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 a geared 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 
     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 
     The present invention relates to controlling the thermostat on both electric and gas powered water heaters based on user programmed settings. 
     BACKGROUND OF INVENTION 
     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. 
     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 drawback is that the manufacturer warranty may be voided since we are tampering with the original design of the product. 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 
     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. 
     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. 
     A third objective is to make the unit cost effective for the consumers to buy and use it. 
     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. 
     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. 
     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 
         FIG. 1  is the prior art of a storage type water heater with a temperature control unit. 
         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. 
         FIG. 3  is the rear view of the preferred embodiment of the programmable water heater thermostat controller with the internal parts revealed. 
         FIG. 4  is a side view of the drive means. 
         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. 
         FIG. 6  is a block diagram of the electronic circuit board used to control the rotation of the temperature control knob. 
         FIG. 7  is a schematic circuit diagram to control the direction of rotation of the geared electric motor shaft using two single pole double throw relays. 
         FIG. 8  is a schematic circuit diagram to control the direction of rotation of the geared electric motor shaft using four opto-isolators. 
         FIG. 9  is the block diagram of the remote user interface. 
         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. 
         FIG. 11  shows the flowchart of the decision process used by the first transmitter/receiver means. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       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 water temperature. Position indicator,  5 , on the temperature control knob  3 , shows the temperature setting with respect to arc  4 . 
       FIG. 2  shows the front view of the preferred embodiment of a programmable water heater thermostat controller of the present invention mounted on top of temperature control unit  2 . The programmable water heater thermostat controller of the present invention 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. Faceplate,  11 , has a window,  13 , through which the temperature control knob  3  and the temperature indicating arc  4  can be seen. A plurality of switches,  7 , are used as first user input means. These switches are used to program user desired time and corresponding user desired temperature information. The components of the present invention are mounted on the reverse side of faceplate  11  as shown in  FIG. 3 . 
     Referring to  FIG. 2 ,  FIG. 3 ,  FIG. 5  and  FIG. 6 , an electronic circuit board,  28 , with a microcontroller  50  on it, is connected by wire to said first display means,  12  and a first transmitter/receiver means,  23 . The plurality of switches,  7 , 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 , fixedly attached to shaft  45  of a potentiometer,  26 . The potentiometer has three terminals,  46 ,  47  and  48 . Terminal  46  is connected to +5 volts supply. Terminal  48  is connected to ground. Terminal  47  is connected to analog to digital 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 a sensor mount,  20 , while the second end,  22 , of sensor mount sticks out from faceplate,  11 . Sensor mount  20  is attached rotatetably to faceplate  11  at second pivot point  21 . A wire,  27 , with three conductors, connects potentiometer  26  with said electronic circuit board,  28 . 
     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 a geared electric motor,  14 , and a driver pinch roller,  41 . Shaft,  35 , of the geared electric motor is rigidly connected to said driver pinch roller,  41 . Drive means  24  is fixedly mounted on the first end of a driver mount  15  while second end,  18 , of the driver mount sticks out from faceplate  11 . Driver mount  15  is attached rotatetably to faceplate  11  at first pivot point  17 . A tension spring,  16 , with a first end and a second end connects driver mount,  15 , with sensor mount,  20 . First end of tension spring is connected to driver mount  15  at first attachment point,  29 . Second end of tension spring is connected to sensor mount,  20 , at 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 , with two conductors, connects geared 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. 
       FIG. 6  is a block diagram of the input/output connection to microcontroller,  50 . The plurality of switches,  7 , are connected to a plurality of input pins,  55 , on said microcontroller. The microcontroller accepts program time and corresponding temperature information from the user through said plurality of switches  7 . It outputs display information to said first display means,  12  via a set of output pins, collectively numbered  52 . The analog to digital input pin  56  of the microcontroller is connected to the center tap 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 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 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 geared 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 . 
       FIG. 7  is a schematic diagram of the relay contact connection with the geared electric motor. Each relay has two fixed contacts and one moveable contact. In relay  57 , the moveable contact,  59 , is connected to terminal  31  on geared 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 terminal  32  on geared 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 . 
     When relay  57  and relay  58  are de-energized, the two terminals of the geared electric motor are connected to ground. Hence the geared electric motor will not turn. When only relay  57  is energized by output signal on pin  65 , geared electric motor terminal  31  is at +5 volts with respect to terminal  32 . Hence the geared 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 , geared electric motor terminal  32  is at +5 volts with respect to terminal  31 . Hence the geared electric motor is energized but with the polarity of the terminals reversed. Hence the geared 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 geared electric motor and thereby, the direction of rotation of the temperature control knob can be controlled. 
       FIG. 8  shows another implementation of the geared 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 geared electric motor as well as the input of  70 . Similarly, output of  68  is connected to terminal  32  of the geared electric motor as well as the input of  69 . Output pin  65  of the microcontroller is connected to control pin of both  67  and  69 . Output pin  66  of the microcontroller is connected to 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 geared electric motor through +5 v— 67 - 31 —geared electric motor— 32 - 69 —ground. For this, let us assume that the shaft of the geared 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 geared electric motor through +5 v— 68 - 32 —geared electric motor— 31 - 70 —ground. Since the polarity on the geared electric motor terminals is reversed, the shaft of the geared 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 geared electric motor and thereby, the direction of rotation of the temperature control knob can be controlled. 
       FIG. 9  is a block diagram of the remote user interface,  71 . It consists of a plurality of switches,  74 , 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. 
       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. 
       FIG. 11  shows the decision logic used by the first transmitter/receiver means to receive data and transmit to the correct recipient. 
     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 faceplate  11  toward each other so that the drive means and the position sensing means are moved farther away from each other. He places the programmable water heater thermostat controller on top of 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 faceplate  11  to temperature control unit with fasteners that are not shown in the diagram. Now, when the geared electric motor is actuated by the microcontroller through one of the two relays, it will turn the driver pinch roller,  41 . Since the driver pinch roller is pressing against temperature control knob  3  due to 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 . 
     A drive driver 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 means will connect the driver 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. In that case, a driven gear should be securely fastened to the top of the temperature control knob so that the axis of rotation of the driven gear is substantially the same as the axis of rotation of the temperature control knob. Similarly, a position sensing gear can be substituted for the driven pinch roller on the position sensing means such that the driven gear on the temperature control knob communicates rotatetably with the position sensing gear to turn the potentiometer shaft. 
     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 implemented using multiple types of components. 
     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 desired temperature setting 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 geared 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 geared electric motor. 
     The microcontroller also checks continually for input from the first transmitter/receiver means and the first user input means. If input comes from the first user input means, then the display result is sent to the first display means. If input comes from the first transmitter/receiver means, then the display result is sent to the first transmitter/receiver means. 
     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 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.