Automatic energy-efficient bathroom exhaust fan controller

Abstract

An automatic control system for an exhaust fan of a room having a water dispensing conduit is disclosed. The system includes a control module that controls delivery of electricity to the exhaust fan to activate and deactivate the exhaust fan, and a sensor suitable for mounting on the water dispensing conduit. The sensor senses temperature of the water dispensing conduit and when a temperature above a predetermined temperature value is reached on the water dispensing conduit, the sensor transmits a control signal to the control module. The temperature increase is due to hot water flowing though the water dispensing conduit (e.g., a shower pipe). Upon receipt of the control signal, the control module activates the exhaust fan for a user selectable time period.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Patent Application No. 60/665,650 filed Mar. 25, 2005.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an automatic energy-efficient controller for a room exhaust fan.

2. Description of the Related Art

Exhaust fans are used to ventilate rooms, such as bathrooms, to prevent humidity from accumulating in the room. Conventional exhaust fans are activated by a wall switch turned on by the home owner. Many homes do not have electronic or mechanical timers operating the bathroom exhaust fan, and consequently when the fan is turned on, it may remain on for a much longer time than is necessary to remove the moist air. Thus much energy is wasted, as the fan expels air that has been expensively heated (in the winter) or cooled (in the summer).

Consequently, devices have been proposed to automatically control bathroom exhaust fans. Japanese Patent Application No. JP3286940 describes a control device for a bathroom fan where the fan is driven for a preset time.

Japanese Patent Application Nos. JP63254339, JP3117838, JP3036445, JP58156134, JP10110982, JP10047719, JP9318111 and JP7120026 describe a control device for a bathroom fan where a humidity sensor provides a signal to start and/or stop the fan. In a related application, the device of Japanese Patent Application No. JP62194136 uses a humidity reading to determine an operating time for the fan. However, humidistat control tends to be imprecise and slow to respond, and is furthermore useless during periods of high humidity in homes that are not air-conditioned.

Japanese Patent Application Nos. JP63254339, JP2003279091 and JP10110982 describe a control device for a bathroom fan where a temperature sensor provides a signal to start and/or stop the fan. However, temperature control also tends to be imprecise and slow to respond.

Japanese Patent Application No. JP2247436 describes a control device for a bathroom fan in which a hot water feeding switch for a bath also starts a ventilating fan. However, this control device appears to require mounting the control device behind a room wall in line with a hot water pipe.

Japanese Patent Application No. JP2004144383 describes a control device for a bathroom fan where a bath water level sensor provides a signal to start the fan. This device may be slow to respond in that it may take a long time before water reaches the sensor level.

Japanese Patent Application Nos. JP1006634, JP9318111 and JP5180475 describe a control device for a bathroom fan where a sensor that detects a person provides a signal to start and/or stop the fan. These devices may be inefficient in that fan operation may be triggered when a person enters a room momentarily.

Japanese Patent Application No. JP3236538 describes a control device for a bathroom fan where a light sensor which detects steam provides a signal to start and/or stop the fan. Like a humidity controller for a fan, this device may be imprecise and slow to respond.

In view of the disadvantages of known automatic controllers for a bathroom exhaust fan, there exists a need for an improved automatic energy-efficient bathroom exhaust fan controller.

SUMMARY OF THE INVENTION

The present invention provides an automatic energy-efficient controller for a room exhaust fan. The invention turns on a bathroom exhaust fan automatically when someone takes a shower. A thumb-sized smart sensor, clipped onto the shower pipe adjacent to the shower head, detects the temperature increase when the hot-water valve is opened. The sensor then communicates wirelessly with a controller module built into the fan's wall-mounted switch, turning the fan on for a user-selectable time interval. A timer permits the homeowner to select the time delay. The smart sensor could also be clipped onto the bathtub faucet. The invention can be installed easily by a homeowner, and is attractive to businesses participating in the burgeoning home-automation retail market.

Thus, the invention provides an automatic control system for an exhaust fan of a room having a water dispensing conduit. The system includes a control module that controls delivery of electricity to the exhaust fan to activate and deactivate the exhaust fan, and a sensor suitable for mounting on the water dispensing conduit wherein the sensor senses temperature of the water dispensing conduit and the sensor transmits a control signal to the control module when a temperature above a predetermined temperature value is reached on the water dispensing conduit. Upon receipt of the control signal, the control module activates the exhaust fan. The control signal may be a radio frequency signal.

In one version of the invention, the control module activates the exhaust fan by providing electricity to the fan. The control module may include a timer circuit that provides electricity to the fan for a predetermined time period after which the fan is deactivated, and the predetermined time period may be a variable time period selectable by a user. The control module may include a control for setting the predetermined temperature value.

In another version of the invention, the control module includes a timer circuit that provides electricity to the fan for a predetermined time period after temperature falls below the predetermined temperature value. The predetermined time period may be a variable time period selectable by a user.

In one use of the invention, the water dispensing conduit is a shower pipe. In another use, the water dispensing conduit is a bathtub spigot.

It is an advantage of the present invention that the user does not have to remember to turn on a bathroom exhaust fan. Yet moist air is reliably removed from the bathroom, where it otherwise could promote mold growth or accumulate in exterior wall insulation, possibly damaging the house.

These and other features, aspects, and advantages of the present invention will become better understood upon consideration of the following detailed description, drawing and appended claims.

DESCRIPTION OF THE DRAWING

FIG. 1 shows an elevational view of a wall of a bathroom including an automatic energy-efficient controller and an exhaust fan according to the invention.

DESCRIPTION OF THE INVENTION

Looking at FIG. 1, there is shown a bathroom 10 having a side wall 12 and a ceiling 14. Mounted in the ceiling 14 is an exhaust fan 20 that exhausts air from the interior of the bathroom 10 and out a conduit 22 to the attic or outside atmosphere through the roof. A wall mounted module 30 communicates via electrical line 32 with the exhaust fan 20 to provide electricity to the fan 20 to operate the fan. The module 30 includes a control 36 that allows a user to set the temperature threshold for allowing the fan to be activated. The module 30 also includes a control 34 that allows a user to set the operating time period for the fan 20 after the temperature falls below the threshold.

The bathroom 10 includes a shower/bath tub stall 40 having a shower pipe 42 that terminates in a shower head 44 and having a bathtub spigot 46. Mounted on the shower pipe 42 is a smart sensor 50 that detects the temperature increase in the shower pipe 42 when the hot-water valve is opened. Alternatively, the smart sensor 50 could be clipped onto the bathtub spigot 43. When a temperature increase is sensed by the sensor 50, the sensor 50 communicates wirelessly with the module 30, which sends a signal to the fan 20 turning the fan 20 on for the user-selectable time interval selected with dial 34. In one form, the sensor 50 communicates wirelessly with the module 30 by way of an radio frequency transmitter and receiver.

Batteries in the smart sensor 50 can be quite small, yet would be expected to last at least 6 months, because a microcontroller in the sensor 50 would be asleep >99% of the time. It would wake up just once or twice per minute to sense the temperature of the shower pipe 42. An IC such as National Semiconductor's LM35 would be one suitable temperature-sensing component of the sensor 50. A thermo-mechanical switch (e.g., bimetallic spring) could be used to activate the circuitry, as an alternative to using the microcontroller's internal watchdog timer.

Thus, the invention provides an automatic energy-efficient controller for a room exhaust fan. Advantageously, the user does not have to remember to turn on a bathroom exhaust fan because of the automatic operation of the controller.

While in one example form the invention is an automatic control system for an exhaust fan of a room having a water dispensing conduit, the invention is suitable for controlling any electrical device in a room having a water dispensing conduit. For example, the invention could control operation of an electric towel warmer or a lighting system or an electrically controlled fragrance dispenser. Also, another electrical device that could be controlled is a ventilation blower for a shower enclosure. It would turn on a few minutes after the shower has ended, and stay on for a programmed time interval, in order to dry off the shower walls and thereby to prevent the growth of mold and mildew. Such a blower system can force air through a 3-inch duct located in a rear bottom corner of the shower, so that the air will circulate in a vortex and exit over the top of the shower door.

Thus, although the present invention has been described in detail with reference to certain embodiments, one skilled in the art will appreciate that the present invention can be practiced by other than the described embodiments, which have been presented for purposes of illustration and not of limitation. Therefore, the scope of the appended claims should not be limited to the description of the embodiments contained herein.

Claims

1. An automatic control system for an exhaust fan of a room having a water dispensing conduit, the system comprising:

a control module that controls delivery of electricity to the exhaust fan to activate and deactivate the exhaust fan; and

a sensor suitable for mounting on the water dispensing conduit, the sensor sensing temperature of the water dispensing conduit, the sensor transmitting a control signal to the control module when a temperature above a predetermined temperature value is reached on the water dispensing conduit,

wherein upon receipt of the control signal, the control module activates the exhaust fan.

2. The system of claim 1 wherein:

the control module activates the exhaust fan by providing electricity to the fan.

3. The system of claim 2 wherein:

the control module includes a timer circuit that provides electricity to the fan for a predetermined time period after which the fan is deactivated.

4. The system of claim 3 wherein:

the predetermined time period is a variable time period selectable by a user.

5. The system of claim 2 wherein:

the control module includes a timer circuit that provides electricity to the fan for a predetermined time period after temperature falls below the predetermined temperature value.

6. The system of claim 5 wherein:

the predetermined time period is a variable time period selectable by a user.

7. The system of claim 1 wherein:

the control module includes a control for setting the predetermined temperature value.

8. The system of claim 1 wherein:

the water dispensing conduit is a shower pipe.

9. The system of claim 1 wherein:

the water dispensing conduit is a bathtub spigot.

10. The system of claim 1 wherein:

the control signal is a radio frequency signal.

11. An automatic control system for an electrical device in a room having a water dispensing conduit, the system comprising:

a control module that controls delivery of electricity to the electrical device to activate and deactivate the electrical device; and

a sensor suitable for mounting on the water dispensing conduit, the sensor sensing temperature of the water dispensing conduit, the sensor transmitting a control signal to the control module when a temperature above a predetermined temperature value is reached on the water dispensing conduit,

wherein upon receipt of the control signal, the control module activates the electrical device.

12. The system of claim 11 wherein:

the control module activates the electrical device by providing electricity to the electrical device.

13. The system of claim 12 wherein:

the control module includes a timer circuit that provides electricity to the electrical device for a predetermined time period after which the electrical device is deactivated.

14. The system of claim 13 wherein:

the predetermined time period is a variable time period selectable by a user.

15. The system of claim 12 wherein:

the control module includes a timer circuit that provides electricity to the electrical device for a predetermined time period after temperature falls below the predetermined temperature value.

16. The system of claim 15 wherein:

the predetermined time period is a variable time period selectable by a user.

17. The system of claim 11 wherein:

the control module includes a control for setting the predetermined temperature value.

18. The system of claim 11 wherein:

the water dispensing conduit is a shower pipe.

19. The system of claim 11 wherein:

the water dispensing conduit is a bathtub spigot.

20. The system of claim 11 wherein:

the electrical device is a blower.