Abstract:
A sensor in a bathroom continuously senses the humidity level therein at periodic intervals and provides the sensed humidity values to a processor, which stores the sensed values and continuously calculates an average humidity value over a time period. The processor continuously checks if the current sensed value exceeds an upper threshold value related to the calculated average humidity value and, if so, turns on an exhaust fan. Once the upper threshold value has been exceeded, the processor continuously checks if the current sensed value has dropped below a lower threshold value related to the calculated average humidity value and, if so, turns off the exhaust fan and, if not, leaves the exhaust fan on for a period of time. If the processor is not controlling the exhaust fan in the on position, a user can manually activate a switch to turn on the exhaust fan for a certain period of time.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates in general to humidity sensing and control devices and in particular to a humidity sensor and fan control device which continuously senses the humidity level in a room and calculates an average humidity value in the room over time, where the device senses when the current humidity level in the room has reached or exceeded a first threshold value higher than the calculated average value and turns on an exhaust fan in the room to lower the humidity level therein, and where the device senses when the current humidity level in the room has reached or decreased below a second threshold value lower than the first threshold value and turns off the exhaust fan. 
         [0002]    In a bathroom, it is known that the humidity can rise to uncomfortable levels, particularly when hot water is being used for a shower, bath or other reasons. The moisture can cause mold and mildew to form, which is a major concern. Bathrooms typically have an exhaust fan that helps to remove the moisture to the outside and make the bathroom less humid and more comfortable. However, the exhaust fan is generally turned on by a person using a manual switch, which causes the exhaust fan to be on longer than required for some times and shorter than required for other times. That is, there is generally little or no correlation between the humidity level in the room and the amount of time that the exhaust fan is operational. 
         [0003]    Also known are wall-mounted exhaust fan control switches where a user can manually select a numerical humidity value at which the bathroom exhaust fan will turn on when the humidity level exceeds the selected value and will turn off when the humidity level drops below the selected value. Drawbacks with these switches include the fact that the humidity levels outdoors and thus also within rooms of a home change significantly throughout the year, more so in some parts of the country than others, and these switches have no means for automatically recognizing and compensating for these different humidity levels. Also, there are some environments (e.g., dressing rooms in health clubs, public restrooms in restaurants) where it is undesirable to have the humidity level switch setting constantly being changed by people in the room. 
         [0004]    Further, it is known to have a bathroom ceiling exhaust fan with a built-in humidity sensor that detects increases in humidity in the bathroom brought about by use of the bath or shower and automatically turns on the exhaust fan. However, this type of device is problematic in that it shuts off the exhaust fan only after a certain period of time and not as a function of the humidity level in the room, which may not allow for adequate removal of undesirable moisture in the room. Also, this type of device does not provide for manual turn-on of the exhaust fan, particularly when the device is not automatically controlling operation of the exhaust fan. Further, such exhaust fans with built-in humidity sensors tend to be relatively expensive. 
         [0005]    What is needed is a humidity sensor and fan control device that is relatively inexpensive and easy to install and operate, and which continuously senses the humidity level in a room and calculates an average humidity value in the room over time, that automatically determines when the current sensed humidity level in a room has increased to a certain value with respect to the calculated average value and turns on an exhaust fan in the room to lower the humidity level, that automatically determines when the current sensed humidity level in the room has decreased to a certain value with respect to the calculated average value and turns off the exhaust fan, that also provides for a manual turn-on of the exhaust fan when the device is not automatically controlling operation of the exhaust fan, and that by controlling the exhaust fan in this manner mold and mildew in the room is reduced or eliminated. 
       SUMMARY OF THE INVENTION 
       [0006]    According to an aspect of the present invention, a humidity sensor mounted in the wall of a bathroom, senses the humidity level of the room at periodic intervals, for example, once per second and provides the sensed humidity values to a processor. The processor stores the sensed humidity values in a memory and continuously calculates and stores an average humidity value in the room over a period of time, for example, four hours. Once the average humidity value has been calculated for a full four hour time period, the processor continuously stores the most recent four hours of sensed humidity values from the sensor and calculates and stores the current average humidity value using the most recent four hours of sensed humidity values. The processor also continuously checks whether the current sensed humidity value from the sensor meets and/or exceeds a first, upper threshold value; for example, if the current sensed humidity value is equal to or greater than ten percent of the current calculated average humidity value. If so, then the device turns on the exhaust fan to remove moisture from the room. All the while the sensor continues to periodically sense the actual humidity level in the room and provide the sensed values to the processor which continues to store the sensed values and also calculates the average humidity value. Once the upper threshold value has been met or exceeded, the processor checks if the current sensed humidity value has met or dropped below a second, lower threshold value; for example, equal to or less than five percent of the current calculated average humidity value. If so, the device turns off the exhaust fan. In the alternative, once the upper threshold value has been met or exceeded and the exhaust fan is turned on and if the current sensed humidity value does not meet or go below the lower threshold value after a set amount of time, for example, thirty minutes, the device will turn off the exhaust fan. 
         [0007]    According to another aspect of the present invention, if at any time the processor is not currently controlling the exhaust fan in the on position as described above, then a user can manually activate a switch to turn on the exhaust fan for a certain period of time; for example, fifteen minutes, and the user can repeatedly activate the exhaust fan for additional fifteen minute intervals as long as the processor is not currently controlling the exhaust fan in the on position. If the exhaust fan is being operated in this manual mode and if the processor at any time determines that the upper threshold humidity value has been met or exceeded by a current actual humidity value, the processor takes over control of the exhaust fan as described above. 
         [0008]    These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of preferred embodiments thereof, as illustrated in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of a humidity sensor and fan control device according to the present invention; 
           [0010]      FIG. 2  is a block diagram of the humidity sensor and fan control device of  FIG. 1  connected with an exhaust fan; and 
           [0011]      FIG. 3  is a flowchart of steps performed by a processor within the humidity sensor and fan control device of  FIGS. 1-2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    In the figures, like reference numerals refer to like elements. Referring to  FIG. 1 , there illustrated in perspective is a wall mounted humidity sensor and fan control device  10  according to an embodiment of the present invention. In a preferred embodiment, the device  10  is the size of a typical single-gang electrical box and mounts within the wall of a bathroom or other room of a home or other building which also contains an exhaust fan located in the ceiling or elsewhere in the room to remove undesirable moisture in the room air resulting, e.g., from hot water usage, such as in the nature of a bath or a shower. The device  10  includes a front panel  12 , a mounting plate  14 , and a rear enclosure or “black box”  16 . On the front panel  12  is mounted a humidity sensor  18 . Typically the sensing portion of the humidity sensor  18  protrudes out from the face of the front panel  12  so as to be able to sense the humidity levels in the room. Also mounted on the front panel  12  is a push button input switch  20  and a light emitting diode (LED)  22 . The operation of the input switch  20  and the LED  22  will be described in detail hereinafter. The mounting plate  14  is used to mount the device  10  to the wall at the appropriate location within the room. The black box  16  may be a plastic enclosure that contains the electronics and electrical devices which implement the functionality of the device  10 , as described in detail hereinafter. Protruding from the back of the black box  16  are three wires  24 ,  26 ,  28  that connect with the standard 120 VAC electrical power supply and also with the exhaust fan ( FIG. 2 ). 
         [0013]    Referring to  FIG. 2 , there illustrated is a block diagram of the electronics and electrical components that comprise a preferred embodiment of the device  10  of the present invention. Although not illustrated, electrical power is provided to the various components in the required form (AC or DC) and at the appropriate values as derived in a known manner from the standard 120 VAC electrical power supply within the home or other building. The humidity sensor  18  is illustrated as being connected on a signal line  30  with a processor  32 , which may comprise, for example, a known general purpose microprocessor, a dedicated programmable application specific integrated circuit (ASIC), or some other type of processing device. The humidity sensor  18  may include, if required, the appropriate known electronics that provide a signal on the line  30  to an input of the processor  32  in the proper form (e.g., voltage or frequency) and indicative of the current sensed humidity value in the room for storage and processing by the processor  32 . Also connected to an input of the processor  32  on a signal line  34  is a signal indicative of the status (i.e., open or closed) of the input switch  20 . The processor  32  may include a writable memory  36  (e.g., RAM) either integral with the processor  32  or separate therefrom. The memory  36  is of sufficient size to store a relatively large number of samples of the humidity values provided over time from the humidity sensor  18 , as described in detail hereinafter with respect to the flowchart of  FIG. 3 . Connected to an output port of the processor  32  on a signal line  38  is the LED  22 . The LED  22 , which is optional, is turned on when the exhaust fan  40  in the room is operational. Alternatively, the LED can be any other type of indicator, either visual or audible, that indicates when the exhaust fan  40  is turned on or is operational. Connected to another output port of the processor  32  on a signal line  42  is an output switch  44 , which is connected by one of the wires  28  to the exhaust fan  40 . Alternatively, the output switch  44  may be omitted if it is possible to connect the corresponding output on the line  42  of the processor  32  directly to the exhaust fan  40  wherein the exhaust fan has its own internal switch that can be controlled by the output from the processor  32  on the line  42 . 
         [0014]    Referring to  FIG. 3 , there illustrated is a flowchart of steps performed by the processor  32  of  FIG. 2  in an example of a routine  50  that may be used to implement the functionality of the device  10  of the present invention. The steps of the routine  50  may be stored in a non-volatile portion of the memory  36  (e.g., ROM, PROM). After an enter step  52 , a step  54  is executed where the current sensed humidity sample value is obtained by the processor  32  from the humidity sensor  18  on the line  30  and stored in the memory  36 . Preferably, the routine  50  of  FIG. 3  is executed by a processor  32  that operates fast enough to implement sampling of the sensed humidity values in the step  54  periodically once every second (i.e., at a frequency of 1 Hz). However, sampling at a frequency of 1 Hz is purely exemplary; other sampling frequencies may be utilized. If the processor  32  operates at a speed where the sample step  54  would occur at a frequency greater than 1 Hz, then appropriate delays can be built into the routine  50  such that the periodic sampling of the humidity values occur at the preferred frequency of 1 Hz. 
         [0015]    Next, a comparison step  56  is executed that determines if the exhaust fan  40  was turned on manually as a result of a user activating the input switch  20  on the front panel  12  of the device  10 . If so, a comparison step  58  is executed to determine if the exhaust fan  40  has been on for, e.g., fifteen minutes. A timer may be implemented in the processor  32  for keeping track of the amount of time that the exhaust fan  40  has been on. Also, whenever the exhaust fan  40  is on the LED  22  also lights up as an indication of the exhaust fan being on. The exhaust fan  40  being on for fifteen minutes is purely exemplary; other amounts of time may be utilized. Alternatively, a separate timer may be included within the device  10 . If the exhaust fan  40  has been on for fifteen minutes as a result of the manual input switch  20 , a step  60  is executed where the exhaust fan  40  is turned off, and the routine  50  branches to a comparison step  62  to determine if the input switch  20  is closed. If the exhaust fan  40  has not been on for fifteen minutes, then the comparison step  62  is executed. If the input switch  20  is closed, the exhaust fan  40  is turned on in a step  64  for another new fifteen minute period of time (i.e., the fifteen minute timer is restarted) and the routine  50  branches to a comparison step  66  to determine whether four continuous hours of humidity samples at 1 HZ have been stored in the memory  36  by the repeated operation of the step  54  by way of repeated performance of the routine  50 . Four continuous hours of humidity samples are purely exemplary; other amounts of sample time may be utilized. Similarly, if the input switch  20  is determined to be open in the comparison step  62 , the routine branches to the comparison step  66 . The aforementioned steps  56 - 64  allow for manual operation of the exhaust fan  40  when the processor  32  is not “automatically” controlling the operation of the exhaust fan  40 , as per the remaining steps in the routine  50  of  FIG. 3  described hereinafter. 
         [0016]    If the result of the comparison step  66  indicates that four hours of humidity samples have not yet been provided to the processor  32  by the humidity sensor  18  and stored in the memory  36 , the routine  50  branches back to the sample and store step  54 . Instead, if four hours of samples have been stored in the memory  36 , a step  68  is executed where the processor  32  calculates the current average humidity value from the four hours worth of stored humidity samples, and the processor  32  also stores this calculated current average humidity value in the memory  36 . A comparison step  70  is then executed where the processor  32  compares the current humidity sample value acquired in the step  54  with a first, upper threshold humidity value that is calculated by the processor  32  to be ten percent (10%) greater than (or 1.1 times) the current calculated average humidity value. A value of ten percent is purely exemplary; other threshold values related to the current calculated average humidity value may be utilized. If the current humidity sample value is a certain predetermined relationship to the upper threshold humidity value, for example, less than or equal to, the routine branches back to the sample and store step  54 . If instead the current humidity sample value is greater than the upper threshold humidity value, then a step  72  is executed where the exhaust fan  40  is turned on for thirty minutes. Thirty minutes of exhaust fan turn-on time is purely exemplary; other amounts of time may be utilized. At this point in the routine  50 , the processor  32  is “automatically” controlling operation of the exhaust fan  40  based on the relationship of the current sensed humidity value to an upper threshold value that is a function of the current calculated average humidity value. The distinction between the exhaust fan  40  being turned on in the step  64  by manual operation of the input switch  20  and the exhaust fan  40  being turned on in the step  72  by the current humidity sample value being greater than the upper threshold value may, for example, be carried out or indicated by one or more bits in a specific location in the memory  36  or in a register in the processor  32 . 
         [0017]    Next, a comparison step  74  is executed where the processor determines if the exhaust fan has been on for thirty minutes as a result of the step  72 . That is, the exhaust fan  40  may be already on for some portion of the fifteen minute interval as a result of the step  64  when the comparison step  70  determines that the exhaust fan  40  should be turned on by the step  72  for an additional thirty minutes. If the exhaust fan  40  has been on for thirty minutes as a result of the step  72 , the exhaust fan is turned off in a step  76  and the routine  50  branches back to the sample and store step  54 . If instead the exhaust fan  40  has not been on for thirty minutes as a result of the step  72 , a comparison step  78  is executed where the current humidity sample value acquired in the step  54  is compared with a second, lower threshold humidity value that is calculated by the processor  32  to be five percent (5%) greater than (or 1.05 times) the current calculated average humidity value. A value of five percent is purely exemplary; other threshold values related to the current calculated average humidity value may be utilized. If the current humidity sample value is in a certain predetermined relationship to this lower threshold humidity value, for example, greater than or equal to, the routine branches back to the sample and store step  54  and the exhaust fan  40  remains on. If instead the current humidity sample value is less than the lower threshold humidity value, a step  80  is executed where the exhaust fan  40  is turned off and the routine  50  branches back to the sample and store step  54 . 
         [0018]    If, as a result of the comparison step  78 , the exhaust fan  40  remains on and the routine  50  branches back to the sample and store step  54 , when the comparison step  56  is next executed the result of that step  56  will be a “NO”. Then the comparison step  62  will cause the processor  32  to look at, for example, the location in memory  36  which indicates the distinction between the exhaust fan  40  being turned on in the step  64  by manual operation of the input switch  20  and the exhaust fan  40  being turned on in the step  72  by the current humidity sample value being greater than the upper threshold value. Because the exhaust fan  40  in this situation is turned on in the step  72  (i.e., “automatically” under control of the processor  32 ), the comparison step  62  is not executed to determine if the input switch  20  is closed. This is because, in a preferred embodiment, the input switch  20  is not allowed to override the control of the exhaust fan  40  by the processor  32  utilizing the sampled humidity values and the calculated humidity average value. 
         [0019]    It should be understood that the flowchart of  FIG. 3  is an example of a routine  50  that causes the humidity sensor and fan control device  10  of the present invention to operate to periodically sample the humidity levels in a room at particular time intervals over time, to periodically calculate an average humidity value, to periodically compare a current sampled humidity value to the current calculated average humidity value, and to turn on and off an exhaust fan accordingly, and to also allow for manual operation of the exhaust fan under certain circumstances. Other routines may be utilized to operate the device  10  as should be apparent to one of ordinary skill in the art in light of the teachings herein. 
         [0020]    In addition, while the humidity sensor  18  has been described and illustrated herein in a preferred embodiment as being part of a “combined” device  10  together with the remaining components of the device, it is entirely possible for the humidity sensor  18  to be located separate from other components of the device  10 . For example, the humidity sensor  18  may be located on or near the ceiling and then provide its sensed humidity signal to the processor which may be located farther down on the wall with the remaining components of the device  10 . 
         [0021]    Although the present invention has been illustrated and described with respect to several preferred embodiments thereof, various changes, omissions and additions to the form and detail thereof, may be made therein, without departing from the spirit and scope of the invention.