The present subject matter relates, in general, to air conditioning devices and, in particular to techniques of monitoring accumulation of particulate matter on inlet filters of the air conditioning devices.
BACKGROUND [0002] Air conditioning is a process of absorbing heat and moisture from air circulating inside a space, thereby dehumidifying and cooling the space. The air circulating inside the space may have pollutants, such as dust, that on entrance into an air conditioning device may affect the operation of various components present therein. Accordingly, an inlet filter is utilized to facilitate filtration of the air entering the air conditioning device, thereby ensuring safety of the components.
BRIEF DESCRIPTION OF DRAWINGS [0003] Figure 1 illustrates an air conditioning device, in accordance with an example of the present subject matter,
[0004] Figure 2 illustrates an air conditioning device, in accordance with another example of the present subject matter,
[0005] Figure 3 illustrates a method of determining presence of accumulated particulate matter on an inlet filter of an air conditioning device, in accordance with an example of the present subject matter, and [0006] Figure 4 illustrates a method of determining presence of accumulated particulate matter on an inlet filter of an air conditioning device, in accordance with another example of the present subject matter.

DETAILED DESCRIPTION [0007] Generally, an air conditioning device draws in air from a space into a housing of the air conditioning device through an inlet. The inlet is an opening formed on the housing to facilitate intake of air from the closed space into the housing. The air is drawn into the housing by employing a suction fan. The suction fan may be an exhaust fan, driven by an electric motor, to draw in hot and humid air out of a localised area and push the air into the housing for cooling and dehumidification. The suction fan may subsequently push the cooled and dehumidified air, via an outlet of the air conditioning device, to be recirculated in the localised area. [0008] The inlet, in general, is coupled to an inlet filter that may facilitate filtration of the air entering through the inlet, thereby avoiding entrance of any particulate matter inside the housing. However, the prolonged usage of the air conditioning device may result in accumulation of the particulate matter on the inlet filter. The accumulation of the particulate matter on the inlet filter reduces a surface area of the inlet filter that is exposed for drawing in the air inside the housing, thereby reducing a volume of the air entering the housing. This, in turn, reduces the operational efficiency of the air conditioning device. Also, the additional load on the suction fan in drawing in the air through reduced surface area of the inlet filter increases the power consumption of the electric motor driving the suction fan, thereby increasing the overall power consumption of the air conditioning device. [0009] To ensure efficiency and cost effectiveness associated with operation of the air conditioning device, the inlet filter may be cleaned whenever accumulation of the particulate matter is detected on a surface of the inlet filter. In existing air conditioning devices, the detection of accumulated particular matter on the inlet filter may be facilitated by utilizing sensors, such as optical dust sensors. In such air conditioning devices, the sensors continuously monitor the presence of the particulate matter on the surface of the inlet filter and raises a notification or an alarm on detecting the accumulation of the particulate matter on the surface. However, the

incorporation of the sensors in the air conditioning device renders assembly of air conditioning device complex and expensive. Also, the prolonged exposure of the sensors to the particulate matter renders the sensors inefficient, thereby raising false alarms of the presence of accumulated particulate matter on the inlet filter.
[0010] According to example implementations of the present subject matter, techniques of monitoring accumulation of particulate matter on an inlet filter of an air conditioning device are disclosed. [0011] In an example, the air conditioning device may have an inlet to facilitate entrance of air in a housing of the air conditioning device. In said example, the inlet may have an inlet filter for filtering the air entering the housing through the inlet. The air conditioning device may further have a suction fan to draw the air to the inside of the housing through the inlet and the inlet filter. The suction fan may further be coupled to an electric motor for operation. The electric motor has been referred to as fan motor, hereinafter.
[0012] The air conditioning device may further have a driving controller coupled to the fan motor. In an example, the driving controller may monitor and control the operation of the fan motor. For instance, in an example, the driving controller may monitor and control a magnitude of current being supplied to the fan motor for operation. In another example, the driving controller may monitor and control a voltage signal applied to the fan motor. [0013] In yet another example, the driving controller may monitor and control revolutions per minutes (RPM) of the fan motor. For instance, the driving controller may identify a threshold RPM for the fan motor at a rated voltage of the air conditioning device. In said example, the driving controller may also determine a pulse width of a voltage signal, say a first pulse width, applied to the fan motor. The driving controller may then monitor a difference between the RPM of the fan motor and the threshold RPM and may alter a voltage being applied to the fan motor to minimize the difference between the RPM of the fan motor and the threshold RPM.

[0014] In an example, the driving controller may monitor the RPM of the fan motor to identify a scenario when an absolute value of the difference between the RPM of the fan motor and the threshold RPM increases beyond a threshold. Based on the identification of the scenario, the driving controller may attribute the change in the RPM of the fan motor to the accumulation of the particulate matter on the inlet filter. Accordingly, the driving controller may determine and alert a user of the air conditioning device, about the presence of accumulated particulate matter on the inlet filter. [0015] In another example, when the driving controller determines absolute value of the difference between the RPM of the fan motor and the threshold RPM to be greater than the threshold, the driving controller may identify if the RPM of the fan motor has increased beyond the threshold RPM or the RPM has fallen below the threshold RPM. Accordingly, the driving controller may vary the pulse width of the voltage signal to compensate the difference between the RPM and the threshold RPM. [0016] In an example, the RPM of the fan motor may increase beyond the threshold RPM to an extent, such that, the absolute value of the difference between the RPM of the fan motor and the threshold RPM increases beyond a threshold. In said example, the driving controller may decrease the pulse width of the voltage signal applied to the fan motor to reduce the RPM of the fan motor, thereby compensating the difference between the RPM and the threshold RPM.
[0017] Alternatively, in another example, the RPM of the fan motor may fall below the threshold RPM to an extent, such that, the absolute value of the difference between the RPM of the fan motor and the threshold RPM increases beyond a threshold. In said example, the driving controller may increase the pulse width of the voltage signal applied to the fan motor to increase the RPM of the fan motor, thereby compensating the difference between the RPM and the threshold RPM.
[0018] Subsequently, the driving controller may determine a pulse width of the voltage signal, say a second pulse width, applied to the fan motor

after a predetermined time interval. The driving controller may determine a variation between the first pulse width and the second pulse width. The driving controller may then ascertain the variation between the first pulse width and the second pulse width to be greater than a threshold variation. Based on the ascertaining, the driving controller may ascertain that the RPM of the fan motor didn't stabilize during the predetermined time interval. Accordingly, based on the ascertaining, the driving controller may determine presence of accumulated particulate matter on the inlet filter. [0019] The indication of clogging of the inlet filter, due to the accumulation of the particulate matter thereon, alerts the user to either clean the inlet filter or have the air conditioning device serviced. Accordingly, the operation of the air conditioning device with the clogged inlet filter is avoided. This, in turn, ensures that the power consumption and the operational efficiency of the air conditioning device is optimized. Further, the determination of the presence of the accumulated particulate matter based on operational parameters of the air conditioning device reduces the complexity and cost involved in assembly of the air conditioning device. [0020] The above and other features, aspects, and advantages of the subject matter will be better explained with regard to the following description and accompanying figures. It should be noted that the description and figures merely illustrate the principles of the present subject matter along with examples described herein and, should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and examples thereof, are intended to encompass equivalents thereof. Further, for the sake of simplicity, and without limitation, the same numbers are used throughout the drawings to reference like features and components. [0021] Figure 1 illustrates an air conditioning device 100, in accordance with an example of the present subject matter. Examples of the air

conditioning device 100, hereinafter referred to as AC 100, may include, but are not limited to, a ductless split AC, a window AC, a portable AC, HVAC, hybrid AC, and integrated AC, such as, ACs fitted into vehicles and aeroplanes.
[0022] In an example, the AC 100 may be formed by assembling multiple electronic and mechanical components in a housing (not shown), where the electronic and mechanical components may be electrically coupled to each other. The housing may form an outer body of the AC 100 that may encompass therein, the multiple electronic and mechanical components of the AC 100.
[0023] In said example, the housing may have an inlet 102, that may be formed as an opening to facilitate entrance of air in the housing of the AC 100. The housing may further include an inlet filter 104 that may allow filtration of the air entering the housing through the inlet 102. The inlet filter 104 may trap particulate matter, such as dust and prohibit them from entering the housing, thereby protecting the various electronic and mechanical components present therein.
[0024] In an example, the inlet 102 and the inlet filter 104 may have a coupling present therebetween to avoid any particulate matter from entering the housing. The coupling may be achieved in a number of ways. In an example, to achieve the coupling, the inlet filter 104 may be formed as a part of the inlet 102. In another example, to achieve the coupling while ensuring modularity, the inlet filter 104 may be formed separately and may then be un-fixedly coupled to the inlet 102.
[0025] The AC 100 may further have a suction fan 106 to draw air in the housing. The suction fan 106 may draw in hot and humid air out of a localised area and push the air into the housing for cooling and dehumidification. Examples of the suction fan may include, but not limited to, a squirrel cage fan and an exhaust fan. In an example, the air may be drawn in the housing through the inlet 102 and the inlet filter 104.

[0026] Further, the AC 100 may have an electric motor, hereinafter referred to as fan motor 108, that may drive the suction fan 106. Examples of the fan motor 108 may include, but are not limited to, alternating current (AC) motors, such as split-phase motor, shaded pole motor, capacitor-start motor, capacitor-start capacitor-run motor, capacitor-start inductor-run motor, and permanent split capacitor motor; and direct current (DC) motors, such as, a DC brushless motor.
[0027] The fan motor 108 may be electrically coupled to a driving controller 110. In an example, the driving controller 110 may be implemented as a combination of hardware and firmware. In examples described herein, such combinations of hardware and firmware may be implemented in several different ways. For example, the firmware for the driving controller 110 may be processor executable instructions stored on a non-transitory machine-readable storage medium and the hardware for the engine may include a processing resource (for example, implemented as either a single processor or a combination of multiple processors), to execute such instructions. In the present examples, the machine-readable storage medium may store instructions that, when executed by the processing resource, implement the functionalities of the driving controller. In such examples, the AC 100 may include the machine-readable storage medium storing the instructions and the processing resource to execute the instructions. In other examples of the present subject matter, the machine-readable storage medium may be located at a different location but accessible to AC 100 and the processing resource. [0028] The driving controller 110 may monitor and control the operation of the fan motor 108. In an example, the driving controller 110 includes modules, such as a feedback module 112 and an analysis module 114 to provide the various functionalities. The modules include routines, programs, objects, components, data structures, and the like, which perform tasks or implement abstract data types.

[0029] In an example implementation of the present subject matter, during the operation of the AC 100, the feedback module 112 may monitor revolution per minute (RPM) of the fan motor 108. The feedback module 112 may monitor the RPM of the fan motor 108 and identify instances when the RPM of the fan motor 108 varies with respect to a threshold RPM. In an example, the threshold RPM indicates an RPM of the fan motor 108 at a rated voltage of the AC 100.
[0030] In an example, during the operation of the AC 100, a voltage signal being applied to the fan motor may be kept constant. In said example, the voltage may be kept constant by employing a voltage stabilizer to stabilize a supply voltage, before the supply voltage is applied to the fan motor.
[0031] In the aforementioned example implementation, the feedback module 112 may identify a scenario when an absolute value of a difference between the RPM of the fan motor 108 and the threshold RPM increases beyond a threshold. Based on the identification, the analysis module 114 may determine a variation in load across the fan motor 108. Accordingly, the analysis module 114 may determine that the variation in load across the fan motor 108 may be a result of clogging of the inlet filter 104. Accordingly, the analysis module 114 may determine and indicate presence of accumulated particulate matter on the inlet filter 104. [0032] In an illustrative example, the fan motor may be a dual-pole split-phase motor having a threshold RPM of 3600. In said example, the threshold difference between the RPM of the fan motor and the threshold RPM may be 300 rpm. Accordingly, the driving controller may monitor the RPM of the fan motor and may identify the instances when the RPM of the fan motor may increase beyond 3900 RPM or may fall below 3300 RPM. In any of the situations described above, the driving controller may identify a variation in the load across the fan motor and may attribute the variation to the presence of accumulated particulate matter on the inlet filter. The presence of the accumulated particulate matter may be indicated to the

users in a number of ways. In an example, the driving controller 110 may turn on a notification light on the AC 100 to indicate the presence of the accumulated particulate matter. In another example, the driving controller 110 may transmit a notification to a mobile device (not shown) coupled to the AC 100.
[0033] In an example, along with the presence of the accumulated particulate matter, the analysis module 114 may also determine a level of accumulation of the particulate matter on the inlet filter 104. In said example, the analysis module 114 may determine the level of accumulation of the particulate matter based on the difference between the RPM of the fan motor 108 and the threshold RPM. In other words, larger the difference between the RPM of the fan motor 108 and the threshold RPM, larger the accumulation of the particulate matter on the inlet filter. In an example implementation, the accumulation of the particulate matter on the inlet filter 104 may further be determined based on a pulse width of a voltage being applied to the fan motor 108. The details of such implementation have been described in reference of Fig. 2
[0034] Figure 2 illustrates an air conditioning device 200, in accordance with another example of the present subject matter. The air conditioning device 200, hereinafter referred to as the AC 200, may include an inlet 202, an inlet filter 204 coupled to the inlet 202, a suction fan 206, a fan motor 208, and a driving controller 210. In an example, the inlet 202, the inlet filter 204, the suction fan 206, the fan motor 208, and the driving controller 210 are similar to the inlet 102, the inlet filter 104, the suction fan 106, the fan motor 108, and the driving controller 110 of the AC 100 shown in Figure 1. [0035] In an example, the driving controller 110, among other things, may include processor(s) 212. The functions of the various elements shown in the Figures, including any functional blocks labelled as "processor(s)", may be provided through the use of dedicated hardware as well as hardware capable of executing instructions. When provided by a processor, the functions may be provided by a single dedicated processor, by a single

shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term "processor" would not be construed to refer exclusively to hardware capable of executing instructions, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing instructions, random access memory (RAM), non-volatile storage. Other hardware, standard and/or custom, may also be included. [0036] The driving controller 210, may include modules 214, such as a feedback module 216, an analysis module 218, and a control module 220, to provide the various functionalities. In an example, the feedback module 216 and the analysis module 218 may be similar to the feedback module 112 and the analysis module 114.
[0037] The driving controller 110 may further include data 222, that serves, amongst other things, as a repository for storing data that may be fetched, processed, received, or generated by the feedback module 216, the analysis module 218, and the control module 220. The data 222 may include input data 224 and other data 226. In an example, the data 222 may be stored in a memory (not shown) coupled to the processor 212. [0038] In operation, the feedback module 216 may determine revolutions per minute (RPM) of the fan motor 208. Along with the RPM of the fan motor 208, the feedback module 216 may also determine a pulse width, say a first pulse width, of a voltage signal applied to the fan motor 208. The feedback module 216 may store the determined RPM and the first pulse width in the input data 224.
[0039] Subsequently, the analysis module 218 may access the RPM of the fan motor 208 by accessing the input data 224. The analysis module 218 may then compute a difference between the RPM of the fan motor 208 and a threshold RPM. As described earlier, the threshold RPM indicates an RPM of the fan motor 208 at a rated voltage of the AC 100.

[0040] The analysis module 218 may then determine an absolute value of the difference between the RPM of the fan motor 208 and a threshold RPM to be greater than a threshold. Based on the determination, the control module 220 may vary the pulse width of the voltage signal to compensate the difference in the RPM of the fan motor 208 and the threshold RPM. [0041] In an example, the RPM of the fan motor 208 may be determined to be less than the threshold RPM. The RPM of the fan motor 208 may fall below the threshold RPM due to a variety of reasons. For example, decrease in the RPM of the fan motor 208 may be attributed to a variance in a supply voltage of the AC 200. That is, the RPM of the fan motor 208 may have fallen below the threshold RPM due to a fall in the supply voltage below the rated voltage of the AC 200. In another example, the decrease in the RPM of the fan motor 208 may be attributed to clogging of the inlet filter due to presence of accumulated particulate matter on a surface thereon along with the type of suction fan 206 being used in the AC 200. For instance, when the type of suction fan 206 being used in the AC 200 is an exhaust fan, the presence of the accumulated particulate matter on the surface of the inlet filter may put additional load on the fan motor 208 in drawing the air into a housing of the AC 200, thereby reducing the RPM of the fan motor 208.
[0042] In the aforementioned examples, in order to compensate the decrease in RPM of the fan motor 208, the control module 220 may increase the pulse width of the voltage signal being applied to the fan motor 208. An increase in the pulse width of the voltage signal may increase the average voltage being applied to the fan motor 208, thereby increasing the RPM of the fan motor 208 and decreasing the difference between the RPM of the fan motor 208 and the threshold RPM.
[0043] In another example, the RPM of the fan motor 208 may be determined to be greater than the threshold RPM. The RPM of the fan motor 208 may increase beyond the threshold RPM due to a variety of reasons. In an example, the RPM of the fan motor 208 may increase beyond the

threshold RPM due to an increase in the supply voltage above the rated voltage of the AC 200. In another example, the increase in the RPM of the fan motor 208 may be attributed to the clogging of the inlet filter due to presence of the accumulated particulate matter on a surface thereon along with the type of suction fan 206 being used in the AC 200. [0044] For instance, when the suction fan 206 being used is a squirrel cage fan, the presence of the accumulated particulate matter may reduce an amount of air being circulated through the housing of the AC 200, thereby decreasing a load on the suction fan 206 and increasing the RPM of the fan motor 208.
[0045] In aforementioned examples, in order to compensate the increase in RPM of the fan motor 208 and prevent the fan motor 208 from heating up and malfunctioning, the control module 220 may decrease the pulse width of the voltage signal being applied to the fan motor, thereby decreasing the RPM of the fan motor 208 and decreasing the difference between the RPM of the fan motor 208 and the threshold RPM. In an example, the determination of the absolute value of the difference between the RPM of the fan motor 208 and the threshold RPM to be above the threshold RPM may be due to variation in the supply voltage. In said example, the feedback module 216 may thus wait for a predetermined time interval for the supply voltage to be stabilized. Once the predetermined time interval is over, the feedback module 216 may re-determine a pulse width of the voltage signal applied to the fan motor 208, say a second pulse width. The analysis module 218 may subsequently access the input data 224 and determine a variation between first pulse width and the second pulse width. [0046] In an example implementation of the present subject matter, the analysis module may determine the variation between the first pulse width and the second pulse width to be greater than a threshold variation. Based on the determination, the analysis module 218 may determine that the first pulse width of the voltage signal has been varied to compensate for the loss in RPM of the fan motor 208. In other words, the analysis module 218 may

determine that the variation in the RPM of the fan motor 208 may be a result of a reason other than the variation in the supply voltage. Accordingly, in an example, the analysis module 218 may attribute the variation in the RPM of the fan motor 208 to variation in load across the fan motor 208 due to clogging of the inlet filter.
[0047] In an example, the analysis module 218 may also determine a level of accumulation of the particulate matter on the inlet filter 204 based on the variation between the first pulse width and the second pulse width. In other words, larger the variation between the first pulse width and the second pulse width, larger the accumulation of the particulate matter on the inlet filter 204.
[0048] Subsequently, the presence of the accumulated particulate matter may be indicated to the users. The presence of the accumulated particulate matter may be indicated to the users in a number of ways. In an example, the driving controller 210 may turn on a notification light on the AC 200 to indicate the presence of the accumulated particulate matter. In another example, the driving controller 210 may send a notification to a mobile device (not shown) coupled to the AC 200.
[0049] In an example of the present subject matter, the AC 200 may also have a filter cleaning assembly (not shown). The filter cleaning assembly may include a base having a set of brushes attached thereto. The base may be mounted on a set of guide rails that may allow the base to be traversed to and fro, along a length of the inlet filter 204. The filter cleaning assembly may further have a dust collector mounted on a rail of the set of guide rails to collect the particulate matter swept off the inlet filter 204. In said example, based on the indication of the presence of the accumulated particulate matter on the inlet filter 204, the control module 220 may indicate to the filter cleaning assembly to sweep off the particulate matter present on the inlet filter 204, thereby facilitating self-cleaning of the inlet filter 204. In an example, the control module 220 may decide a number of traversals of the base over the inlet filter 204 based on the level of accumulation of the

particulate matter on the inlet filter 204. In other words, lower the level of accumulation of the particular matter, lower the number of traversals of the base over the inlet filter 204.
[0050] Figure 3 and Figure 4 illustrate methods 300 and 400 of determining presence of accumulated particulate matter on an inlet filter of an air conditioning device, according to examples of the present subject matter.
[0051] Although the methods 300 and 400 may be implemented in a variety of air conditioning devices, but for the ease of explanation, the description of the methods 300 and 400 is provided in reference to the above-described air conditioning device 200. The order in which the methods 300 and 400 are described is not intended to be construed as a limitation, and any number of the described method blocks may be combined in any order to implement the methods 300 and 400, or an alternative method.
[0052] It may be understood that blocks of the method 300 and 400 may be performed in the air conditioning device 200. The blocks of the method 300 and 400 may be executed based on instructions stored in a non-transitory computer-readable medium, as will be readily understood. The non-transitory computer-readable medium may include, for example, digital memories, magnetic storage media, such as magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media. [0053] At block 302, revolutions per minute (RPM) of a fan motor 208 driving a suction fan, are determined. In an example, the suction fan draws air to the inside of a housing of the air conditioning device 200 through the inlet filter 204. In said example, the RPM of the fan motor 208 are determined by a feedback module 216 of a driving controller 210 of the air conditioning device 200.
[0054] At block 304, a first magnitude of a current being applied to the fan motor 208 is determined. In an example, the first magnitude of current is determined by the feedback module 216.

[0055] At block 306, a difference between the RPM of the fan motor and a threshold RPM is determined, where the threshold RPM indicates an RPM of the fan motor 208 at a rated current for the air conditioning device. The rated current for an appliance may be defined as a level of current at which the appliance device may operate with complete safety for a prolonged time. In an example, the difference in the RPM of the fan motor 208 and the threshold RPM may be attributed to a variation in magnitude of a supply current of the air conditioning device 200. In another example, the difference in the RPM of the fan motor 208 and the threshold RPM may also be attributed to a variation in load across the fan motor 208 due to clogging of the inlet filter 204.
[0056] At block 308, an absolute value of the difference between the RPM of the fan motor 208 and the threshold RPM is determined to be greater than a threshold. In an example, the first magnitude of current may be varied to compensate for the in magnitude of the supply current. In said example, if it is determined that the RPM of the fan motor 208 has increased beyond the threshold RPM, the first magnitude of current may be decreased to reduce the RPM of the fan motor 208. Similarly, if it is determined that the RPM of the fan motor 208 has fallen below the threshold RPM, the first magnitude of current may be increased to increase the RPM of the fan motor 208. In either case, a control module 220 of the driving controller 210 may vary the first magnitude of current in response to the variance in the magnitude of the supply current. Further, the feedback module 216 may wait for a predetermined time interval of time for the magnitude of the supply current to be stabilized.
[0057] At block 310, after waiting for the predetermined time interval, a second magnitude of current applied to the fan motor 208 may be determined. In an example, the second magnitude of current may be determined by the feedback module 216.
[0058] At block 312, a deviation between the first magnitude of the current and the second magnitude of the current may be determined. In an

example, the deviation between the first magnitude of the current and the second magnitude of the current is determined by an analysis module 218 of the driving controller 210.
[0059] At block 314, the deviation between the first magnitude of current and the second magnitude of current may be ascertained to be greater than a threshold deviation. Accordingly, it may be identified that even after the stabilization of the magnitude of the supply current during the predetermined time interval, the first magnitude of the current had to be varied to maintain the RPM of the fan motor 208. The method may then proceed to block 318. [0060] At block 318, based on the ascertaining, the analysis module 218 may determine the presence of the accumulated particulate matter on the inlet filter 204. In an example, the analysis module 218 may also determine a level of accumulation of the particulate matter on the inlet filter 204 based on, at least in part, on the deviation between the first magnitude of current and the second magnitude of current. The method may then proceed to indication of the presence of the accumulated particulate matter on the inlet filter 204. In an example, the presence of the accumulated particulate matter may be indicated by switching on a LED indicator formed on a housing of the air conditioning device 200. In another example, the presence of the accumulated particulate matter may be indicated by sending a notification on a mobile application displaying operational condition of the air conditioning device 200. In said example, the mobile application may also display various techniques that may be employed by a user of the air conditioning device to remove clogging from the inlet filter 204 and restore normal operation. In an example, based on the ascertaining, the analysis module 218 may also facilitate self-cleaning of the inlet filter by activating a filter cleaning assembly of the air conditioning device 200. The filter cleaning assembly may sweep off the accumulated particulate matter from the inlet filter 204, thereby facilitating auto-cleaning of the inlet filter 204.

[0061] Figure 4 illustrates a method 400 of determining presence of accumulated particulate matter on an inlet filter of an air conditioning device, according to another example of the present subject matter. [0062] At block 402, revolutions per minute (RPM) of a fan motor 208 of the air conditioning device 200 is determined. In addition, a first pulse width of a voltage signal applied to the fan motor 208 is also determined. In an example, the RPM of the fan motor 208 and the first pulse width of the voltage signal may be determined by a feedback module 216 of a driving controller 210 of the air conditioning device 200.
[0063] At block 404, a difference between the RPM of the fan motor 208 and a threshold RPM is determined, where the threshold RPM indicates an RPM of the fan motor 208 at a rated voltage of the air conditioning device 200. In an example, the difference between the RPM of the fan motor 208 and a threshold RPM may be determined by an analysis module 218 of the driving controller 210.
[0064] At block 406, an absolute value of the difference between the RPM of the fan motor 208 and the threshold RPM is determined to be greater than a threshold. In an example, the absolute value of difference between the RPM of the fan motor 208 and the threshold RPM may be determined to be greater than the threshold by the analysis module 218. [0065] At block 408, after a predetermined time interval, a second pulse width of the voltage signal applied to the fan motor 208 is determined. In an example, the second pulse width of the voltage signal may be determined by the feedback module 216.
[0066] At block 410, a variation between the first pulse width and the second pulse width is determined. In an example, the variation between the first pulse width and the second pulse width is determined by the analysis module 218.
[0067] At block 412, the variation between the first pulse width and the second pulse width is ascertained to be greater than a threshold variation. In an example, the variation between the first pulse width and the second

pulse width is ascertained to be greater than the threshold variation by the
analysis module 218.
[0068] At block 414, based on the ascertaining, presence of
accumulated particulate matter on the inlet filter 204 is determined. In an
example, the analysis module may determine the presence of the
accumulated particulate matter on the inlet filter 204.
[0069] Although examples of the present subject matter have been
described in language specific to methods and/or structural features, it is to
be understood that the present subject matter is not limited to the specific
methods or features described. Rather, the methods and specific features
are disclosed and explained as examples of the present subject matter.

We Claim:

1.An air conditioning device comprising:
an inlet to facilitate entrance of air in a housing of the air conditioning device, the inlet having an inlet filter to filter the air entering the housing through the inlet;
a suction fan to draw the air to the inside of the housing through the inlet and the inlet filter, wherein the suction fan is coupled to a fan motor for operation; and
a driving controller coupled to the fan motor to:
determine revolutions per minute (RPM) of the fan motor; determine a difference between the RPM of the fan motor and a threshold RPM, wherein the threshold RPM indicates an RPM of the fan motor at a rated voltage of the air conditioning device;
ascertain an absolute value of the difference between the RPM of the fan motor and a threshold RPM to be greater than a threshold; and
based on the ascertaining, determine presence of accumulated particulate matter on the inlet filter.
2. The air conditioning device as claimed in claim 1, the driving controller further is to determine a first pulse width of a voltage signal applied to the fan motor.
3. The air conditioning device as claimed in claim 2, wherein the driving controller is to increase a pulse width of the voltage signal applied to the fan motor based on determining the RPM to be less than the threshold RPM.
4. The air conditioning device as claimed in claim 2, wherein the driving controller is to decrease a pulse width of the voltage signal applied to the fan motor based on determining the RPM to be greater than the threshold RPM.

5. The air conditioning device as claimed in claim 3, wherein the driving
controller is to:
determine a second pulse width of the voltage signal applied to the motor after a predetermined time interval;
determine a variation between the first pulse width and the second pulse width;
ascertain the variation between the first pulse width and the second pulse width to be greater than a threshold variation; and
based on the ascertaining, determine the presence of the accumulated particulate matter on the inlet filter.
6. The air conditioning device as claimed in claim 5, wherein the driving controller further is to indicate the presence of the accumulated particulate matter on the inlet filter by switching a notification light, transmitting a notification to a mobile device coupled to the air conditioning device, or a combination thereof.
7. The air conditioning device as claimed in claim 1, wherein the driving controller is to determine a level of accumulation of particulate matter on the inlet filter based on the difference between the RPM of the fan motor and the threshold RPM.
8. An air conditioning device comprising:
an inlet to facilitate entrance of air in a housing of the air conditioning device;
an inlet filter coupled to the inlet, to filter the air entering the housing through the inlet;
a suction fan to draw the air to the inside of the housing through the inlet and the inlet filter, wherein the suction fan is coupled to a fan motor for operation; and

a driving controller coupled to the motor to:
determine revolutions per minute (RPM) of the fan motor and a first pulse width of a voltage signal applied to the fan motor;
determine a difference between the RPM of the fan motor and a threshold RPM, wherein the threshold RPM indicates an RPM of the fan motor at a rated voltage of the air conditioning device;
determine an absolute value of the difference between the RPM of the fan motor and the threshold RPM to be greater than a threshold;
determine a second pulse width of the voltage signal applied to the fan motor after a predetermined time interval;
determine a variation between the first pulse width and the second pulse width;
ascertain the variation between the first pulse width and the second pulse width to be greater than a threshold variation; and
based on the ascertaining, determine presence of accumulated particulate matter on the inlet filter.
9. The air conditioning device as claimed in claim 8, wherein the driving controller is to determine a level of accumulation of particulate matter on the inlet filter based on the variation between the first pulse width and the second pulse width.
10. The air conditioning device as claimed in claim 8, wherein the driving controller further is to indicate the presence of the accumulated particulate matter on the inlet filter by switching a notification light, transmitting a notification to a mobile device coupled to the air conditioning device, or a combination thereof.

11. The air conditioning device as claimed in claim 9, further comprising a filter cleaning assembly to sweep off the accumulated particulate matter from the inlet filter.
12. The air conditioning device as claimed in claim 11, wherein an operation of the filter cleaning assembly is based on the level of accumulation of the particulate matter on the inlet filter.
13. A method for determining presence of accumulated particulate matter on an inlet filter of an air conditioning device, the method comprising:
determining revolutions per minute (RPM) of a fan motor driving a suction fan, wherein the suction fan draws air to the inside of a housing of the air conditioning device through the inlet filter;
determining a first magnitude of current applied to the fan motor;
determining a difference between the RPM of the fan motor and a threshold RPM, wherein the threshold RPM indicates an RPM of the fan motor at a rated current for the air conditioning device;
determining an absolute value of the difference between RPM of the fan motor and the threshold RPM to be greater than a threshold; determining a second magnitude of current applied to the fan motor after a predetermined time interval;
determining a deviation between the first magnitude of current and the second magnitude of current;
ascertaining the deviation between the first magnitude of current and the second magnitude of current to be greater than a threshold deviation; and
based on the ascertaining, determining presence of accumulated particulate matter on the inlet filter.
14. The method as claimed in claim 13, further comprising determining a
level of accumulation of the particulate matter on the inlet filter based on the

deviation between the first magnitude of current and the second magnitude of current.
15. The method as claimed in claim 13, further comprises using a filter cleaning assembly for sweeping off the accumulated particulate matter from the inlet filter.