An electronic, microprocessor-based controller was developed
and tested for automating surface irrigation systems. Communication
between the central controller and individual satellite field stations
is by tone telemetry over a single 3-conductor wire. The reliable Dual
Tone Multiple Frequency or Touch Tone system is the same as that used in
telephone communications. The system is designed to actuate momentarily
energized pilot valves commonly used in automated surface irrigation
systems. Because of its low power requirement, the control system can
be battery-powered. It is being field tested in three different, automated
surface systems

Fisher, H.D.

Humpherys, A.S.

Young, D.A.

Northwest Irrigation & Soils Research Laboratory Publications

Automated Telemetric Irrigation Controller

USDA - ARS - NWISRL

AUTOMATIC IRRIGATION CONTROLLER 	 251AUTOMATED TELEMETRIC IRRIGATION CONTROLLERBy H. D. Fisher,1 A. S. Humphsrys,2 M. ASCE,and D. A. YoungABSTRACT: An electronic, microprocessor-based controller was developedand tested for automating surface irrigation systems. Communicationbetween the central controller and individual satellite field stationsis by tone telemetry over a single 3-conductor wire. The reliable DualTone Multiple Frequency or Touch Tone system is the same as that uses intelephone communications. The system is designed to actuate momentarilyenergized pilot valves commonly used in automated surface irrigationsystems. Because of its low power requirement, the control system canbe battery-powered. It is being field tested in three different, auto-mated surface systems.INTRODUCTIONAutomation is being used increasingly to improve farm water applic-ation efficiency. Irrigation on lands that are suited for surfaceirrigation can usually be automated to achieve water and _Leber savingsat lower cost and with less energy than is generally required forsprinkler methods of irrigation.Irrigators have wanted timer-controlled devices and structures formany years to automatically change their irrigation sets, especially atnight. An irrigation of less than 12 hours, or between 12 and 24hours, is often sufficient to refill the soil's root zone. However,irrigators commonly use either 12- or 24-hour sets because it is con-venient to change the water only once or twice each day. Thus, irrig-ation is scheduled according to the farmer's work schedule rather thanby soil and crop conditions. These fixed-time sets are usually satis-factory for sprinkler systems because sprinklers can be designed toapply the desired amount of water in a fixed-time period. Much of thedecision making is in the system design rather than with the operator,and when the system is operated according to design, a reasonably ef-ficient irrigation can be expected.. However, with surface irrigationsystems, which are used on about two-thirds of the irrigated acreage iuthe United States, both the application rate and irrigation timing arecontrolled by the irrigator. The irrigation system capacity as well as1Electronics Engineer, Snake River Conservation Research Center,Kimberly, Idaho.2Agricultural Engineer, Snake River Conservation Research Center,Kimberly, Idaho.3Research Associate, Colorado State University, Grand Junction,Colorado.soil and field conditions often limit the irrigator's ability to varythe application rate; whereas, irrigation duration is under his directcontrol and is usually the most important factor influencing irrigationefficiency. Another factor which increases the need for timer-controlled, automated devices is the cost and limited availability ofcompetent irrigation laborers.Commercial controllers are designed predominantly for systemswhich use sprinklers or, more recently, drip equipment and do notfully meet the needs of surface irrigation. Many of them are designedfor relatively short time periods; whereas, automated surface systemsmay require irrigation sets of 24 hours or longer. Most commercialcontrollers also require at least one separate connecting wire or tubefor communication between the controller and each controlled valve orgate outlet. Thus, the number of wires or tubes that must be handledfor most field installations becomes very cumbersome and difficult tomanage.Most controllers require AC line power, but this is seldom avail-able in fields where surface irrigation equipment is used. Also, thecontroller's electrical output, used to control or actuate solenoidvalves, is usually not compatible with the valves used in surfacesystems. The controllers are designed to operate continuously-energized solenoid valves while most automated surface systems use!.:'momentarily-energized pilot valves which can be powered by batteries.Continuously-energized solenoid valves commonly used in pressurizedirrigation systems require pressure for sealing and/or shifting.Since they are pressure-assisted, their wattage requirement is oftensmaller than that required by some momentarily-energized solenoidvalves (8) powered by capacitor discharge. Latching solenoid valvesused in some surface systems require a reversed polarity voltage notobtainable from controllers designed for continuously-energizedsoleniod valves. Therefore, controllers are needed which have anoutput that is compatible with solenoid pilot valves used in surfaceirrigation systems.A number of electronic timers or controllers have been used on anexperimental basis. Edling at al. (3) described a solid state timerto control a single, pneumatically-actuated irrigation turnout valve.Duke et al. (2) and Dedrick and Allen (1) used an electronic controllerto provide volumetric control of an automated farm irrigation systemwith water supplied from open cnannels. Fisher et al. (5) usedelectronic controllers both for single station, automatic furrowcutback systems and as central controllers. Menges et al. (9) used aradio-operated controller for a gated pipe system.Since a controller compatible for use with momentarily-energizedvalves in a surface irrigation system was not commercially available,we designed and tested a controller to satisfy this need. The objec-tive of this paper is to describe a control system which uses tonetelemetry and a single, 3-conductor control wire for communicationbetween the controller and all controlled stations in the irrigationsystem. The system's operation and field tests are also described.ELECTRONIC CONTROLLERSElectronic timer/controllers using microprocessors have manydesirable characteristics and capabilities for use in irrigation.252	 ADVANCES IN IRRIGATION AND DRAINAGE	AUTOMATIC IRRIGATION CONTROLLER	 253Their low power requirement enchances the feasibility of using solarand wind energy sources as well as batteries for power. Their timebase is a quartz crystal oscillator which provides a high degree oftiming accuracy. This is necessary where gates or valves'are control-led by individual controllers and are operated in sequence. Cumulativeerrors with inaccurate timers could result in overtopping of ditchesor canals or damage to the system by having all system outlets closedsimultaneously. Controllers using microprocessors can be programmedto control irrigation in any sequence from a large number of turnoutsand for varying time intervals. The basic components are relativelyinexpensive and once the design and circuit 'boards are developed for agiven unit, they can be economically produced in quantity. Completesystem control incorporating soil and crop conditions, weather para-meters, water supply limitations, and irrigation scheduling consider-ations is feasible.TONE TELEMETRY CONTROLLERThe design of this system is such that the timing, programmingand control functions are concentrated into one versatile centralcontroller. The satellite station controllers contain only the cir-cuitry necessary to decode commands from the central controller and toactuate the valves. This design allows the central controller to bequite sophisticated, since only one is needed for a given instal-lation, while the number of individual stations can be expanded easilyand at nominal cost.Three wires connect the station controllers and the centralcontroller daisy-chain fashion. Two wires carry power to the stationcontrollers, while the third carries the on-off commands from thecentral controller. The distance that any station can be from thecentral controller is limited by the voltage drop along the powersupply wires. Heavier wire can be used to increase the effectivedistance, but this increases the installation cost. Radio links tothe stations would remove this limitation, but would increase the costof the station controllers..Central Controller The central controller is based on an 1802 microprocessor. ARead Only Memory (ROM) contains the main program so that field program-ming is not necessary to activate the system. The operator enterscontrol information which determines how the system will operate for agiven irrigation cycle. These parameters are stored in Random AccessMemory (RAM) and can be easily adjusted at random and at any time.The controller communicates with the controlled field stations usingthe full 4 x 4 matrix of telephone Dual Tone Multiple Frequency (DTMFor Touch Tone)— 	These represent the hexadecimal digitsO F (0 - 15 decimal). This system uses two-digit station addresses01 - FE (00 and FF are stable states). Commands 01'- 7F (hex) openvalves 1 - 127 (dec), while the l's complements FE - 80 (hex) closethem. The DTMF system was developed for telephone communication and is4/ Touch Tone is a registered trademark of American Telephoneand Telegraph.very dependable. The chance of a malfunction resulting from lightingor other electrical disturbances is remote since the system is resist-ant to interfenence by noise from outside sources. Earlier models ofthe controller were designed to operate from a 12 VDC power source.The latest model, however, was designed to operate from 120 VAC tosimplify supplying the short-term voltage required by station control-lers a long distance away from the central station.To obtain reliable operation of momentarily-energized, 3- and 4-way pilot valves at the end of 1300 ft (400 m) of 18 AWG wire, theshort-term voltage at the central controller had to be in the range of32 - 36 VDC. The actual power demand of the system is quite low, 6 maat 5 VDC, when the station controllers are powered down, and 600 ma at32 VDC for about 45 seconds when 16 stations are controlled. A storagebattery and a DC to AC inverter can supply this demand at a locationwhere line power is not available. Part of the power requirement atthe central controller is used to charge capacitors in the individualstation controllers. Power at the controller can be reduced by usingbatteries at the field station controllers to charge the capacitors.Thus, a completely battery-powered system is feasible.Station Controllers Each station controller is assigned an address 1 - 127 (dec) whenthe system is designed. The single chip DTMF tone receiver at eachstation decodes commands from the central controller and the decodedcommands are compared to the address set in the station controller.If the command is valid, the station controller generates the appro-priate signal to shift the valve. The output structure and solenoiddrivers can be readily modified to accommodate most momentarily-energized, bistable valves for air or water. Two types of solenoid-operated pilot valves are being controlled by the station controllersnow in use. One is a magnetically-latched solenoid valve which re-quires a reversed polarity electrical output from the station controller to open and close the valve. Three-way pilot valves of this typeare commonly used with pneumatically-operated irrigation valves (2, 3,4, 6). The other pilot valves are 3- and 4-way momentarily-energizedspool valves used with both water and air operated irrigation valves(7, 8). The pilot valves are powered by the electrical discharge fromcapacitors in the station controllers. The capacitors are chargedfrom the central controller. A schematic representation of a stationcontroller and its associated pilot valve is shown in Fig, 1,Operation The operator supplies the operational parameters: (a) presentdate and time, (b) date system is to operate, (c) time of operation,and (d) duration of irrigation for each station. By selecting afuture operational date, the system can be programmed up to 31 daysin advance of when It is to operate. The duration of irrigation islimited to 23 hours 59 minutes for each station. The number of sta-tions that can have the same address and their relative locations inthe field are not limited. This provides great flexibility in boththe amount and pattern of water application. If 127 discrete addressesis inadequate, the central and station controllers can be modified toTone Code	es	e	 CommonControlWireStation Controllerw/Tone ReceiverExhaust .4C:SolenoidOperatedPilot Valve Flow ControlDevice(Outlets, Gatesor Valves)       Air or IrrigationWater Supply Line 	254	 ADVANCES IN IRRIGATION AND DRAINAGE	AUTOMATIC IRRIGATION CONTROLLER	 255use a 3-digit address. This expands the capability of the system to2047 discrete addresses.Using the appropriate switches, the operator can review the opera-tional parameters, query for system and individual valve status, andmanually change the state of the individual valves. The system locksout after one complete cycle to prevent undesirable multiple operations.To run another cycle using the same operational data, the operatormerely changes the date of operation and executes a soft reset. Thecontroller can be used for multiple irrigation cycles such as surgeirrigation, for example, if the software is modified for this type ofoperation.Fig. 1. Station controller with tone code receiverand solenoid operated pilot valve used tooperate an irrigation valve or other flowcontrol device.FIELD TESTSThree identical central controllers were made for field testingin three different automated irrigation systems. The first systemnear Kimberly, Idaho, consists of two parts, one of which is a 900-ft(300 m), single-pipe system with pneumatically-operated outlets. Thissection consists of a conveyance/distribution pipe with automatically-controlled discharge outlets for individual furrows. The outlets arecontrolled in groups or banks of 15 to 25 outlets each. Each group ofoutlets constitutes one field station. A 3-way, magnetically latched,solenoid pilot valve controls air flow to and from each group ofoutlets. These pilot valves require a reversed polarity electricaloutput from the station controller. A telemetry station controller islocated adjacent to the pilot valve for each controlled bank of outlets.The control wire from the central controller extends the length of thepipe line system as shown schematically in Fig. 2, and is connected toeach station controller such that all field stations are connectedelectrically in parallel. Each station controller sees all of thetone code addresses transmitted by the central controller, but onlyresponds to its own address.The other part of the automated system is in an adjacent fieldand uses both water- and air-operated irrigation valves. The water-operated valves use 3-way, momentarily-energized spool type pilotvalves (8). These pilot valves direct water from the pipe line into awater filled bladder inside the irrigation valve or drain water fromthe bladder to either close or open the irrigation valve. The air-powered, irrigation valves are butterfly valves actuated by air cylin-ders. Four-way momentarily-energized solenoid spool valves (7) controlair flow to and from the air cylinders. A telemetry station controlleris used at each valve station. These units receive instructions fromthe main controller and open or close the irrigation valves by control-ling their respective pilot valves.The central controller for the Kimberly system is powered by aphotovoltaic solar cell battery charger, Fig. 2, and two 12-voltstorage batteries. Since the power requirement for the original con-troller used in this field was relatively high, the controller wasredesigned. Three new controllers were built and tested in the labora-tory under simulated field conditions. The simulation included four-teen station controllers located at the far end of a 1300-ft (400 m)control wire. These were repeatedly operated with their associatedpilot valves in a random sequence. One of the new controllers will beused to control approximately 25 valve stations in the Kimberly systemduring the 1983 irrigation season. An inverter will be used to provide120 VAC from the solar charged batteries to power the controllersystem.The second irrigation system is in the Grand Valley of Coloradoand uses air-powered butterfly valves attached to risers from a buriedwater supply pipeline. The 14 irrigation valves in this system controlwater flow into gated pipe. Four-way, momentarily-energized solenoidpilot valves are used with the butterfly valves (7). The early-modelcontroller used during 1982, was underpowered and was replaced by oneof the new controllers for the 1983 season. The controller will bepowered by 110 VAC line power which is available near the field.The third irrigation system, located near Twin Falls, Idaho usesI:oaP. P-14-10. I.of 0110 0CaaI-wa• cV256	 ADVANCES IN IRRIGATION AND DRAINAGE	AUTOMATIC IRRIGATION CONTROLLER	 257water-operated valves and the same 3-way, momentarily-energized pilotvalves noted earlier. The controller for this system is identical tochose for the other two systems and is powered directly from 110 VAC.Field tests conducted with the first models of the controller showedthat the basic design and principles of operation were sound. Debuggingof program and power requirement problems were solved such that thenew controllers, which include updated components, performed satis-factorily in simulated field tests conducted in the laboratory.SUMMARYAn electronic microprocessor-based controller was developed forautomating surface irrigation systems. The control system consists ofa central controller containing the timing, programming and controlfunctions and individual satellite station controllers at each fieldstation. Communication between the central controller and the satellitestations is by tone telemetry over a single 3-conductor wire. Thiseliminates multiple wires or tubes between the central controller andfield stations which are common with conventional controllers. TheDual Tone Multiple Frequency (DTMF or Touch Tone) system is the sameas that used in telephone communication and is very reliable. Eachstation controller contains a tone code receiver/decoder which respondsto its own address. The output of each station controller is designedto operate battery-powered, magnetically-latched, poppet and momentarily-energized spool type solenoid pilot valves that are commonly used inautomated surface irrigation systems. Early models of the centralcontroller where field tested in three different irrigation systems.Three controllers of an updated design were tested under simulatedfiels conditions in the laboratory and will be used in the three fieldsystems during 1983. The controller system has a relatively low powerrequirement.APPENDIX - REFERENCE1. Dedrick and R. F. Allen. 1981. Open channel flow sensing for auto-matic control. ASAE Paper No. 81-2562, ASAE, St. Joseph, MI. 49085.2. Duke, H. R., M. L. Payne and D. C. Kincaid. 1978. Volumetriccontrol for irrigation automation. ASAE Paper No. 78-2545, ASAE,St. Joseph, MI. 49085.3. Edling, R. J., H. R. Duke and M. L. Payne. 1978. Utilization of aportable solid state furrow irrigation valve controller. ASAEPaper No. 78-2546, ASAE, St. Joseph, MI. 49085.4. Fischbach, P. E. and R. Coodding II. 1971. An automated surfaceirrigation valve. Agr. Eng. 52(11):584-85.5. Fisher, H. D., A. S. Humpherys and R. V. Worsteli. 1978.Electronic Timers for Automated Surface Irrigation Systems. ASAEPaper No. 78-2544, ASAE, St. Joseph, MI. 49085.258	 ADVANCES IN IRRIGATION AND DRAINAGE6. liaise, H. R., E. G. Kruse, M. L. Payne and H. R. Duke. 1980.Automation of surface irrigation: Summary of 15 years USDA Researchand Development at Fort Collins, Co. U. S. Department. ,ofAgriculture, Production Research Report No. 179, 60 p.7. Humpherys, A. S. 1983. Automated air-powered irrigation butterflyvalves. Accepted for publication in Trans. ASAE.8. Humpherys, A. S. and R. S. Pauliukonis. 1983. Momentarily-energized pilot valves for irrigation systems. Accepted forpublication in Trans. ASAE.9. Manges, H. L, D. K. Matteson and K. G. Butler. 1980. Radiocontrols for gated-pipe irrigation. ASAE Paper No. 80-2557, ASAE,St. Joseph, MI. 49085.

https://eprints.nwisrl.ars.usda.gov/id/eprint/1034/1/512.pdf

Automated Telemetric Irrigation Controller

Abstract

Similar works

Full text

Available Versions

Northwest Irrigation & Soils Research Laboratory Publications

USDA - ARS - NWISRL