Title:
MOISTURE VAPOR EXHAUST SYSTEM
Kind Code:
A1


Abstract:
An exhaust system for evacuation of vapor and gases from an area, the system including a fan mounted on a motor, an activation circuit coupled to the motor and adapted to couple the motor to a first voltage source, a detection circuit adapted to sense the presence of moisture on a sensor surface and to generate a detection signal when moisture is sensed and to not generate a detection signal when moisture is not sensed, and a control circuit. In one embodiment the control circuit is coupled to the detection circuit and the activation circuit and adapted to generate a control signal in response to the detection signal, the control signal received at the activation circuit to cause coupling of the motor to the first voltage source after a delay programmed in to a programmable logic chip in the control circuit.



Inventors:
Roux, Clifford (Gig Harbor, WA, US)
Skelton, Glenn C. (Port Orchard, WA, US)
Anderson, Dale Mark (Gig Harbor, WA, US)
Application Number:
11/778390
Publication Date:
01/17/2008
Filing Date:
07/16/2007
Primary Class:
International Classes:
F24F3/14
View Patent Images:
Related US Applications:
20070017668Apparatus for controlling cooling device and cooling systemJanuary, 2007Park et al.
20020084336Apparatus for preventing moisture on the rear window glass of an automobileJuly, 2002Shin
20060054712Vertical dehumidifierMarch, 2006Wu et al.
20040262410Graphical thermostat and sensorDecember, 2004Hull
20100078492Solar Powered Smart Ventilation SystemApril, 2010Cislo
20050132726Inverter system and vehicleJune, 2005Sasaki et al.
20100044448Ventilation System and MethodFebruary, 2010Wolfson
20050270151RF interconnected HVAC system and security systemDecember, 2005Winick
20080207109Ventilation Register and Ventilation SystemsAugust, 2008Bagwell et al.
20070262162LIMITED LOSS LAMINAR FLOW DAMPERS FOR HEATING, VENTILATION, AND AIR CONDITIONING (HVAC) SYSTEMSNovember, 2007Karamanos
20080314999WATER HEATER STACKING DETECTION AND CONTROLDecember, 2008Strand



Primary Examiner:
OREILLY, PATRICK F
Attorney, Agent or Firm:
SEED INTELLECTUAL PROPERTY LAW GROUP LLP (701 FIFTH AVE SUITE 5400, SEATTLE, WA, 98104, US)
Claims:
1. A controller for a fan, comprising: a sensor adapted to detect the presence of condensed water; and a circuit coupled to the sensor and adapted to control operation of the fan in response to the sensing of condensed water by the sensor.

2. The controller of claim 1 wherein the circuit is adapted to activate the fan for a fixed period of time.

3. The controller of claim 1 wherein the sensor comprises exposed leads that conduct current when the leads are coupled together by condensed water.

4. The controller of claim 3 wherein the circuit is configured to compare current conducted by the sensor in the presence of condensed water to a reference current and to activate the fan when the current from the sensor reaches a level of the reference current.

5. A fan for exhausting air, the fan comprising: a motor for rotating the fan; and a controller for the motor, the controller comprising: a sensor adapted to detect the presence of condensed water; and a circuit coupled to the sensor and adapted to control operation of the motor in response to the sensing of condensed water by the sensor.

6. The fan of claim 5 wherein the circuit is adapted to activate the fan for a fixed period of time.

7. The controller of claim 5 wherein the sensor comprises exposed leads that conduct current when coupled together by condensed water.

8. The controller of claim 7 wherein the circuit is configured to compare current conducted by the sensor to a reference current and to activate the fan when the current from the sensor reaches a level of the reference current.

9. A fan controller, comprising: a sensor configured to detect moisture condensed from water vapor; and a circuit coupled to the sensor and configured to operate the fan when the sensor detects the moisture.

10. The fan controller of claim 9 wherein the circuit coupled to the sensor is configured to operate the fan for a fixed duration of time when the sensor detects the moisture condensed from water vapor.

11. The fan controller of claim 9 wherein the circuit coupled to the sensor is configured to alert a user when the sensor detects moisture condensed from water vapor.

12. A method for reducing moisture in an enclosed area, the method comprising: detecting water condensed from water vapor; and activating a fan for a fixed duration of time in response to detecting water condensed from water vapor.

13. The method for reducing humidity of claim 12 further comprising checking repeatedly for the presence of water condensed from water vapor after the fixed duration of time and activating the fan for the fixed duration of time in response to detecting water condensed from water vapor.

14. The method of reducing humidity of claim 12 further comprising illuminating a light source in response to detecting water condensed from water vapor.

15. A method for reducing humidity in an enclosed area, the method comprising: detecting condensation using a sensor; processing an output signal from the sensor; and activating a fan for a fixed duration of time in response to the output signal from the sensor.

16. The method of reducing humidity of claim 15 further comprising operating the fan manually.

17. A device for eliminating water vapor from an enclosed area, the device comprising: a condensed water detector; a first circuit having an automatic switch to activate a fan assembly when condensation is detected by the detector; and a second circuit coupled to the first circuit, the second circuit having a manual switch for controlling the fan assembly.

18. The device of claim 17 wherein the first circuit coupled to the sensor is configured to illuminate a light when condensation is detected by the detector.

19. A fan assembly, the assembly comprising: means for sensing condensed water vapor; and means for activating a fan when the sensing means detects the condensed water vapor.

20. The fan assembly of claim 19 wherein the means for activating the fan is configured to alert a user to the sensing of condensed water vapor.

21. An exhaust system for evacuation of vapor and gases from an area, the system comprising: a fan mounted on a motor; an activation circuit coupled to the motor and adapted to couple the motor to a first voltage source; a detection circuit adapted to sense the presence of moisture on a sensor surface and to generate a detection signal when moisture is sensed and to not generate a detection signal when moisture is not sensed; and a control circuit coupled to the detection circuit and the activation circuit and adapted to generate a control signal in response to the detection signal, the control signal received at the activation circuit to cause coupling of the motor to the first voltage source after a delay programmed in to a programmable logic chip in the control circuit.

22. The system of claim 21 further comprising a low voltage circuit adapted to receive the first voltage and generate a second voltage that is at a lower voltage level than the first voltage to provide operating power for the activation circuit, detection circuit, and control circuit.

23. The system of claim 22, wherein the sensor comprises interlaced exposed gold lines on a printed circuit board in which each line has a width in the range of 0.4 to 0.6 mm, and the gap between the exposed gold lines is in the range of 0.2 mm to 0.4 mm in width.

24. The system of claim 23, wherein the gold lines have a preferred width of 0.5 mm and a preferred gap between them of 0.3 mm.

25. A controller for an exhaust fan motor that utilizes an existing voltage source for power, the control circuit comprising: an activation circuit adapted to couple the motor to the existing voltage source; a detection circuit adapted to sense the presence of moisture on a sensor surface and to generate a detection signal when moisture is sensed and to not generate a detection signal when moisture is not sensed; and a control circuit coupled to the detection circuit and the activation circuit and adapted to generate a control signal in response to the detection signal, the control signal received at the activation circuit to cause coupling of the motor to the first voltage source after a delay programmed in to a programmable logic chip in the control circuit.

26. The controller of claim 25 further comprising a low voltage circuit adapted to receive the existing voltage and generate a second voltage that is at a lower voltage level than the existing voltage to provide operating power for the activation circuit, detection circuit, and control circuit.

27. The controller of claim 25, wherein the sensor comprises interlaced exposed gold lines on a printed circuit board in which each line has a width in the range of 0.4 to 0.6 mm, and the gap between the exposed gold lines is in the range of 0.2 mm to 0.4 mm in width.

28. The system of claim 27, wherein the gold lines have a preferred width of 0.5 mm and a preferred gap between them of 0.3 mm.

Description:

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosed embodiments pertain to the evacuation of vapor or gas from an enclosed room and, more particularly, to the detection of moisture or water, particularly condensed water on a surface, and the control of an exhaust fan in response to the detection.

2. Description of the Related Art

The present disclosure provides a solution for preventing fungal and bacterial destruction of materials that are subject to moist environments. Current devices are both inadequate and non-functional with respect to providing protection from moisture and properly maintaining dry conditions. Considerable economic and physical loss may be experienced by both user and maintenance personnel either not switching on an exhaust fan or switching it on for such short times as to be ineffective as a means of preventing the accumulation of both fungal and bacterial outbreaks that are health threatening and destructive of the structures or stored objects themselves. This situation has long been and still is a large and growing economic and health issue.

Hence, there is a need for automated control of exhaust systems used in bathrooms, shower rooms, kitchens, and other enclosed areas where moisture vapor, condensed moisture, and various gases must be exhausted. Numerous electro-mechanical solutions have been proposed. For example, in The IC User's Casebook, 1988, Howard W. Sams, publisher, it shows at pp. 235-239 various generic circuits using contacts that trigger an output if liquid shorts the contacts. The liquid level detector shown in FIG. 16-7 of this reference fails to provide sufficient reliability in the environment to which the present disclosure is directed. This is due to the great need for sensitivity and reliability in sensing small amounts of moisture, which is neglected in these proposed designs. Moreover, the use of gold traces on sensor contacts was found to be useful only for corrosion control, and no recognition has been given to the use of gold to control circuit behavior.

BRIEF SUMMARY OF THE INVENTION

The embodiments disclosed herein are directed to an exhaust system, including an electronic controller for a fan that is adapted to be used in environments in which moisture vapor, moisture in the form of condensation, and gases in various forms is undesirable. In accordance with one aspect of the disclosure, an exhaust system is provided that includes a fan mounted on a motor and in fluid communication with an exhaust duct; a detection circuit, a control circuit having a programmable circuit for receiving a detection signal from the detection circuit and generating an activation control signal in response thereto, and an activation circuit for coupling and uncoupling a current source to a fan motor in response to the control circuit.

In accordance with another aspect of the disclosure, a low-voltage supply circuit provides a low voltage current for operation of at least one or more of the control circuit, the detection circuit, and the activation circuit without using a transformer.

In accordance with another aspect of the disclosure, the system utilizes low-voltage components in the detector circuit, which includes a sensor and a conditioning circuit, and in the control circuit, which includes a programmable integrated circuit, as well as in the activation circuit, which generates a low voltage control signal to a relay that couples a high voltage line to the fan motor.

In accordance with another aspect of the present disclosure, the sensor utilizes interlaced exposed gold lines on a printed circuit board in which each line has a width in the range of 0.4 to 0.6 mm and a preferred width of 0.5 mm, and the gap between the exposed gold lines is in the range of 0.2 mm to 0.4 mm in width with a preferred gap width of 0.3 mm.

In accordance with another embodiment of the present disclosure, a controller for a fan is provided, the controller having a sensor adapted to detect the presence of condensed water and a circuit coupled to the sensor that is adapted to control operation of the fan in response to the sensing of condensed water by the sensor.

In accordance with another aspect of the disclosure, a controller for an exhaust fan is provided that includes a sensor having electronic leads adapted to be bridged by condensed moisture to conduct current, and a circuit coupled to the sensor and adapted to control operation of the fan in response to the flow of current in the sensor.

In accordance with another aspect of the present disclosure, the controller is fully automated in that it automatically activates the fan when condensed water is detected on the sensor and maintains activation of the fan for a set period of time. Alternatively, the controller can be adapted to permit manual deactivation of the fan or to permit both manual deactivation and automatic deactivation of the fan.

In accordance with another aspect of the present disclosure, the sensor and the circuit are hardwired together and the circuit is coupled to the fan via either a hardwire or a wireless connection.

In accordance with another aspect of the disclosure, the sensor is formed from exposed electrically-conductive leads that are designed to conduct current when the leads are bridged by condensed moisture.

In accordance with another aspect of the present disclosure, the circuit is adapted to compare the amount of current conducted by the sensor with a reference current and to activate the fan when the conducted current by the sensor is at an appropriate level.

In accordance with another aspect of the present disclosure, the controller utilizes an optical coupler to isolate high voltage or high current circuit components from low voltage components, such as sensing and switching components.

In accordance with another aspect of the disclosure, an electronic circuit is provided for sensing moisture in any enclosed space (especially a bathroom with shower/tub) and by the use of appropriate signal conditioning, amplification, timing and on-site power switching causing the already installed exhaust fan to be switched on for a time appropriate to dry the affected space and then be automatically switched off. In the case of an average residential bathroom, this is about 20 min.

In another embodiment of the present disclosure, miniature electronic components are provided to fit into the space provided for and replacing an ordinary and standard manual switch used to switch on a fan in a room or other chosen space. In accordance with one preferred embodiment, no additional wiring to the building's electrical system is required, and it is a direct replacement for the manual exhaust fan switch installed as standard practice in all toilet or shower facilities.

In accordance with another aspect of the present disclosure, the controller automatically turns on the exhaust fan to air out or dry out the confined space in the event that a factory predetermined level of moisture or other substance or material has been exceeded, thereby limiting any destruction or health risks caused by negligence on the part of users or infrequent maintenance. Periodic maintenance schedules are often extended so far as to be ineffective in moisture control. In one embodiment, the controller of the present disclosure takes out of a user's control the option to turn off the exhaust fan but not the option to turn it on.

In accordance with another embodiment of the disclosure, the controller is manufactured in such a way that all electronic components, sensor and pc board mounting fit into any ordinary switch box in a building electrical system and wire directly into the already installed wiring for the manual switch which it will replace.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing features and advantages of the present disclosure will be more readily appreciated as the same become better understood from the following detail description when taken in conjunction with the accompanying drawings, wherein:

FIGS. 1A-1C are a schematic of an exhaust fan controller formed in accordance with the present disclosure;

FIGS. 2A and 2B are illustrations of alternative applications for the exhaust fan controller formed in accordance with the present disclosure;

FIGS. 3A and 3B are an illustration of an alternative embodiment of an exhaust fan and accompanying controller formed in accordance with the present disclosure;

FIG. 4 is a block diagram illustrating another embodiment of the present disclosure;

FIG. 5 is a circuit schematic for circuits in the embodiment of FIG. 4; and

FIGS. 6A-6B illustrate replacement of an existing fan switch with a controller of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the embodiment of a vent fan controller shown in schematic form in FIG. 1, the components with reference labels SENS 1, R7, R1, R2 & R3, Q1, and U2 form the moisture sensing and post sensing conditioning circuit. The moisture sensor itself has in this case been chosen for its cost effect manufacture and low component requirements to reliably trigger the rest of the exhaust fan controller circuitry. In one embodiment, it has been made as a half inch by half inch PC board with gold leads arranged as two interleaved four pronged forks spaced at about 1/20 an inch between the tines. (Refer to FIG. 1, SENS1 symbol details on the schematic).

The NPN transistor(Q1) receives a “moisture present” signal from the sensor and shapes it appropriately to be used to drive the LM311 Comparator (U2), which, when the appropriate level is reached as determined by comparison to a reference current, will trigger the LS7213 Timer (U5) to drive the output triac (U4) for the appropriate time chosen, which is established by the values of R9 and C5. Nominal time is 20 min. Other values chosen for particular applications are adjustable from 1 second to hours. A signal from the Timer IC (U5) pin 12 thru resister R11 to D2 will light the LED whenever the exhaust fan is on. The LED is optional but recommended.

IC U1 is a triac driver optical coupler used to isolate the 110V AC being switched on and off by the triac to the exhaust fan motor. This optoisolation decouples the triac 110V AC switching current from the low voltage supplied IC and transistors of the circuits.

The low voltage power supply shown is known and certain versions are readily commercially available and will not be described in detail herein. In FIG. 1 the miniature transformer (T1), full wave bridge rectifier (D1), electrolytic capacitor (C1), and the IC 5 volt regulator (U3) supply the necessary regulated 5 vdc to the entire circuit. Capacitors C2, C3, C4, and C6 are bypass capacitors necessary to short unwanted voltage transients to ground.

We have also found by experiment that the power supply can benefit from slight changes, substituting a 9V DC regulator to supply the entire circuit, with the exception of the LSI timer, which requires a 5V DC regulator. This makes a much more sensitive circuit, both in the lower level of moisture vapor it will detect and the speed of its response.

FIG. 1 also shows the single 5V DC regulator option for the entire controller. While this makes it less sensitive to the amount of moisture vapor present, taking several minutes to switch on the exhaust fan motor, in most applications this delay is insignificant. In others the dual supply (9V DC and 5V DC) regulators are preferred as being more sensitive and timely.

The light switch circuit shown at the bottom right of FIG. 1 is another option for sites that may operate both the exhaust fan and the lights from the same manual switch. The miniature low voltage switches shown on the Schematic (SW1 and SW2) make the manual switching functions of turning on the fan motor at will, or turning the room lights on and off possible from a electrical box that formerly held only one manual electrical switch. Again, the optocoupler (U6) isolates the AC being switched at the triac (U7) from the low voltage portions of the circuits. The detailed parts list is shown below:

Vent Fan Controller
DescriptionQtyLocation
CAP 220 UF 25 V ELECT WT SMD1C1
CAP CERM. 1 UF 10% 25 V X7R 06032C3, 4
CAP CER 2000 PF 50 V 5% C0G 06031C5
FUSE 4 A 125 V SLO BLO NANO 2 SMF1F2
LED BLUE CLEAR 0805 SMD1D2
IC REG LDO MICROPOWER SOT23-51U3
IC DIFF COMP STROBE 8-SOIC1U2
IC, LS7213-S, DELAY TIMER, 14-SOIC1U5
PHOTOCOUPLER TRIAC OUT 4-MSOP1U1
RECT BRIDGE SMD 100 V 1 A 4P DF-S1D1
RES 1.00K OHM ¼ W 1% 1206 SMD1R6
RES 100 OHM 1/10 W 1% 0603 SMD1R4
RES 100K OHM 1/10 W 1% 0603 SMD2R1, 3
SWITCH TACT SPST-NO 300GF G-WING1SW1
TRANS SS GP NPN 25 V LN SOT231Q1
TRANSFORMER 9 V, 167 mA SECONDARY,1T1
115 V PRIMARY
TRIAC, 600 V 4 A, DPAK, SMD1U4
CAP CERAMIC .01 UF 100 V X7R 06031C6
CAP CER 2.2 UF 10 V 10% X5R 06031C2
RES 1.00K OHM 1/10 W 1% 0603 SMD1R11
RES 56.2K OHM 1/10 W 1% 0603 SMD1R9
RES 10K OHM 1/10 W 5% 0603 SMD1R5
RES 200 OHM 1/10 W 5% 0603 SMD1R7
RES 30K OHM 1/10 W 5% 0603 SMD1R2
PCB, VENT FAN CONTROLLER rev 0410
CONN RECEPT 4POS 2 MM GOLD SMD10
ASSEMBLY CHARGES FAN CONTROLLER10
BOARD REV04

Sensor Board
DescriptionQtyLocation
PCB, SENSOR rev 0110
CONN HEADER 4POS 2 MM GOLD SMD10
ASSEMBLY CHARGES SENSOR BOARD REV0110

The present disclosure provides an economical and practical means to detect and exhaust moisture vapor from indoor spaces. In checking patents published on the USPTO website, none were found to address or to be aimed at detecting and exhausting moisture automatically from indoor spaces, as this disclosure provides. There are proposed manually adjustable humidity sensors, requiring or allowing the user to determine if or when the exhaust fan motor will be switched on. The present disclosure is wholly dissimilar in several ways. First, the present disclosure is not based on sensing humidity, but the more direct moisture or condensation sensing. Second, the disclosure in one embodiment is truly automatic and does not allow users the option of turning the fan motor off, but only to turn it on. The third major difference is the adaptability of the various means the circuits offer to different room and electrical installations to accomplish condensation sensing and fan control.

In the detail show in FIG. 2A the vent fan controller is configured to be installed as a direct replacement of an ordinary fan motor control switch. The configuration in FIG. 2B takes advantage of the flexibility allowed in new installations, as this allows the exhaust fan and the controller to be mounted on the ceiling of the subject room and permanently wired there before the room walls are installed.

FIG. 3A depicts a configuration that would mount on the ceiling of larger rooms, possibly in multiples, and using only the sensor, signal conditioning circuit, and a miniature radio frequency transmitter, would become the monitor of moisture events from the more ideal location on the ceiling. Upon triggering, this unit would send a radio frequency “moisture present” signal to a wall mounted receiver, timer, and triac controller, which would turn on the vent fan motor or motors in the case of multiple installations. The wall-mounted unit can also include a sensor.

Each of these different adaptations of the basic design of the present disclosure are necessary in certain indoor situations; however, it should be noted that all of them could utilize either the small gold tined fork sensor of FIG. 1 or the sensor found in any generic smoke detector interchangeably if each sensor is given its suitable signal conditioning circuit.

Turning next to FIG. 4, shown therein is a block diagram of a exhaust fan controller circuit 50 formed in accordance with the present disclosure. The circuit 50 includes a detector circuit 52 coupled to a processor or control circuit 54, which in turn is coupled to an activation circuit 56. Not shown in this figure is a low voltage circuit that provides a low voltage, (e.g., 0.5, 1.0, 1.5, 3.0, or 5.0 volts) to these three circuits. While a transformer can be used to provide power from conventional house current, such has the disadvantages of inefficient use of energy, increased temperature at the circuit board, consumption of space, and increased costs to manufacture the circuit and hence the exhaust system. A more efficient source of low voltage is described herein below.

The conditioning circuit 52 shown in FIG. 4 includes a sensor 58 having an output 60 coupled to an input 62 of a transistor 64 in which the output 66 “Signal Out” is conditioned by the transistor 60 and a resistor 68. The Signal Out is generated in response to the sensor 58 completing an open circuit between the interleaved leads 70, such as with condensed moisture.

Ideally, the leads 70 are deposited gold traces on a printed circuit board in which each trace is in the range of 0.4 to 0.6 mm in width, and having a preferred width of 0.5 mm, and the gap 72 between the exposed gold lines or traces 70 is in the range of 0.2 mm to 0.4 mm in width, with a preferred width of 0.3 mm. These size ranges and preferred dimensions in combination with the gold traces 70 provide a workable sensor circuit. While other materials can be used, they suffer from low resistance to corrosion, and they are not compatible with the trace width and gap width listed above due to conductivity properties. The use of gold traces 70 having the noted gaps 72 has been found to be reliable in moisture detection and exhaustion.

However, the output signal of the detector 50 described above requires processing through the control circuit 54 in order to generate a reliable and usable control signal for the activation circuit 56. More particularly, the control circuit 54 includes a memory 74 having software 76 stored therein, a user interface 78 for storing and modifying the software 76, and a signal monitor 80 to receive as input the Signal Out from the detector circuit 52.

In one embodiment, the software 76 is in the form of BASIC or Assembly language code, such as the code shown below, that processes the output of the detector 52 to include a timing delay for the operation of the fan motor.

list p=10F200
#include <p10F200.inc>
_CONFIG _MCLRE_OFF & _CP_OFF &
_WDT_OFF
cblock0x010
delayl
delaym
delayh
delayhh
delaylL
delaymL
delayhL
endc
;************************************************************
ORG0xFF
ORG0x000
movwfOSCCAL
GOTO start
;——————————————————————————————————————
;INITIALIZE MICROCONTROLLER
SETUPmovlw b‘00000111’
option
movlwB‘00001001’
trisGPIO
clrfGPIO
retlw 0x000
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
start call SETUP
MAIN CLRF GPIO
BTFSSGPIO,3
GOTOFANON
BTFSSGPIO,0
GOTOFANON
GOTOMAIN
;——————————————————————————————————————
FANON
HOBSF GPIO,2
BTFSS GPIO,0
GOTOHO
BSFGPIO,2
BSFGPIO,1
CALLDELAY
GOTO FANOFF
GOTO MAIN
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
FANOFF
A BTFSSGPIO,0
GOTO A
BCFGPIO,2
BCFGPIO,1
GOTO MAIN
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
DELAY
clrfdelayl
CLRF delaym
movlw.000
movwfdelayh
movlw.14
movwfdelayhh
wait
decfszdelayl,f
goto wait
BTFSSGPIO,0
GOTOFANOFF
decfszdelaym,f
goto wait
decfszdelayh,f
goto wait
decfszdelayhh,f
goto wait
RETLW 0X000
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
GOTO MAIN
END

The control circuit 54 can utilize a low voltage programmable integrated chip, such as the MIC 10F200T-I/OT, which is readily commercially available and will not be described in further detail herein. Included in the control circuit 54 is a on-reset switch 82 that enables a user to turn the fan on or to reset the timing of the operation of the fan motor. The low-voltage/low current output 84 of the control circuit 54 carries the control signal to the activation circuit 56, which includes a relay 86 coupled to conventional house current/voltage as described above. Energizing of the relay 86 with the control signal closes the contacts 88. In the illustrated embodiment of FIG. 4, the contacts 88 are shown in a position in which the fan motor is not energized.

Preferably, the delay time is 20 minutes, meaning the circuit energizes the fan for 20 minutes. the fan can be turned off via the manual switch, but the sensor can override the manual switch if moisture is detected or is still present on the sensor.

This is shown more clearly in the detailed circuit schematic of FIG. 5 in which like components are identified with the same reference numbers. Additional components are also shown, and these are identified on the parts list below:

PARTS LIST TO SCH REV.9.BBBI
DescriptionLocation
CAP CER 4.7 uF 10 V Y5V 0603C1
CAP CER.01 uF 100 V X7R 0603C2
CAP 470 uF 25 V ELECT VZ RADIALC3
CAP 1.5 uF 305VAC EMI SUPPRESSIONC4
DIODE ZENER 5 W 6.8 V DO41D1
IC RECT BRIDGE 0.5 A 200 V MBS-1D2
DIODE SMD STANDARD BLOCKINGD3
LED BLUE CLEAR 0805 SMDD4
FUSE FAST-ACT 10. A 250 V UL TR5F1
DIODE TVS 150 V 600 W BIDIR 5% SMBD5
TRANS SS GP NPN 25 V LN SOT23Q1
TRANS SS GP NPN 25 V LN SOT23Q2
RELAY PCB HI-CAPACITY 10 A 5VDCRLY1
RES 1.0 M OHM ¼ W 5% 1206 SMDR1
RES 47 OHM ½ W 5% 2010 SMDR2
RES 1K OHM 1/10 W 1% 0603R3
RES 1M OHM 1/10 W 1% 0603R4
RES 1K OHM 1/10 W 1% 0603R5
RES 1K OHM 1/10 W 1% 0603R6
SWITCH-TACT SPST-NO MOM SMT J TYPES1
IC REG LDO MICROPOWER SOT23-5U1
IC PIC PROCESSOR 10F200T-I/OTU2
PCB CIRCUIT TO MOUNT PARTSPCB1
PCB SENSOR IMMERSION GOLDPCB2
BLACK 18AWG STRANDED 105deg C.W1
WHITE 18AWG STRANDED 105deg C.W2
BLUE 18AWG STRANDED 105deg C.W3
WIRE 26AWG STRANDED 50 mmW4
WIRE 26AWG STRANDED 50 mmW5

Improvements in this embodiment include additional tines in the sensor. The tines are wider and spaced closer together. In one embodiment, the tines are formed of copper that is coated with gold material, 24 ct. gold using standard PCB emersion coating. It was found that these changes make the sensor very sensitive to dew point, and it provides a heretofore unexpected improvement over existing similar sensors.

In a wall-mount version the sensor is readily accessible through a window formed in the housing for inspection and cleaning. The sensor can easily be cleaned because of the gold deposition on a fiberglass PCB, and it is corrosion resistant because it is not made of a porous material that absorbs moisture. The non-porous material of the present embodiment is easily cleaned and maintained by wiping the sensor face with a mild degreaser, such as household window cleaner. The sensor can be manufactured at most PCB manufacturers, resulting in a lower cost to produce.

The reaction time has been improved by using the PIC processor, which controls the reaction time, deletes parts, and results in a simpler controller that is more reliable and less costly to manufacture.

The controller is no longer powered by a transformer, which is replaced by a transformerless circuit that saves energy, drops temperature to the circuit board, gives the PCB more room for future add-ons, and it is also less costly to manufacture.

The signal conditioning circuit has utility with sensors other than those that sense moisture, making for a much approved approach to other types of sensors.

FIGS. 6A-6B illustrate the steps of replacing a conventional fan wall switch 90 with the controller 92 of the present disclosure. FIG. 6A shows the existing switch 90 removed from the wall box after power to the switch 90 has been shut off. Once the wires 94, 96 are removed from the existing switch 90, the new controller 92 is hooked up as shown, i.e., blue controller wire to the existing black wire, the white controller wire to the existing white wire, and the black controller wire to the remaining wire in the wall box.