Abstract:
A programmable water heater thermostat controller that attaches over the temperature control unit of existing gas or electric water heaters. The user programs the temperature of water required at different times of the day. A microcontroller then compares the current temperature setting against desired setting every minute and rotates the temperature control knob accordingly using an electric motor. If vacation mode is chosen, then the microcontroller skips program times and keeps the temperature control knob at the lowest temperature setting.

Description:
PRIORITY CLAIM 
       [0001]    This patent application claims priority from provisional U.S. patent application entitled “Programmable water heater thermostat controller”, having an application No. 61/241,480 filed on Sep. 11, 2009, the contents of which are incorporated herein by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates to controlling the thermostat on both electric and gas powered water heaters based on user programmed settings. 
       BACKGROUND OF INVENTION 
       [0003]    Water heaters come with a thermostat to adjust the temperature of water. When the set temperature is reached, the burner in gas powered water heater or the electric coil in electric water heater is turned off. When the temperature drops below the set temperature, the water heater is turned on again. This process repeats all the time. The user sets the temperature high enough to get hot water during periods of peak usage even on the coldest day of the year. This temperature is maintained during the day as well as night when there is not much need for hot water. People seldom change the setting of the thermostat. Hence the high temperature is maintained even during summer. This results in wastage of fuel. This also shortens the life of the water heater. There is a need for a programmable thermostat that can be programmed to heat water in the morning to the required high temperature, then turn down the thermostat during daytime when there is no one in the house to use hot water, turn it up again to a moderate temperature in the evening for dinner time usage and turn it down for the night. Since there are already millions of water heaters in use, the programmable thermostat should be easy to install on an existing water heater. 
         [0004]    In U.S. Pat. No. 6,920,843, William Wilson uses a solenoid in the gas supply line to interrupt supply of gas. It has two drawbacks. The first is that the user will have to get the unit installed by a licensed plumber. The second but very severe drawback is that when the solenoid shuts off gas to the water heater, the pilot lamp will also be extinguished. The user will have to light it every time the timer shuts off the solenoid. So this is not a practical one. In U.S. Pat. Nos. 7,380,522 and 6,375,087, the system has to be built in by the manufacturer. It cannot be attached to the millions of water heaters already in use. 
       SUMMARY OF INVENTION 
       [0005]    The primary objective of the present invention is to conserve energy by way of a programmable controller that can vary the temperature setting at different times of the day. 
         [0006]    Another objective of the present invention is to make it easy for anyone to attach the unit to an existing water heater without the need to call a plumber. 
         [0007]    A third objective is to make the unit cost effective for the consumers to buy and use it. 
         [0008]    The foregoing objectives are attained by having a programmable microcontroller vary the temperature setting by turning the temperature control knob based on user preprogrammed temperature settings at user preprogrammed times of the day. 
         [0009]    In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. 
         [0010]    As such, those skilled in the art will appreciate that the concept, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is the prior art of a storage type water heater with a temperature control unit. 
           [0012]      FIG. 2  is the front view of the preferred embodiment of the programmable water heater thermostat controller attached to the temperature control unit on the water heater. 
           [0013]      FIG. 3  is the rear view of the preferred embodiment of the programmable water heater thermostat controller with the internal parts revealed. 
           [0014]      FIG. 4  is a side view of the drive means. 
           [0015]      FIG. 5  is the side view of the position sensing means that is used to sense the position of the temperature control knob on the water heater. 
           [0016]      FIG. 6  is a block diagram of the electronic circuit board used to control the rotation of the temperature control knob. 
           [0017]      FIG. 7  is a schematic diagram to control the direction of rotation of the electric motor shaft using two single pole double throw relays. 
           [0018]      FIG. 8  is a schematic diagram to control the direction of rotation of the electric motor shaft using four opto-isolators. 
           [0019]      FIG. 9  is the block diagram of the remote user interface. 
           [0020]      FIG. 10  is the flowchart of the decision process used by the microcontroller to rotate the temperature control knob at different times of the day. It also shows the logic used to program the time and temperature information by the user. Vacation mode decision logic is also illustrated. 
           [0021]      FIG. 11  shows the flowchart of the decision process used by the first transmitter/receiver means. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]      FIG. 1  is the prior art of a storage type water heater,  1 . Unit  1  has a temperature control unit  2 , to control the temperature of water heated. Temperature control unit  2  has a temperature control knob  3  that the user turns to set the desired temperature for hot water. Arc  4  above the temperature control knob shows the direction the temperature control knob should be turned to increase water temperature. In this illustration, the temperature control knob should be turned in a counter clockwise direction to increase the temperature. The position indicator,  5 , on the temperature control knob  3 , shows the temperature setting with respect to arc  4 . 
         [0023]      FIG. 2  shows the front view of the preferred embodiment of the programmable water heater thermostat controller of the present invention mounted on top of the temperature control unit  2 . It consists of a faceplate,  11  with a first display means,  12 , to display the current time, or, at the time of programming, the program information, which will be discussed later. It also has a window,  13 , through which the temperature control knob  3  and the temperature indicating arc  4  can be seen. Buttons,  7 ,  8  and  9  are a set of switches used as the first user input means. These buttons are used to program the time and temperature information. The components of the present invention are mounted on the reverse side of face plate  11  as shown in  FIG. 3 . 
         [0024]    Referring to  FIG. 2 ,  FIG. 3 ,  FIG. 5  and  FIG. 6 , the electronic circuit board,  28 , which has a microcontroller  50  on it, is connected by wire to the first display means,  12  and the first transmitter/receiver means,  23 . The plurality of switches,  7 ,  8  and  9  are also mounted on the electronic circuit board,  28 . On the periphery of window  13  are two subsystems, numbered  19  and  24 . Subsystem  19 , henceforth called the position sensing means, consists of a driven pinch roller  49 , attached to shaft  45  of potentiometer  26 . The potentiometer has three terminals,  46 ,  47  and  48  on it. Terminal  46  is connected to +5 volts supply. Terminal  48  is connected to ground. Terminal  47  is connected to input pin  56  of microcontroller  50 . Since the resistance varies when the potentiometer knob is turned, it is a good candidate as a rotation sensor. The position sensing means is fixedly mounted on the first end of sensor mount  20  while the second end,  22 , of sensor mount sticks out from face plate,  11 . Sensor mount  20  is attached to face plate  11  rotatetably at second pivot point  21 . A wire,  27 , connects potentiometer  26  with the electronic circuit board,  28 . 
         [0025]    Referring to  FIG. 2 ,  FIG. 3  and  FIG. 4 , drive means,  24 , is used to turn temperature control knob,  3 . Drive means  24  consists of an electric motor,  14 , a reduction gear assembly,  36  and a driver pinch roller,  41 . The reduction gear assembly consists of a plurality of gears, numbered  37 ,  38 ,  39  and  40 . Shaft,  35 , of the electric motor is rigidly and rotatetably connected to gear  37 . The electric motor provides rotational input to the reduction gear assembly. Gear  40 , which is the output from the reduction gear assembly, is rigidly and rotatetably connected to driver pinch roller,  41 . The number of teeth on the gears and the arrangement of the gears is such that the rotational speed of driver pinch roller  41  is substantially less than the rotational speed of shaft  35  of electric motor  14 . The reduction gear assembly is fixedly mounted on the first end of driver mount  15  while the second end,  18 , of the driver mount sticks out from face plate  11 . Driver mount  15  is attached to face plate  11  rotatetably at first pivoted point  17 . A tension spring,  16 , with a first end and a second end connects driver mount,  15 , with sensor mount,  20 . The first end of tension spring is connected to driver mount  15  at the first attachment point,  29 . The second end of tension spring is connected to sensor mount,  20 , at the second attachment point,  30 . The spring tension keeps driver pinch roller,  41 , and driven pinch roller,  49 , pressed against temperature control knob  3  when the programmable water heater thermostat controller is mounted on temperature control unit,  2 . A wire,  25 , connects electric motor  14 , to the electronic circuit board,  28 . When the second end,  18  of driver mount and the second end,  22  of sensor mount are pushed toward each other, the driver pinch roller and the driven pinch roller disengage from the temperature control knob. This is done when the programmable water heater thermostat controller is installed or uninstalled from the temperature control unit. 
         [0026]      FIG. 6  is a block diagram of the input/output connection to microcontroller,  50 . The plurality of switches,  7 ,  8  and  9  are connected to the input pins,  53 ,  54  and  55 . The microcontroller accepts program time and temperature information from the user through switches  7 ,  8  and  9 . It outputs display information to the first display means,  12  via a set of output pins, collectively numbered  52 . The input pin  56  of the microcontroller is connected to the center tapping terminal  47  of potentiometer  26 . The voltage between ground and terminal  47  varies proportional to the rotational position of temperature control knob  3 . The analog value of the voltage on pin  56  passes through an analog to digital converter on the microcontroller to provide a corresponding digital value for the position of the potentiometer shaft and thereby, the position of the temperature control knob,  3 . Output pin  65  of the microcontroller is connected to one terminal of the relay coil in relay  57  while the other terminal of the relay coil is connected to the positive power supply. Similarly, output pin  66  of the microcontroller is connected to one terminal of the relay coil in relay  58  while the other terminal of the relay coil is connected to the positive power supply. The two relays are of the single pole double throw (SPDT) type. The direction of rotation of the electric motor is controlled by controlling power to the coils in the two relays. The microcontroller communicates with the first transmitter/receiver means,  23 , via input/output pin  51 . 
         [0027]      FIG. 7  is a schematic diagram of the relay contact connection with the electric motor. Each relay has two fixed contacts and one moveable contact. In relay  57 , the moveable contact,  59 , is connected to one terminal on electric motor  14 . Fixed contact  60  is connected to ground while fixed contact  61  is connected to +5 volts. Similarly, in relay  58 , the moveable contact,  62 , is connected to the second terminal on electric motor  14 . Fixed contact  63  is connected to ground while fixed contact  64  is connected to +5 volts. When the coil in relay  57  is not energized, moveable contact  59  is in electrical communication with fixed contact  60 . When the coil in relay  57  is energized, contact  59  is in electrical communication with contact  61 . Similarly, when the coil in relay  58  is not energized, moveable contact  62  is in electrical communication with fixed contact  63 . When the coil in relay  58  is energized, contact  62  is in electrical communication with fixed contact  64 . 
         [0028]    When relay  57  and relay  58  are de-energized, the two terminals of the electric motor are connected to ground. Hence the electric motor will not turn. When only relay  57  is energized by output signal on pin  65 , electric motor terminal connected to moveable contact  59  is at +5 volts with respect to the terminal connected to contact  62 . Hence the electric motor is energized and turns in one direction. Let us assume it to be clockwise direction. When only relay  58  is energized by output signal on pin  66 , electric motor terminal connected to moveable contact  62  is at +5 volts with respect to the terminal connected to contact  59 . Hence the electric motor is energized but with the polarity of the terminals reversed. Hence the electric motor will turn in the counter clockwise direction. Thus, by controlling the output signal on pins  65  and  66  of the microcontroller, the direction of rotation of the electric motor and thereby, the direction of rotation of the temperature control knob can be controlled. 
         [0029]      FIG. 8  shows another implementation of the electric motor control. Here four opto-isolators,  67 ,  68 ,  69  and  70  are used. The opto-isolator will conduct only when the LED in the opto-isolator is energized. In the configuration shown in  FIG. 8 , the input to opto-isolators  67  and  68  are connected to +5 v power supply. The output from opto-isolators  69  and  70  are connected to ground. The output of  67  is connected to terminal  31  of the electric motor as well as the input of  70 . Similarly, output of  68  is connected to terminal  32  of the electric motor as well as the input of  69 . Output pin  65  of the microcontroller is connected to the control pin of both  67  and  69 . Output pin  66  of the microcontroller is connected to the control pin of both  68  and  70 . When there is an output signal only on pin  65 , opto-isolators  67  and  69  are active. This completes the circuit for the electric motor through +5 v- 67 - 31 -electric motor- 32 - 69 -ground. For this, let us assume that the shaft of the electric motor rotates in a clockwise direction. When there is an output signal only on pin  66 , opto-isolators  68  and  70  are active. This completes the circuit for the electric motor through +5 v- 68 - 32 -electric motor- 31 - 70 -ground. Since the polarity on the electric motor terminals is reversed, the shaft of the electric motor will now turn in a counter clockwise direction. Thus by controlling the output signal on pins  65  and  66  of the microcontroller, the direction of rotation of the electric motor and thereby, the direction of rotation of the temperature control knob can be controlled. 
         [0030]      FIG. 9  is a block diagram of the remote user interface,  71 . It consists of a plurality of switches,  74 ,  75  and  76  to act as the second user input means. It also has a second display means,  73 , and a second transmitter/receiver means,  72 . In this, the second transmitter/receiver means is designed to communicate seamlessly with the first transmitter/receiver means. Thus the user need not go to the basement where the water heater is generally kept. They can use the remote user interface from any location in the house to change the time and temperature settings programmed. 
         [0031]      FIG. 10  shows the decision logic used by the microcontroller to turn the temperature control knob based on current time and the user desired temperature settings stored by the user. It also shows the decision logic used when the vacation mode is selected by the user. The microcontroller keeps checking its input lines to see if any user data is coming to it to process. If there is any user input on any of its input lines, it goes into programming mode to accept and store user furnished time and corresponding temperature data. 
         [0032]      FIG. 11  shows the decision logic used by the first transmitter/receiver means to receive data and transmit to the correct recipient. 
         [0033]    To attach the present invention to the temperature control unit  2 , on water heater,  1 , the user presses or pushes the ends  18  and  22  protruding out from face plate  11  toward each other so that the drive means and the position sensing means are moved farther away from each other. He places the water heater thermostat controller on top of the temperature control unit,  2  and then releases the grip on  18  and  22 . Because of tension spring,  16 , driver pinch roller  41  and driven pinch roller  49  move toward each other and press against temperature control knob  3 . The user fastens unit  11  to temperature control unit with fasteners that are not shown in the diagram. Now, when the electric motor is actuated by the microcontroller through one of the two relays, the electric motor will turn the gears in the reduction gear assembly, which in turn will turn the driver pinch roller,  41 . Since the driver pinch roller is pressing against temperature control knob  3  due of spring tension from spring  16 , temperature control knob  3  will rotate. Since driven pinch roller,  49  is also pressing against temperature control knob  3 , driven pinch roller  49  and hence, potentiometer shaft  45  will rotate. When shaft  45  rotates, the voltage on center tap  47 , of the potentiometer will vary. This varies the digital output from the analog to digital converter on the microcontroller. Thus the microcontroller, by comparing digital value of the potentiometer voltage with the stored digital value, can determine when to de-energize the relay and stop the rotation of temperature control knob  3 . 
         [0034]    A drive pulley can be substituted for the driver pinch roller. In this case, a driven pulley should be securely fastened to the top of the temperature control knob so that the axis of rotation of the driven pulley is substantially the same as the axis of rotation of the temperature control knob. A belt will connect the drive pulley with the driven pulley. Based on space availability, this drive means might be advantageous. If a positive drive is desired, then the driver pinch roller can be substituted with a driver gear. Here again, the driver gear is securely fastened to the top of the temperature control knob so that the axis of rotation of the driver gear is substantially the same as the axis of rotation of the temperature control knob. 
         [0035]    Relays  57  and  58  can be substituted with opto-isolators or solid state relays to achieve the same function. The circuit connection for opto-isolators is shown in  FIG. 8 . Similarly, for position sensing, instead of a potentiometer, optical sensors can be used. Thus the same function can be achieved using multiple types of components. 
         [0036]    Every minute, when the time changes, the microcontroller checks to see if the family is on vacation. If not, it compares the current time against the plurality of stored times. If it matches any one of them, it reads the corresponding temperature setting that should be set for the temperature control knob. Then it checks the digital value for the present position of temperature control knob  3 . Comparing the two values, it determines whether the temperature control knob should be turned clockwise or counter clockwise and energizes the appropriate relay. While the relay is energizing the electric motor, the microcontroller continually reads the potentiometer center tap voltage and compares it with the stored temperature setting. Once the two values match, the microcontroller de-energizes the relay to stop the electric motor. 
         [0037]    The microcontroller also checks continually for input from the first transmitter/receiver means and the first user input means. If the input comes from the first user input means, then the display result is sent to the first display means. If the input comes from the first transmitter/receiver means, then the display result is sent to the first transmitter/receiver means. 
         [0038]    The first transmitter/receiver means continually checks for wireless input from a plurality of devices with which it is configured to communicate. Some examples of such devices are the remote user interface and the cellular telephone. The user may change the program from a different part of the house using the remote user interface. Or the user might realize, while on the road that he has forgotten to set the unit for vacation mode. In that instance he might use the cellular telephone to change the mode of operation. When the first transmitter/receiver means receives input wirelessly, it sets certain flags in its memory to indicate the source of the input. Then it decodes the input and presents it to the microcontroller. When the microcontroller responds with display information, the first transmitter/receiver means encodes the information and transmits it wirelessly to the device from which it received the input data originally. For this purpose, it reads the status of flags it had set previously and determines the recipient of the display information. Then it clears those sets of flags, getting the unit ready for next wireless input.