said test of said sensor by causing said output power control device to disconnect AC power from said first and second power output terminals .

13. A programmable electrical termination device in accordance with claim 1, wherein said sensor is a voltage sensor connected to sense the voltage between said first and second output power terminals, said programmable electrical termination further including a power status indicator coupled to said microcontroller, said microcontroller being programmed to cause said output power control device to disconnect AC power from said first and second power output terminals, and thereafter detect a lack of change in voltage between said first and second output power terminals as said fault condition, wherein said microcontroller is further programmed to respond to said fault condition by activating said power status indicator.

14. A programmable electrical termination device in accordance with claim 1, wherein said microcontroller is programmed to respond to said detected fault condition by causing said output power control device to disconnect AC power from said first and second power output terminals, and after a predetermined time interval said microcontroller being further programmed to re- test whether said electrical value represents a detected fault condition, said microcontroller further being programmed to respond to said electrical value not representing a detected fault condition by causing said output power control device to re-connect said AC power to said first and second power output terminals.

15. A programmable electrical termination device in accordance with claim 1, further including a power status indicator coupled to said microcontroller, said microcontroller further being programmed to respond to said detected fault condition by activating said power status indicator.

16. A programmable electrical termination device in accordance with claim 1, wherein said output power control device is a bistable relay.

17. A programmable electrical termination device in accordance with claim 1, wherein said output power control device is a triac.

18. A programmable electrical termination device in accordance with claim 1, wherein said microcontroller further causes said output power control device to connect and disconnect AC power to said first and second power output terminals so as to control the amount of power output delivered to a load device connected to said AC receptacle at said first and second power output terminals .

19. A programmable electrical termination device in accordance with claim 1, wherein said sensor is a first sensor connected to sense the presence of a first contact blade at said first output power terminal, said programmable electrical termination device further comprising a second sensor connected to a second control input of said microcontroller, said second sensor connected to sense the presence of a second contact blade at said second output power terminal, said microcontroller being programmed to determine that the presence of only one of said first and second contact blades, but not both contact blades at said first and second output power terminals, represents a detected fault condition, said microcontroller further being programmed to respond to said detected fault condition by causing said output power control device to disconnect AC power from said first and second power output terminals .

20. A programmable electrical termination device in accordance with claim 1, wherein said sensor is a first sensor connected to sense the presence of a first contact blade at said first output power terminal, said programmable electrical termination device further comprising a second sensor connected to sense the presence of a second contact blade at said second output power terminal, and an output ground terminal, said programmable electrical termination device further comprising a third sensor connected to sense the presence of a third contact blade at said output ground terminal, said microcontroller having second and third control inputs responsive to said second and third sensors, said microcontroller being programmed to determine that the lack of any one of one of said first, second and third contact blades at said first, second and third output power terminals, represents a detected fault condition, said microcontroller further being programmed to respond to said detected fault condition by causing said output power control device to disconnect AC power from said first and second power output terminals.

21. A programmable electrical termination device in accordance with claim 1, further comprising an output ground terminal, wherein said sensor is connected to sense the presence of a contact blade at said output ground terminal, said microcontroller being programmed to determine that the lack of said contact blade at said output ground terminal represents a detected fault condition, said microcontroller further being programmed to respond to said detected fault condition by causing said output power control device to disconnect AC power from said first and second power output terminals .

22. A programmable electrical termination device in accordance with claim 1, further comprising a data interface for coupling data to and from said microcontroller, said data interface receiving data and transmitting data external to said AC power receptacle.

23. A programmable electrical termination device in accordance with claim 22, further comprising:

first and second network bus terminals for receiving a two-wire network bus;

a high pass filter having respective pairs of input and output high pass filter terminals, said input terminals of said high pass filter being coupled to said first and second network bus terminals, said output terminals of said high pass filter being coupled to a data input of said microcontroller; and

a low pass filter having respective pairs of input and output low pass filter terminals, said input terminals of said low pass filter being coupled to said first and second network bus terminals, said output terminals of said low pass filter being coupled to a power input of said microcontroller.

24. A programmable electrical termination device for use in an AC power receptacle, said programmable electrical termination device comprising:

first and second input power terminals for receiving input AC electrical power;

a first sensor connected to sense the presence of a first contact blade at said first output power terminal;

a second sensor connected to sense the presence of a second contact blade at said second output power terminal; a microcontroller having at least two control inputs and one control output, said control inputs coupled to said first and second sensors respectively, and said control output coupled to said power control terminal of said output power control device,

said microcontroller being programmed to determine that the presence of only one of said first and second contact blades, but not both contact blades at said first and second output power terminals, represents a detected fault condition, said microcontroller further being programmed to respond to said detected fault condition by causing said output power control device to disconnect AC power from said first and second power output terminals wherein said output power control device, said microcontroller and said first and second sensors are disposed within said AC power receptacle.

25. An AC power control network comprising:

a central computer; and

a plurality of programmable electrical termination devices for use in plurality of AC power receptacles respectively, each said programmable electrical termination device comprising:

first and second input power terminals for receiving input AC electrical power;

a sensor for measuring an electrical value;

a microcontroller having at least one control input and one control output, said control input coupled to said sensor and said control output coupled to said power control terminal of said output power control device, said microcontroller being programmed to determine when said electrical value represents a detected fault condition, said microcontroller further being programmed to respond to said detected fault condition by causing said output power control device to disconnect AC power from said first and second power output terminals; and

a data interface for coupling data to and from said microcontroller, said data interface receiving data from said central computer to said AC power receptacle,

wherein said output power control device, said microcontroller, said data interface and said sensor are disposed within said AC power receptacle.