the present invention has proved to be particularly successful when applied to a laundry drying machines , preferably a front load type laundry drying machine . it should in any case be underlined that the present invention is not limited to this type of application . on the contrary , the present invention can be usefully applied to all the laundry treating machines , such as a laundry washing machine or a combined laundry washing and drying machine . with reference to fig1 a laundry drying machine 1 according to a first embodiment of the invention is described . the laundry drying machine 1 , hereinafter referred to as dryer 1 , comprises a casing 10 formed by two couples of upright side walls 2 a - 2 d arranged perpendicularly one another , respectively on the dryer rear and front part , and on the lateral side thereof . an upper wall , not illustrated , and a bottom wall 4 close the ends of the box - like structure formed by the upright side walls 2 a - 2 d joined together . in fig1 the upper side wall has been removed for showing some of the dryer parts accommodated within casing 10 . a laundry container comprising a rotatably drum 7 is provided within the casing 10 . a front door 8 , pivotally coupled to the front upright side wall 2 a , is provided for allowing access to the drum interior region to place laundry to be dried therein . the drum 7 is advantageously rotated by an electric motor m 1 , not shown , which transmits the rotating motion to the drum 7 . in a preferred embodiment , the electric motor m 1 transmits the rotating motion to the drum by means of a belt / pulley system . in different embodiments the motor transmits directly the rotating motion to the drum . for example , in a laundry washing machine or in a combined laundry washing and drying machine where the drum is placed inside a washing tub , the electric motor may be arranged so as to have the stator connected to the washing tub and the rotor connected to the drum . the dryer 1 is connectable to a mains supply , typically 220 volts ac , by means of a power cord with a suitable plug , not illustrated the dryer 1 comprises an air circulating system adapted to circulate a flow of drying air into the drum 7 . the air circulating system preferably comprises a fan f 1 , not illustrated , which blows a flow of drying air through the drum 7 and the laundry placed therein . the fan f 1 preferably comprises an electrical motor connectable to the mains supply , wherein the electrical input power of the motor is preferably less than 50 watt , more preferably 30 watt . the air circulating system preferably comprises a heating device h 1 , not illustrated , adapted to heat up the air flow at a location upstream of the drum 7 . preferably the heating device h 1 comprises an electric heating element r 1 , such as an electrical resistance , arranged upstream of the drum 7 along the air flow . the electric resistance r 1 is preferably connectable to the mains supply and preferably has a dissipated power value about 2 kwatt . the dryer 1 , then , advantageously comprises a temperature sensor t 1 for the control of the temperature inside the drum 7 and / or the control of the temperature of the laundry placed therein . the dryer 1 is advantageously of the condenser type and comprises condensing means arranged downstream of the drum 7 for cooling and dehumidifying the moist air coming from the drum 7 . preferably , condensing means are in the form of an air - air cross - flow type heat exchanger which is preferably provided on the bottom portion of the dryer 1 . condensation water formed in the condensing means is advantageously collected in a sump at the bottom of the dryer , not illustrated , and conveyed to an extractable moisture tank 9 located at the upper portion of the dryer 1 . the moisture tank 9 is preferably in the form of a drawer slidably arranged on said upper portion of the dryer 1 so that it can be easily and periodically emptied by a user . a pump p 1 , not illustrated , opportunely pumps the condensation water from the sump to the tank 9 . the pump p 1 preferably comprises an electrical motor connectable to the mains supply . the electrical input power of the motor is preferably less than 100 watt , more preferably 50 watt . the dryer 1 preferably comprises a humidity sensor s 1 that detects the moisture level of the laundry . the moisture level detected represents a useful parameter which may be used to determine the duration of the drying cycle . furthermore , the dryer 1 preferably comprises a door switch sw 1 which detects the closed position of the door 8 . a user control interface 11 is preferably arranged on the top of the casing 10 . the user control interface 11 is preferably accessible to the user for the selection of the drying program and insertion of other parameters , for example the load in terms of weight of the laundry to be dried , the type of fabric of the load , the degree of dryness , etc . the user control interface 11 preferably displays machine working conditions , such as the remaining time , alarm signals , etc . for this purpose the user control interface preferably comprises a rotatable selector 12 and a display 13 . in different embodiments , for example in a laundry washing machine or in a combined laundry washing and drying machine , the user may selects and inserts other types of parameters , for example the washing temperature , the spinning speed , etc . according to the invention , a control unit 20 is arranged inside the casing 10 at the top portion thereof . the control unit 20 is advantageously connected to the various parts of the dryer 1 , or peripheral units , in order to ensure its operation . the control unit 20 comprises a printed circuit board 21 that supports the electric and / or electronic devices 22 which assure functioning of the peripheral units and of the dryer 1 , as will be better explained hereinafter . the control unit 20 also preferably comprises a cover 23 which protects the electric and / or electronic devices 22 . the control unit 20 is advantageously laterally arranged inside the casing 10 close to an upright side wall 2 a , the right one with reference to fig1 . the control unit 20 is preferably placed inside the casing 10 and above the drum 7 or the washing tub through snap - in fastener means . more preferably electrical connectors are associated to said snap - in fastener means allowing therefore both the mechanical and the electrical connection . fig4 shows a schematic view of the control unit 20 according to the invention wherein blocks represent different sections 24 - 32 of the control unit 20 . each section 24 - 32 comprises suitable electric and / or electronic devices 22 . fig5 shows the control unit 20 of the dryer 1 connected to various peripheral units m 1 , f 1 , h 1 , t 1 , p 1 , s 1 , sw 1 , 11 . the control unit 20 preferably comprises a power section 24 , indicated with a dashed line in fig4 , a low power loads section 27 , a high power loads section 28 , a machine sensors section 29 , a humidity sensor control section 30 and a control and communication section 31 . the power section 24 preferably comprises an input line section 25 and a power supply section 26 . the input line section 25 comprises devices suitable for lowering and / or rectifying the voltage from the mains supply to which the dryer 1 is connected . devices of this section may comprise , for example , transformers rectifiers , filters , etc . the power supply section 26 is connected to the input line section 25 and furnishes the proper supply voltage to other sections of the control unit 20 . devices of this section may comprise , for example , linear regulators . in different embodiments the input line section 25 and / or the power supply section 26 may be connected to energy storage devices such as batteries , fuel cells , solar cell , etc . the low power loads section 27 preferably comprises devices suitable for controlling low power loads , such as the fan f 1 or the pump p 1 . the expression “ low power loads ” may be generally referred to loads wherein the power dissipation is preferably less than 100 watt . the low power loads and section 27 preferably comprises switching devices suitable for controlling , for example switch on and / or switch off , the motors of the fan f 1 and / or of the pump p 1 . in different embodiments , this section 27 may control and drive other components . for example this section 27 may control electrovalves or may control and drive the pumps which are disposed in the water inlet circuit and / or in the water outlet circuit of a laundry washing machine . further , this section 27 may advantageously control a steamer in laundry treating machines where a steamer unit is provided . in fact a steamer unit may be provided in laundry washing machine in order to increases the washing temperature of the laundry and / or to assist cleaning of the laundry . a steamer unit may be provided in a dryer in order to soften and refresh laundry during the drying treatment . the steamer unit can be any type of device that converts the liquid to steam . a first type of steamer unit can be a tank - type steam generator that stores a volume of liquid and heats the volume of liquid to convert the liquid to steam . the steamer unit preferably comprises an electrical heater , preferably an electrical resistance , which is immersed in a minimum quantity of water of said tank for the production of steam . in a preferred embodiment , the water is preferably conveyed into the tank through a water supply pipe from an external water supply by means of a controlled water supply valve . in this case , the low power loads section 27 preferably controls and drives such water supply valve . in a further embodiment the water may be preferably conveyed into the tank by means of a water pumping motor connected to an external water supply . the water pumping motor preferably comprises an electrical motor connectable to the mains supply . the electrical input power of the motor is preferably less than 100 watt , more preferably 50 watt . in this specific case , the low power loads section 27 preferably controls and drives the water pumping motor . a second type of steamer unit can be an in - line steamer unit . the in - line steamer unit converts the liquid to steam as the liquid flows through the steam unit itself . the steamer unit in this case preferably comprises an electrical heater , more preferably an electrical resistance , which heats the water flowing in a duct . the water is conveyed into the duct by means of a water pumping motor which suck water from a tank . the water pumping motor preferably comprises an electrical motor connectable to the mains supply . the electrical input power of the motor is preferably less than 100 watt , more preferably 50 watt . in this case , the low power loads section 27 preferably controls and drives the water pumping motor . in a further embodiment the in - line steamer unit can be connected directly to the water mains via a valve and the low power loads section 27 preferably controls and drives said valve . devices of this section 27 may comprise , for example , electronic components like solid - state relays ( triac , acs , etc . ), optical isolators , transistors , capacitors , resistors , etc . the high power loads section 28 preferably comprises devices suitable for controlling high power loads , such as the heater h 1 . the heater h 1 preferably comprises an electrical resistance r 1 , as said before . the expression “ high power loads ” may be generally referred to loads wherein the power dissipation is preferably higher than 100 watt . the high power loads section 28 preferably comprises high power switching devices suitable for controlling , for example switch on and / or switch off , the electrical resistance r 1 . in different embodiments , the heater h 1 may comprises a second electrical resistance r 2 in order to better control the air temperature of the drying air flow . in this case , the high power loads section 28 preferably controls , i . e . switches on and / or switches off , the second resistance r 2 too . the second electric resistance r 2 is preferably connectable to the mains supply and preferably has a dissipated power value about 600 watt . for example in case of a laundry treating machine having a steamer unit , as mentioned above , this section 28 may switch on and / or switch off the electrical resistance of the steamer unit itself . the electric resistance of a steamer unit is preferably connectable to the mains supply and preferably has a dissipated power value about 2 kwatt . in a further embodiment , for example in a laundry washing machine , the high power loads section may comprise a switch which activates and deactivates the heater which heats the washing water , the heater being typically an electrical resistance . the electric resistance of such water heating unit is preferably connectable to the mains supply and preferably has a dissipated power value about 2 kwatt . if the laundry washing machine is also provided with a steamer unit then this section 28 advantageously controls also the electrical resistance of the steamer unit itself . devices of this section 28 may comprise , for example , electromagnetic or solid - state relays , transistors , etc . the machine sensors section 29 preferably comprises devices suitable for detecting and elaborating signals coming from sensors of the dryer 1 , such as the temperature sensor t 1 and the door switch sw 1 . in different embodiments , this section 29 may detect and elaborate other signals , such as a signal coming from a water level sensor placed inside the sump which collects the moisture , or a signal coming from a water level sensor placed inside the washing tub in a laundry washing machine or a signal coming from a lint filter monitoring sensor in a dryer . the sensors section 29 is preferably powered by the power supply section 26 . devices of this section 29 may comprise , for example , transistors , capacitors , resistors , etc . the humidity sensor control section 30 preferably comprises devices suitable to detect and elaborate signals coming from the humidity sensor s 1 . such elaborated signals are preferably used to determine the dryness of the clothes and therefore the duration of the drying program . in a preferred embodiment the humidity sensor s 1 may comprise elements which are contacted by the tumbling clothes during a drying operation . preferably the elements comprise a pair of electrodes which are provided within the dryer and face toward the interior of the dryer drum 7 such that clothes being tumbled and dried will periodically engage and bridge the electrodes . the sensed resistance between the electrodes is used to determine the dryness of the clothes . a high resistance between the electrodes is indicative of dry clothes . a low resistance between the electrodes is indicative of wet clothes . appropriate control circuitry , including time delays , make it possible to determine when the clothes have reached a desired dryness condition . in different embodiments any other equivalent sensor device may be used in order to detect the dryness condition of the clothes . devices of the humidity sensor control section 30 may comprise , for example capacitors , resistors , etc . preferably this section is electrically insulated from the humidity sensor s 1 and advantageously comprises insulator devices like optical isolators or transformers . in different embodiments where the electrical insulation is not required for the humidity sensor s 1 , this humidity sensor control section 30 may be part of the above described machine sensors section 29 . the control and communication section 31 advantageously communicates with all said sections 24 - 30 and with the user control interface 11 . the control and communication section 31 preferably comprises a main microcontroller . this section 31 gets data from the rotatable selector 12 , outputs data for the display 13 and controls other sections 24 - 30 during the drying cycle . in different embodiments data from the rotatable selector 12 and to the display 13 may be elaborated in an intermediate local microcontroller which , in turn , communicates with the main microcontroller . the control and communication section 31 is preferably powered by the power supply section 26 . according to the invention , the control unit 20 preferably comprises a motor control section 32 . more preferably , the control unit 20 comprises a drum motor control section 32 . in different embodiments , the control unit 20 may alternatively comprise a compressor motor control section , preferably a compressor motor of a heat pump unit , as described later in the description . the motor control section 32 preferably comprises an inverter motor control so that the speed of the drum electric motor m 1 may be controlled . therefore , the motor control section 32 advantageously sets and controls the speed of the drum 7 during the drying cycle . the motor control section 32 is preferably powered by the input line section 25 . in particular the inverter motor control is connected to a direct current ( dc ) source provided by a rectifier section of the input line section 25 . devices of the motor control section 32 may comprise , for example , oscillators , igbt , mosfet , drivers , logic control units , sensors for temperature protection and current limiting , etc . in further embodiments , said devices may be integrated into a single embedded device . advantageously , the control unit 20 of the invention with its sections 24 - 32 incorporates almost all the electric and / or the electronic devices 22 indispensable for the dryer functioning . the quantity of wiring connections between the devices 22 and the peripheral units 24 - 32 are therefore widely reduced with respects to the known dryers , and more in general to the known laundry treating machines . reduction of the wiring connections causes also a reduction of electromagnetic emissions and , at the same time , increases immunity with respect external electromagnetic disturbance . more , the provision of such a control unit 20 with a preferably single printed circuit board 21 allows positioning of the electric and / or electronic devices 22 with an efficient layout in order to reduce the overall dimensions of the control unit 20 and , eventually , of the machine . furthermore , the provision of such a control unit 20 with almost all the devices of the machine mounted thereon helps detection and repairing of failures when they occur . with reference to fig6 and 7 a further construction variant of a control unit 120 is described . this control unit 120 differs from the control unit 20 previously described for the fact that it comprises a further motor control section 132 . the control unit 120 is suitable to be installed in a dryer of the type previously described which further comprises a heat pump unit hp . dryers provided with a heat pump unit hp are widespread . the heat pump unit hp both dehumidifies and heats the air flow which dries the laundry . the heat pump unit hp preferably comprises a closed circuit formed by a first heat exchanger , for example an evaporator or a gas heater , a second heat exchanger , for example a condenser or a gas cooler , a compressor connecting the two heat exchangers and expansion means . the first heat exchanger of the heat pump hp cools and dehumidifies the moist air coming from the drum 7 . the cooled and dehumidified air is then heated up by the second heat exchanger of the heat pump hp and conveyed again inside the drum 7 . in the preferred embodiment here described , the dryer is also provided with a heating device h 1 which helps the second heat exchanger to heat up the air . preferably the heating device h 1 comprises an electric heating resistance r 1 arranged upstream of the drum 7 along the air flow . more preferably the heating device h 1 comprises a second electrical resistance r 2 in order to better control the air temperature of the drying air flow . activation and deactivation of the first and / or of the second electric heating resistances r 1 , r 2 is properly controlled by the high power loads section 28 . preferably both the resistances r 1 , r 2 are activated at the beginning of the laundry drying program while one or both of them are deactivated when the heat pump hp reaches an optimal working condition . in different embodiments , only the heat pump hp may be provided to heat up the air temperature while the heating device h 1 may be avoided . the compressor of the heat pump hp preferably comprises a variable speed electric motor m 2 . the motor control section 132 , therefore , preferably comprises an inverter motor control so that the speed of the heat pump motor m 2 may be easily controlled . devices of this section may comprise , for example , oscillators , igbt , mosfet , drivers , logic control units , sensors for temperature protection and current limiting , etc . in further embodiments , said devices may be integrated into a single embedded device . the control and communication section 31 then advantageously communicates with the further motor control section 132 . with reference to fig8 and 9 a further construction variant of control unit 220 is described . the control unit 220 comprises a printed circuit board 221 that supports the electric and / or electronic devices which assure functioning of the machine where it is installed . on the printed circuit board 221 a plurality of sections are provided , namely : a power section 24 , a low power loads section 27 , a high power loads section 28 , a machine sensors section 29 , a humidity sensor control section 30 , a control and communication section 31 and a motor control section 32 . the printed circuit board 221 further comprises a first empty seat 221 a predisposed to receive devices of a further motor control section 132 , for example a control section for a heat pump motor . the printed circuit board 221 further comprises a second empty seat 221 b inside the high power loads section 28 , predisposed to receives devices for a steamer control section , for example a steamer switch sw 2 which activates and deactivates the electrical resistance of a steamer unit . advantageously a multipurpose printed circuit board 221 according to this embodiment may be used for the realization of control units 20 , 120 , 220 of different types , for example a control unit 120 for a dryer with a heat pump or a control unit 20 for a dryer without a heat pump . this multipurpose printed circuit board 221 allows reduction of the overall production costs of laundry treating machines wherein such a multipurpose boards 221 are installed . in further embodiments , the laundry treating machines may comprise further temperature sensors . for example a laundry washing machines may preferably comprise a temperature sensor which detects the temperature of the washing water . other temperature sensors may be used to control overheat of peripheral units . for example a sensor temperature may be placed near the electrical resistance or near the condenser of a heat pump to check its working temperature . in the following some examples of laundry treatment machines in which a control unit according to the invention may be installed are provided . a laundry drying machine having an air heating device comprising one or two electrical resistances to heat up the air . a laundry drying machine having an air heating device comprising one or two electrical resistances to heat up the air and having a steamer unit comprising an electrical resistance and a water supply valve . a laundry drying machine having an air heating device comprising one or two electrical resistances to heat up the air and having a steamer unit comprising an electrical resistance and a water supply pumping motor . a laundry drying machine using a heat pump to heat up the air . the heat pump may preferably comprise a compressor motor , more preferably a speed controlled electric motor . a laundry drying machine using a heat pump and one or two electrical resistances to heat up the air . the heat pump may preferably comprise a compressor motor , more preferably a speed controlled electric motor . a laundry drying machine using a heat pump to heat up the air and having a steamer unit comprising an electrical resistance and a water supply valve . the heat pump may preferably comprise a compressor motor , more preferably a speed controlled electric motor . a laundry drying machine using a heat pump to heat up the air and having a steamer unit comprising an electrical resistance and a water supply pumping motor . the heat pump may preferably comprise a compressor motor , more preferably a speed controlled electric motor . a laundry drying machine using a heat pump and one or two electrical resistances to heat up the air and having a steamer unit comprising an electrical resistance and a water pumping motor . the heat pump may preferably comprise a compressor motor , more preferably a speed controlled electric motor . a laundry washing machine having a water heating device comprising an electrical resistance to heat up the water . a laundry washing machine having a water heating device comprising an electrical resistance to heat up the water and having a steamer unit comprising an electrical resistance and a water supply valve . a laundry washing machine having a water heating device comprising an electrical resistance to heat up the water and having a steamer unit comprising an electrical resistance and a water supply pumping motor . a combined laundry washing and drying machine which may comprises one or more features of the above listed laundry drying machine and laundry washing machine . it has thus been shown that the present invention allows all the set objects to be achieved . in particular , it makes it possible to obtain a laundry treating machine with a reduced constructional complexity with respect to the laundry treating machines of known type . clearly , changes may be made to the laundry drying machine as described herein without , however , departing from the scope of the present invention . therefore , while the treating drying machine has been described with reference to a laundry drying machine , it should be noted that the present invention is not limited to the specific embodiment illustrated and described herein ; on the contrary , further variants of the embodiments described herein fall within the scope of the present invention , which is defined in the claims .