Abstract:
An safety control system especially useful for controlling the irrigation of crops. The system includes a transmitter having an extended range over two miles. A repeat cycle timer provides a repetitive time delayed input signal to the transmitter which transmits a signal while an irrigation system is operational. A receiver for receives the signal from the transmitter, and a time delay relay latches upon receipt of the signal by the receiver to close a circuit and provide power to a pump unit for a fixed amount of time. If the time delay relay times out without receiving a signal from the transmitter, the irrigation pump unit is shut off.

Description:
This application claims benefit of provisional application No. 60/133,215 filed May 7, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to safety shut-off systems for agricultural irrigation systems, and, more particularly, to an improved wireless safety shut-off system that is reliably operable over an extended range of several miles. 
     In irrigation systems used in agricultural applications, a typical irrigation system consists of an electrically powered pivot system that circles a field comprising an agricultural crop. The irrigation system further includes a pumping unit that is usually a distance of several thousand feet or even a few miles from the pivot system. To avoid costly damage and wasted resources, the pivot system and pump unit has an automatic shut-off that is triggered by a loss in water pressure, a burn out of underground electrical lines, or a pipe breakage between the pump unit and the pivot system. Malfunctions of the drive motor on the pivot system tower or misalignment of the pivot system could also trigger an automatic shut-off of the pivot system and the pump unit. 
     In the conditions described, the result could be costly if the pivot system and the pump unit did not shut down properly. For instance, water could run in one place which would result in the system not restarting and could cause the field to erode and damage the crop and hamper harvesting. If an underground pipe broke, a large hole could form in the field that would require costly repairs. If the system was being used to spray nitrogen and the system kept watering, but the system stopped in one place, the nitrogen could harm the crop. Further, a stalled system could cause wastefulness in the use of water, fuel, and chemicals. 
     In practice, if a farmer does not have an operational safety on his irrigation system, he must operate his system manually with human supervision of the system&#39;s operating condition, or he risks severe damage to his crops. Electricity rates are generally cheaper during off-peak hours. Therefore, the farmer must stay awake and supervise the irrigation system at night to reduce costs by taking advantage of the lowest electricity rates. 
     In the prior art there are wireless type safety systems that are generally being used for water system control and sewage pump stations. However, these wireless systems are generally expensive because of the cost of materials to provide a reliable safety control system. For example, the cost of materials for a safety control system for one irrigation pivot system and one pumping unit would be a minimum of $4000 using known wireless systems. A system this expensive is generally cost prohibitive to farmers. 
     Other systems have been proposed that use radio waves for switching loads on and off. The systems include a radio transmitter and receiver and work well, except for two major faults. These prior radio wave wireless systems operated by having a transmitter and receiver in the line of sight of each other only. Further, these prior radio wave systems had a range of less than a mile. These disadvantages or faults cause the known methods of using radio waves for irrigation safety control systems to be impracticable because of the distance between a pivot system and a pumping unit in an irrigation system. Other known wireless systems such as cellular communications systems carry costly periodic charges. 
     The present invention overcomes the above-mentioned and other disadvantages of the prior art systems with a novel and improved wireless safety shut-off system that is reliably operable over an extended range of several miles. 
     SUMMARY OF THE INVENTION 
     The present invention provides a wireless irrigation control safety system having a range of two to four miles by using a transmitter operating at 10 watts and providing a 27.255 MHz frequency digital signal. A receiver is provided for receiving said digital signal. The extended range transmitter product used by the present invention is also used in the home security industry. However, this product and receiver did not prove to be very dependable for use in an irrigation control safety system without further improvement. In the known applications using the extended range transmitter and receiver disclosed herein, the transmitter sends one signal to the receiver. If the receiver does not recognize or receive the signal, nothing happens. Experiments found the receiver would fail to receive a signal about 10% of the time, which is an unacceptable fault rate for a critical function such as irrigation system safety control. 
     In the present invention, a signal is sent every 30 seconds from the transmitter to the receiver. The signal received from the transmitter causes the system to continue running. The signal is used at the receiver to latch a relay in the made position (pump on). This relay starts timing off at an adjustable rate, for example 100 seconds, when a signal is received from the transmitter by the receiver. Every time a signal is sent from the transmitter, the latch relay starts back at timing off at 100 seconds. This latch relay with time delay allows the receiver to miss three signals from the transmitter before the system will safety-off. 
     Therefore, it is an object of the invention to provide an inexpensive and simple wireless safety shut-off system for agricultural crop irrigation systems. 
     It is another object of the invention to provide a wireless safety shut-off system that is very reliable. 
     It is yet another object of the invention is to provide a wireless safety shut-off system having a range of at least two miles. 
     Still a further object of the invention is to provide a wireless safety shut-off system for agricultural crop irrigation systems that may be packaged and marketed for others to install in the quantity required by the user. 
     And another object of the invention is to provide a means to replace old safety wiring in agricultural irrigation systems with a reliable wireless safety shut-off system. 
     The above and other objects, features and advantages of this invention will become more apparent from the following detailed description, when considered in connection with the accompanying drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of the receiver panel of the present invention. 
     FIG. 1 a  is a schematic view of the relay output of the receiver contained within the receiver panel of FIG.  1 . 
     FIG. 2 is a schematic view of a typical irrigation system safety circuit. 
     FIG. 3 is a schematic view of the transmitter switch panel of the present invention. 
     FIG. 3 a  is a schematic view of the transmitter trigger device contained within the transmitter switch panel of the present invention. 
     FIGS. 4 and 4 a  are schematic views of a variation of the wireless safety control system of the present invention. 
     FIG. 5 is a schematic view of a variation of the wireless safety control system of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 is a receiver panel unit  18  for the wireless safety control system. The receiver panel unit includes a multi-tap hook up terminal  20  for connecting a 120-volt AC power source or a 12-volt DC power source. All of the relays connected to the panel operate on 12-volt DC. Thus, a 120-volt AC to 12-volt DC transformer  22  is installed in each switch or panel to convert power provided at 120-volt AC to 12-volt DC so that the user can hook up to either power source without further action. The above features and others make the safety shut-off system herein one that may be packaged and marketed for others to install. 
     A time delay off relay  24  is connected to the 12-volt DC source and a switch  26  is provided to initiate contact with the relay  24 . The signal received by a receiver  28  causes the time delay relay  24  to latch an internal solid state latching relay in the made position which causes the pump unit  34  to become and remain activated. Upon latching, the time delay relay  24  starts timing off at an adjustable rate. One-hundred seconds would be a suitable time delay for the relay  24  to time off if a signal is not received by the time delay relay start switch  26 . When a subsequent signal is received from a transmitter  30  by the switch  26 , the relay  24  resets and begins timing again for one-hundred seconds. The one-hundred second time delay permits the system to miss receiving three consecutive signals from the transmitter  30  before the relay  24  will safety-off. The delay process and requirement for the system to miss three consecutive signals before latching off creates a very reliable safety system that does not incur false safety-off occurrences. The preferred embodiment of the invention uses a solid state device  24  that includes a latching relay and a time delay relay in one unit  24 . The solid state time delay relay  24  operates on 12 volts DC and provides a reliable and cost-effective relay. The time delay relay  24  receives its input from an output relay  32  on the radio frequency receiver  28  that receives a signal from the remote transmitter  30 . 
     The receiver panel unit  18  further includes terminals  46  and  48  that connect to a starter of a pump unit  34  for automatic operation of the pump unit  34  or shut down circuitry of a diesel pump unit  34 . Should the receiver  28  not receive a signal from the transmitter  30  in the one-hundred seconds allotted by the time delay relay  24 , the receiver panel  18  will provide an output and trigger the shut down of the pump unit  34 . 
     Typically, an irrigation system will include an irrigation control panel  36  located on the pivot system tower near the pivot axis of the pivot system. As shown, the irrigation control panel  36  has a safety circuit  38  with terminals  50  and  52  located on the irrigation control panel  36 . 
     In the present invention, a transmitter switch panel  16  is connected to the irrigation control panel circuitry  36  and is powered by a 120-volt AC current that is converted to 12-volt DC. The transmitter switch panel  16  includes a repeat cycle solid state timer  42 , labeled RC 1  in FIG. 3, that operates on the 12-volt DC current and repeats its clock cycle at an interval of time. In the preferred embodiment, the repeat cycle timer  42  provides an on input cycle for two seconds and then times for a thirty second delay before it sends another two second on input cycle signal. These time delays may be set according to the desired application settings. The inventor has found that setting the time delay for fifteen seconds rather than thirty may cause transmitter  30  to overheat because of the transmission frequency. As long as the transmitter switch panel  16  is receiving power from the irrigation system control panel  36 , the on input signal will be generated periodically by the timer  42  and will be carried by the transmitter switch panel circuitry  16  to triggering relay contacts  44  on the transmitter  30  that is connected to the timer  42 . The transmitter triggering contacts  44  are set to the normally open position. Thus, when the on input signal is received by the transmitter  30 , the transmitter contacts  44  close and send a latching signal to the receiver  28 . 
     FIGS. 4 and 5 represent a variation of the wireless safety control system of the present invention. The system depicted in FIGS. 4 and 5 provide additional improvements to the basic control system unit shown in FIGS. 1 and 3. In particular, the design illustrated in FIGS. 4 and 5 provides safeguards against false activation signals and isolates the wireless safety system controls from the existing controls on the irrigation system. 
     The transmitter panel  54  of the irrigation safety control system shown in FIG. 4 includes a three position switch  56 . When the switch is turned left to a start position  58 , the circuit causes the transmitter  60  to transmit a signal at a first channel selection, channel A, by closing the relay  62 , labeled CH-A, on the circuit. In the preferred embodiment of the invention, channel A is set as channel one on the transmitter  60  and receiver  72 . The receiver panel circuitry  70  of FIG. 5 is configured such that a signal on channel A must be received for further operation. The switch  56  may be spring loaded when turned to the left start position  58  so that the switch  56  will automatically return to a middle or off position  64  when released. Transmitting the signal on the first channel, channel A, to the receiver  72  latches a twenty (20) second time delay off relay  74 , labeled TD 1 , located in the receiver panel  70  as shown in FIG.  5 . This gives the user twenty (20) seconds to turn the three position switch  56  to the right to a third position, which is the run position  66 . The time delay of the time delay off relay  74  may be changed according to the users desired specifications. 
     When the switch  56  is turned to the run position  66  a repeat cycle relay  68 , labeled RC 1  in FIG. 4, is activated on the transmitter panel  54  causing the auxiliary contacts  75  to close. The repeat cycle relay  68  causes the transmitter  60  to transmit a signal at a second channel selection, channel B, by closing the channel B transmitter contacts  76 , labeled as CH-B, on the transmitter panel circuit  54  of FIG.  4 . In the preferred embodiment of the invention, channel B is set as channel four on the transmitter  60  and receiver  72 . The channel B signal is activated by the repeat cycle relay  68  for two (2) seconds every thirty (30) seconds. The channel B signal cycle is repeated until the irrigation safety control system is turned off or until the safety circuit  38  on the irrigation system pivot control box is kicked out. 
     As shown in FIG. 5, when the receiver  72  receives a channel A signal and contacts  96  are closed, the internal switch  94  of time delay off relay  74  is activated and gives the user twenty seconds to turn the switch  56  to the run position  66  and cause the channel B signal to be transmitted to the receiver  72 . During the twenty seconds that the time delay off relay  74  is energized and latched, the contacts  78  of the time delay relay  74  will be closed. If the channel B signal is not received by the receiver  72 , the receiver panel  70  will not provide activation of the irrigation pump unit  34 . However, if the channel B signal is received by the receiver  72 , then the channel B contacts  100  are closed and an internal switch  98  is activated and latches a one-hundred second time delay off relay  80 , labeled as TD 2 . The time delay of the second time delay off relay  80  may be varied according to the users desired settings and the timing of the repeat cycle relay  68  that causes the transmitter  60  to send a signal to the receiver  72 . 
     Latching the time delay relay  80  activates the control relay  82 , labeled as CO 1 , and closes the contacts  102 . As the time delay off relay  80  is timing off for one-hundred seconds, the transmitter  60  is sending channel B signals to the receiver  72  every thirty (30) seconds as regulated by the repeat cycle relay  68 . Every time the receiver  72  receives the channel B signal time delay off relay  80  resets at one-hundred seconds and begins timing off again. Time delay off relay  74  will time out at the end of 20 seconds, but time delay relay  80  will stay energized because relay  82  is latching the time delay off relay  80  at contacts  90 . Therefore, the receiver  72  will continue to operate until channel B signals are no longer received. The receiver  72  may miss a two signals before the time delay off relay  80  will time out and cause the system shut off. While energized, the relay  82  holds closed a remotely mounted control relay  84 , labeled as CO 2 , through isolated contacts  86  on the control relay  82 . Dry contacts  88  on the control relay  84  are used to operate the pump unit  34 . When channel B signals stop, the time delay off relay  80  will time out and relays  82  and  84  will de-energize causing the isolated contacts  86  and contacts  88  on the control relays  82  and  84  to open and cause the pumping unit  34  to stop. 
     In the embodiment disclosed, the receiver  28  is the model XR-1 receiver and receiver  72  is the model XR-4 receiver. Both preferred receivers are manufactured by Linear Corporation. The companion transmitters  30  or  60  are the models XT-1 and XT-4, respectively, also manufactured by Linear Corporation. The XR-1 and XR-4 receivers are known for use in various applications where the receiver receives a signal and performs an operation, but is unique in its present application for an irrigation safety control system that is reliable and uses repetitive latching circuitry. The receiver  28  or  72  is used for the present irrigation safety control system because it provides a means for receiving a digital signal from a companion transmitter  30  or  60  over a distance of two to five miles. Further, the transmitters and receivers described may operate without being within the line of sight of each other. The receiver units include two 8-position switches used to set the units&#39; system codes. More than 65,536 codes are possible for the unit. The code set in the receiver is matched to the code of the companion transmitter. These codes may be preset to match the location as not to interfere with other like safety control systems that are nearby. These codes can be easily changed if there is any conflict. 
     The XT-1 and XT-4 transmitters are extended range FM frequency transmitters that send a 10 watts, 27.255 MHz, digital encoded, FSK modulated, signal to a companion receiver. The transmitters include switches to set one of more than 65,536 codes to coincide with the code set on the receiver described previously. 
     The component transmitting panels  16  and  54  and receiver panels  18  and  70  of the present invention are enclosed in weatherproof enclosures. Back plates of aluminum or similar heat conductive material may be provided, especially for the transmitter panel  16  or  54 , to act as a heat sink to help cool the panels. Usually the safety system of the present invention will consist of one transmitter panel  16  or  54 , which is located at the irrigation system location (i.e., the pivot system tower), and one receiver panel  18  or  70 , which is located at the pump unit  34  location. Antennas are provided at each location for transmitting and receiving signals generated by the system. The safety system is expandable to accommodate combinations of multiple pivot systems or pump units, according to the farmer&#39;s needs. The safety system can include additional receivers assigned complementary tasks such as activating an alarm in the farmer&#39;s home, if it is within range of the transmitter, should the pump units shut down. 
     From the preceding description of the preferred embodiment of this invention, it will be apparent to those skilled in the art that modifications or alterations may be made therein within the scope and spirit of the invention.