CA1217259A - Zone condition controller and method of using same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

An electrically-powered zone condition control apparatus includes a first multiplexing means adapted for receiving analog status signals emanating from a plurality of passive signaling devices such as temperature or humidity sensors or potentiometers and transmitting these status signals in multiplex fashion to an analog-to-digital converter. The converter changes these analog status signals to digital data signals and directs them to a microcomputer. A second multiplexing means receives binary input signals which may indicate, for example, that an electrical contact is open or closed and also transmits these signals in multiplex fashion to the microcomputer. The microcomputer is adapted to perform algorithmic decisional functions relative to the signals received therein and is adaptable to periodically, selectively transmit digital output signals to one or more of a plurality of digitally-addressable load devices coupled to it by a two-wire communication bus. The microcomputer is also adaptable to periodically receive digital input signals from one or more of the load devices.
A method for controlling a condition in a zone, temperature for example, includes the steps of generating a plurality of signals representative of the status of a plurality of signalling devices, converting selected status signals to digital data signals and directing the data signals and unconverted status signals to a computing means such as a microcomputer. The microcomputer performs algorithmic decisional functions relative to the signals received thereat and periodically, selectively transmits digital output signals along a communication bus to one or more of a plurality of uniquely, digitally addressable load devices. Digital input signals are periodically received from one or more of the load devices.

Description

~Z9 7Z5~ 1 ZONE CONDITION CONTROLLER
. . _ .
AND METHOD OF USING SAME

BACKGP~OUND OF THE INVENTION

This invention relates generally to process control apparatus and ~ore particularly to a first level zone condition control apparatus for controlling the operation of heating, ventilating, humidifying and air conditioning ~HVAC) equipmen~ to effect environmental conditioning.
Computerized control systems are in wide use for controlling a variety of processes 9 petrochemical~ power generation and steel making being exemplary. Typically, each such process comprises a plurality of process subsystems or zones which may have control requirements peculiar thereto and which may be controlled by an apparatus dedicated to the proper functioning of the particular zone. Such controllers are usually coupled to a more sophisticated, master controller disposed at a second or higher hierarchical level within the overall control system and coupled to the first level controllers by a communication bus. For processes having a relatively small number of parameters to be sensed and controlled, it is desirable to employ a zone controller which is constructed and arranged to define a less sophisticated and therefore less expensive apparatus which is carefully matched to the parameters of the zone being controlled.
Another type of process which may require zone control or which mzy be adapted to control by zones includes environmental processes related to heating, ventilating, humidifying and air conditioning.
Sophisticated and relatively expensive hierarchical systems are known and in common u~e for controlling the HVAC systems in locations such as large office buildings, universities~ industrial complexes and the like. Such ~7~

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2 ~ ~ ~ 5 ~ :

systems will usually include a master con~rol computer ~i coupled to a number of subcontrollers which are distributed throughout a building and are capable of more limi~ed computerized ~unc~ion~ These subcontrollers, in turn are typically coupled to a number o~ individual modules and load devices for controlling the HVAC
equipment. While these sys~ems provide highly acceptable performance in those installations, their complexity and resultant coæt makes them undesirable ~or use in smaller HVAC processes such as might be found in supermarkets, smaller warehouseæ 3 Q~fice buildings and the like. In constru~tions of this latter type, the HVAC equipment will typically include only a single set of in~errelated ducts, termed an air handlin~ unit, coupled to a zone or space, the temperature and/or humidity environment of which is to be controlled. While these spaces are most frequently intended for human occupancy 9 such spaces may be devoted to the storage of food or other goods requiring a closely-controlled ambient.
The ducts comprising the air handling unit are constructed and arranged for drawing outdoor ambient air into the space, for exhausting air from the space to the outdoor ambient and for controllably mixing intake and return air. Such air handling units are equipped with adjustable dampers for controlllng the flow of air and include heat dissipating or absorbing coils formed of tubing placed in ~he air flow path within the duct.
These coils may be arranged in two sets, one each for flowing heated or chilled water or refrigerant therethrough, thereby permitting the duct air temperature to be raised or lowered. Valves are provided for controlling water flow. These dampers and valves may be controllably position~d by load devices such as motorized rotary actuators coupled thereto.
In the alternative, a water-type heater coil may be replaced by a group of electrically-powered heater strips ~2~;2S~

~hich may be energized in one or more ætages for air heating. These heater strips may be energized by a load device such as a sequencer in response ~o command signals received by it. Control of the load devices, the exemplary actuators and sequencers, may be in discrete stages or in a continuum.
In systems of this type, energy savlngs may be realized by incorporating economizing functions within the control scheme. For outdoor air tempera~ure and humidity which fall within a predetermined band of temperature and humidity values, the cooling effect inherent in the outdoor air may be utilized for appropriate conditioning of the space while yet avoiding ~he expenditure of supplemental energy for this function.
One type of microcomputer-based zone controller incorporates a small number of resistive elements, the output signals of which are used by the controller for selecting the desired setpoints of certain process parameters or for sensing tempera~ure and relative humidity values. Such controllers are arranged around a centrali~ed intelligence concept; that is, the data management and computational algorithms are embodied exclusively in the controller microcomputer or microprocessor and associated memory functions. The load devices to be connected to and operated by the controller include no provision for device programming, memory f~nction or communication with the controller. Such a controller incorporates one or more multiplexers for sequentially directing sensed and setpoint parameters to a microcomputer for processing. Signals so processed are inverted and used to selectively energize one or more of a plurality of controller-mounted electromagnetic relays for actuating staged heating, cooling or a combination thereof. Other signals as, for example, from a heat/cool changeover switch are inverted, directed to a comparator ~Z~7;259 network and used to positionably control a rotatahle actuator for powering outdoor air dampers. A
potentiometer is used to select that actuator position which provides the mini~um air flow requlred for ventilation. With such a controller~ each heating and/or ~ooling stage would be coupled to a predetermined set of relay output contacts by a pair o~ wires, both the contacts and the wire pair associated therewith being dedica~ed solely to the ~ask of controlling ~he particular stage coupled thereto. Econo~izer control by a method known as differential enthalpy may be accomplished only by connection of a separate enthalpy control module to the controller. An example o such a zone controller is shown and described in Un;ted States Letters Patent No. 4,347,712.
While such zone controllers have hitherto provided a satisfactory means for controlling XVAC equipment, they tend to be characterized by certain disadvantages. In particular, each controller relay contact i3 required to have a pair of dedicated wires coupled between it and the associated heating or cooling s~age. The analog output terminals for controlling the economizer motor are likewise required to have a pair of dedicated conductors coupled thereto. Since the distances between the controller and the economizer motor or heating and coolin~ stages may be substantial, the. cost of installing this wiring, eight or more conductors in all, may be quite significant. Additionally9 the controller microcomputer, having a predetermined number of lnput/output ports, may be bound by the number of such ports to a maximum number and type of load devices connected to the controller. Therefore, if a process control application requires an output configuration other than that which may be available from the predetermined number of relay output contacts and analog output terminals, it will be necessary to modify the ~ L7Z~

controller and its self-contalned hardware in order to accommodate the controller to such an application. It is difficult or impossible to adapt a controller of this type to a system wherein the combined number of heating and cooling stages exceeds the relatively limlted number of electromagnetic output relays embodied in the ; controller~ Another disadvantage of such a controller relates to the fact that HVAC air handling units tend to have varying numbers of heating, humidifylng and/or cooling stages required from application to application.
Notwithstanding, it may be hi~hly desirable from comfort and energy conservation standpoints to cause the progressive energizat~on or de-energization of the heating and cooling stages to occur in evenly~spaced increments across the wldth) in temperature degrees, of the heating or coollng proportional bands, irrespective of the width of these bands or of the number of heating or cooling stages. Kno~l zone controllers are somewhat inflexible and therefore not easily adapted to such operating en~ironments.
Yet a further disadvantage of a controller of this type which uses a system of centralized ~nteLligence is that no means are included whereby the controller may selectively poll or otherwise communlcate with the load devices coupled thereto. The controller is therefore unable to identify, by digitally coded signals, the precise type of load device coupled thereto nor to interrogate and receive signals rom the load devices indicative of their respective positlons or status.
A zone controller which utilizes a microcomputer and is adapted to control microcomputer based load devices such as actuators and sequencers to ~orm a sys~em having distributed intelligence, which is capable of co~municating with any one or all of a plurality of such load devices by a single, two-wire communication bus coupled therebetween, whlch is adapted to communicate with such load devices by a pair of microcomputer digital signal input/output (I/O) ports and which is adapted to communicate with a central processing unit at a higher hierarchical level would be a significant advance over the prior art.
SUMMARY OF THE INVENTION
In accordance with an aspect of the invention there is provided a process zone control apparatus for control-ling an environmental condition within a single zone of a 13 building and including a power supply means for providing a plurality of output voltages; first multiplexing means coupled to said power supply means to receive analog status signals from a plurality of signaling devices and multi-plexing said status signals to a converting means; con-verter means coupled to said first multiplexing means,said converter means receiving analog status signals therein, converting said status signals to digital data signals and directing said data signals ~o a computing means; second multiplexing means receiving binary input signals and multiplexing said binary input signals to said computing means; computing means coupled to said first and second multiplexing means for performing algorithmic decisional functions relative to signals received therein, said computing means periodically, selectively transmitting digital output signals to a plurality of digitally~
addressable load devices coupled to said computing means by a single communication bus, said computing means periodically receiving digital input signals from said load devices r said apparatus thereby controlling an environmental condition within the zone said digital output signals including a first set of nonredundant interrogating messages beng uniquely addressed for each of all possible addresses of load devices which may be coupled to said apparatus by said bus.
In accordance with another aspect of the invention there is provided a method for controlling an environmental condition within a single zone of a building including generating a plurality of signals representative of the status of a plurality of signalling devices; converting 7;ZS~

selected of said status signals to digital data signals and directing said data signals and unconverted status signals to computing means; performing algorithmic decisional functions relative to said signals received at said com-puting means; transmitting digital output signals from saidcomputing means along a single communication bus for reception by a plurality of uni~uely, digitally addressable load devices coupled to said communication bus for effect-ing control of a zone temperature and; periodically receiving at said computing means digital input signals transmitted from at least one of said load devices, said signalling devices include a plurality of sensors and a plurality of setpoint potentiometers; said step of trans-mitting digital output signals including the steps of transmitting a first set of digital ou~put signals to each of all possible digital addresses of load devices capable of being coupled to said communication bus, receiving and storing the address of each load device responsive to said fixst set of output signals and thereafter transmitting digital output signals only to said responsive load devices.
In a preferred embodiment, the controller includes a power supply adapted to receive an input voltage of 24VAC
and generate a plurality of output voltages for utilization 2~ throughout the controller. The first multiplexing means includes a first multiplexer, a second multiplexer and a third multiplexer, the first multiplexer being adapted to receive analog voltage signals from a plurality of control parameter sensors such as those used to sense temperature 3Q and/or humidity. The second multiplexer receives analog voltage signals representative of the status or settings of a first group of potentiometers while a third multiplexer similarly receives analog voltage signals representative of the status or settings of a second group of potentio-meters. As commanded by the computing means, the first,second and third multiplexers serially transmit analog status signals to converter means embodied as an analog-to-digital converter. The converter means is adapted to convert the analog status signals to digital data signals L72S~
- 7a -representative of those status signals and direct the data signals to the microcomputer. The controller also includes second mul~iplexing means adapted to receive a group of binary status signals and serially transmit those signals to the microcomputer upon its command. A signal-amplifying buffer circuit is coupled between the microcomputer and the level 1 communication bus which links the controller with a plurality of microprocessor-based, controlled load devices.

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Optionally, the controller may also include a second buffer circuit for linking the controller with a master controller at a higher hierarchical level by a level 2 communication bus. If the zone controller is so linked, it preferably includes address selection means whereby a user may select any one of a plurality of di~itally-coded addresses to which the controller will be responsive to a higher level controller coupled thereto by the level 2 bus.
The preferred controller is capable o~ receiving, upon request, coded signals from a sequence panel coupled to the controller by the level 1 bus, such signals representing the number of electromagnetic relays embodied in the sequence panel and available for the control of heating and/or cooling stages. The controller is adaptable to automatlcally cause these stages to be energized and de-energized in predetermined incremental spacing including evenly spaced increments across the heating or cooling proportional bands.
I~ is an object of the invention to provide a zone condition controller which is adapted to control microcomputer-based load devices in a condition con~rol system having distributed intelligence.
Another object of the invention is to provide a controller which is capable of communicating with any one or all of a plurality of such load devices by a single, two-wire communication bus coupled therebetween.
Yet another object of the invention is to provide a controller which is adapted to communicate with microcomputer-based load devices by a pair of microcomputer digital signal input-output ports~
Still another object of the invention is to provide a controller adapted to communicate with a master controller at a higher hierarchical level.
Another object of the invention is to provide a condition controller capable of receiving both analog and ~2~7Z5~

digital status signals from temperature and humidity sensors, setpoint potentiometers, relay contacts and the like~
Another object of the present invention is to provide a general purpose con~roller capable of bein8 adapted to a wide variety of con~rol strategies by efecting a change only in the microcomputer programming.
Yet another object of the present invention is to provide a zone controller adaptable to automatically cause heating and/or cooling stages to be energized and de-energiæed in increments of predetermined spacing across the heating or cooling propor~ional bandsO . These and other objects of the inventlon will become more apparent from the detailed description thereof taken with the accompanying drawlng.

DESCRIPTION OF THF DRAWING

FIGURE 1 is a simplified pictorial view of a typical air handling unit to which the controller of the present invention may be coupled;
FIGURE 2 îs a simplified electrical schematic diagram showing ~he inventive controller coupled to a plurality of load devices by a communication bus;
FIGURE 3 is a simplified electrical schematic diagram of the controller of the present invention3 FI&URES 4A and 4B, taken together, comprise the electrical schematic diagram of the first multiplexer means and circuitry associated therewith, all forming a portion of the controller of the present invention;
FIGURE S is a graphic depiction of the relationship of certain voltage input signals to the first mul~iplexing meane to corresponding voltage output signals therefrom;
FIGU~ES 6A and 6B, taken together, comprise the electrical schematic dia8ram o the converter means, ~L725~

compu~ing means, second multiplexer means and circuitry associated therewith~ all forming ano~her portion of the controller of the presen~ invention;
FI~URE 7 is an electrical schematic diagram of the power supply portion of the inventive controller;
FIGURE 8 is an elec~rical schematic dia8ram of the buffer interfacing circuits of the controller, FIGURES 9A and 9B, taken together, comprise the electrical schematic diagram for a service module, a type of load device useful with the controller of the present inven~ion;
FIGURE 10 is a front elevation viP.w of a sequence panel, another type of load device useful wîth the controller;
FIGURES llA and llB, ~aken together, comprise the electri~al schematic diagram of the chassis of ~he sequence panel of FI&URE 10~ and 9 1, FIGURE 12 is a graphical representation depicting certain operating aspects of the controller.

DESCRIPTION OF THE PREFFRRE~ EMBODIMENT

In FIGURE 1, the zone condition con~roller 10 is shown in connection with an air handling unit 11 which is utilized to control the temperature and/or humidity in a conditioned space 13 such as, for example, a supermarket, small group of offices, or the like. A typical air handllng unit 11 is formed of sheet metal constructed and arranged to define a plurality of passageways or ducts 15, each having a square or rectangular cross-section.
The air handling unit 11 includes a first duct 17 or directing air rom the outdoor ambient to the space, a second duct 19 for exhausting air from the space to the outdoor ambient and a cross durt 21 for air mixing. Fans 23 are provided for air movement. The ducts 15 include louvered dampers 25 which may be positioned for 25i~

~, controlling the amount of air flowing there~hrough.
Disposed within the first duct 17 is a plurality of electrically-powered heater strips 27 which, when ener~ized, hea~ the air which is discharged ln~o the space 13. The first duct 17 also includes a chiller coil 29 disposed therein for air cooling. The amount of cooling fluid flow~n~ through the chiller coil 29 and the position of the damper,s 25 may each be independently controlled by a load device 31 as, for ex~mple, a motorized rotary actuator. Selective energiza~ion of the heater strips 27 is by anothPr type of load device, a sequence panel 33 described below. The load deviees 31 are preferably microcomputer-based and are adapted to receive digital command signals from the controller 10 by a two-wire, level 1 bus 35 linking the controller 10 and the load devices 31. The load devices 31 are also adapted to transmit certain signals to the controller lO
via the bus 35. An example of a suitable load deYice 31 embodied as a microprocessor-based rotary actuator is sho~m in United States Patent Application Serial No.
469,928, entitled "Controllable P~otary Actuator" which was filed on February 25, 1983, and is assigned to the same assi~nee as this invention. The aforementioned application is incorporated herein by reference.
A temperature sensor 37 is disposed in the first duct 17 adjacent the cooling coil 29 for transmitting an analog signal to the controller 10 which ls representative of the temperature of the air being discharged into the conditioned space 13. A setpoint potentiometer 39 may be disposed within the space 13 for selection of the temperature which is desired to be maintained therein. As will be apparent from the following description, thls and other setpoint potentiometers may be incorporated into the controller 10 itself to help pre~ent unauthorized ~djustment thereof.
Additionally, one or more humidity sensors (not shown) 7 ~ 5 . 12-may be disposed in the sp~ce 13 for sensing the relative humidity ther ein.
Referring now to FIGURE 2, the controller 10 is shown to be coupled to a level 1, two~wire communication bus 35 to which is attaehed a plurality of lo~d devices 31. In addition to the actuators and sequencers described above, these load devices 31 may inolude a status panel 41, a service module 42 and/or additional sensors (not shown) which may be constructed using microcomputPr-based circultry and such "intelligent" sensors would thereby be capable of generating and transmitting digital signals back to the controller lO via the bus 35 in re~p-onse to controller signals. It should be appreciated that the mixture of load devices 31 coupled to the level l bus may include any combinat~on of those types of devices described above. Further, the disclosed controller 10 is capable of communicating wi~h up to 24 such load devices 31 and the use of a repeater would permit an even greater number of load devices 31 to be utilized.
The controller lO is adapted to recei~e .a first group of analog voltage signals at a first group of input terminals 43, the terminals 43 being wired to sensors such as sensor 37 which generate these voltage signals in response to the temperature or humidity of the air immediately surrounding the sensor. The controller 10 also includes a second group of input terminals 45 adapted to be wired to resistive devices such as potentiometers in or~er that a second group of analog voltage signals representative of the status or settings of those potentiometers may be received into the controller lO.
The controller ~lso includes a third group of input terminals 47 for receiving binary input signals, typically indicative o the energized or de-energized

3~ state of an item of equipment associated with the HVAC
system. For example, such a binary input signal may , ~

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indicate whether or not a fan, pump or humidifier motor is operating.
Briefly stated, the controller 10 functions to compare the desired ~emperature or humidity at a 5 particular location in the system, space 13 for example, and as represented by a setpoin~ signal with the actual temperature or humidity at tha~ same location and as represented by the sensor signals. ~ased upon the results of that comparison, the controller 10 selectively generates error signals and transmits an appropriate command or group of commands by specific address to one or more of the load devices 31 coupled to the bus `35.
Such command signals are generated to cause system adiustments which will redu~e or eliminate the error between the signals being compared.
In FIGURE 3~ the con~roller is shown to include a power supply 49 for providing a plurality o~ output voltages to the controller 10. A first multiplexing means 51 is coupled to the power supply 49 and is arranged for receiving analog status signals emanating from a plurality of signaling devices such as temperature or humidity sensors or potentiometers and transmi~ting these status signals in multiplex fashion to an analog-to-digital converter 53. The converter 53 changes these analog status signals ~o digital data signals and directs them to computing means 55 such as a microcomputer. A second multiplexlng means 57 receives binary input signals along a f;rst channel 59 and these input signals may indicate, for example, that an electrical contact is opened or closed. These binary signals are similarly transmitted in multiplex fashion to the computing means 55. Referring additionally to FIGURE
2, the preferred controller 10 is also equipped with circuitry which permits several such controllers or other digitally-addressable devices to be linked by a level 2 bus 61 to a central processing unit (CP~ - not shown) 2 ~Z 5 located at a higher hierarchical level. By properly coded address signals, the CPU may selectively communicate with any one oE the controllers or devices linked thereto. Accordingly, the controller 10 also S includes an address selection means 63 whereby a user may select any one of a plurality of digitally-coded address signals, preferably eight, to which the controller 10 will be responsive when such a CPU-generated signal is received by the controller 10 from the level 2 bus 61.
At certain times during the operation of the controller 13, it is preferable to generate a reset signal for bringing the controller microcomputer 55 to a predetermined state. Internal reset is desirable upon the first application of power to the controller 10 as well as periodically thereafter and, accordingly~ a reset circuit 65 is provided for generating such sisnals.
An optional feature of the controller 10 is the ` provision of an electromagnetlc relay 67 which may be discretionarily used by the system installer. The relay contact 69 may be used, for example, to operate a fan or may be used to sound an alarm in the event o~ a controller malfunc~ion.
The controller microcomputer 55 is coupled to the level 1 bus 35 by a transmit-mode amplifying buffer circuit 71 which converts the very low power digital signals emanatin8 from the microcomputer 55 into digital signals of a power level sufficient to operate the load devices 31 coupled to the bus 35. A receive-mode buffer circuit 73 conditions bus signals to a digital form unimpaired by spurious noise for best utilization by th~
microcomputer 55. In the event that it is desired to use the zone controller 10 in conjunction with a CPU linked thereto by the level 2 buæ 61, the controller 10 also includes an amplifying buffer circuit 75 to facilitate such communications.

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~ ore particularly and referrîng nex~ to FrGuRE5 4A
and 4B, the first multiplexlng means 51 is sho~*n to include a first, master multiplexer 77 adapted to receive - analog voltage signals from a plurality of sensors 79 such as temperature and/or humidity sensors. It is preerred that suc~ temperature sensors are of ~he precislon silicon type such as Amperex KTY81Bl having a voltage output range of lVDC-2VDC over the full range of ~emperature to be sensed. A temperature sensor product suitable for use wi~h the controller is available from Johnson Controls 9 Inc. under catalog nos. A960 and T960.
A preferred rela~ive humidity (RH) sensor or transmitter will likewise have a voltage output range of lVDC~2VDC
over the full range of humidity to be sensed. Controller input signals resultin~ from the activity of these sensors is capable of being resolved to 13 bits. A
plurality of reference resistors 80 are provided to linearize the output voltage of thPrmistor sensors of a type most commonly used. In the alternative, any type of sensor h~ing a voltage output may be coupled to any one of the sensor input terminals so long as the output voltage of the sensor is in the preferred range of lVDC~2VDC over the full range of the parameter sensed, e.g., from 0% to lnO% relative humidity or -40F to 216F air ~emperature. Each sensor input line is provided with a resistor-capacitor filter network 81, for filtering electrical noise from the sensor slgnals as they are directed to the first multiplexer 77.
The controller also includes a second multiplexer 83 30 and a third multiplexer 85 for receiving, respectively, status or settings from a first ~roup of setpoint potentiometers 87 and from a second group of setpolnt potentiometers 89. These potentiometers 87, 89 may be adjusted to select a wide variety of system control parameters as, for example, the zone setpoint temperature desired to be maintained in the space 13 during periods ~ 725~ ~

of human occupancy. Other parameters include the set-up temperature to be maintained in the space 13 during periods of non-occupancy and in those seasons when cooling is normally required and the se~ back temperature 5 to be maintained in the space 13 during periods of non-occupancy and in those seasons when heating is normally required. It should be appreciated that the set-up temperature will be several degrees higher than the zone setpoint temperature during those seasons when cooling is required to m~intain the latter. Similarly, the set-back temperature will be several degrees lower than the zone setpoint temperature during thosP seàsons when heating is required to maintain that nominal space temperature comfortable to the occupants. Other parameters which may be selected by potentiometer settings include the bandwidth9 in degrees Fahrenheit, of the cooling and heating deadbands, of the cooling and heating proportional bands~ low and high air temperature limits and the like. While the aforementioned setpoint potentiometers 87, 89 may be separa~ely supplied and mounted by the user, a preferred controller 10 will be adapted to include a plurality of plug-in contacts 90 for receiving a subassembly having therein a plurality of individually adjustable potentiometers. The user will thereby find it convenient to make all setpoint adjustments directly at the controller 10.
The controller circuitry is arranged so that the potentiometer signals applied to the input terminals 91 are resolved to nominal 12 bit accuracy. Each input line has a pull-up resistor 92 coupled thereto. These resistors 92 preferably have a value selected to be sufficiently low to maintain the voltage on an open input terminal 91 at approximately the value of the VC5 voltage applied at the terminal 91a and yet su~ficiently large to result in negligible loading of the setpoint potentiometers 87, 8~. It is preferred that each ~2::L'7Z~9 ~ -17-potentiometer input terminal 91 be coupled to its associated multiplexer 83 or 85 through a resistor-capacitor circuit 93 for fil~ering electrical noise.
In a preferred embodiment 7 ~he voltage applied at the terminal 91a is 5VDC and the second and third multiplexers 83, 85 will be operative to generate serially-transmitted analog signals for all setpoint voltages falling within the range 0-5VDC.
1~ Notwiths~anding the generation of multiplexed signals in that range, the microcomputer 55 is programmed to recognize only ~hose digital signals representative of potentiometer voltage signals occurring within the narrower first range of 0.5VDC-4.5VDC. Voltage signals falling outside of this range will have predetermined default v~lues substituted there~or by the microcomputer 55.
Signals em~nating from the second multiplexer 83 and the third multiplexer 85 are directed to the first multiplexer 77 through an amplifying means 94 having a high input impedance, a unity gain first stage 95 and a second, fractional gain inverting stage 97. Resistors 99 are provided for setting the attenuation value of the inverting stage 97 whlle the power supply voltage applied ?S to terminal 101 acts as a reference voltage for enabling voltage summations to provide DC level shifting. The output o the amplifying means 94 is directed to the first multiplexer 77 which multipl~xes all analog signals to the converter 53.
In a preferred controller 10, voltage summation and DC level shifting and inversion circuitry is incorporated so that the representative analog signals received by the first multiplexer 77 from the second and third multiplexers 83, 85 and directed to the convPrter 53 will 3~ occur in the second range of 2VDC to lVDC for all values of potentiometer voltage signals occurring in the range ~2~725~

of 0.5VDC-4.SVDC as well as for those potentiometer voltage signals occurring in th~ OVDC-0.5VDC and

4.5YDC-5.0VDC ranges. As prior stated, voltage signals occurring in these latter two ranges will cause the computer means SS to substi~ute predetermined default values. This concept will be better appreciated ~y reference to FIGURE S which illustrates the relationship of the potentiometer voltage signals occurring within the f~rst range 103 and the default-triggering voltage si~nals occurring at the band edges 105 of the first range 103, both of which are re-formed to voltage signals within the second range 107.
Referring next to FIGURES 6A and 6B, the controller 10 further includes converter means 53 preferably embodied as an analog-to-digital converter for receiving analog status sign~ls occurring within the second voltage range 107, converting these s~gnals to digital data s~gnals representative thereof and directing the data signals to a computing means 55 such as a microcomputer.
An integration capacitor 109 is coupled to the converter 53 for permittlng the use of dual-slope integration conversion therewithin. The reception of a signal having a value outside the second ran8e 107 o 2VDC-lVDC will represent an overload to the converter 53. It is thereupon necessary to immediately discharge the capacitor 109 to a voltage value which is sufficiently low to permit the capacitor 109 to correctly perform its integration function. Accordingly, an overload recovery circuit 111 is provided which includes a compara~or 112 and a field effect transistor 112, the latter being coupled to the capacitor 109. Upon the conclusion of each integration period, the transistor 112 is gated to a conducting state for approximately five milliseconds for causing the rapid discharge of the capacitor 109. The converter 53 is clocked by a crystal 114 having a ~Z~7~5~

frequency selected to maximize the rejection of spurious 60Hz electrical noise.
The microcomputer 55 stores data signals, performs algorithmic computations with respect thereto and generates output signals which are directed to the transmission line 115 comprising a portion of the level 1 bus 35. These output signals may be of a first type for commanding a load device 31 to execute a particular function. For example, a loacl device 31 comprising a rotary actuator may be commanded to incremen~ally rotate its output shaft, thereby further opening or closing an air damper 25. In the alternatîve, the output signals may be o a second, interrogating type whereby a load device 31 is caused to transmit certain information back to the controller 10 along the reception line 116 which is part of the level 1 bus 35. An example of a load device response resulting from the reception of an interrogating command would be the transmission of a binary coded message which represents the actual angular position of an act~ator shaft. Yet a third type of output signal may ~e generated by the controller for resetting all load devices 31 to a known, predetermined state.
In a preferred embodiment and as explained above~ the controller 10 is arranged for receiving a plurality of analog voltage signals, preerably six in number, at a first group of input terminals 43 which are adapted to be wired to sensors. Additionally, the controller 10 is adapted to receive a plurality of second analog voltage signals, preferably sixteen in number, at a second group of input terminals 91 adapted to be wired to groups 87, 89 of potentiometers. The microcomputer 55 is programmed to cycle at approximately a one-second time period and during each cycle, the controller 10 accepts and stores digital data signals which are representative o the analog voltage signals of all six sensors 7~ and of all ~L2~ 5~9 binary input signals ~eceived at the third group of input terminals as described below. Digital data signals representative of the analog voltage signals of two potentiometers are also stored during ea~h cycle. Data signals representative of the settings of other potentiometers are also sequentially accepted and stored, two such signals for each consecutive cycle and therefore, upon the occurrence of eight consecutive cycles, the microcomputer 55 will have sequentially accepted and stored one set o data signals representative of the analog volta~e signals of each of all potentiometer groups ~7, 89, eight sets of data si~n~ls representative o~ the binary input signals and eight sets of data signals, each of the latter set being lS representative of the voltage signals of all sensors 79.
The third group of terminals 47 for receiving binary input signals is coupled to a second multiplexing means 57 for generation of serial analog slgnals to be d~rected to the converter 53. An address selection means 63 is connected to the second multiplexing means 57 and is preferably embodied as a plurality of slide action switches, three in number, for permitting the selection of any one of eight possible addresses to which the controller 10 will be responsiv~ if a message so addressed is received thereat along the level ~ bus 61.
Pull-up resistors 117 are coupled to the input terminals 47 for permitting these terminals to be activated by either the closure of an external switch contact or by a digital logic "0" signal. Filtering of unwanted electrical noise is accomplished by the inclusion of a resistor-capacitor network 119 coupled to each input terminal.
Since the proper performance of the microcomputer 55 may be impaired by the presence of transient volta~es applied to or induced within its circuit nodes, it is desirable to provide means by which the microcomputer 55 Z5~1 may be periodically reset. Reset i~ also preferred for bringing the microcomputer 55 to a predetermined s~ate at that time when power is initially applied to the controller 10. Accordingly, the controller lO also includes reset means 121 for periodically generating a reset signal and directing such signal to the microcumputer 55. The microcomputer 55 of a preferred controller 10 will be programmed to perform a review of the integrity of the dat~ stored therewithin immediately subsequent to the receipt of the reset signal.
More specifically, the receipt of an internal reset signal ~t the microcomputer 55 will initiate a sta`rt-up routine which includes the steps of self-checkin~ for prop r unction~ accepting and storing digital signals representative of ~he binary state of the input signals received at the third group of terminals 47 and of those signals being generated by the address selection means 63. The self-checking step includes a test of random access memory (RA~) to verify the accurancy of all data, both incoming to the microcomputer 55 and calculated therewithin. Subsequent steps include accepting and storing digital signals representative of the values of a plurality of sensor and potentiometer analog voltages, switching the level 1 bus 35 to a logic "0" condition ~or a predetermined period of time and switching the level 1 bus 35 ~o a logic "1" condition for a predetermined period of time. In a preferred embodiment, these time periods will be approximately one second each and will result in a resetting of the load devices 31 and a verification of the operation of the transmit and receive functions. Thereafter, the microcomputer 55 transmits a first set of digital output signals comprising a plurality of polling or interrogating messages, each one of which is unique to each of all possible addresses of the remote load devices 31 which may be coupled to the controller by the level 1 bus 35. The microcomputer 55 then recelves and stores the address o~ each responsive load device 31 and thereafter transmits digital output signals only to those load devices 31. Additionally, the addresses of ~on-responsive devices are periodically polled and if an answering response is generated, digitally-coded addresses of responding devices are likewise stored.
The controller 10 also includes an optional relay circuit 123 for ~electively actuating an electromagnetic relay 67. The circuit 123 includes a transistor 125 for ener8i~ing the relay coil 127, a current-limiting resistor 129 and a diode 131 for protecting the transistor 125 from voltage spikes whic~ may occur when the coil 127 is de~energized. The relay contacts 132 may be used for operating an external fan, for sounding an audible alarm or the likeD
Referring next to FIGURE 7, the power supply 49 is shown to include terminals 133 for receiving an input voltage, pre~erably 24VAC, and a plurality of output terminals 134 for powering various portions of ~he controller 10. The power supply 49 includes a half-wave, negative regulated supply section 137 and a regulated, switching positive supply section 139. A first regulator 140 maintains a voltage at its output terminal which is nominally 8VDC in the preferred embodiment. The illustrated circuitry functions to switch the transistor 141 to a conducting state whenever the output voltage of the regulator 140 falls below the predetermined regulated value. The regulator 140 is thereupon partially bypassed by a current flowing through the inductor 142 to the capacitor 143. If the voltage at the capacitor 143 exceeds the predetermined regulation value, the transistor 141 is switched to a nonconducting state. The output of the first regulator 140 is coupled to the input 35 of a second regu~ator 144 for providing a regulated output voltage at nominally SVDC. A capacitor 145 is L7;25~

coupled to the output terminal ~hereof ~or providing transient stability, a plur lity of resistors 146 define a voltage divider network for providing a plur~lity of reference voltages while a capacitor 147 provides noise filtering.
Referring next to FIGURE 8, there is shown a first interface circuit 149 and a second interface clrcuit 151 or rejecting several ~ypes of spurious el~ctrical noise which may interfere with communications. These interface circuits 149, 151 permit the microcomputer 55 to transmit and receive signals on both the level 1 bus 35 and the level 2 bus 61. Interfacing between the microcomputer 55 and the buses 35, 61 is as shown ~n FIGURE 8 taken in conjunction with FIGURES 6A and 6B.
Referring to FIGURES 2, 9A and 9B, one type o load device which is useful with the present invention includes a service module 43 for providing ~ystem setup and troubleshooting functions. A preferred service module 43 is constructed and arranged to operate in either a command, an override or a monitor mode. When used in the command mode~ the level 1 bus 35 is disconneeted from the interf~ce circuit 149 of FIGURE 8, the service module 43 is conne~ted to the level l bus 3S
and may thereupon be utilized to generate commands to the load devices 31. For example, depression of a predetermined combination of buttons 151 disposed upon the service module 43 will cause the generation of a command signal requesting a microcomputer-based temperature sensor (not shown) to transmit a digital signal representative of the sensed parameter. The digitized signal from the responding sensor is displayed upon the module luminary 153, preferably in engineering units, e. g., degrees Fahrenheit. If the service module 43 is used for generating override commands during those times when the level 1 bus 35 is connected to the controller 10, a preferred module 43 is capable of ~LZ~Z~
. -24-,.
generat~ng such command as, for example, to override the controller 10 and bring a rotary ~ctuator shaft to a new pos~tion. I~ i~ apparent then, th~t ~he service module 43 is capable not only of de~ectin~ and displ~ying data stored within ~he controller 10 but is also capable of generatlng command signals for posl~ioning load device6 31, either singly or in plural.
When used as a monitoring device~ the serv~ce module 43 receives all digitally-coded information b~ing transmitted on the level 1 bus 35, irrespective of whether such transmiss-ion is by the controller 10 or by a respondi~g load dev~ce 31. Depression of R pred~termined sequence of module buttons 151 wlll permit the module 43 to receive and display any message &ppearing on the bus 35.
From the oregoing description9 it will be appreciated that the u~er may employ the controller 10 in con;unction with a service module 43 to control a condition ~n a zone as, for example, the zone temperature or humidity~ Control in this manner may be for setup 9 troubleshooti~g or other purposes. A method for controlling a zone condition i~ this manner would include the steps of providing a controller 10 coupled to a plurality of load devices 31 by a communication bu~ 35, providing a service module 43 coupled to the bus 35, generating a controller-originated signal for commandi~g a lcad device 31 to a first position, receiving a module-ori~inated overr~de signsl within the eontroller 10 and generating ~ controller-originated override sig~al or commanding the load device lO to a second position.
Yet another type of load devlce useful with the controller 31 of the present invention i5 shown ~n FIGURES 1, 10, llA and llB to include a sequence p~nel 155 for selectively controlling heat transfer stages such as heating stages 27, cooling ~tage~ 29 or a combination thereof. A preferred panel 155 includes a sequencer chassis 157 and one or more relay packs 159, the latter ~7 for controllably ac~uating the stages 27, 29. Referring particularly to FIGURES llA and llB a the chassis 157 is shown to include a regul~ted, switching positive supply section 161 for providing power to the chassis microprocessor 163. The section 161 is closely similar to the section 139 shown in FIGURE 7 but includes an adjustable regulator 165 in place of the fixed regulator 144 shown in the latter FIGURE. An interfece circuit 167 facilitates substantially noise-free communication between the level 1 bus 35 and the microcomputer 163 to which it is coupled. Referring additionally to FIGURE
10, a first group of terminals 169 is provided for facilitating the electrical connection of a first electromagnetic inter~ace device embodied as a relay pac~k 159. Addit;onal second, third and fourth group6 of relay pack terminals, 170, 171, and 172 respectively, permit ~he connection of yet other relay packs (not shown) if such are requlred for the application. Each relay pack 159 inclu~es ~ known plurality of electromagnetic relays, preferably four~ each relay having its contacts made availsble at external spade terminals 173 and internally connected as shown in FIG~RE 10. It is con~enient to construct the panel 155 to include a housing 175 having mounting holes 177 adapted to receive one or two relay packs 159 atop the housing 175. Additional relay packs 159 may be wall mounted adjacent the housing. Connection of the relay packs 15g to the groups of terminals 169-172 is by multiconductor wire assemblies and edge mounted terminal strips (not shown) located at the upper end and lower end of the housing 175, A plurallty of screw terminals 17~ is provided for connection of 24VAC, level 1 bus 35 and ground connections.
The sequence panel 155 includes a binary coded decade switch 181 for selecting the number of system heating stages to be controlled by one or more relay packs lSg, The chassis circuitry is configured such that the number . . . ~

L7 ~5~39 selected at the sw~tch 181 ls equal to one-hal the number o~ heating stages in the system to b~ con~rolled.
Additionally, ~he panel microcomputer 163 may be programmed for providing unal~erable, predetermined system timing constraints. For example, the microcomputer 163 may be programmed to provide a minimum time over which the coollng stages will be maintained in ~ de-energized state, once de-energization occurs.
Simllarly, minimum time periods may be programmed for providing a maximum number o cooling cycles per ho~r, of heating cycles per hour, for energizin~ any two consecutive heating stages or ~or maintainin8 a heating or cooling stage in a de-energized state. I
However, in a preferred embodimentg the panel 155 is. I
lS provided with a plurality of switches 184 whereby the user m~y select one of two time constraints which have been predetermined by the panel designer.
Each group of relay pack terminals 169-172 is coupled to a separate resistor 185~ the pllrpose of which ls to provide a signal to the microcomputer 163 whenever a relay pack 159 is connected to a particular terminal - group. The microcomputer 163 is programmed to read the number of system heating stages as selected by the switch 181, read the number of relay packs 159 connected to the terminal groups 169-172, each pack 159 being assumed by the program to include four relays~ subtract the number of heating stages from the total number of relays available and control the remaining relays as being connected to cooling stages. I
Referring next to FIGURE 12, there is shown a zone temperature axis 187 upon which has been superimposed certain vertlcal axes 189 to deine, for example, the width in degrees of the heating and cooling proportional bands 191 and 193, respectively, heating and cooling dead bands 195 and 197, respectively, an economiæer proportional band lg9 and the set point temperature 201 i3L;217Z59 desired to be maintained within the zone or space 13. A
feature of the zone controller 10 is that its microcomputer 55 may be programmed to distribute the-actuation of those coolîng stages coupled to a sequence panel 155 in virtually any manner over the temperature degree width of the cooling proportional band 193, notwithstanding the fact that the band 193 may have a variable width, within limits~ as selected by the controller user. As an exemplary illustration of this feature, it is assumed that the system coDtrolled includes two cooling stages, the first of which has an operating hysteresis loop 203 and the second of which has an operating hysteresis loop 205, with the sp~cing of the loops 2p3, 205 being distributed, in thls example, evenlY
over the width of the proportional band 193. Wh~le not illustrated, i~ should be appreciated that a preferrcd csntroller 10 may likewise be programmed to d~fitribute, .
evenly or une~enly, the activlty of the heating stages over the width of the heating proportional band 191.
It is preferable that the program embodied i~ the panel microcomputer 163 be configured to recognize separate addresses for the heating funct;on and for the cooling function. Optionally, the program may also be configured to recognize a thir~ address used to control selected electromagnetic relays (not shown) which are under no time delay or other constralnts. For example, a relay contact may be used to energ~ze ~nd de-energize a fan in accordance with a suitable command received at the third address.
When preparing tv operate the controller 10 of the present invention and if a fiequence panel 155 will be used in conjunction therewith, the panel switches 181 and 184 are set in accordance with the configuration of the particular air handling unit(s~ 11 being controlled. If load devices 31 embodied as actuators are used for analog positioning control of valvefi and/or d~mpers 25, the ~72S9 -2~-address switches of each are appropriately set in accordance with the particular function being controlled by it, e.g., intake air, exhaust air or air mixing. The actuator is then caused to rotate its output shaft to the extremes of its travel, the 0~ and 100% travel positions, and the mechanical linkages between the actuator and the device controlled, an exemplary damper 25, are then adjusted.
The program embodied in the controller microcomputer 55 is preferably conigured such that ~he addresses of each of all actuators will be sele ted from a first group of addresses, the addresses of each of all sequence panel heat1ng stages will be selected from a second group o addresses and the addresses of each of all sequence panel cooling stages will be selected from a third group of addresses. Similarly, particular sensors and set points will be programmed and assumed to be at predetermined addresses.
Referring to FIGURES l and 2 and with the load devices 31 coupled ~o the level 1 bus 35, the bus 35 and sensors 79 coupled to the controller and the setpoints selected by adjustment of the groups 87, 89 of potentiometers, power is applied to the system and the controller 10 will thereupon function to controllably condition the temperature and/or humidity in a zone.
A method for controlling the condition of a zone includes the steps of providing a zone controller 10 adapted to communicate wlth a level 1 bus 35 having a plurality of load devices 31 coupled thereto, scanning and storing the output values of a plurality of sensors 79 coupled to the controller 10 and scanning and storing the output values of a plurality of setpoint devices 8~, 89 coupled to the controller 10. Following this scanning activity, the controller 10 generates a synchronous reset signal for assuring proper operation of the controller microcomputer program. If the program is operating ~Z~L72~9 properly, the microcomputer 55 will anticipate and accept this reset signal and, upon so doing, will re-scan all values and parameters in memory such as those of sensors 79, set points and addresses. The controller 10 is programmed to compare the values and parameters existing prior to reset with thosP exi~ting after reset. If the compared values and parameters are identical before and after reset, the controller 10 thereupon initiates operation of the control algorithm. This initiating step preferably includes the generation of an initializing or polling message to each of every possible address of load devices 31 that may be coupled to the con~roller 10, irrespective o whether a load device 31 is, in fact, coupled to the controller 10 at that address. Each coupled load device 31 is thereupon caused to generate a responsive identifier signal which includes digital bits delineating the unique address of the responding load device 31. The controller 10 thereupon compares all of the possible addresses of load devices 31 with those addresses of load devices 31 actually coupled thereto and subsequently communicates only with addresses of the latter. Thereafter, the controller 10 performs algorithmic decisional ~unctions relative to the signals received therein, selectively transmitting digital output signals to one or more of a plurality of uniquely, digitally-addressable load devices 31 coupled thereto by a communication bus 35 and periodically receiving digital input signals from one or more of these load devices 31.
During certain phases of operation of the controller 10, it may be desirable to generate a signal for resetting all load devices 31 coupled to the level 1 bus 35. This may occur when, for exa~ple, there is an interruption of power at the controller 10 but not at the load devices 31. It may also be desirable to assure that the bus 35 is not inadvertently short-circuitedO In these eventr and prior to the 6canning steps delineeted ~2~7Z5 above, the controller 10 generates a bus reset signal for a first predetermined tlme of approximately one second by holding the bus 35 ~t a logic "0" value. The controller 10 also generates a fault detection signal by switching the bus 35 to a logic "1" sta~e for a second, predetermined ti~e of approximately one second to assure that no external device is causing an inadvertent short circuit upon the bus 35~
In the event that a service module 43 is coupled to the level 1 bus 35~ the operator may desire to cause the generation of an override signal or to read the value of a particular sensor 79 or set point value. If th operator wishes to override an output signal from the controller 10, he may sequentially depress certain buttons 151 disposed upon the service module 43 whereupon ~he digital output signal is intercepted~ a command signal is generated and directed to the controller 10 as a request for a new output signal based upon the override value selected by the operator. The controller 10 will thereupon be caused to generate a replacement digital output signal based upon the override valueO
The operation of the inventive controller 10 has been described in connection with what is known in the HV~C
art as a hot deck, cold deck type of air handling unit 11. However, it will be appreciated by those of ordlnary skill in the art that the controller 10 is an apparatus of broad 9 general purpose application and the controller 10 may be readily adapted for use with variable air volume ~VAV) systems. Such systems include, or cooling, a source of air at a temperature a few degrees less than that of the space to be cooled. The temperature of the source air is maintained relatively constant and the space is controllably cooled by varying the volume of air introduced thereto. The only change in the controller 10 which is required to permit its use with VAV systems is a change in the progremming of the microoomputer 55.

lZ1725~ 1 It is to be appreciated that wherever the terms "microcomputer" or "microprocessor" are used herein, they are intended to be syn~nymous with a digital computing structure such as an integrated chip, ~rrespective of whether the ~emory function is incorporated therewith as an integral part or ~s a separate memory device coupled to the structure. The following component values have been found useful in the controller of the pre~ent invention. Capacitance values are in microfarads unless otherwise specif~ed; resistors are 5% ~nd capacitors are 20% tolerance unless o~herwise specified.

FIGURES 4A, 4B

R26-R31 2320, 0.1% R32-R37 lOOK
R38 69.8K, l~o R39 lOK, 1%

C10-C15, C46 0.22 C16-C31 0.022 C47 0.001 U5 CD4069B

FIGURES 6A, 6B

R72-R82, R89, R94 4.7K R83-R87 470K
R88,R93 lK R90,R100 lM
R91, R92 27K R95 330 R96, R97 47K R98, R99 lOOK
R101 lOK C32-.C36 0.022 C37, C39, C92 0.22 C38 0.001 C40, C41 27pf C43 10 C44 0.15 C45 0.33 C48 0.1 D10-D13 lN4148 !

Ull CD4024B U12 MC6801-1 U13 lCL7109 Yl 4~9152 MHZ
Y2 3.5795MHZ

FI&URE 7 Dl, D2 lN5060 D3 lN4935 Cl 330/SOV C2 22/50V
C3 2.2/50V C4 0~01 C5 100/16V low ESR C6, C50 0.22 C49 0.1/200V Rl 680 R4 lOOK R5 lM
R6 240 R7 1.3K
R10 2670, 0.1% Rll 90.9; 0.1%
R12 - 1060, 0.1% Rl3 229, 0.1%
Ul 79L05 U2 317L
U3 7805 ~1 2N6107 Ll 350 microh.

D4 lN4736 D5, D6, D8~ D9 lN4148 D7 lN5060 RTl, RT2 22, ~t R14 470 Rl5, R21 lOK
R16, R22 20K R17, R23 47K
R18, R24 6.8K Rl9, R25 330K
R20 lOOK C7 0.22 C8, C9 0.0033 X7R C51 0.022 Q2, Q3 GES5822 FIGURES 9A, 9B

Rl 2K R2, R7 lOK
R3 20K R4 3.3K

~12~25~ , R8 lM R9 lOM
R10, R14-R17 4.7K Rll 240 R12 2.7K R13 1.2K
Cl 0.0033 X7R C2 0.01 C3 0.001 X7R C4, C8 Q.l C59 C6 ~2p~ C7 47, 50V.
C9 100, lOV~ RTl 10, +t low leak Dl, D4~D6 IN5060 D2, D3 IN4148 Ql GES5~22 Ul ICM7555I

U7 NMC27C16 LDCl PCI183 S2, S3 87AB3-201 U3 MC146805EZ
Yl 5MHz FIGURES llA, llB

Rl lOOK R2, R18, R27-R30 lOK

R3 20K R4 3.3K
R5 47K R6-R8, Rll 470K

R12, R17 lM R13 240 R14 1.3K R15 768, 1%
R16 243, 1% R19-R26, R31-R52 4.7K
Cl 0.0033 X7R C2 0.22 C3, C9 0.01 C4, C5, Cll 0.10 CS 27pf C7 0.10, 250V.
C8 33~, 50V. C10 100, 16V., low ESR
Dl, D6 5060 D7 4935 D2-D5 lN4148 RTl 22, ~t Ql 5822 Q2 2N6107 Q3 5823 ~1 556 !

~72~g Yl 4.00MHZ 52 Model 230002G
by EEC0 Inc.

S While a single preferred embodiment of the zone temperature controller and of a method for using same have ~een shown and described, they are not intended to be lImited thereby but only by the scope of the appended cl~

"

Claims (13)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process zone control apparatus for controlling an environmental condition within a single zone of a building and including:
a power supply means for providing a plurality of output voltages;
first multiplexing means coupled to said power supply means to receive analog status signals from a plurality of signaling devices and multiplexing said status signals to a converting means;
converter means coupled to said first multiplexing means, said converter means receiving analog status signals therein, converting said status signals to digital data signals and directing said data signals to a computing means;
second multiplexing means receiving binary input signals and multiplexing said binary input signals to said computing means;
computing means coupled to said first and second multiplexing means for performing algorithmic decisional functions relative to signals received therein, said computing means periodically, selectively transmitting digital output signals to a plurality of digitally-addressable load devices coupled to said computing means by a single communication bus, said computing means periodically receiving digital input signals from said load devices, said apparatus thereby controlling an environmental condition within the zone said digital output signals including a first set of nonredundant interrogating messages being uniquely addressed for each of all possible addresses of load devices which may be coupled to said apparatus by said bus.

2. The invention set forth in claim 1 wherein said first multiplexing means includes first, second and third multiplexers;
said first multiplexer receiving analog voltage signals from a plurality of control parameter sensors;

said second multiplexer receiving analog voltage signals representative of the settings of a first group of potentiometers, and;
said third multiplexer receiving analog voltage signals representative of the settings of a second group of potentiometers.

3. The invention set forth in claim 2 wherein said output signals include a signal for commanding movement of one of said load devices to a predetermined position and said input signals include a signal representative of the actual position of said one of said load devices.

4. The invention set forth in Claim 3 wherein said interrogating messages initiate a response by each of said load devices and said input signals include identifier signals generated by each of said load devices in response to said interrogating messages, said identifier signals being representative of the type and status of each of said load devices.

5. A zone condition controller for incorporation within a zone control system utilizing elements having distributed intelligence, said controller being devoid of user programming devices and including:
a first group of input terminals for coupling to a plurality of sensors, said sensor having a characteristic used for generating a first group of signals, each of said signals of said first group being representative of a sensed system parameter;
a second group of input terminals for coupling to a plurality of resistive devices, said devices each having a resistive value used for generating a second group of signals, each of said signals of said second group being representative of a system parameter set to a predetermined value;
a third group of terminals for receiving input signals representative of the binary state of selected system equipment;
means coupled to said first group and to said second group of input terminals for multiplexing and converting said first group and said second group of signals to digital data signals and directing said data signals to a microcomputer, and;
means coupled to said third group of terminals for multiplexing said binary input signals to said microcomputer, said microcomputer being programmable to store said data signals and said binary input signals, perform algorithmic computations with respect to said signals and generate output messages for transmission to microprocessor-based load devices coupled to said controller by a communication bus, said load devices being devoid of user keyboard programming devices, said controller including terminals for coupling to a central processor unit at a higher hierarchical level, said controller thereby being enabled to have signals down loaded thereto from said central processing unit, and;
said controller further including means for selecting a digitally coded address to which said controller will be responsive when a signal is received from said central processing unit.

6. The invention set forth in claim 5 wherein at least one of said output messages is of a first type for commanding one of said load devices to execute a function.

7. The invention set forth in claim 5 wherein at least one of said output messages is of a second, interrogating type whereby at least one of said load devices is caused to transmit digitally-coded information to said controller along said communication bus.

8. The invention set forth in claim 6 wherein at least one of said output messages is of a third type for resetting said load devices to a known, predetermined state.

9. The invention set forth in claim 7 wherein at least one of said output messages is of a third type for resetting said load devices to a known, predetermined state.

10. A method for controlling an environmental condition within a single zone of a building including:
generating a plurality of signals representative of the status of a plurality of signalling devices;

converting selected of said status signals to digital data signals and directing said data signals and unconverted status signals to computing means;
performing algorithmic decisional functions relative to said signals received at said computing means;
transmitting digital output signals from said computing means along a single communication bus for reception by a plurality of uniquely, digitally addressable load devices coupled to said communication bus for effecting control of a zone temperature and;
periodically receiving at said computing means digital input signals transmitted from at least one of said load devices;
said signalling devices include a plurality of sensors and a plurality of setpoint potentiometers;
said step of transmitting digital output signals including the steps of transmitting a first set of digital output signals to each of all possible digital addresses of load devices capable of being coupled to said communication bus, receiving and storing the address of each load device responsive to said first set of output signals and thereafter transmitting digital output signals only to said responsive load devices.

11. A method for controlling an environmental condition in a zone including:
providing a zone controller incorporating a microcomputer for communicating with a level one bus having a plurality of uniquely, digitally addressable load devices coupled thereto;
scanning and storing the output values of a plurality of sensors and setpoint devices coupled to said controller;
providing a reset signal for assuring proper operation of the program embodied in said microcomputer;
rescanning and storing said output values of said sensors and setpoint devices;
comparing said output values existing prior to said reset signal with those same values existing subsequent to said reset signal;

initiating operation of a control algorithm embodied in said microcomputer for performing algorithmic decisional functions relative to said output values;
selectively transmitting digital output signals to at least one of said load devices for effecting control of an environmental condition within said zone, and;
periodically receiving digital input signals from at least one of said load devices;
said initiating step including the steps of generating a polling message to each of every possible digital address for load devices that may be coupled to said bus; comparing said possible digital addresses with said addresses responsively received, and;
thereafter selectively transmitting digital output signals only to load devices actually coupled to said bus.

12. The method set forth in claim 11 and further including the steps of:
generating a bus reset signal for resetting load devices coupled to said bus, and generating a fault detection signal for assuring that said bus is not inadvertently short circuited, said generating steps occurring prior to said scanning and storing step.

13. A method for controlling an environmental condition in a single zone of a building and including:
providing a zone controller incorporating a microcomputer for communicating with a level one bus having a plurality of uniquely, digitally addressable load devices coupled thereto, said load devices being devoid of usar programming input devices and including at least one sequence panel adapted to control heat transfer stages;
determining the number of heat transfer stages comprising heating stages coupled to said sequence panel;
determining the number of electromagnetic interface devices incorporated into said sequence panel;
subtracting said number of heating stages from said number of interface devices, said difference being representative of the number of cooling stages coupled to said sequence panel;

determining the bandwidth of a heating proportional band;
determining the bandwidth of a cooling proportional band;
controllably actuating said heating stages in a manner to be substantially evenly distributed across said bandwidth of said heating proportional band, and;
controllably actuating said cooling stages in a manner to be substantially evenly distributed across said cooling proportional band.