MXPA98002040A - System and method for sensing the dryness of clothing articles - Google Patents

Abstract

A system and method for sensing the dryness of clothing articles in a clothes dryer. In one embodiment, the clothes dryer uses a temperature sensor and a phase angle sensor to determine the dryness of the clothing articles as a function of the heated air temperature and the motor phase angle. In another embodiment the clothes dryer uses a humidity sensor to determine the dryness of the clothing articles as a function of the humidity of the heated air temperature. In a third embodiment the clothes dryer uses a temperature sensor, a phase angle sensor, and a humidity sensor to determine the dryness of the clothing articles as a function of the heated air temperature, the motor phase angle, and the humidity of the heated air temperature.

Description

SYSTEM AND METHOD TO CAPTURE THE DRYING OF CLOTHING ARTICLES Field of the Invention The present invention relates generally to an apparatus for drying articles, and more particularly to a system and method for capturing the dryness of the articles in the apparatus.

BACKGROUND OF THE INVENTION Typly, an apparatus for drying items such as a clothes dryer to dry clothing articles uses an open control cycle to dry the articles of clothing. The open control cycle allows a user to set a drying time to dry clothing items. Setting the drying time requires an estimate by the user of when the articles of clothing will be dry and generally results in the articles being either overheated or subheated. Overheating of clothing items results in longer unnecessary drying times, increased energy consumption, and the potential to damage items. On the other hand, the subheating causes great inconvenience because the user has to re-set the drying time and wait again for the laundry items to dry. In accordance with the foregoing, there is a need for a clothes dryer that can automatly capture the dryness of the articles of clothing in a dryer without having to depend on the user's subjective estimate of the drying time.

SUMMARY OF THE INVENTION According to a first embodiment of this invention, an apparatus is provided as a clothes dryer for drying articles of clothing. In this embodiment, the dryer comprises a container for receiving the articles of clothing. A heater supplies hot air to the container. A blower motor pulls the hot air from the container. A duct directs hot air out of the container. A temperature sensor captures the temperature of the hot air and provides signal representations of it. A phase angle sensor captures the motor phase angle and provides representations of the motor signal. A controller that responds to both the temperature sensor and the phase angle sensor determines the dryness of the articles of clothing in the container as a function of the temperature of the hot air and the phase angle of the motor. According to a second embodiment of this invention an apparatus is provided as a clothes dryer for drying articles of clothing. In this embodiment, the dryer comprises a container for receiving the articles of clothing. A heater supplies hot air to the container. A duct directs hot air out of the container. A humidity sensor captures the humidity of the hot air in the duct and provides representations of hot water signals. A controller that responds to the humidity sensor determines the dryness of the articles of clothing in the container as a function of the humidity of the hot air. Clothing items are dry when the representations of the humidity signals are within a range of humidity previously determined and when the values of the differences of the representations of the humidity signal are within a predetermined interval. According to a third embodiment of this invention, an apparatus such as a clothes dryer is provided to dry clothing items. In this embodiment the dryer comprises a container for receiving the articles of clothing. A heater supplies hot air to the container. A blower motor pulls the hot air from the container. A duct directs hot air out of the container. A sensor The temperature captures the temperature of the hot air and provides representations of the signals of the same. A phase angle sensor captures the motor phase angle and provides representations of the motor signal. A humidity sensor captures the humidity of the air heated in the duct and provides the representations of the signal thereof. A controller that responds to the temperature sensor, the phase angle sensor, and the humidity sensor determines the dryness of the articles of clothing in the container as a function of the hot air temperature, the phase angle of the motor, and the humidity of the hot air.

Description of the Drawings Figure 1 shows a perspective view of a clothes dryer used in a first embodiment of this invention; Figure 2 shows a block diagram of a controller used in the first embodiment of this invention; Figures 3a-3c show a flowchart showing the steps used to determine the dryness of articles of clothing used in the first embodiment of this invention; Figures 4a-4c are time series graphs illustrating the operation of the clothes dryer presented in the first embodiment of this invention; Figure 5 represents a perspective view of a clothes dryer according to a second embodiment of this invention; Figure 6 shows a block diagram of a controller used in the second embodiment of this invention; Figure 7 shows a flowchart showing the steps used to determine the dryness of articles of clothing according to a second embodiment of this invention; Figures 8a-8c are time series graphs • illustrating the operation of the laundry dryer presented in the second embodiment of this invention; Figure 9 depicts a perspective view of a clothes dryer according to a third embodiment of this invention; Figure 10 shows a block diagram of a controller used in the third embodiment of this invention.

Detailed Description of the Invention Figure 1 shows a perspective view of a clothes dryer 10 used in a first embodiment of this invention. The clothes dryer includes a cabinet or a main housing 12 having a front panel 14, a rear panel 16, a pair of side panels 18 and 20 separated from each other by the front and rear panels, a panel below, and a cover 24. Within the housing 12 is a drum or container 26 mounted for rotation about a substantially horizontal axis. The drum 26 is generally cylindrical in shape, having an imperforate outer cylindrical wall 28 and a flange or wall front defining an opening 32 towards the drum. The # items of clothing and other fabrics are loaded into the drum 26 through the opening 32. A plurality of stirring ribs (not shown) are provided inside the drum 26 for lifting the articles and then letting them fall back to the bottom of the drum as the drum rotates. The drum 26 includes a rear wall 34 rotatably supported within the main housing 12 by a convenient fixed bearing. The rear wall 34 includes a plurality of ¥ holes 36 that receive hot air that has been heated for a heater such as a combustion chamber 38 and a rear conduit 40. The combustion chamber 38 receives ambient air via an inlet 42. Although the clothes dryer 10 shown in Figure 1 is a gas booster, it could also be an electric dryer without the combustion chamber 38 and the rear duct 40. Hot air is pulled from the drum by a blower motor 44 to evaporate moisture from the articles in the drum. The air passes through a sieve filter 46 that traps any fluff particles. As the air passes through the sieve filter 46, it enters a trap duct seal (permagu) 48 and pass out of the laundry dryer through an exhaust duct 50. After the laundry items have been dried, they are removed from the drum 26 via the opening 32. In this modality the dryness of articles of Clothes in the clothes dryer 10 are captured using a # temperature sensor 52 and a phase angle sensor 54. The temperature sensor 52 captures the temperature of the hot air passing through the sieve filter 46 and the angle sensor phase 54 captures the phase angle of the blower motor 44 as the air 5 is pulled out of the drum 26. The temperature sensor may be a commercially available sensor such as a thermocouple O type K and the phase angle sensor 54 may be a single phase induction motor sensor for general purposes.

• * The temperature sensor 52 and the phase angle sensor 54 provide signal representations of the hot air temperature and the phase angle of the motor, respectively, to a controller 56. The controller 56 responds to both the temperature sensor 52 and the phase angle sensor 54 and determines the dryness of the clothes items in the drum as a function of the hot air temperature and the phase angle of the motor. The controller 56 determines the dryness by deciding when the percentage of water content in the articles of clothing reaches a previously defined level of water content. water. The percentage of water content is defined as: % Cont. Of Water = _ Weight of acrua x 100 (1) 'Weight of water + Weight of articles 25 In this invention, the percentage of water content is divided into five categories that are classified as' wet, less dry, normal , dry, and very dry. The water content percentage ranges for the ratings are from 100 percent to approximately 16 percent for the wet classification, from approximately 16 percent 5 to approximately 10 percent for the less dry classification, approximately 10 percent up to approximately 5 percent for the normal classification, approximately 5 percent to approximately 3 percent for the dry classification, approximately 3 percent * 10 percent to 0 percent for the classification of very dry. In this embodiment, the controller 56 determines the dryness by deciding when the percentage of water content is in the range of about 10 percent to about 3 percent water content, being the preferred range from 5 percent to approximately 3 percent. The steps performed by the controller 56 to determine dryness are described below in greater detail. As soon as the controller 56 has determined that the laundry items are dry, then the controller ends the drying cycle. An advantage of the present invention over the open control cycle dryer is that the energy consumption is reduced and there is less potential to damage the articles due to overheating, since the dryness is automatically detected. A more detailed view of the controller 56 used in this embodiment is shown in Figure 2. The controller comprises an analog-to-digital (A / D) converter 58 for receiving signal representations sent from the temperature sensor 52, a counter / stopwatch 60 to receive the 5 representations of the signal sent from the phase angle sensor. The representations of the signal of the analog to digital converter 58 and the counter / timer 60 are sent to a central processing unit (CPU) 62 for further processing of the signal. It is also • within the scope of this invention to use the clock within the central processing unit 62 to directly receive the representations of the signal from the phase angle sensor 54 instead of the timer / timer 60. The central processing unit, which receives the energy of a power supply 64, comprises a decision logic stored in a read-only memory (ROM) 64 to determine the dryness of the articles of clothing in the container as a function of the representations of the hot air temperature and temperature signals. phase angle of the engine. The decision logic used to determine the dryness is described later in greater detail. As soon as it has been determined that the laundry items are dry, then the central processing unit 62 sends a signal to an output circuit 68 which sends a shutdown signal of a cycle selector knob 70 located in a control panel 71 of the dryer 10. The position of the selector knob 70 is monitored by a position encoder 72 that sends signals to a counter / timer 74 that is connected to the unit. central processing 62. As the 5th cycle shuts down, the controller activates a buzzer via a ringer circuit enable / disable 76 to indicate the end of the cycle.

'In this modality, dryness is based on a correlation between the representations of the motor phase angle signal and the hot air temperature. A problem associated with other dryers that only use one motor phase angle to capture dryness is that the conclusions regarding dryness can be wrong. In In particular, as a drying cycle progresses, articles of clothing lose weight continually because there is less water in the articles. As the articles of clothing lose weight, the peak-to-peak values of the engine phase increase. When these values stop increasing then one can deduce that the articles of clothing are already dry, although of more. In addition, the values of the phase angle sensor usually have noise and can result in wrong drying conclusions. This invention has overcome the problems associated with using an engine phase angle sensor correlating the representations of the signal of the phase angle with the representations of signals generated from the temperature sensor. Figures 3a-3c describe flowcharts that present the steps used to determine the dryness of the 5 articles according to the first embodiment of this invention. Figures 3a-3b describe the steps of the signal processing performed on the generated signal representations of the phase angle sensor, and the sensor * of temperature, respectively. The processing steps of The signals described in both Figures 3a-3b are performed in parallel in real time. In this invention the representations of the motor phase angle signals are loaded into the central processing unit 62 at a sampling rate of 10 Hz, while the representations of the temperature signals are recorded in the central processing unit at a sampling rate of 1 Hz. In this embodiment, the central processing unit 62 has five buffers A, B, C, D, and E reserved therein. The buffers A, B, and C are reserve for the representations of the phase angle signal, the buffers D and E are reserved for the representations of the temperature signal. The buffer A is capable of storing 14 data points, while the buffers B and C are capable of store 32 and 4 data points, respectively. For the processing of the temperature signal, the buffer D is capable of storing 16 data points, while the buffer E is capable of storing 4 data points. Referring now to Figure 3a, the steps of signal processing of the phase angle signal representations will be described. The processing of the signals starts at 78 when the phase angle sensor is read. The signal of the phase angle is denoted as PQ (Í) where i denotes its sampling sequence in time. The phase angle signal P0 (i) is transformed into a relative phase angle Pn (i) at 80, where Pn (i) equals 90 ° -P0 (i). The value of the data Pn (i) is placed in the buffer A at 82. One by one the data values Pn (i) are are placed in the buffer A until it has been determined that the buffer is full at 84. When the buffer A is full, the range of all the values stored in the buffer is calculated at 86 and placed in the memory intermediate B in 88 and memory Intermediate A is emptied at 90. If buffer B is not full at 92, then the phase angle sensor is read again and steps 80-90 are repeated until buffer B is full. When the buffer B is full, the median of all the values stored in the buffer B is calculated at 94 and placed in the buffer C at 96 and then the buffer B is emptied at 98. If the buffer C It is not full at 100, then the phase angle sensor is read again and steps 80-98 are repeated until buffer C is full. When buffer C is full, the median of all values stored in the buffer memory is calculated. C at 102. As soon as the median of all the values stored in the buffer C has been calculated, then the value of the median Pn (i) is passed in 104 to the dryness algorithm described later in Figure 3c and the buffer C is emptied at 106. This process is repeated until the end of the drying cycle. As mentioned above, the steps of the signal processing for the phase angle and the temperature signal are performed in parallel in real time. Referring now to Figure 3b, the steps of signal processing of the temperature signal will be described. The processing of the temperature signal starts at 108 where the temperature sensor is read. The temperature signal is denoted as T (j) where j denotes its time sampling sequence. The data value T (j) is placed in the buffer D at 110. One by one the values of the data T (j) are placed in the buffer D until it is determined that the buffer is filled at 112. When the buffer D is full, the median of all the values stored in the buffer is calculated at 114 and placed in the buffer E at 116 and then the buffer D is emptied at 118. If the buffer E does not 5 is filled at 120, then the temperature sensor is read again and steps 110-118 are repeated until buffer E is full. When the buffer E is full, the median of all stored values is calculated "^^ in the buffer E in 122. Regarding the median of all the values stored in the buffer E have been calculated then the value of the median T (j) is passed in 124 to the dryness algorithm described in Figure 3c and the buffer E is emptied into 126. This process is repeated until the end of the drying cycle. As soon as the processing steps of the signal representations for the phase angle and the temperature have been carried out, the dryness algorithm presented in Figure 3c is started. Referring now to Figure 3c, the dryness algorithm will be described.

Detection of dryness begins at 128 where T (j) is monitored to determine if its value exceeds 49 ° C. If the value T (j) does not exceed 49 ° C, then Figure 3b starts at 130 and the temperature sensor is read and steps 110-126 are repeated until T (j) exceeds 49 ° C. As soon as T (j) has exceeded 49 ° C, then T (j) is examined at 132 to find the local maximum. In the present invention, the local maximum is found if T (j) < T (jl) and (T (j -1) _> T (j -2). If the local maximum of T (j) has not been found at 134, then Figure 3b starts again at 130 and the The temperature sensor is read and steps 110-126 are repeated until the local maximum is found.As soon as the local maximum has been found then the dryness algorithm changes the attention to the phase angle Pn (i) at 136. It is examined then the value of the phase angle Pn (i) at 138 to find the local minimum In the present invention, the local minimum is found if P (i) > P (i-1) and P (i-1) < P (i-2) If the local minimum of Pn (i) has not been found at 140, then Figure 3a starts again at 142 and the phase angle sensor is read and steps 80- are repeated 106 until the local minimum is found, as soon as the local minimum has been found then the articles of clothing are considered dry and the dryer is turned off at 144. In essence, the dryness is captured when determining when the representations The signals of the hot air temperature have reached a local maximum and the representations of the motor phase angle have reached a local minimum. Figures 4a-4c are time series graphs illustrating the operation of the clothes dryer presented in the first embodiment according to this invention. Figure 4a is a graph of the phase angle P (i) against i, the time sampling sequence. More specifically, Figure 4a shows the median of the peak-to-peak phase change over the sampling time steps for a particular drying cycle. Figure 4b is a graph of the temperature T (j) against j, the sampling time steps. Figure 4c is a graph of the percentage of the water content against the sampling time step. In the example illustrated in Figures 4a-4c, the drying detection algorithm described above does not begin until the temperature of the laundry T (j) exceeds 49 ° C. The first local maximum that occurs occurs in the time step 17 of Figure 4b. At this time the drying detection algorithm then searches for the local minimum of P (i) in Figure 4a. In this example, the first local minimum of P (i) is presented in time step 7 in Figure 4a. Then the drying detection algorithm will issue a turn off command in the next time step (ie time step 8) in Figure 4a. At this time the water content in the articles of clothing is almost at its lowest value as shown in Figure 4c. Note that the percentage of water content in clothing items is well within the range of about 10 percent to about 3 percent water content and within the preferred range of 5 percent to about 3 percent. As mentioned earlier this invention prevents clothing items from overheating or sub-heat and reduce energy consumption.

# Figure 5 shows a perspective view of a clothes dryer 146 according to a second embodiment of this invention. Clothes dryer 146 is similar to the clothes dryer of the first mode except that there is no temperature sensor or a phase angle sensor in this mode. Instead, this method uses a humidity sensor 148 to detect the dryness of the articles of clothing. The humidity sensor 148 captures the moisture of the hot air * which passes through the exhaust conduit 50. The humidity sensor can be an immediate commercial product such as a Parametrics HT-119. The humidity sensor 148 provides signal representations of the humidity of the hot air to a controller 150. The controller 150 responds to the humidity sensor 148 and determines the dryness of the articles of laundry in the drum as a function of the humidity of the hot air in the exhaust duct 50. • A more detailed view of the controller 150 according to the second embodiment of this invention is shown in Figure 6. The controller in this modality is similar to controller presented in the first mode except that the counter / timer to receive the representations of signals sent from the phase angle sensor have been removed. In this embodiment an A / D converter receives the representations sent from the humidity sensor 148. The The central processing unit comprises decision logic # stored in a read-only memory to determine the dryness of the articles of clothing in the container as a function of the representations of the processed signal of the hot air humidity. A problem associated with 5 other dryers that use moisture to capture dryness is that the typical humidity sensors used are quite expensive. The present invention can overcome cost problems by using a low end moisture sensor that has a range * Relative humidity from about 0 percent up approximately 30 percent with a dryness detection algorithm which is described in more detail below. Figure 7 describes a flowchart that presents the steps used to determine the dryness of the articles of clothing according to the second embodiment of this invention. In this embodiment, the representations of the humidity signals are recorded in the central processing unit at a sampling rate of 1 Hz and the central processing unit has two buffers A and B reserved in it. The buffer A is capable of storing 16 data points, while the buffer B is capable of storing 4 data points. Signal processing begins at 152 where the humidity sensor is read. The humidity signal is denoted as m (i) where i denotes its time sampling sequence. The data value m (i) is placed in the buffer A at 154. One by one the data values m (i) are placed in the buffer A until it has been determined that the buffer is filled at 156. When the buffer A is full, the median of all the values stored in the buffer is calculated at 158 and placed in the buffer B at 160 and then the buffer A is emptied at 162. If the buffer B does not is filled at 164, then the humidity sensor is read again and steps 154-162 are repeated until buffer B is full. When the buffer B is full, the median of all the values stored in the buffer B is calculated at 166. As soon as the median of all the values has been calculated then the value of the median m (i) is passed to the step 168 where the detection of the onset of dryness begins. The data value m (i) is now monitored to determine if its value is less than 30 percent. If the value m (i) exceeds 30 percent, then the buffer B is emptied at 170 and the humidity sensor is again read and steps 154-166 are repeated until m (i) is less than 30 percent. As soon as m (i) is less than 30 percent then m (i) is examined at 172 to determine if there are more than two data values m (i). If there are no more than two data values m (i) then the humidity sensor is read again and steps 154-168 are repeated until there are more than two data values m (i). As soon as there are more than two data values m (i) then the difference dm (i) is determined at 174. In this invention, the difference dm (i) is equal to m (i) -m (i-l). In step 176, the dryness algorithm determines whether dm (i) is the same value for a previously determined range. In this embodiment, the preferred range is three consecutive values within a tolerable small band. This relationship is • * described below in the ratio 2: 10 dm (i-2) e [-3,3] and dm (il) e [-3, 3] and dm (i) e [-3, 3] (1 ) Once it has been determined that there are three consecutive values within a tolerable small band, then the articles of clothing are considered dry and the dryer is turned off at 178. 15 Figures 8a-8c are time series graphs illustrating the operation of the laundry dryer presented in the second embodiment according to this invention. Figure 8a is a graph of the humidity m (i) against i, the time sampling sequence. Note that the scale of the Y axis in the Figure 8a varies from 0 percent to 30 percent. Figure 8b is a graph of the difference of the humidity signal dm (i) against i, the sampling time steps. Note that the scale of the Y axis in Figure 8b varies from -3 to 3. Figure 8c is a graph of the percentage of water content against the passage of sampling time. In the example illustrated in Figures 8a-8c, the dryness detection algorithm described above detects that there are three consecutive values dm (i) that start after the time step number 30. The dryness detection algorithm then 5 emits a order to turn off at time step 33 where the third consecutive value has been noted. At this time the water content in the articles of clothing is saturated and is almost at its lowest value as shown in Figure 8c. Note that the percentage of water content in the items of clothing is well within the range of about -10 percent to about 3 percent water content and within the preferred range of about 5 percent to about 3 percent. As mentioned earlier this invention avoids that clothing items overheat or underheat and reduce energy consumption. Figure 9 shows a perspective view of a clothes dryer 180 according to a third embodiment of this invention. The clothes dryer 180 is similar to the clothes dryer shown in the first and second modes except that in this embodiment there is a temperature sensor 52, a phase angle sensor 54, and a humidity sensor 148 that are used to detect the dryness of the articles of clothing. The temperature sensor 52, the angle sensor motor phase 54, and humidity sensor 148 provide # signal representations of hot air temperature, motor phase angle, and hot air humidity to controller 182, respectively. The controller 182 responds to the temperature sensor 52, the angle 5 sensor of phase 54, and the humidity sensor 148 and determines the dryness of the articles of laundry in the drum as a function of the hot air temperature, the angle of motor phase, and hot air humidity. A more detailed view of controller 182 of According to the third embodiment of this invention is shown in Figure 10. The controller in this mode is similar to the controllers presented in the first and second modes except that there is a counter / timer 60 to receive the signal representations sent from the sensor of the phase angle 54, an analog-to-digital converter 58 for receiving the representations of signals sent from the temperature sensor 52, and an analog / digital converter 184 for receiving the signal representations sent from the humidity sensor 148. The unit of The central processing comprises decision logic stored in the read-only memory to determine the dryness of the articles of clothing in the container as a function of the representations of processed signals of the phase angle of the motor, the temperature of the hot air, and the humidity of the air hot. The decision logic contains the aforementioned $ dryness algorithms presented in Figures 3a-3c and Figure 7. In accordance with the above, the controller determines the dryness of the articles of clothing following the steps presented in the two aforementioned algorithms. . Plus 5 specifically, if and only two algorithms agree, then the clothes dryer goes off. As in the first and second embodiments, the third embodiment provides another method for detecting the dryness of the articles of clothing and prevents the articles from being overheated or subheated and reduces energy consumption. It is therefore apparent that a system and method for capturing the dryness of the articles in an apparatus that has been provided according to the present invention has been provided. fully satisfies the goals and advantages and objectives previously presented herein. The invention has been described with reference to various modalities, however, it will be appreciated that a person of ordinary skill in the art could make variations and modifications without depart from the scope of the invention.

Claims (9)

1. An apparatus for drying articles of clothing comprising: a container for receiving articles of clothing; a heater to supply hot air to the container; a blower motor to pull the hot air from the # container; 10 a conduit for directing the hot air out of the container; a temperature sensor for sensing hot air and providing representations of signals thereof, - a phase angle sensor for capturing the phase angle of the motor and providing signal representations • of the same; and a controller that responds to the temperature sensor and the phase angle sensor to determine the dryness of 20 the items of clothing in the container as a function of the hot air temperature and the phase angle of the motor.

The apparatus according to claim 1, wherein the controller comprises a signal processing unit for processing the signal representations of the 25 hot air temperature and the motor phase angle.

3. The apparatus according to claim 2, wherein the controller further comprises a logic decision unit for determining the dryness of the articles of clothing in the container as a function of the signal representations of the hot air temperature and the angle of motor phase. .

The apparatus according to claim 3, wherein the decision logic unit decides whether the representations of the processed signals of the temperature 10 of the hot air have reached a local maximum and the representations of the processed signals of the phase angle of the motor have reached a local minimum.

5. An apparatus for drying articles of clothing comprising: a container for receiving articles of clothing; F a heater to supply hot air to the container; a conduit for directing the hot air out of the container; 20 a humidity sensor for capturing the humidity of the hot air entering the duct and providing representations of the signal thereof; and a controller that responds to the humidity sensor to determine the dryness of the articles of clothing in the container as a function of the humidity of the hot air, the articles of clothing being dry when the representations of the humidity signal are within a moisture range previously determined and when the consecutive difference values of the representations of the humidity signal 5 are within a predetermined range.

The apparatus according to claim 5, wherein the controller comprises a signal processing unit for processing the signal representations of the 10 hot air humidity.

The apparatus according to claim 6, wherein the controller further comprises a decision logic unit for determining the dryness of the articles of clothing in the container as a function of the representations 15 of the processed signal of hot air humidity.

The apparatus according to claim 5, wherein the previously determined humidity range is from about 0 percent humidity to about 30 percent humidity.

9. An apparatus for drying articles of clothing comprising: a container for receiving articles of clothing; a heater to supply hot air to the container; 25 a blower motor for pulling the hot air from the container; a conduit for directing the hot air out of the container; a temperature sensor to feel hot air and provide representations of the same; a phase angle sensor for capturing the phase angle of the motor and providing signal representations thereof; 10 a humidity sensor for capturing the humidity of the hot air entering the duct and providing representations of the signal thereof; and a controller that responds to the temperature sensor, the phase angle sensor and the sensor 15 moisture to determine the dryness of the articles of clothing in the container as a function of the temperature of the hot air, the phase angle of the engine, and the humidity of the hot air.