Patent Publication Number: US-2010131119-A1

Title: Communication system between control units for irrigation devices

Description:
The present invention relates to a communication system between control units for irrigation devices. 
     The control of irrigation devices by means of control units placed at positions which are easily accessible from the irrigation area is known in the state of the art. The control units may be programmed by a user to set the irrigation time periods on various days of the month and during each month of the year. The setting of the irrigation time periods may be modified depending on the environmental conditions or on other events. 
     Each control unit may control up to a given number of irrigation devices; the use of a greater number of irrigation devices and a certain number of control units is therefore required for very broad irrigation areas. 
     In some cases, the irrigation systems include a main control unit and secondary control units and communication devices between the main control unit and the secondary control units are provided for the transmission of data regarding the irrigation time periods and the state of the control units. In the case in which the control units are battery powered, the communication between the control units may require an excessive consumption of energy to the detriment of the battery life. 
     In view of the state of the art, the object of the present invention is to provide a communication system between control units for irrigation devices which allows the exchange of data between control units, specifically for battery powered control units. 
     According to the present invention, such an object is achieved by means of a communication system between a main control unit for irrigation devices and at least one secondary control unit for irrigation devices, specifically for battery powered control units, each control unit including a module for the transmission of data to the other control unit and for the reception of data from the other control unit, characterised in that said main control unit and said at least one secondary control unit include means adapted to allow the power supply of said data transmission and reception modules only during the time periods required for the exchange of data between the main control unit and at least one secondary control unit. 
    
    
     
       The features of the present invention will become more apparent from the following detailed description of a practical embodiment thereof, shown by way of non-limitative example in the accompanying drawings, in which: 
         FIG. 1  is a diagram of a communication system between irrigation device control units according to a first embodiment of the invention; 
         FIG. 2  is a diagram of a communication system between irrigation device control units according to a second embodiment of the invention. 
     
    
    
       FIG. 1  shows a diagram of a communication system between irrigation device control units according to a first embodiment of the invention. The diagram shows a main control unit or a main module  100  and at least one secondary control unit or expansion module A 1  . . . An, although a plurality of secondary control units A 1  . . . An is preferable; the control units are battery powered and therefore have a limited power supply in the course of time. The control unit  100  includes a module  10  for the transmission and the reception of data and each of the control units A 1  . . . An includes a module  20  for the transmission and the reception of data. 
     In  FIG. 1 , the modules  10  and  20  are provided with two terminals A and B for the connection by means of a connection cable  30 , for instance a standard RS-485 wire, and a terminal C for the connection to ground GND. 
     The main control unit  100  and each secondary control unit A 1  . . . An are provided with a terminal W for another connection by means of a cable  40 . The connection by means of the cable  40  allows to minimize energy consumption during the communication between the control units; the cable  40  is a two-way wake-up line. 
     Both the control unit  100  and each of the control units A 1  . . . An include respective data processing devices  4 ,  8  provided with a memory on which an application software is installed and runs. The devices  4  and  8  provide for the control of the modules  10  and  20 . 
     When the main control unit  100  must communicate with one or more control units A 1  . . . An, the device  4  operates to enable the line  40  in order to send the information regarding the request for communication between the main control unit  100  and the secondary control units A 1  . . . An which are addressed by means of the cable  30  and it then operates to enable the device  10  for the transmission of data by means of a signal En. 
     The devices  8  of all of the control units A 1  . . . An which receive the request for information from the control unit  100  operate to enable the modules  20  for the reception of data by means of an enabling signal En and the communication starts. At the end of the communication, the wake-up line is disabled again by the device  4  of the main control unit  100  and the system returns to a low energy state. Therefore, the modules  10  and  20  are enabled only for the time T required for the exchange of data between the main control unit  100  and the secondary control units A 1  . . . An which have received the request for information. 
     It may also occur that one of the secondary control units A 1  . . . An must communicate with the main control unit  100 ; in this case the device  8  of the control unit A 1  . . . An which requests the communication operates to enable the line  40  to send the information regarding the request for communication with the main control unit  100  by means of the cable  30  and then operates to enable its own device  20  by means of a signal En for the transmission of data. The device  4  of the main control unit  100  operates to enable the module  10  for the reception of data by means of an enabling signal En and the communication starts. At the end of the communication the wake-up line is disabled and the system returns to the low energy state. Therefore, the modules  10  and  20  are enabled only for the time T required for the exchange of data between the main control unit  100  and the secondary control unit A 1  . . . An which has requested the communication. 
     The communication between the main control unit  100  and the control units A 1  . . . An may be requested by the control unit  100  when there is a variation in the state of the irrigation devices, when the single control units need to be initialized, when the operation of the single control units needs to be set or the firmware of the single control units needs to be updated. 
     The communication between the main control unit  100  and the control units A 1  . . . An may be requested by one of the control units A 1  . . . An when a variation of the state of the sensors results in the need to inform the control unit  100  so that it operates accordingly. 
       FIG. 2  shows a diagram of a communication system between irrigation device control units according to a second embodiment of the invention. Said communication system differs from the system in  FIG. 1  in that it communicates in a different manner, i.e. not through a connection cable but instead by means of the data transmission by radio frequency over the air. 
     The main control unit or main module  100  and the plurality of secondary control units A 1  . . . An are always of the battery powered type. The main control unit  100  always includes the module  10  for the transmission and the reception of data and each one of the control units A 1  . . . An includes the module  20  for the transmission and the reception of data; the modules  10  and  20  are always controlled in order to transmit or receive data from the processing devices  4  and  8 . The modules  10  and  20  are generally provided in this case with two radiofrequency transceivers  101  and  200 , preferably a 433 MHz radio frequency, with a corresponding antenna for the transmission and reception of data over the air; the transceiver  101  is generally arranged outside the body of the control unit  100  which includes the module  10  and the processing device  4 , although it may also be arranged within the body of the control unit  100 . The transceivers  101  and  200  may also allow a data transmission with a Bluetooth or Wireless Lan system. 
     The main control unit  100  and the secondary control units A 1  . . . An are reciprocally synchronized by sending a global command by the control unit  100  to all of the control units A 1  . . . An at predetermined time intervals Tp, for instance corresponding to one minute. In this manner, the devices  8  of the control units A 1  . . . An hold the transceiver  200  always disabled although the module  200  is activated every minute, synchronously with all of the control units A 1  . . . An, by means of a signal En to verify the presence of data to be transferred. 
     The communication between the main control unit  100  and the control units A 1  . . . An may be requested by the control unit  1  when there is a variation in the state of the irrigation devices, when the single control units need to be initialized and synchronized, when the operation of the single control units needs to be set or the firmware of the single control units needs to be updated. 
     The communication between the main control unit  100  and the control units A 1  . . . An may be requested by one of the control units A 1  . . . An when a variation of the state of the sensors results in the need to inform the control unit  100  of the variation. 
     The state of the irrigation devices may be sent by the secondary control units A 1  . . . An to the main control unit  100  each minute when the synchronism occurs. Such a communication occurs over a time period T 1  . . . Tn assigned to each secondary control unit and is related to its identification number. 
     In this manner, when the state of the sensor needs to be sent and only then, does a secondary control unit A 1  . . . An also enable its transmitter module  200 . As the transmission power is higher than that required when receiving, this technique also allows to considerably limit energy consumption. 
     For instance, a minute may be subdivided into 20 3-second time windows, each one of which has a duration of 3 seconds. 
     During the first time window T 0 =3s, the state of the valves and a command informing all of the secondary control units A 1  . . . A 19  on how to behave during the remaining sequential time windows T 1  . . . T 19  are sent by the main control unit. 
     Normally, after the first time window, the main control unit  100  starts to receive and the secondary control units A 1  . . . An one at a time transmit only during the time windows T 1  . . . Tn assigned thereto. The commands sent by the main control unit  100  during the first time window T 0  could request the secondary control units A 1  . . . An not to transmit for the following minute or to receive again during the time window assigned thereto for possible operation parameter update functions. Another command could be for instance to reprogram the firmware of all of the secondary control units A 1  . . . An. The possibility to receive commands during the first time window allows for other possibilities or future requirements. 
     A communication system between the control units of the irrigation devices may be provided according to a variant of the above said embodiments, the main control unit  100  of the communication system being provided both with a module  10  having terminals A and B for the cable connection with some control units, such as in  FIG. 1 , and with a radiofrequency transceiver  101  for the communication over the air with other control units, such as in  FIG. 2 . 
     For the system in  FIG. 1 , in the case in which there are no energy consumption issues, for instance when the control units  100  and A 1  . . . An are power supplied by a network or have recharged batteries, the number of cables may be reduced by eliminating the line  40  and short-circuiting it towards the ground GND on each control unit.