Intelligent Controller for Equipment Heater

1. Field of Invention

The present invention relates to a control system for heating or cooling equipment. More particularly, the invention concerns an intelligent system for efficiently heating or cooling an item of equipment such as a gasoline combustion engine, by selectively applying power to one or more heating or cooling devices, in response to certain input parameters.

2. Description of Related Art

Most gasoline combustion engines become more and more difficult to start with lower and lower ambient temperatures. This presents a formidable problem in cold climates, where automobile engines can be especially difficult to start during the winter season. Even if a cold engine can be started, starting the engine at a less-than-optimum temperature significantly increases the wear and stress experienced by the engine.

A common solution to this problem is to pre-heat the engine before starting it. Engines have been pre-heated with a variety of known heaters. Such heaters are typically used to heat the engine's circulating coolant or the engine's lubricant. These heaters usually require some modification to the engine. For example, some circulating coolant heaters require a heating element to be connected in the circulating water system, and others require a freeze plug to be attached to the engine block. With another type of heater, a device is placed into the dip stick column of the lubricant well. A more primitive approach is to simply place a heat generating device such as a flood lamp or a space heater under the engine to directly heat the engine by convection.

Although some of the above-mentioned heaters burn liquid or gaseous fuel, many utilize an electric heating element that operates on alternating current (a.c.) power from a source such as a wall outlet. In many cases, the vehicle's user leaves the heater running continuously throughout the night. Alternatively, the user may manually connect the heater to electrical power a sufficient time before starting the engine; another option is for the owner to use a timer switch to connect the heater to electrical power at a selected time.

A number of automobile engine heaters are discussed in various patents, such as U.S. Pat. No. 5,048,753 ('753), entitled "Portable Engine Preheating System," issued on Sep. 17, 1991 to Michael Kellie. The '753 patent concerns a portable engine preheating system with a timer-operated heating cycle, where a thermostat overload protection system operates if the temperature of the engine rises above a predetermined critical value.

Another example of an automobile engine heating system is U.S. Pat. No. 3,877,639 ('639), entitled "Auxiliary Automobile Heater," issued on Apr. 15, 1975 to Charles Wilson and George Wilson. The '639 patent involves an automobile heating system in which a gasoline-fueled heater operates for a heating cycle of adjustably predetermined duration. The duration of the heating cycle is selectively determined either by a timer or by remote radio control. The heating cycle may be automatically activated when the ambient temperature drops below a predetermined value. If this occurs, the heating cycle will then terminate once the engine temperature reaches a second predetermined value. The '639 patent utilizes a battery heater in addition to the engine heater.

Since electricity rates for many consumers today are higher than ever, many people reduce their electricity consumption to save money. Additionally, many people conserve electricity for environmental reasons, since they realize that most electrical power plants generate electricity by burning fossil fuels. In this context, the previously-mentioned heating systems are not as advantageous as some might like, although such devices may be useful for certain applications. In particular, these devices are limited, since their engine heating cycles may be longer than the minimum time necessary. Arrangements that use timers are optimally efficient only if the user knows in advance how much heat will be required to safely start the vehicle's engine; this quantity depends upon the engine's size, the ambient temperature, the heater's power rating, and other related factors. For most drivers, such calculations are inconvenient or even impossible. Even if the user is capable of making such calculations, mistakes may lead to an inadequate preheating cycle, and an engine that will not start. Therefore, the previously-discussed methods are limited, and, as a result, they waste electrical power or they are unreliable.

Furthermore, these types of devices are not as beneficial as some might require, since they do not enable simultaneous operation of diverse types of heaters such as auxiliary engine heaters, vehicle interior heaters, battery heaters, and transmission heaters. Additionally, these systems do not accommodate a user who decides not to start his/her vehicle, since these systems permit the engine heaters to run indefinitely.

The present invention is directed at the problems set forth above, and in a general sense comprises a control system for heating or cooling equipment prior to startup. The invention includes a temperature sensor for sensing the temperature of equipment whose temperature is to be controlled. Using an input device, the user of the invention may provide input parameters such as the expected start time of the equipment, the size of the equipment, and the rating of the heating or cooling device(s) to be used. A computer utilizes the input parameters and the temperature of the equipment to calculate an activation time at which the heating or cooling device should begin heating or cooling the equipment to provide the equipment with a desired temperature at the expected start time. At the activation time, the computer provides an initiation signal, which causes the heating or cooling device to begin heating or cooling the equipment.

In a more specific embodiment, the invention comprises a system for efficiently preheating an engine under frigid conditions by selectively applying power to one or more heaters. The system receives a.c. power from a wall outlet and selectively provides a.c. power to one or more heaters, such as engine heaters, fuel heaters, battery blankets, transmission heaters, vehicle interior heaters, and the like. The operation of multiple heaters may be multiplexed to avoid exceeding the maximum current capacity of the a.c. power supply and "tripping" a circuit breaker. The system of the invention additionally includes a power converter to convert a.c. input power to a direct current (d.c.) voltage for charging the vehicle's battery. Remote communication components may be provided for remotely operating the invention. The invention also provides for fail-safe operation under certain conditions such as a.c. power loss, and improper power supply wiring.

The nature, objects, and advantages of the invention will become more apparent to those skilled in the art after considering the following detailed description in connection with the accompanying drawings, in which like reference numerals designate like parts throughout, wherein:

FIG. 1 is a diagram illustrating an exemplary use of the invention to pre-heat a vehicle engine;

FIG. 2A is a block diagram illustrating the electrical hardware components and interconnections of a base unit 100 and a remote unit 200 of the invention;

FIG. 2B is a block diagram of the electrical hardware components and interconnections of the base unit 100 of the invention;

FIG. 3 is a timing diagram of a typical operating sequence of the invention;

FIG. 4 is a flowchart of the d.c. power on routine of the invention;

FIG. 5 is a flowchart of the main program of the invention;

FIG. 6A is a flowchart of a first part of the periodic interrupt routine of the invention;

FIG. 6B is a flowchart of a second part of the periodic interrupt routine of the invention; and

FIG. 7 is a flowchart of the maintenance routine of the invention.

In an exemplary implementation (FIG. 1), the invention is used during frigid weather to heat the components of a vehicle 102 prior to the anticipated use of the vehicle 102, by selectively applying power to one or more heaters. Energy efficiency is realized by applying power to the heater(s) based upon the engine's temperature and various user-specified input parameters. The invention includes a base unit 100, preferably mounted in the engine compartment of the vehicle 102. To avoid damage from engine heat, the base unit 100 may be mounted between the radiator and the radiator grille, or another location substantially distanced from the heat-generating components of the engine.

The base unit 100 may receive a.c. power from an extension cord 104, electrically connected to an a.c. power source via a wall outlet 105. The outlet 105 may be located in a garage or another location where the vehicle 102 is stored when it is dormant. The base unit 100 converts the received a.c. power to another voltage, for charging a battery 114. In a preferred embodiment, the battery 114 comprises the d.c. engine-starting battery of the vehicle 102, and the base unit 100 converts received a.c. power to a d.c. voltage such as 12 V. In this embodiment, the battery 114 provides d.c. power to the electronic circuitry of the base unit 100 through a number of interconnections that, for ease of understanding, are not shown. The base unit 100 is removably connected to one or more conventional heaters, the operation of which is already well known. The present example depicts a primary engine heater 106, an auxiliary engine heater 108, a transmission heater 110, an interior space heater 112, and a fuel heater 113. Operation of other heaters (not shown) is also contemplated.

Referring to FIG. 2A, the electrical hardware components of the invention include the base unit 100 and a remote unit 200. As mentioned above, the electronic circuitry of the base unit 100 receives d.c. electrical power from the battery 114, through a number of interconnections that, for ease of understanding, are not shown. In addition to d.c. power, the base unit 100, as mentioned previously, receives a.c. electrical power from an outlet 105; in an illustrative example, the received a.c. electrical power comprises a 60 Hz voltage waveform having an amplitude of about 120 V. The outlet 105 is electrically connected to building wiring 252, which is electrically connected to other wall outlets, such as a second wall outlet 254. In the present example, the outlet 254 is located inside the same building as the outlet 105, and the outlet 254 provides a.c. electrical power to the remote unit 200. In an exemplary embodiment of the invention, the outlet 254 may be located in the user's kitchen, bedroom, or another location from which the user may conveniently and remotely operate the base unit 100.

In a preferred embodiment, communications between the base unit 100 and the remote unit 200 are conducted through the building wiring 252 in accordance with one or more known communications protocols, such as one of the National Electrical Association (NEA) standards. Such protocols involve the transmission of information by superimposing radio frequency (R.F.) data upon the 120 V a.c. power supply waveform carried by building wiring. Alternatively, communication between the base unit 100 and the remote unit 200 is also contemplated via radio transceivers, hardwired connections, or another known method for data communications.

As discussed in greater detail below, the remote unit 200 provides the user with status reports and receives commands from the user. The remote unit 200 includes a remote transmitter 256, a remote receiver 258, a remote input device 260, a display 262, and an acoustic annunciator 264. As described more fully below, the remote transmitter 256 and the remote receiver 258 function to exchange signals over the building wiring 252 with a base receiver 232 (FIG. 2B) and a base transmitter 240 of the base unit 100.

The remote input device 260 may comprise a keypad, one or more buttons, a number of rotatable wheels bearing imprinted alphanumeric digits, or another suitable device for the user to select data and input the data to the base unit 100. The display 262 may comprise a liquid crystal display (L.C.D.), electro-luminescent (E.L.) display, an array of light emitting diodes (L.E.D.s), or another suitable device for the remote unit 200 to provide information to the user. Likewise, the acoustic annunciator 264 comprises a beeper, vibrating reed, speaker, or another suitable device to provide the user with audible feedback.

Referring now to FIG. 2B along with FIG. 2A, the base unit 100 includes a microprocessor 202 to manage operations of the base unit 100. In an exemplary embodiment, the microprocessor 202 comprises an Intel.RTM. 8051 or 8031 microprocessor. The microprocessor 202 is electrically connected to a read only memory (ROM) 204, which may comprise an erasable programmable read only memory (E.P.R.O.M.). The ROM 204 may be a component that is independent from the microprocessor 202, or the ROM 204 may be built into the microprocessor 202. The microprocessor 202 additionally includes a random access memory (RAM) 203, which may be independent from the microprocessor 202, or incorporated therein. An input buffer 206 and an output buffer 208 are also electrically connected to the microprocessor 202. For ease of explanation, the input buffer 206 is divided into first, second, third, and fourth address groups, referred to as regions 206a, 206b, 206c, and 206d. In an illustrative embodiment, the input buffer 206 and the output buffer 208 are incorporated into the microprocessor 202. The output buffer 208 may also include an output latch (not shown), such as a National Semiconductor model MM74C374N circuit. The microprocessor 202 is also electrically connected to a combination clock-calendar 210, which may comprise a model ICM7170IPC circuit manufactured by Harris Semiconductor.

The base unit 100 also includes a number of user interface components, including a display 214 and a local input device 212. The local input device 212 may comprise a keypad, one or more buttons, a number of rotatable wheels bearing imprinted alphanumeric digits, or another suitable device for a user to enter data into the base unit 100. The local input device is electrically connected to the region 206b of the input buffer 206. The display 214 may comprise an L.C.D., E.L. display, an array of L.E.D.s, or another suitable device by which the base unit 100 provides information to the user. The display 214 is electrically connected to the output buffer 208.

The base unit 100 also includes an analog input module 216. In an exemplary embodiment, the analog input module 216 may comprise an analog-to-digital converter such as a model ADC0808CCN circuit manufactured by National Semiconductor. The analog input module 216 receives analog signals from a number of analog components, and provides the input buffer 206 with digital representations of the analog signals. These analog components include an ambient temperature sensor 218, a d.c. voltage sensor 222, and an a.c. sensing array 224. The analog components may also include an optional engine temperature sensor 220. The ambient temperature sensor 218 may comprise a thermistor, thermocouple, semiconductor temperature sensor, or another component capable of accurately sensing the temperature of the air near the vehicle 102. The ambient temperature sensor 218 may be located with the components of the base unit 100, or at another location, for accurately sensing ambient air temperature.

The engine temperature sensor 220 may comprise a thermistor, thermocouple, semiconductor temperature sensor, or another component capable of accurately sensing the temperature of the engine (not shown) of the vehicle 102. The engine temperature sensor 220 may be affixed to or placed near the engine block, the engine cooling system, the oil circulation system, or another switchable location for accurately sensing engine temperature. The d.c. voltage sensor 222 is electrically connected to the battery 114, and functions to sense the voltage of the battery 114. The a.c. sensing array 224, which is electrically connected to the a.c. power source via the outlet 105, senses the voltage and current provided by the outlet 105.

The base unit 100 also includes a digital input module 230, which is electrically connected to the region 206a of the input buffer 206. The module 230 receives signals from one or more alarm devices 230a, 230b, 230c, and 230d that are installed on the vehicle 102. The alarm devices 230a-230d may comprise known alarm units such as tamper alarms, door-open detectors, motion detectors, or other conventional alarm devices that produce digital output signals indicative of their status. The operation of the digital input module 230 and the related alarm devices 230a-230d is described in greater detail below.

The base unit 100 also includes the base receiver 232, which is electrically connected to the region 206d of the input buffer 206. The base receiver 232, which operates on a.c. electrical power from the outlet 105, receives signals transmitted by the remote unit 200 over the building wiring 252. Operation of the base receiver 232 is discussed in greater detail below.

The base unit 100 also includes an output module 236, which is electrically connected to the output buffer 208. The output module 236 includes an acoustic annunciator 238, a base transmitter 240, five heater outlets 242a-242e, and a trickle charge unit 246. The acoustic annunciator 238 comprises a beeper, vibrating reed, speaker, or another suitable device to provide the user of the invention with audible feedback. The base transmitter 240, which receives a.c. electrical power from the outlet 105 via a line 226, operates to transmit data to the remote unit 200, as explained in greater detail below. In an illustrative embodiment, the heater outlets 242a-242e comprise switched electrical outlets for receiving two-prong or three-prong plugs of the electrical heaters to be used with the invention. The microprocessor 202 selectively provides the heaters with a.c. electrical power from the outlet 105 by selectively enabling and disabling the heater outlets 242a-242e.

The trickle charge unit 246 comprises a system to convert a.c. power received from the outlet 105 into d.c. power, for the purpose of charging the battery 114, via a line 227. A bus (not shown) interconnects the trickle charge unit 246 with the microprocessor 202, the input buffer 206, and the output buffer 208. In a preferred embodiment, the trickle charge unit 246 comprises a system such as that disclosed in U.S. patent application Ser. No. 07/913,598 ('598) entitled "Intelligent System for Transferring Energy From a Power Source to a Load," filed on Jul. 14, 1992 in the names of Thomas Logan Wakefield and George Rex Plunkett. The '598 application is hereby incorporated herein by reference. The '598 application concerns a microprocessor system utilizing multiple electrical switching units to selectively transfer power from a power source to a load via an energy accumulator. One of the distinct advantages of the '598 device is that it completely isolates the a.c. power source from the components receiving d.c. power, without the power loss, expense, weight, and other disadvantages associated with transformer-based power supplies.

In the '598 application, the microprocessor provides d.c. power by executing an interrupt routine at certain times. Although the microprocessor component of the trickle charge unit 246 may be separate from the microprocessor 202, the microprocessor 202 is preferably programmed to perform the functions required for the trickle charge unit. This arrangement is contemplated in FIG. 2B, and has the advantage of avoiding the need for two microprocessors with overlapping functions.

A typical operating sequence of the invention is shown in FIG. 3. After leaving work, the user returns home and "plugs" the base unit 100 into the outlet 105 at 6:30 p.m. This event marks a time 300, when a.c. power is restored to the base unit 100. In this example, the user expects to start the vehicle again at an expected-engine-start-time 302 of 7:30 a.m., so the user enters this time into the base unit 100 using the local input device 212. The user also enters various other parameters, such as the size of the engine, the engine heater's ratings, the maximum current capacity of the outlet 105, and other related data.

The parameters input by the user are stored by the base unit 100 in the RAM 203 and need not be entered again, unless there is an interruption in d.c. power received by the unit 100, or unless the user desires to change the parameters. Using the parameters entered by the user and the engine temperature measurement provided by the engine temperature sensor 220, the base unit 100 calculates the minimum preheat-period 303. To bring the engine to a safe-starting temperature at the start-time 302, a.c. power should be applied to the engine heaters 106, 108 for a length of time equal to the preheat-period 303. Subtracting the preheat-period 303 from the start-time 302 yields a heater-activation-time 304, i.e. the time at which a.c. power should be applied to the engine heaters 106, 108 to enable safe starting of the engine at the start-time 302. When the time indicated by the clockcalendar 210 matches the heater-activation-time 304, the base unit 100 connects a.c. power to the heater outlets 242a-e to begin operating the heaters.

At the start-time 302, if the base unit 100 is still plugged into the outlet 105, this indicates that the vehicle 102 has not departed, and it is therefore assumed that the vehicle has not been started. In this case, the base unit 100 begins an engine-heating-maintenance-mode 305 to keep the engine warm until the user starts the vehicle 102, or until the maintenance-mode 305 ends at an end-maintenance-time 306. In an illustrative embodiment, the engine-heating-maintenance-mode 305 lasts for one hour. During this period, a.c. power is intermittently applied to the heaters to maintain engine warmth sufficiently for safe starting. It has been found that, even after engine heating completely ceases at the time 306, an average engine will typically remain warm enough to be safely started for about three hours.

The invention is operated according to a number of software routines, including a d.c. power on routine, a main program, and a periodic interrupt routine. The periodic interrupt routine includes a maintenance routine, described separately. The d.c. power on routine is executed when the base unit 100 is connected to the battery 114, i.e. when the base unit 100 first receives d.c. power. The d.c. power on routine operates primarily to (1) receive and store user input concerning the engine heating process, (2) determine the preheat-period 303, the heater-activation-time 304, and a heater multiplexing schedule to accomplish the user's objectives, and (3) begin the main program when the base unit 100 receives a.c. power.

The main program continuously detects certain operational conditions, and responds to such conditions appropriately. These conditions include, for example, the base unit 100 being disconnected from a.c. power, the base unit 100 receiving user input, and the base unit 100 receiving communications from the remote unit 200. The main program additionally controls operation of the trickle charge unit 246.

The periodic interrupt routine is performed on a microprocessor interrupt basis, preferably once each minute. The periodic interrupt routine resets all heaters and the trickle charge unit 246 by momentarily shutting them down. The periodic interrupt routine also implements, based upon the parameters input by the user, the desired method of heating. In the periodic interrupt routine, the engine is generally heated from the heater-activation-time 304 to the expected-engine-start-time 302. The maintenance routine is performed when the base unit 100 is not unplugged from the outlet 105 soon after the start-time 302. The communications routine is performed when data is received from the remote unit 200.

FIGS. 4-7 illustrate the software routines of the invention in greater detail. These routines are embodied in a number of software programming lines written in Intel.RTM. 8051 microprocessor code, shown in order of execution in the attached Appendix, which is incorporated herein.

In an exemplary embodiment of the invention, various interrupts, variables, and flags are used, as shown in Table 1 (below).

These flags, variables, and interrupts are described in detail in conjunction with FIGS. 4-7. However, a brief introductory description follows. The MAINTENANCE FLAG is a software variable that is set when the start-time 302 arrives if the base unit 100 has not been unplugged from the wall outlet 105; under these circumstances, it is assumed that the vehicle has not been started. In this case, the base unit 100 enters the maintenance-mode to keep the engine warm for possible later use.

The HEATING FLAG is a software variable utilized to indicate that, due to a given event, it is time to apply heat to the equipment. Such an event may occur, for example, when the activation-time 304 arrives, when the user selects a "continuous mode" of operation, when the user triggers manual starting, or when the maintenance mode 305 begins.

The MANUAL START FLAG is a software variable that indicates whether the user has opted to manually start the heaters. This option is selected by repeatedly plugging and unplugging the base unit 100 into/from the outlet 105. In an exemplary embodiment, two disconnections within five seconds initiates a manual start. In this case, the planned pre-heating schedule is abandoned in favor of immediate pre-heating.

The TIME-ON variable is utilized to keep track of the length of time that the heaters have been operating. When TIME-ON exceeds the preheat-period 303, this indicates that the start-time 302 has arrived, and the maintenance-mode 305 should begin.

The STAGE variable monitors the advancement of TIME-ON, to coordinate multiplexing of the heaters, as described in greater detail below. STAGE is incremented along with TIME-ON, and in an exemplary embodiment STAGE continuously counts from 1 to 6. As described more specifically below, STAGE indexes a heater multiplexing table to determine which heater(s) should be turned on at any given time.

The PERIODIC INTERRUPT is an interrupt of the microprocessor 202 that occurs once each minute. Each time the microprocessor 202 experiences the PERIODIC INTERRUPT, the microprocessor 202 automatically performs the periodic interrupt routine.

The POWER-SUPPLY INTERRUPT is an interrupt of the microprocessor 202 that occurs when the a.c. signal from the wall outlet 105 reaches selected voltage levels, as described in detail in the '589 application. When this interrupt occurs, power from the wall outlet 105 is transferred to the battery 114 via an energy accumulator (not shown), as described in the '598 application.

Having described the primary interrupts, variables, and flags of the invention, the software routines will now be explained. The d.c. power on routine (FIG. 4) comprises a number of tasks 400, which are initiated in task 402 when the base unit 100 is connected to the battery 114, thereby providing d.c. power to the electronic circuitry of the base unit 100. The d.c. power on routine is contained in the ROM 204, and is executed automatically when the microprocessor 202 receives d.c. power. The microprocessor 202 initializes the base unit 100 in task 410. Specifically, in task 410 the microprocessor 202 configures the base unit 100 for operation by (1) disabling PERIODIC INTERRUPT; (2) retrieving one or more default parameters from the ROM 204, such as default selections for engine size, heater ratings, presence or absence of auxiliary heaters, start-time 302, time of day, and the like; (3) retrieving default flags and variables from the ROM 204; and (4) verifying that the clock-calendar 210 is present and properly operating. Also in task 410, the microprocessor 202 performs various other steps to help ensure proper operation of the base unit 100, such as resetting the output buffer 208, initializing the local input device 212, and initializing other components of the base unit 100 as necessary.

The routine of FIG. 4 then proceeds to task 430, in which the display 214 presents messages requesting input from the user. In an illustrative embodiment, task 430 may request and receive various user specified parameters related to the heating cycle, such as: the size of the engine to be heated; the ratings of any engine heaters to be used; the maximum current capacity of the outlet 105; the start-time 302; and whether the user desires to enter the continuous mode to immediately begin heating the engine. In an illustrative embodiment, the user inputs the engine size by selecting from small, medium, large, and extra-large engine sizes. Likewise, the user enters the rating of each heater by selecting from low, medium, medium-high, or a high heater ratings. Preferably, the user is provided with an owners' manual that crossindexes the different engine sizes and heater ratings with specific sizes and ratings, as shown in Table 2 (below).

In one embodiment of the invention, where the display 214 comprises an L.C.D., the user may enter the desired parameters by advancing through a software menu using the local input device 212. The specific software of such a menu system is not discussed further, since menu systems are well known, and an ordinarily skilled computer programmer with the benefit of this disclosure is capable of generating the required software. As an alternative arrangement to the menu system, the display 214 may comprise a number of L.E.D.s (not shown), and the local input device 212 may comprise one or more Wheels that bear alphanumeric digits about their circumference. In this embodiment, different patterns of illuminated L.E.D.s serve as prompts for different items of data. For example, when a specific pattern of L.E.D.s is illuminate as a prompt for "engine size," the user may rotate the wheel(s) until it displays one or more alphanumeric digits representative of a "large" engine size.

After task 430 determines that the user has finished entering the parameters, task 440 proceeds to utilize the parameters in establishing a schedule for operating the heaters. Task 440 first performs various error checking algorithms on the entered parameters, and then stores the error-checked parameters in the RAM 203. Task 440 also resets the clock-calendar 210 based upon the user's input. Task 440 then performs a number of computations. For example, task 440 calculates a "heating coefficient" by crossreferencing heater size and engine size using a lookup table such as Table 3 (below).

As explained in greater detail below (task 630, FIG. 6A), the heating coefficient of Table 3 is utilized in calculating the preheat-period 303.

After the heating coefficient is determined, if multiple engine heaters are being used, the heating coefficient is adjusted according to the number of engine heaters present. This adjustment is performed because the preheat-period 303 will be shorter when multiple heaters are used. The heating coefficient is adjusted as follows: one adjustment constant is subtracted from the heating coefficient for each auxiliary heater used, i.e., each heater used in excess of one. In any case, the adjusted heating coefficient may never be less than one. The adjustment constant may obtained from a lookup table, such as Table 4 (below). As an example, if small and large auxiliary heaters are employed, the heating coefficient would be reduced by four. However, if the non-adjusted heating coefficient was three, the adjusted heating coefficient would be one.

Alternatively, instead of the additive adjustment constant of Table 4, a multiplicative constant may be used. Under this arrangement, if a single engine heater is present, the heating coefficient is simply multiplied by 1. If multiple heaters are present, the heating coefficient will be multiplied by a factor less than one, such as 0.9, 0.8, 0.75, etc., to compensate for the decreased preheat-period 303 needed when multiple engine heaters are used. Such factors would be provided in an appropriate lookup table (not shown). After calculating the adjusted heating coefficient using the appropriate additive or multiplicative adjustment constant, the adjusted heating coefficient is stored in the RAM 203.

In addition to calculating the heating coefficient, task 440 selects a multiplexing schedule from a number of tables stored in the ROM 204, to prevent the heaters from drawing excessive current from the outlet 105. The various multiplexing tables correspond to different maximum current capacities of the outlet 105, and different numbers and ratings of heaters. Task 440 selects a multiplexing table that most nearly corresponds to the maximum current capacity input by the user in task 430, considering the power consumption of each heater, as entered by the user in task 430. Adding in a safety factor, the heaters are considered to exceed the maximum current capacity of the outlet 105 if all heaters operating together would draw within about 350 W of the maximum current capacity selected in task 430.

An exemplary multiplexing table is shown in Table 5 (below), wherein three high-current heaters are used along with one or more low-current auxiliary heaters. In Table 5, a "1" indicates that the respective heater is on during a particular stage, and a "0" indicates that the respective heater is off during that stage. In the schedule of Table 5, the heaters of the invention are operated on a time sharing basis, such that one or more different heaters are rotatably activated.

From Table 5, it may be seen that the heaters are operated according to the following schedule; during STAGE 1, heater no. 1 is on; during STAGE 2, heater no. 2 is on; during STAGE 3, heater no. 1 is on; during STAGE 4, heater no. 3 is on; during STAGE 5, heater no. 2 is on; and during STAGE 6, all auxiliary heaters are on. Table 5 would be appropriate when heater nos. 1, 2, and 3 each draw a substantial current, since this schedule ensures that heater nos. 1, 2, and 3 are never operated simultaneously.

However, if all heaters are low-current heaters, or if the outlet 105 has a large current capacity, task 440 would choose a table such as Table 6 (below), instead of Table 5. With Table 6, all heaters are operated together.

If some, but not all, heaters may be safely operated together, a table such as Table 7 (below) may be utilized.

After task 440, task 460 clears all program flags and interrupts to prepare the base unit 100 for normal operation. For example, task 440 clears the MAINTENANCE FLAG, TIME-ON, PERIODIC INTERRUPT, and STAGE. Then, query 462 determines whether the user in task 430 requested operation in the continuous mode. As explained in detail below, when the continuous mode is initiated, the base unit 100 immediately enters the preheat-mode; if the base unit 100 has not been disengaged from a.c. power at the start-time 302, the base unit 100 then initiates the maintenance-mode 305, and thereafter continues in the maintenance-mode 305 indefinitely. Thus, if the continuous mode is selected, task 464 sets the HEATING FLAG and advances to query 470. If the user did not request the continuous mode, control simply passes from query 462 to query 470.

Query 470 asks whether the base unit 100 is receiving a.c. power from the outlet 105. Query 470 also verifies, using the a.c. sensing array 224, whether the a.c. waveform from the outlet 105 is sufficiently close to 60 Hz, 120 V. If query 470 determines that adequate a.c. power is present, control passes to query 480. However, if a.c. power is missing or inadequate, control passes to query 472, which checks for any user input at the local input device 212. When the local input device 212 is utilized, it triggers a flag (not shown) of the microprocessor 202. If query 472 determines that this flag is set, query 472 returns to task 430 to receive the user's parameters, store the parameters in the RAM 203, and process the parameters. However, if no user input has been attempted, query 472 returns control to query 470. Thus, so long as the base unit 100 is without adequate a.c. power, and the user does not attempt to enter any parameters, the d.c. power on routine continuously cycles through queries 470 and 472. By continuously monitoring any attempts of the user to enter new parameters, the d.c. power on routine helps ensure that equipment heating will be conducted according to the user's most recent specifications.

When query 470 detects adequate a.c. power, query 480 asks whether the MANUAL START FLAG is set, which would indicate that the user has requested manual starting. As explained above, manual starting occurs when the user directs that heating should begin immediately, even though the activation-time 304 has not arrived. The user initiates manual starting by repeatedly plugging and unplugging the base unit 100 into/from the outlet 105. In an exemplary embodiment, two disconnections and connections within 5 seconds initiates a manual start. If this condition occurs, task 482 establishes the necessary flags of the microprocessor 202 to immediately begin continuous heating. Then, whether the user has requested a manual start or not, the d.c. power on routine ends in task 490 by advancing to the main program (FIG. 5).

The main program (FIG. 5) includes a number of tasks 500, which generally function to oversee operation of the invention by: (1) detecting a.c. power loss, receipt of user input, and communications from the remote unit 200, and (2) initiating the appropriate software routine. After the main program commences in task 502, task 520 initializes the trickle charge unit 246. The operation of the trickle charge unit 246 is not described in further detail, as operation of the preferred trickle charge unit 246 is described in detail in the '598 application, which is discussed above and previously incorporated by reference. However, if a different trickle charging device is employed, or such charging is not performed at all, tasks 520 and 560 are omitted.

After task 520, a series of queries 530, 540, and 550 are performed. First, query 530 ascertains whether the base unit 100 is receiving adequate a.c. power. If so, task 532 records the time indicated by the clock-calendar 210, and task 534 advances to task 450 of the d.c. power on routine (FIG. 4); as discussed above, the d.c. power on routine waits for a.c. power to return in query 470.

If adequate a.c. power is being received, query 540 determines whether the user has started to input any parameters via the local input device 212. If so, task 542 advances to task 420 of the d.c. power on routine (FIG. 4) to receive the user's input in task 430.

If no new user input has been received, query 550 asks whether any data are present in the regions 206a or 206d of the input buffer 206. The presence of data in these regions indicates the receipt of communications from the base receiver 232 or an alarm condition from the digital input module 230. If such data are present, task 552 advances to task 685 of the periodic interrupt routine (FIG. 6B) to perform certain communications handling tasks.

However, if query 550 answers in the negative, then task 560 enables POWER-SUPPLY INTERRUPT, thereby enabling the trickle charge unit 246 to charge the battery 114. The series of queries 530, 540, and 550 repeats continuously, subject to being interrupted periodically by the periodic interrupt routine or a loss of adequate a.c. power.

The periodic interrupt routine (FIGS. 6A, 6B) includes a number of tasks 600 that generally function to verify that adequate a.c. power is being received, and to commence engine heating at the proper time. As mentioned previously, the periodic interrupt routine, in an exemplary embodiment, is executed once per minute on a microprocessor interrupt basis. After the periodic interrupt routine commences in task 602, task 610 initializes the equipment of the invention by disabling all interrupts, turning off all heaters, and turning off the trickle charge unit 246. By shutting down all heaters every minute, this guarantees that no heater will be operated unintentionally--only the desired heaters are turned back on again, as described below (task 684, FIG. 6B).

After initialization, query 620 ascertains whether the a.c. power received from the outlet 105 is adequate. In particular, in query 620 the microprocessor 202 receives input from the a.c. sensing array 224 via the analog input block 216 and input buffer 206, and analyzes that input. For example, query 620 determines whether the magnitude and frequency of the a.c. power is adequate, e.g., approximately 120 V, 60 Hz. If query 620 establishes that the a.c. power is inadequate, task 622 records the current time indicated by the clock-calendar 210, and generates one or more appropriate warning messages using the display 214 and the acoustic annunciator 238. Then, task 624 advances to the d.c. power on routine, and waits for a.c. power to be restored (query 470, FIG. 4).

However, if query 620 identifies an adequate a.c. power signal, task 630 calculates the preheat-period 303. The preheat-period 303 is the heating period needed to raise the engine temperature to the safe starting temperature using the heaters previously selected by the user in task 430. The safe starting temperature is stored in the ROM 204, and, in an illustrative embodiment, is about 30.degree. F. To calculate the preheat-period 303, the microprocessor 202 first obtains the time from the clockcalendar 210. Then, the microprocessor 202 obtains the engine temperature from the engine temperature sensor 220, and stores the measured engine temperature in the RAM 203. Then, task 630 calculates the necessary temperature change by subtracting the present engine temperature from the safe starting engine temperature. Alternatively, if an engine temperature sensor 220 is not provided, the ambient temperature sensor 218 may be utilized to provide the engine temperature, under the assumption that the engine has cooled to the ambient temperature. Then, task 630 utilizes a lookup table such as an exemplary Table 8 (below) to determine the average heating time for the desired temperature change.

Then, task 630 multiplies the adjusted heating coefficient calculated in task 440 by the average heating time found in Table 8. The product of these two values provides the desired preheat period 303, i.e. the amount of time that will be required to heat the engine to the safe starting temperature.

After task 630, query 640 asks whether the HEATING FLAG is set. If the HEATING FLAG is set, control advances to query 670. Otherwise, task 650 subtracts the preheat-period 303 from the start-time 302 to obtain the activation-time 304. Then, query 652 determines whether the present time (obtained in task 630) is later than the activation-time 304; if so, it is time to start heating the Vehicle 102, and task 654 sets the HEATING FLAG.

After task 654, or after a negative answer to query 652, query 660 determines whether the HEATING FLAG is set. If the HEATING FLAG is not set, then it is unnecessary to execute the remainder of the periodic interrupt routine, since no heating is to be performed. However, to monitor possible messages received from the remote unit 200 or the digital input module 230, task 662 advances control to task 691 (FIG. 6B) to attend to communications handling. However, if query 660 establishes that the HEATING FLAG is set, query 670 asks Whether the MAINTENANCE FLAG is set. The MAINTENANCE FLAG, which is discussed in greater detail hereinbelow, indicates whether the start-time 302 has arrived. If the MAINTENANCE FLAG is set, task 672 advances to the maintenance routine (FIG. 7), the operation of which is explained in greater detail below. However, if query 670 determines that the MAINTENANCE FLAG is not set, task 680 advances to query 681 (FIG. 6B).

Query 681 asks whether TIME-ON is greater than the preheat-period 303. This condition would indicate that the preheat-period 303 has ended, and that the start-time 302 has passed without the vehicle 102 being started. If the vehicle had been started, then it is assumed that the base unit 100 would have been unplugged from the outlet 105; under such circumstances, an a.c. power loss would have been detected, and control would have advanced to query 470 (FIG. 4) to await a.c. power restoration. Therefore, after an affirmative answer to query 681, it is assumed that the start-time 302 has passed without the vehicle being started, and task 682 thus prepares the base unit 100 to end the pre-heating mode and enter the maintenance-mode. Specifically, task 682 sets the MAINTENANCE FLAG, clears TIME-ON, and clears STAGE.

Additionally, if the base unit is equipped with an engine temperature sensor 220, query 681 may ask whether the engine temperature has already reached the safe starting temperature. If so, control would advance to task 682.

However, if query 681 establishes that TIME-ON has not exceeded the preheat-period 303, and that the engine temperature has not reached the safe starting temperature, then task 683 increments TIME-ON and STAGE. Since TIME-ON is increased by task 683 throughout the preheat-period 303, and the periodic interrupt routine is preferably performed once each minute, TIME-ON represents the number of minutes that any one or more of the heaters have been operating.

After tasks 682 or 683, task 684 turns on the appropriate heaters in accordance with the selected multiplexing table (i.e. Tables 5-7). In particular, task 684 utilizes the present value of STAGE to turn on the appropriate heaters in accordance with the multiplexing table that was selected in task 440.

After task 684, task 685 disables POWER-SUPPLY INTERRUPT, and performs certain communications handling. Additionally, various other functions are performed to facilitate remote communications with the remote unit 200. Generally, when the base receiver 232 receives data from the remote unit over the building wiring 252, the data are directed into the region 206d of the buffer 206. In an illustrative embodiment of the invention, each data signal exchanged over the building wiring 252 includes an address, a command, and associated data. If multiple base units (not shown) are connected to the building wiring 252, each base unit will be assigned a unique address, enabling each base unit to ignore commands and data prefaced by another base unit's address. In this way, communications may be conducted between multiple base units and remote units over common building wiring 252.

Accordingly, if data have been received and stored in the region 206d of the buffer 206, the microprocessor 202 in task 685 fetches the address from the region 206d and asks whether this address corresponds to the unique address of the base unit 100. If not, the routine proceeds with task 686. However, if the address contained in the region 206d matches the unique address of the base unit 100, the microprocessor 202 in task 685 fetches the command and data bytes from the region 206d and executes the fetched command. This command, for example, may require the base unit 100 to send the remote unit 200 a status report including data such as the engine temperature, the time remaining before the starttime 302, the status of the alarm devices 230a-d, whether adequate a.c. power is being received, and the like. Additionally, the commands received from the remote unit 200 may require the base unit 100 to alter previous user input stored in the RAM 203, such as the engine size, heater ratings, start-time 302, or other parameters.

If data have been received and stored in the region 206a of the buffer 206, this indicates receipt of data from one of the alarm devices 230a-230d. As mentioned above, the alarm devices 230a-230d may comprise, for example, tamper alarms, door-open detectors, motion detectors, or other alarm devices that produce a digital output signal indicative of their status. Generally, the presence of data in the region 206a from an alarm device 230a-d will trigger the microprocessor 202 to formulate a status report, transmit the report to the remote unit 200 via the base transmitter 240, and sound the acoustic annunciator 264 with a noise such as a "beep".

After completing the communications handling of task 685, task 686 re-enables PERIODIC INTERRUPT, which was previously disabled in task 610 (FIG. 6A). Task 687 then exits from the periodic interrupt routine and returns to the main program.

The maintenance routine (FIG. 7) is performed each time the periodic interrupt routine determines that the MAINTENANCE FLAG is set (task 670, FIG. 6A). In the maintenance-mode 305, power is applied to one or more heaters according to the multiplexing table selected in task 440 (FIG. 4), but only during certain periods. These selected periods are arranged so that the heaters supply the minimum amount of heat needed to keep the engine ready for safe starting. To accomplish this, heating according to the selected multiplexing table is enabled during certain periods, and completely disabled during the remaining periods. TIME-ON is utilized to keep track of one minute intervals during the maintenance mode 305.

The maintenance routine includes a number of tasks 700, which are initiated in task 702. Task 710 increments TIME-ON and STAGE by one, and then query 720 determines whether heating is enabled or disabled. In an exemplary implementation, one complete sequence of enabling and disabling the heaters, called a "maintenance cycle", lasts 30 minutes: the heaters are enabled for a period equal to [0.1.multidot.(the preheat-period 303)], and disabled for [30-0.1.multidot.(the preheat-period 303)]. In other words, the heaters are enabled for one tenth of the preheat-period 303, and disabled for the remainder of the 30-minute "maintenance cycle". If query 720 determines that heating should be disabled, task 722 advances to task 685 (FIG. 6B) to attend to communications. Otherwise, query 730 asks whether the maintenance cycle has ended (this period is 30 minutes in the present example). If the maintenance cycle has not concluded, then query 730 advances to task 780, where control is advanced to task 690 (FIG. 6B) to turn on the appropriate heaters. However, if the maintenance period has ended, TIME-ON is reset to 0 in task 740. Then, query 750 asks whether the continuous mode has been selected. If the continuous mode has not been selected, query 760 asks whether the time indicated by the clock-calendar 210 is equal to the end-maintenance-time 306. If the maintenance-mode 305 has not ended, control advances to task 780. However, if the time 306 has arrived, indicating the end of the maintenance-mode 305, task 770 clears the HEATING FLAG and the MAINTENANCE FLAG, and progresses to task 780.

If query 750 determines that the continuous mode has been selected, query 750 jumps to task 780 to immediately apply power to the appropriate heaters in task 690 (FIG. 6B). It can thus be seen that selecting the continuous mode causes the maintenance routine to bypass query 760 and task 770, foregoing the possibility of terminating the maintenance-mode 305. As a result of selecting the continuous mode, then, the invention operates in the maintenance-mode 305 indefinitely.

The present invention provides a number of advantages to its users. For instance, the invention advantageously employs engine heaters to expand a cooled engine to its normal size, and to warm the coolant and lubricants of the engine. Accordingly, the invention reduces stress on the engine, decreases engine maintenance, and extends the engine's life. In addition, the invention facilitates the use of interior heaters to increase driver and passenger comfort, battery heaters to increase battery cranking power, fuel heaters to achieve the proper fuel viscosity, and transmission heaters to ensure proper transmission operation.

The invention automatically performs calculations to facilitate the most efficient pre-heating of automotive components prior to starting the vehicle. Moreover, the invention automatically stops increasing the temperature of the vehicle components when a selected time is reached, or when a safe starting temperature is reached. The invention additionally maintains a minimum starting temperature for a designated period of time.

A user may fully operate the invention from the remote unit 200. For example, the invention enables a user to effectively begin heating various components of his/her vehicle, or to control the time of such heating, from a remote location. Additionally, the invention supports various types of vehicle alarms, by forwarding alarm signals to the user via the remote unit 200.

While there have been shown what are presently considered to be preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims. For example, in an alternative embodiment, the present invention is contemplated to include a base unit (not shown) configured to heat components of multiple vehicles (not shown), such as a fleet of vehicles. Such a base unit is preferably located apart from the vehicles, and is preferably placed in a fixed central location near an a.c. power supply. This base unit provides a sufficient number of outlets to accommodate the heaters of each vehicle in the fleet. In this embodiment, since there are multiple vehicles to heat, the maintenance-mode 305 may be commenced if any vehicle of the fleet still has not been started at the expected-engine-start-time 302. However, loss of a.c. power is not useful to determine when any of the vehicles is started since the base unit's location is fixed, and it is connected to a.c. power irrespective of its connection to any of the vehicles. In this embodiment, the base unit determines whether a vehicle has been started, not by detecting a.c. power loss, but by another method, such as detecting disconnection of a vehicle's battery from the base unit. In this embodiment, the electronic components of the invention may receive d.c. power from a battery (not shown) that is separate from any of the vehicles' batteries, to avoid shutting down the base unit when all vehicles are disconnected from the base unit.

Furthermore, although the invention is explained in the context of a motor vehicle, the application of the invention is not limited to motor vehicles. The invention may be used in conjunction with a variety of equipment, such as shipboard power plants, pallet equipment such as pumps, stationary generator sets, and the like. Moreover, the invention is not limited to heating items, since it may be utilized in an analogous fashion to cool items. Such a cooling technique would be apparent to a person of ordinary skill in the art equipped with this disclosure. ##SPC1##