Programmable thermostat employing a fail safe real time clock
Contents
1. 1 a central processing unit 2 a first memory coupled to said central processing unit for storing program and data information and 3 an input output unit including a a sensor input coupled to said temperature sensor for receiving said electrical signal therefrom and b a control output coupled to the space conditioning equipment for issuing control signals thereto 4 a real time clock 5 a non volatile random access memory and 6 a control program stored in said first memory directing a said real time clock to periodically read its current time and date information into said non volatile memory and b upon restart after a loss and then return of power from said space conditioning equipment read the time and date information stored in said non volatile memory into said real time clock 2 The thermostat of claim 1 in which said non volatile random access memory is included in said first memory 3 The thermostat of claim 2 which includes a vacation mode of operation 4 The thermostat of claim 1 which includes a vacation mode of operation 5 The thermostat of claim 1 which further includes a receiver adapted to receive current time and date informa tion from an external source of the current time and date said receiver being coupled to said real time clock such that the time and date information thereof is updated from said receiver 6 The thermostat of claim 5 in which said receiver receives wireless signals fr2. last update and the return of power The real time clock can subsequently be set to the current time in the usual manner Thus the need for backup power such as a battery or a supercap is eliminated In one embodiment the real time clock is also periodically updated by a signal from the National Institute of Standards and Technology or other source of precision time Accordingly the real time clock is always close to the correct time during normal operation and when the thermostat is recovering from a power failure the real time clock will be sufficiently close to effectively permit resumption of normal or vacation mode operation as in the simpler embodiment and will also automatically promptly be set to the correct current time If the precision time signal is unavailable for some reason the real time clock will still be reset by the information store in the non volatile random access memory DESCRIPTION OF THE DRAWING The subject matter of the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification The invention however both as to organiza tion and method of operation may best be understood by reference to the following description taken in conjunction with the subjoined claims and the accompanying drawing of which FIG 1 is a block diagram of an exemplary space condi tioning system incorporating a thermostat with backup power in case of an outage supplied from a battery
3. 1 then the I O unit 10 may only constitute simple switching circuits Thus in the usual manner during normal operation the temperature sensor 5 sends an electrical signal e g if the sensor 5 is a simple thermistor a resistance value several types of temperature sensors are widely used representative of the temperature within the conditioned space 4 which the processor can compare against a previously entered set point to determine if control signals need to be sent to the space conditioning equipment 3 For example if the temperature in the conditioned space 4 is found to be too low when operation is in the heating mode the processor 1 signals the space conditioning equipment 3 to circulate through ducts 6 7 air from to the conditioned space 4 which is heated by the space conditioning equipment before return to the con ditioned space This heating phase continues until the sensor 5 indicates that the space is now too hot or approaching too hot with reference to the current set point such that the processor 1 sends signal s to the space conditioning equip ment 3 to cease the heating function all as very well known in the art In a cooling mode a counterpart procedure is followed Those skilled in the art will understand that the control process typically includes such refinements as antici US 7 185 825 B1 5 pation hysterisis accommodation fan control etc which are acknowledged but are not directly relevant to the i
4. of power the ther mostat enters a programming mode as if the thermostat were newly installed and because all programming and or current time and date information has been lost the nor mally conditioned space will not be heated or cooled as the case may be such that the reasons set forth above for using the vacation mode will not be met Even if the thermostat has the capability of restarting in its operational mode at the time of the outage e g if the processor memory includes non volatile random access memory for storing changeable information such as set up and mode data and can restart the real time clock at say some default date the thermostat real time clock will not have the correct time or date such that for example in the vacation mode the system will not correctly anticipate the return of occupants and thus will not necessarily earlier resume normal operation to render the space comfortable by the time the occupants return It will therefor be apparent to those skilled in the art that it would be highly desirable to provide a fail safe real time clock in a programmable clock particularly a thermostat incorporating a vacation mode of operation OBJECTS OF THE INVENTION It is therefore a broad object of this invention to provide a thermostat which incorporates a fail safe real time clock It is another broad object of this invention to provide a thermostat which does not require a backup source of energy for continuing
5. thermostat status during an outage US 7 185 825 B1 3 It is a more specific object of this invention to provide a thermostat having a real time clock and a non volatile random access memory in which the current time and date are periodically read from the real time clock into the random access memory such that in the event of an outage the last time and date previously stored is recovered from the non volatile random access memory upon the restoration of power to reset the real time clock in anticipation of resuming operation in the mode running at the time of the outage In an alternative and supplementary aspect it is a more specific object of this invention to also periodically update and also initialize after an outage the real time clock by a signal from the National Institute of Standards and Tech nology or other source of precision time SUMMARY OF THE INVENTION Briefly these and other objects of the invention are achieved in a programmable thermostat having a real time clock by periodically during normal powered operation storing the current time and date in a non volatile random access memory such that in the event of an outage the last time and date previously stored is recovered from the non volatile random access memory and used for subse quent operations when power is restored This provides an acceptable reset of the clock which will only be off current time by an amount represented by the period between the
6. United States Patent US007185825B1 12 10 Patent No US 7 185 825 B1 Rosen 45 Date of Patent Mar 6 2007 54 PROGRAMMABLE THERMOSTAT 6 344 861 B1 2 2002 Naughton EMPLOYING A FAIL SAFE REAL TIME 6 478 233 B1 11 2002 Shah CLOCK Continued 76 Inventor Howard Rosen Lyncroft Road FOREIGN PATENT DOCUMENTS Hampstead Quebec CA H3X 3E3 DE Sasae Andes Notice Subject to any disclaimer the term of this patent is extended or adjusted under 35 Continued U S C 154 b by 241 days OTHER PUBLICATIONS 21 Appl No 10 875 579 ADI Leopard User Manual 93 pages 2001 No Continued 22 Filed Jun 24 2004 Primary Examiner Marc Norman Attorney Agent or Firm Marc E in Hankin 51 Int Cl 74 y Ag F Marc E Hankin Hanki G05D 23 19 2006 01 Patent Law GO5D 23 32 2006 01 F25B 17 00 2006 01 67 ABSTRACT GO5B 15 00 2006 01 A ble th tat fi trolli diti E TSP E 236146 C7233694 GISTs POBAN NAN E ETNOSA Or COT TOTE Space Conemon 621231 700 276 ing equipment receives power from the equipment The i i thermostat has an interactive interface for user program 58 Field of Classification Search 236 94 ming a temperature sensor and a processor including a 236 1 C 46 R 46 C 62 157 231 700 275 central processing unit a memory for storing program and 700 276 data information a real time clock and a non volatile random See application file for complete search history acces
7. e time and date informa tion thereof is updated from said receiver 12 The thermostat of claim 11 in which said receiver receives wireless signals from said external source 13 The thermostat of claim 12 which includes a vacation mode of operation 14 The thermostat of claim 11 in which said receiver receives signals via the Internet from said external source 15 The thermostat of claim 14 which includes a vacation mode of operation 16 The thermostat of claim 11 which includes a vacation mode of operation 10 15 20 25 30 35
8. ess memory ee prom Such memories of which there are various types are characterized in that they will hold their contents indefinitely upon a power failure but may during normal operation be rewritten essentially limitlessly in the same manner as a volatile RAM which however does lose its contents as a result of a power loss It may be noted as represented by the dashed communication line 33 that in practicing the inven tion the memory 8 may include a non volatile RAM section 32 which eliminates the need for the separate non volatile RAM 33 As a practical matter as the state of the art of circuit integration progresses most or all the components of a programmable thermostat according to the invention may be incorporated as a single configurable and programmable integrated circuit or in a very few chips The thermostat including the real time clock 30 is normally conventionally powered via line 35 and an isola tion diode 36 from the equipment to which the thermostat is connected However it is a feature of the invention that no source of backup power such as a battery or supercap is required Referring also now to the process flow chart of FIG 3 the relevant portion of the control program normally running in the CPU 9 is described In accordance with the invention at some suitable point in the loop of the control program an inquiry is made step 40 as to whether a predetermined period since the time and date informati
9. essor to run a process control program stored in the memory to accurately measure the temperature of a temperature sensor disposed in the conditioned space and to send control signals to the heating and or cooling equipment to closely control the temperature of the conditioned space The use of pro grammed thermostat systems permits anticipating and mini mizing hysterisis or overshoot of the temperature in the conditioned space In addition the program can specify different set points at different times of the day and days of the week and may also include a vacation mode which employs different set points when the conditioned space is not occupied for an extended period Most such modern thermostats are programmable by a user Typically a programmable thermostat incorporates a tactile user interface with various buttons or representations of buttons on a touch screen to be touched in a precise sequence to program set points which may vary with the time of day and day of the week for programmable time periods and which may include both normal and vacation modes The programming sequence may be followed on a display typically a liquid crystal display and when the programming steps have been completed the thermostat is switched the immediately desired operational mode The purpose of a vacation mode is to maintain the temperature of a conditioned space which will be unoccu pied for a period at a value which will substantially lower t
10. ets RECEIVER US 7 185 825 B1 Page 2 U S PATENT DOCUMENTS 6 595 430 Bl 6 621 507 Bl 2003 0040842 Al 2003 0121652 Al 7 2003 Shah 9 2003 Shah 2 2003 Pot sssr 700 275 7 2003 Carey et al oo 165 238 FOREIGN PATENT DOCUMENTS EP 0985994 WO WO 97 11448 WO WO 97 39392 3 2000 3 1997 10 1997 OTHER PUBLICATIONS Business Wire MicroTouch Specialty Products Group to Capital ize on Growing Market for Low Cost Digital Matrix Touchscreens p1174 2 pages Jan 6 1999 DeKoven et al Designing Collaboration in Consumer Products 2 pages 2001 Freudenthal et al Communicating extensive smart home func tionality to users of all ages the design of a mixed initiative multimodal thermostat interface pp 34 39 Mar 12 13 2001 Honeywell News Release Honeywell s New Sysnet Facilities Integration System For Boiler Plant and Combustion Safety Pro cesses 4 pages Dec 15 1995 Honeywell W7006A Home Controller Gateway User Guide 31 pages Jul 2001 High tech options take hold in new homes 200 08 28 Dallas Business Journal http biziournals com dallas stories 2000 08 28 focus4 3 pages dated Aug 28 2000 printed Aug 19 2004 Product Review Philips Pronto Remote Control http homethreaterhifi com volume 6 2 philipsprontoremotecontrol html 5 pages dated May 1999 printed Aug 20 2004 http www cc gatech edu computing classes cs675 1 94 fall 2ro
11. he cost of energy to heat cool the conditioned space but which ensures that the temperature will not fall into a range at which damage to the premises for example freezing pipes will occur The operation of programmable thermostats in the vacation mode is straightforward and well known A separate program from normal operation is entered by whatever procedure is provided in a given thermostat The vacation mode may include one or more periods a day for which set point temperatures may be entered In cold cli mates a heating temperature set point will be selected by a user to be suitable say 45 F such that freezing of water 20 25 30 35 40 45 50 55 60 65 2 pipes will not take place If for example self sufficient pets are left behind for a few days a higher temperature say 60 F might be selected The choice is within the purview of the user Similarly in hot climates a user might select a tem perature of say 90 F or even higher to effect substantial savings in the cost of energy for cooling but not so high as to cause damage to items in the space Again if for example pets are left behind a more comfortable tempera ture of 80 F or so might be selected Some programmable thermostats incorporating a vacation mode of operation also provide for storing the date and even time of day that the occupant s of the conditioned space will return such that operation of the space conditioning equi
12. nvention In accordance with the prior art power to the processor 1 is conventionally supplied from the space conditioning equipment 3 via a line 30 through an isolation diode 33 In the event of a power outage power is supplied from a backup battery 31 or a very high capacity capacitor super cap 32 to ride out equipment power failure until power is restored However these are not fail safe expedients Batteries must be changed at intervals and often are not to ensure that the thermostat or at least the clock will continue to operate during a power failure Supercaps are susceptible to developing leakage which greatly diminish their charge storing capacity i e they may develop a resistance across the plates sufficiently low that a charge stored during normal operation discharges during an outage before power is restored Attention is now directed to FIG 2 which is a block diagram of the clock 13 modified according to a first exemplary embodiment of the invention and the compo nents with which it communicates As previously described the clock 13 provides real time information to the CPU 9 to facilitate the timely institution of or stopping of diverse operations The clock 13 in accordance with the present invention includes a real time clock module 30 which is an off the shelf integrated circuit component and a small non volatile random access memory RAM 31 such as a flash RAM or electrically eraseable random acc
13. om said external source 7 The thermostat of claim 6 which includes a vacation mode of operation 8 The thermostat of claim 5 in which said receiver receives signals via the Internet from said external source 9 The thermostat of claim 8 which includes a vacation mode of operation 8 10 The thermostat of claim 5 which includes a vacation mode of operation 11 A programmable thermostat for controlling space conditioning equipment comprising 5 A means coupling suitable power for energizing said thermostat from said space conditioning equipment to said thermostat B an interactive interface for a user to enter programming information into said thermostat C a temperature sensor for providing an electrical signal indicative of the temperature of a conditioned space in which the temperature sensor is situated D a processor said processor including 1 a central processing unit 2 a first memory coupled to said central processing unit for storing program and data information and 3 an input output unit including a a sensor input coupled to said temperature sensor for receiving said electrical signal therefrom and b a control output coupled to the space conditioning equipment for issuing control signals thereto 4 a real time clock and 5 a receiver adapted to receive current time and date information from an external source of the current time and date said receiver being coupled to said real time clock such that th
14. on in the real time clock 30 were last stored has been exceeded Merely by way of example the predetermined period might be one hour but it could be as often as every time the control program runs through the routine shown in FIG 3 which would eliminate the need for step 40 If not the control program continues However if the predetermined period has been exceeded the stored time and date is updated step 41 from the real time clock before continuing the control program Referring now to FIG 4 it will be seen that in the event of a power failure and then a restart after power has been restored the restart procedure of the control program includes resetting the real time clock from the time and date 20 25 30 35 40 45 50 55 60 65 6 value stored in the non volatile RAM 31 Accordingly the time and date will be off no more than the period of the outage plus the period since the time and date were last updated before the outage as described above Most outages are relatively short term a few minutes to perhaps an hour such that it will be apparent that a restart with a time and date resident in the real time clock which is only this limited amount slow will permit resumption of operation with little problem As previously mentioned this is of particular importance when the thermostat is operating in the vacation mode FIG 5 illustrates a second exemplary embodiment of the invention In this embodimen
15. or supercap in accordance with the prior art FIG 2 is a block diagram of a portion of the processor component of the thermostat particularly showing aspects of the thermostat clock and its support circuitry in a first exemplary embodiment of the invention FIG 3 is a process flow chart illustrating a part of the thermostat control program by which an updating operation is carried out according to the practice of the invention FIG 4 is a process flow chart showing a part of the control program restart when power has just been restored after an outage according to the invention and 20 25 30 35 40 45 50 55 60 65 4 FIG 5 is a block diagram of a portion of the processor component of the thermostat particularly showing aspects of the real time clock and its support circuitry in a second exemplary embodiment of the invention DESCRIPTION OF THE PREFERRED EMBODIMENT S Referring first to FIG 1 an exemplary thermostat includes a processor 1 a touch screen 2 and a temperature sensor 5 which is disposed in a conditioned space 4 It will be understood that the processor 1 and the touch screen 2 are typically situated in a common housing not shown The sensor 5 may also be situated in the common housing or remotely as shown all as very well known in the art The common housing is usually but not necessarily placed in the conditioned space 4 Thus those skilled in the art will understand that the block diag
16. p ment may automatically earlier be returned to a normal mode of operation in anticipation of the return of the occupant s thus ensuring a comfortable temperature in the conditioned space at that time Most commonly power to a programmable thermostat is supplied from the controlled space conditioning equipment and either a battery or very high capacity capacitor super cap provides backup power to ride out equipment power failure outage until power is restored However these are not fail safe expedients Batteries must be changed at intervals to ensure that the thermostat will continue to hold its time and setting throughout an outage but this mainte nance task is often ignored or followed sporadically Super caps on the other hand are susceptible over time to devel oping leakage which greatly diminish their charge storing capacity i e they may develop a resistance across their plates which is sufficiently low even though the resistance value might ordinarily thought to be very high in other circuits that a charge stored during normal operation dis charges to an insufficient level during a power outage before power is restored In either instance the real time clock loses its current time and date values This state particularly if the outage occurs while the thermostat is operating in the vacation mode can have drastic consequences and at best can be a significant inconvenience If upon the restoration
17. r 6 2007 Sheet 5 of 5 US 7 185 825 B1 NON VOLATILE RAM RECEIVER REAL TIME CLOCK FIG 5 US 7 185 825 B1 1 PROGRAMMABLE THERMOSTAT EMPLOYING A FAIL SAFE REAL TIME CLOCK FIELD OF THE INVENTION This invention relates to the art of thermostats and more particularly to a programmable thermostat incorporating a fail safe real time clock and which does not require battery or other backup device in case of a power failure BACKGROUND OF THE INVENTION Thermostats have been used for many years as tempera ture sensitive switches which control heating and or cooling equipment for conditioning a space in which a thermostat or a temperature sensor connected to the thermostat is placed In the well known manner a simple thermostat can be adjusted to establish a temperature set point such that when the temperature in the conditioned space reaches the set point the thermostat interacts with the heating and or cooling equipment to take suitable action to heat or cool the conditioned space as may be appropriate for the season Modern thermostats which take advantage of the ongoing rapid advances in electronic technology and circuit integra tion have many features which provide more precise super vision of the heating and or cooling equipment to achieve more economical and more comfortable management of the temperature of a conditioned space Many modern thermo stat include a real time clock a memory and a data proc
18. ram of FIG 1 is very general in order to best explain an exemplary environment in which the invention can be practiced as will be discussed below The processor 1 includes a central processing unit CPU 9 in communication with a memory 8 for storing data and program information and also via an input output unit I O unit 10 a touch pad 11 and a liquid crystal display LCD 12 which constitute the touch screen 2 The memory 8 may include a read only part which is factory programmed and a random access part which stores data subject to change during operation A settable real time clock 13 is used to keep time in the thermostat to facilitate diverse operations such as different temperature set points desired tempera tures during different periods of the day cycle An analog to digital converter 27 which may not be required in all systems serves to convert any analog information received by the I O unit 10 to digital information which is suitable for use by the CPU 9 Temperature information from the sensor 5 and output signals to a space conditioning heating and or cooling unit 3 pass through the I O unit 10 under control of the CPU 9 Those skilled in the art will understand that if the corre spondents external to the processor 1 communicating with the CPU 9 are all digital in nature e g if the temperature sensor 5 incorporates its own analog to digital converter and sends a digital representation of temperature to the processor
19. s memory A control program stored in the memory causes the real time clock to periodically read its current 56 References Cited P y U S PATENT DOCUMENTS 4 224 615 A 9 1980 Penz 4 267 966 A 5 1981 Neel etal oe 236 46 A 4 431 134 A 2 1984 Hendricks et al 236 46 R 4 818 428 A 4 1989 Scheuble et al 5 086 385 A 2 1992 Launey et al 5 170 935 A 12 1992 Federspiel 5 460 327 A 10 1995 Hill etal wo 236 46 R 5 818 428 A 10 1998 Eisenbrandt et al 6 059 195 A 5 2000 Adams et al 6 192 282 B1 2 2001 Smith et al 6 285 912 B1 9 2001 Ellison et al 6 330 806 B1 12 2001 Beaverson et al NON VOLATILE RAM time and date information into the non volatile RAM Upon restart after an outage the time and date information stored in the non volatile RAM is read into the real time clock to provide an acceptable time and date basis for resuming operation Accordingly the need for providing a backup power source such as a battery or a supercap is eliminated In one exemplary embodiment the thermostat also includes a receiver for accessing precision time and date signals from for example WWVB The output of the receiver is used to periodically update the time and date in the real time clock such that even after an outage the real time clock will be accurate If the receiver is not operating for some reason after an outage then the real time clock will still be set from the non volatile RAM 16 Claims 5 Drawing She
20. t a wireless receiver 50 is tuned to a source of precision time such as WWVB which operates at 60 khz Such receivers are well known in the art and may be implemented in small integrated circuits which can readily be incorporated into a thermostat For example a single chip WWVB receiver is available from Micro Analog Systems of Espoo Finland and is designated by part number MAS9178 in data sheet DA9178 000 The output from the receiver 50 is a once per second data set of the exact time which can be adjusted to a time zone and date This information is used to periodically update the time and date information running in the real time clock 30 It will now be understood that the embodiment of the invention shown in FIG 5 will normally keep and resume after an outage precision time from a suitable source such as WWVB In addition if WWVB is not being received because it is off the air there is interference etc then the clock is still fail safe because this embodiment will then operate in the manner of the embodiment shown in FIG 2 and the process flow charts of FIGS 3 and 4 While a wireless source of precision time has been discussed it should be noted that precision time from for example the National Institute of Standards and Technol ogy is also available on the Internet such that it is contem plated that the source 50 can receive its time signals via that medium In another embodiment of the invention for use in areas
21. upe climate 2 node 1 html Contents 53 pages printed Sep 20 2004 HAI Company Background http www homeauto com AboutHAT abouthai main htm 2 pages printed Aug 19 2004 Cardio Manual available at http www secant ca En Documenta tion Cardio2 Manual pdf Cardio Home Automation Inc 55 pages printed Sep 28 2004 RC X10 Automation Forum Control your Heating and Cooling System with Pronto 1 1 http www remotecentral comlcgi binlmboardlre x 1 0 thread c i 12 2 pages dated Apr 23 1999 printed Aug 20 2004 cited by examiner US 7 185 825 B1 Sheet 1 of 5 Mar 6 2007 U S Patent Luv Y Oldd Ola AW1dSIG WILSAYD anon LNN LNdLNO LAGNI JOWdS GANOILIGNOD INAWdINOA ONINOLLIGNOD AOVdS AYOWAN U S Patent Mar 6 2007 Sheet 2 of 5 US 7 185 825 B1 NON VOLATILE a REAL TIME CLOCK FIG 2 U S Patent Mar 6 2007 Sheet 3 of 5 US 7 185 825 B1 FROM SUITABLE POINT IN CONTROL PROGRAM PRE DETERMINED TIME ELAPSED SINCE UPDATE SEND CURRENT RTC TIME AND DATE TO NON VOLATILE RAM RETURN TO SUITABLE POINT IN CONTROL PROGRAM FIG 3 U S Patent Mar 6 2007 Sheet 4 of 5 US 7 185 825 B1 FROM SUITABLE POINT IN RESTART OF CONTROL PROGRAM SEND CURRENT RTC TIME AND DATE TO NON VOLATILE RAM RETURN TO SUITABLE POINT IN CONTROL PROGRAM FIG 4 U S Patent Ma
22. where the wireless reception of time and date signals is reliable or when the Internet now very reliable is used as the communications medium then the non volatile RAM 31 may be omitted and the sub processes shown in FIGS 3 and 4 need not be carried out Rather the real time clock 30 will be constantly or as often as desired updated from the external precision time source and in the event of an outage and restart the real time clock 30 will be promptly accu rately set Thus while the principles of the invention have now been made clear in an illustrative embodiment there will be immediately obvious to those skilled in the art many modi fications of structure arrangements proportions the ele ments materials and components used in the practice of the invention which are particularly adapted for specific envi ronments and operating requirements without departing from those principles What is claimed is 1 A programmable thermostat for controlling space con ditioning equipment comprising A means coupling suitable power for energizing said thermostat from said space conditioning equipment to said thermostat B an interactive interface for a user to enter programming information into said thermostat C a temperature sensor for providing an electrical signal indicative of the temperature of a conditioned space in which the temperature sensor is situated US 7 185 825 B1 7 D a processor said processor including
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