design and fabrication of a bulk paddy sampling …ejtafs.mardi.gov.my/jtafs/28-2/paddy sampling...

143

O. Muhamad IsaJ. Trop. Agric. and Fd. Sc. 28(2)(2000): 143–156

Design and fabrication of a bulk paddy sampling equipment(Reka bentuk dan fabrikasi peralatan untuk persampelan padi pukal)

O. Muhamad Isa*

Key words: design, fabrication, bulk paddy equipment, automation

AbstrakDalam urusan jual beli padi di kilang beras, proses penentuan kualiti padi perludilaksanakan dengan pantas dan tepat supaya petani dapat menerima pembayarandengan adil dan segera bagi hasil mereka. Dalam kes padi pukal yang dibawaoleh trak, sampel padi pada beberapa aras tertentu perlulah diperoleh dahulu.Kemudian padi ini digaul dan saiz sampel dikurangkan untuk menghasilkankuantiti dan keseragaman padi yang sesuai untuk penggredan. Alat proba pendeksedia ada yang digunakan untuk mengambil sampel padi di dalam guni didapatitidak sesuai digunakan pada padi pukal. Walaupun reka bentuk proba ini bolehdipanjangkan tetapi kekuatan diperlukan untuk membenam proba ke dalam padipukal.

Sebuah peralatan untuk mempercepat pengambilan sampel padi pukal didalam trak telah direka bentuk dan dibina. Peralatan ini dapat mengambil sampelpadi pukal di lokasi tengah dan empat penjuru trak. Berat sampel padi ialah2.5 kg dengan mengambil masa 2–3 minit bergantung pada kecekapan operator.Sebahagian daripada proses pembangunan peralatan ini merangkumi reka bentukdan ujikaji alat kawalan menggunakan pemproses mikro untuk membolehkanperalatan berfungsi secara automatik. Seterusnya, alat penggaul padi bermotoryang boleh menghasilkan kuantiti dan keseragaman padi yang sesuai untukpenggredan telah juga direka bentuk. Alat ini dapat menghasilkan sampel padiyang seragam dengan melaraskan masa alat beroperasi kepada 99 saat dengankelajuan motor 140 pusingan seminit.

AbstractIn paddy procurement transaction at the rice mill, fast and accurate qualitydetermination process of the paddy is needed so that farmers are quickly andfairly paid for their produce. In the case of bulk paddy delivered by truck, it isnecessary that representative samples over depth of bulk paddy are taken first atpredetermine locations. Then these paddy samples are mixed uniformly andreduced to proper size for use in grading exercise. The existing short length handtype probe commonly used to sample sack paddy is unsuitable for takingrepresentative samples throughout the depth of the bulk paddy. Even the probecan be made longer, but it requires a great effort to insert throughout the bulkpaddy.

*Strategic, Environment and Natural Resources Research Centre, MARDI Headquaters, P.O. Box 12301, 50774 Kuala Lumpur, MalaysiaAuthor’s full name: Muhamad Isa Othman©Malaysian Agricultural Research and Development Institute 2001

144

Design and fabrication of a bulk paddy sampling equipment

An equipment for quick sampling of bulk paddy in local truck size wasdesigned and fabricated. It was designed for deep sampling of the bulk paddy atthe centre and four corner locations of the truck. The amount of paddy samplewas 2.5 kg with the overall time taken 2–3 minutes depending on the operatorskill. Part of the development work on this equipment was concentrated ondesigning and testing of the microprocessor based controller to automate thesampling operation of the bulk paddy on the truck. Subsequently a motorisedpaddy mixer capable of producing uniform and proper weight of paddy samplefor grading had also been designed. The device could produce uniform paddysample by setting its mixing time to 99 seconds with the motor speed of 140rpm.

suitable for sampling paddy over the bulkpaddy depth inside the truck. Although alonger probe is available, it requires a greateffort to insert it in the bulk paddy. On theother hand, the imported bulk samplerequipment used in some rice complexes arebulky and expensive, and they are made forhandling large scale bulk grains of differenttypes and moisture content from the localcondition (Newman 1987). An equipmentthat is capable of taking sample throughoutthe depth of the bulk paddy at differentlocations in systematic manner andsubsequently transports the grains to a mixeris envisaged as an efficient system for thebulk paddy sampling.

An equipment for samplings of bulkpaddy delivered by trucks and motorisedmixer for mixing paddy samples weredeveloped between 1991 and 1994. Thedevelopment of the bulk paddy samplingequipment composed of design andfabrication of a hydraulic actuated bulkpaddy probe, probe transporter andinstallation of pneumatic equipment forconveying paddy samples to a collectionbox. Concurrently, a microprocessor basedcontroller to automate operation of theequipment was also designed and tested.

Materials and methodsThe description of paddy bulk samplingequipmentThe bulk paddy sampling equipment isshown in Plate 1. The equipment isdesigned for sampling bulk paddy in truckscurrently used by industry (Abdullah 1987).

IntroductionThe prevailing practice of post harvestpaddy handling contributes to high grainlosses due to frequent transferring of graininvolving large bagging units duringtransportation from field to a millingcomplex. It is a time consuming operationand requires high labour input. The adoptionof bulk handling technology using trucks forthe transportation of harvested paddy isregarded as an efficient system to overcomethe problem besides reducing direct handlingcost (Ahmad 1984; Bramall 1987). Bulkpaddy handling technology has been adoptedin some rice schemes in Malaysia.

In bulk system, an improved handlingtechnology in the form of modifications tothe present bagged handling facilities andthe introduction of new equipment forreceiving bulk harvested paddy in truckstransported from the farm have to be madeat the rice milling complex. An importantoperation associated with the bulk handlingis the sampling of bulk paddy in truck andtaking the grain samples into a laboratorywhere the samples are mixed and reduced insize for grading purposes. To haverepresentative samples of bulk paddy, itrequires a hardware that is able to takepaddy samples at predetermined locationsthroughout the depth of the bulk paddy. Inaddition, this operation needs to be donequickly so that the paddy procurementtransaction process in the rice mill is notdelayed.

A common short hand type probe usedto sample paddy in gunny sack is not

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It consists essentially of a hydraulic poweredpaddy deep probe, a probe transporter, apneumatic suction pump, a collection boxand a motorised paddy mixer. The probetransporter is mounted on to an ‘A’ steelframe bolted against concrete wall, while acollection box, control instrument and amotorised paddy mixer are located at adistance inside a laboratory. The transporteris mounted with the probe tip positionedslightly above the bulk paddy. The functionsof the probe transporter are to carry theprobe horizontally at the desirable samplinglocations and to assist pushing the probevertically throughout the depth of the bulkpaddy. The bulk paddy sampling equipmentshould meet the following criteria:

• The probe can penetrate to 1.3 metersdepth of bulk paddy and collect paddysamples at predetermined layer.

• The probe can be transported to thecentre and four corners of the localtrucks sizes in a manner shown inFigure 1 in accordance to the ISA

standard of bulk grain sampling ontrucks.

• The probe can be installed anddismantled easily for repairing andreplacement.

• The paddy samples collected by theprobe can be conveyed into a collectionbox in a laboratory which is located at adistance from the sampling area.

• The machine should be operatedautomatically for rapid, accurate andconsistent sampling task.The operation of the equipment is

performed by energising respectivesolenoids of hydraulic actuators andelectrical motor of pneumatic pumpmanually, or it can be automated by using asuitable controller. In the case of anautomatic operation, upon pressing the startbutton, the probe is pushed vertically intothe depth of paddy until it reaches thelowest position set by a lower limit switch.The probe collects a specific amount ofpaddy samples and then pneumaticallyconveys it into a collection box. The probeis removed from the bulk paddy by lifting itto the highest position set by an upper limitswitch and then it is brought to anotherlocation by a probe transporter for repetitivetask. When sampling of paddy at alllocations are completed, the probetransporter returns to a home position withthe probe at the highest position providing

Figure 1. Bulk grain sampling locations onlorries

x x

x x

x x

x x

x x

Plate 1. Bulk paddy sampler equipment

146


enough clearance to another truckundertaking a similar bulk paddy samplingoperation. The paddy sample at thecollection box is poured into a motorisedpaddy mixer where it is uniformly mixedand then a proper paddy sample size can beextracted for grading.

Design of the paddy bulk samplingequipmentThe hydraulic operated paddy probe Thedesign of the hydraulically operated deepbin probe and the transporter mechanismcomponents of the bulk paddy samplingequipment is shown in Figure 2 while thecross sectional view of the probe is shownin Figure 3. The probe is 1.6 meters longand consisting of concentric outer and innertubes. The tubes have five pairs of slottedhole equally spaced at alternate side of thetube wall. The inner tube freely rotatesagainst the outer tube by means of a lowerand an upper bearing and it is driven by a135 degree turn hydraulic rotor throughchain sprocket. The slotted holes of innerand outer tubes are aligned when the inner

Figure 2. Hydraulic operated probe and probetransporter

tube is rotated by 135 degree anticlockwiseto allow the entry of grain inside the probe.An opposite turn of the inner tube closes theslotted holes thus preventing grain entry. Along double acting hydraulic ram mountedon the probe transporter is utilized to pushdown or lift up the probe over the bulkpaddy. The vertical movement of the probeis guided by its upper roller device rolledover a vertical beam of the probe transporterand fixed lower roller device which rolledover the body of the probe. When the tip ofthe probe reaches the lowest set position, ahydraulic rotor twists the inner tube 135degree anticlockwise to align the slottedholes for samples collection. An oppositeturn of the rotor closes the slotted holes andthe probe is lifted out of the bulk paddyuntil it reaches the highest set position.

Buckling of the probe is avoided byaligning slotted holes on the alternate side ofthe tube walls and with probe tip made of acone shaped bullet to reduce drag over thebulk paddy. A high pneumatic suction ofgrain inside the probe is obtained by makingtwo small holes at the cone bullet which

Probe guide roller

Slotted holes

Probe

Single turnhydraulic rotor

Hose fixingbracket

Hydraulic cylinder


Guide rollerbracket

Hose

Rail

Transporter

Lower mountingbracket

Collection box

Upper mountingbracket


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Figure 3. Cross sectional view of paddy probe

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�48 mmPlastic hose

Hose fixing bracket

Chain and sprocket

Single turn hydraulicrotor

Inner tube

Outer tube

42 mm

Probeholder

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cause the air to flow from the bottom to thetop opened end of the inner tube. Theclearance between tube walls is made veryclose so that air suctioning through this gapwhen slotted holes misalign is very minimal.A long flexible plastic hose is connected tothe top opened end of the inner tube toconvey sucked paddy grain into a collectionbox. It is connected by a bracket speciallydesigned to prevent warping of the hose.

The hydraulic probe transporter Thefunctions of the probe transporter are tomove the probe vertically, throughout thedepth of the bulk paddy and thenhorizontally from one location to another.

The probe transporter must also havestructural strength to withstand high draftfrom the probe while inserting through thebulk paddy. In designing the probetransporter, several concepts wereconsidered and the final design of the probetransporter as illustrated in Figure 2 waschosen.

The probe transporter consists of twoarticulating arms of rectangular frame whichcarries a probe in the ‘X’ and ‘Y’ directionsand also provides railing for a long verticalmovement of the probe through the bulkpaddy. The arm structure has geometricaldimensions in such a way that it couldlocate the probe at the centre and four

148


corner positions in a truck compartment.The structure of transporter arm is made oflightweight hollow square beams withsufficient strength to withstand thrust of theprobe while inserting into the bulk paddy.The advantage of lightweight structuraldesign of the probe transporter is that it canfacilitate a high speed automated bulk paddysampling operation.

Two different capacity of 270° turnhydraulic rotors are used to provide anindependent rotation of the probe transporterarm. The use of single turn rotor simplifiesthe design of transporter drive in which therotor and the transporter arm shafts arecoupled directly by a simple collar. Theprobe transporter is mounted on an ‘A’frame with a height slightly above the bulkpaddy level inside the truck.

A schematic drawing of hydraulicsystem to power the probe and the probetransporter is shown in Figure 4. The systemis powered by a 3-hp hydraulic pump drivenby a single phase ac motor. The hydraulicactuators of the probe and the probetransporter arms are controlled by energizing

Figure 4. Hydraulic power system forbulk paddy sampling equipment

the respective electrical hydraulic valveswhich links through a cable to a push buttonpanel or a dedicated control instrument. Inthis experiment all actuators, except a rotorfor twisting the probe inner tube, wereinstalled with flow control valves. This is tofacilitate travelling speed of the probe andtransporter arm be adjusted to obtainoptimum sampling time of the bulk paddy.As a safety measure, a 12-volt dc supplywas used to power the electrically operatedhydraulic control valves.

Design of a motorised paddy mixerThe paddy sample taken from the bulkpaddy needs to be mixed uniformly and thenreduced in size to produce a requiredworking sample for rapid and accuratequality assessment. A motorised mixer wasdesigned and constructed as shown in Plate2. The mixer is made of ‘Y’ shapedcylindrical metal container with flapperchute at the bottom and powered by 1/8 hpmotor through a chain sprocket and a gearbox reduction drives. A spring loaded valveis installed at the lower end of the chute

Front armsingleturn

Rear armsingleturn rotor

Flow controlvalve

Solenoidoperatedcontrolvalve

Pressurereliefvalve

Pressure indicator

3hp Hydraulicpump

Electrical motor

P M

Suctionstrainer

Oiltank

Probesingleturn rotor

Hydrauliccylinder

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O. Muhamad Isa

which could be tilted to release a specificamount of sampled paddy into a can. Thechute could be opened by loosing a wing nutso that paddy sample inside the collectionbox could be poured quickly into the ’Y’shaped container of the mixer. The mixerrotates along its spindle shaft which is laidthrough the centroid of the ‘Y’ shapedcylinder to minimize wobbling. Theoperation of the motor is controlled by atimer relay circuit of which mixing time ofthe sample paddy could be set manually.

In addition the motor is also wiredusing push buttons for an anticlockwise andclockwise turning option to bring the chuteat either to a top or down position after acompletion of paddy mixing operation. Themixer rotates when the start push button ispressed, and stops automatically at the endof pre-set mixing time. Then the chute isbrought to a lower position and the sampleis released slowly into a can. The excesspaddy samples can be removed quickly byopening the chute of the mixer. The chute isaligned to a top position to pour new paddysample inside a mixer.

Designing and testing of a microprocessorcontroller for bulk paddy samplingequipment automationThe main considerations to automateoperation of the bulk paddy samplingequipment are to have fast, uniform andconsistent process of paddy sampling whichare lacking when carried out manually. Bymeans of automation, the positioning,pushing and lifting of the probe from onelocation to another over the bulk paddy canbe performed in a sequence at relatively fastspeed and avoiding mishap on operating theequipment. In addition the sampling processcan be monitored in a comfortable roomavoiding operator fatigue from long hours ofworking under dusty and hot temperatureenvironment. Therefore, the overall time forthe bulk paddy sampling operation on manytrucks arrived at the rice mill can be reducedsubstantially.

To automate the bulk paddy samplingoperation, the controller functions as follows :i. The controller activates and monitors

the transporter arms to locate the probeat the desired sampling locations.

Plate 2. Paddy motorised mixer

150


ii. At the sampling location, the controlleractivates the probe to the lowest depthin the bulk paddy. The slotted holes ofthe inner and outer tubes are aligned fora short duration to collect paddysamples and then the slotted holes aremisaligned to block the grains bycontrolling the single turn rotor.

iii. The probe is raised to the highestposition slightly above the surface ofthe bulk paddy. A pneumatic pump isactivated to convey paddy sample fromthe probe to a collection box.

The controller repeats step (i) to (iii) for theother locations and after completion of thesampling process, the transporter arms isactivated to a home position.

Automation of the bulk paddysampling equipment operation requires acustomized standalone microcomputer/microprocessor link with appropriate sensorsfor monitoring sampling locations and depthof the probe over the bulk paddy. Amicroprocessor base relay controller whichcontrols the switching of respectivehydraulic solenoid valves and pneumaticmotor by monitoring limit switches andanalogue signal output sensors of the bulkpaddy equipment were designed and tested(Anon. 1988, 1989; Bishop 1981). Thedesign of the controller is shown in Figure 5consisting of microprocessor, the analogueto digital converter, voltage reference, relaydriver and power supply electronic circuitsubsystems.

The microprocessor subsystem is madeof a 6802 Motorola microprocessor withbuilt-in 128 bytes internal RAM, interfacedwith one megabyte EPROM and aPeripheral Interface Adapter (PIA). Thesubsystem is wired by a NE555 timer poweron reset circuit for initializing themicroprocessor and PIA during power on.The EPROM device contains machine codeprogram instructions to implementequipment control strategy for the bulkpaddy sampling operation. A programmablefour input channel UP7002 NEC integratinganalogue to digital converter (ADC) circuit

is developed for measuring voltage outputsfrom the potentiometers which monitors thesampling location of the probe. The ADCaddress, data and control bus are directlyconnected to a processor and it isprogrammed to read eight bit digital valueconversion from two of its input channelswhich are connected to potentiometer outputvoltage terminals by twisted pair wires. ThePIA is programmed by configuring its input/output peripheral pins as three inputs and 15outputs. The three input pins are for theprocessor to read signals from the start pushbutton, upper and lower stop limit switchesof the sampling equipment. The other 15output pins through a Darlington transistorswitching relay drive circuit are for on/offcontrol of hydraulic actuators and pneumaticpump.

The voltage reference subsystemproduces one stable voltage output for theADC voltage reference terminals andanother two output voltages for biasing thelow cost potentiometer sensors. Eachpotentiometer shaft couples directly to thetransporter shaft so that the potentiometerproduces a linear output voltages inproportion with the respective rotationalangles of the transport’s arm which is readby a processor to determine a probesampling locations. The potentiometers arewired wound type with 270 degree electricalrotation, and they are selected because oflow cost and simplicity which do not requireamplifiers circuitry. Plate 3 shows afunctional PCB design of a microprocessorcontroller excluding the power supply andthe relay driver subsystems.

A program for the microcomputersubsystem to control operation of the bulkpaddy sampling equipment was written andcompiled by using 6802 microprocessorcross assembler software. The program flowchart is illustrated in Figure 6. It consists ofPIAINIT subprogram, PROBEHOME andPROBE subroutine. The PIAINITsubprogram is to configure or initialize thePIA into two separate eight peripheral datapins as input pins at the ‘A’ side and output

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O. Muhamad Isa

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pins at the ‘B’ side. The ‘A’ input and ‘B’output side pins of the PIA are interfacedwith limit or push button switches andrelays of the hydraulic solenoid valvesrespectively. Therefore under a programcontrol, specified data bits written by themicroprocessor to the PIA eight data lines isproduced on the output pins, and similarlysignals from limit switches or push buttonappeared at the input pins can be read by themicroprocessor through the data lines. Oncethe PIA is initialised, the rest of the programcan directly communicate input signals fromswitches or deliver output signals onrespective relays which operate thehydraulic actuators.

The purpose of the PROBEHOMEsubroutine is to bring the probe transporterarms to a home position with the probe atthe highest position away from the bulkpaddy truck. Immediately after themicroprocessor system power is up or reset,the PROBEHOME subroutine respondswhen initial press at the start push button ismade. The subroutine is designed to ensurethat in case of power supply failure oremergency shut off, the operation of thebulk paddy sampling can be restarted. Theactual bulk paddy sampling programresponds only when a start push button is

pressed for a second time after a short timedelay. The program contains instructions forthe equipment to perform samplingoperations in sequence at the centre and fourcorners locations of the bulk paddy. It ismade up of five loop instructions calledPROBE subroutine. The instructions in eachloop read digital values of bothpotentiometers which represent the angularposition of the transporter arms and thesevalues are compared against the setsampling location values stored in RAM ofthe microprocessor system. Once reading ofrespective potentiometer equals to the setvalue, the corresponding probe transporterarm is stopped by sending output signal todeenergise its hydraulic rotor solenoid. Theloop ensures that both arms are stoppedbefore calling the PROBE subroutine.

The PROBE subroutine is called uponfor collection and conveying of samplepaddy by the probe and pneumatic pumprespectively. The subroutine consists ofinstructions, first to activate a hydrauliccylinder pushing the probe into the bulkpaddy and while it is sinking, the programcontinuously looks for an output voltagefrom the lower limit switch. When the probereaches the lowest set position, the lowerlimit switch outputs a signal to instruct the

Plate 3. 6802 Motorola microprocessor controller module

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O. Muhamad Isa

Figure 6. Program flow chart of bulk paddy sampling equipment automation

PROBEHOME

PROBEHOME

Start

No No

No

No

No

No

No No

No

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

PIAINIT

Startbutton ispressed?

Read potentiometerADC data

Move transporter armsto home position

Read potentiometerADC dataTransporter

arms at homeposition?

Startbutton ispressed?

Delay loop

Move transporterarms to 1st sampling

location

ADC data oftransporter armsat 1st location?

PROBE subroutineMove transporter

arms to 2nd samplinglocation

ADC data oftransporter armsat 2nd location?

PROBE subroutine

Move transporterarms to 3rd sampling

location

ADC data oftransporter armsat 3rd location?

Move transporterarms to 4th sampling

location

Move transporterarms to 5th sampling

location

ADC data oftransporter armsat 4th location?

ADC data oftransporter armsat 5th location?

PROBE subroutine

PROBE subroutine

PROBE subroutine

Transporterarms at home

position?

Move transporterarms to home

position

Stop�

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program to stop further sinking of the probe.Further instructions in the subroutine alignthe inner and outer tube slotted holes of theprobe for a few seconds to collect thesample paddy. Then pneumatic pump isactivated for conveying paddy sample into acollection box. Finally the subroutine givesinstructions to lift the probe and then stop atthe highest position which is acknowledgedby an upper limit switch voltage signal. Atthe end of the fifth bulk paddy samplinglocation loop, the program callsPROBEHOME subroutine to bring thetransporter arms to a home position.

Tests were carried out on themicroprocessor hardware and software,analogue to digital, voltage reference circuit,potentiometer measurement and relay drivercircuit subsystems. For the microprocessorsubsystem, several short test programs onthe microprocessor alongside with eachprogrammable device were carried out untilit worked successfully. The test programswere the processor communication with thePIA and the analogue to digital converter bywriting short machine code programs in theEPROM memory. In case of testingcommunication of the processor with thePIA, a short program was run on theprocessor to read signal from switchesconnected with ‘A’ side of the PIA inputpins, and once it was detected a known bytecode signal was written on the ‘B’ sideoutput pins. Test on the processor linkingwith the ADC was done by running a shortprogram converting a known input voltagesignals on the input channels and thendisplay the digital value conversions on the‘B’ side of the PIA output pins. The digitalvalues in the test were verified with logicsignals using a logic probe tester. Theoperation of the relay drivers was tested bysending output signal from ‘B’ side of thePIA to the relay driver base input transistorsand then observed the closure of the relaycontact points. The accuracy and stability ofthe voltage outputs of the voltage referencecircuits are essential for a proper digitalconversion or resolution of the ADC and the

potentiometer voltage biasing. The voltagereference was calibrated to output accuratedigital conversion values of the ADC whileapplying a known accurate input voltage atits input channels using a YOKOGAWAcalibrator. The potentiometers were alsobiased accurately and the test result showeda good linear relationship of output signalvoltages versus shaft angle positions of thepotentiometer.

In the latter stage, the designing andtesting of an assembly language programalongside with the microprocessor systemhardware for controlling operation of thebulk paddy sampling equipment as describedearlier were carried out. The program wastested with several relays, limit switches andpotentiometers attached to the respectiveinput or output pins of the PIA and ADC ofthe microprocessor system. In the tests, thepotentiometers and limit switches weremanually operated simulating the controlstrategy of the bulk sampling equipment andsimultaneously observed the response of theprogram to actuate respective relay contacts.

Results and discussionThe bulk paddy sampling equipment wastested in a laboratory using a freshlycombine harvested paddy of 20% moisturecontent obtained from a farmer in NegeriSembilan. The paddy was poured inside acontainer to about the depth of the bulkpaddy inside the truck. The bulk paddysampling equipment was tested at the centreand the four extreme corners similar to thesampling locations of the bulk paddy in thetruck. The results of the functional testshowed that the bulk paddy samplingequipment worked satisfactorily. The deepprobe penetrated smoothly throughout thedepth of bulk paddy without buckling. Theinner tube rotated freely against the outertube of the probe and the alignment andnonalignment of the slotted holes of thetubes were quite fast. The probe collectedthe paddy sample by aligning the slottedholes of the inner tube against the outer tubefor a few seconds then the sample paddy

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O. Muhamad Isa

conveyed effectively over a long hose to acollection box by a pneumatic suction. Thefront and rear arms of the transportmechanism were able to articulate inclockwise and anticlockwise turns forlocating the probe at the centre and fourextreme corners. The maximum probe depthinside the bulk paddy was 1 200 cm and anaverage weight of sample paddy collectionwas 500 g. A total amount of 2.5 kg ofsample paddy was collected for all fivesampling locations of the bulk paddy.

After the equipment had undergoneseveral tests, the probe transporter structureand brackets were found sufficiently strongto push the probe throughout the bulk paddy.The brackets mounted on the ‘A’ framewhich supported the transporter were testedfor strength by applying the brackets to amaximum bending stress. This wasaccomplished by pushing the probe over thebulk paddy while the transporter arms werestraightened. The sampling time of usingthis equipment depends on the operator'sskill in manoeuvring the transporter to locatethe probe at desired sampling spots andspeed of penetration or retraction of theprobe over the bulk paddy. To optimize thesampling time, the penetration of the probethroughout the bulk paddy was set at a lowspeed to avoid any possible buckling, whilethe retraction of the probe was set at a muchhigher speed. The articulation speed oftransporter arms was adjusted by trial anderror until the arms gave minimal overshootwhen stopped.

The performance of the equipment wastested manually by pressing in sequence thebuttons of control box which activatehydraulic actuator, and the time to samplethe bulk paddy was recorded. The time tosample bulk paddy on one location wasabout 20 seconds. It was measured frominserting the probe into the bulk paddy, alignand then non align its slotted holes, lift it toa top position and convey the paddy samplesto a collection box. The time taken forsampling paddy at all five locations over thebulk paddy was between two and three

minutes depending on the operator skill.There is a tendency for the probe to bendwhen the transporter arms are rotated whilethe probe is still inside the bulk paddy.Therefore it is necessary for the operator tooperate the equipment with caution to avoiddamaging the probe. However, it isenvisaged that the problem can be avoidedonce the probe transporter is manoeuvredautomatically by an appropriate controlinstrument.

The design of drive mechanism for thetransporter arms was simplified by using asingle turn rotor. However from a series oftests, it was observed that the swing of thetransporter arms tended to overshoot whentrying to stop the probe at the samplinglocation due to lack of damping of thehydraulic rotors. The use of existing directshaft drive was suitable for low speed butunsuitable for fast speed of bulk paddysampling operations. The speed of the probetransporter could be improved by driving theshafts with a continuous turn hydraulic rotorcoupled with a high reducer ratio spur wormgearbox which provide better torque and selfbraking. The transporter arms can be haltedimmediately and hence the probe can bepositioned at a precise location over the bulkpaddy.

The microprocessor based controllermodule for application of the bulk paddysampling automation were designed andtested in the instrumentation laboratory. Theresults from the tests show that themicroprocessor based controller workedwell. The program codes written andcompiled in assembly language for controlstrategy of the bulk sampling equipmentwere executed successfully by themicroprocessor hardware. Throughout thisexperiment, we finally established thehardware and software design requirementsfor the 6802 Motorola microprocessor basecontroller. Although the controller wasdesigned specially to control operation ofthe bulk paddy sampling equipment, themodule could also apply to other machine

156


control application by writing differentprogram codes in the EPROM device.

Further works on the bulk paddysampling equipment are still required beforeit can be fully tested for automation. Theseinclude modification on the transport armdrive mechanism for ease of manoeuvringand accurate positioning of the probe at thesampling locations, improvement of existinghydraulic lines layout of the equipment forhigher hydraulic efficiency and neatness andthe fabrication of control instrument.Calibration of potentiometer voltage outputsvalues against desired sampling locationsneed to be carried out and their valuesstored in the microprocessor memory.

The tests on motorised mixer wereconducted in the postharvest laboratory inMARDI Alor Setar. The motorised mixerfunctioned satisfactorily and it rotated at 140rpm. Various sizes of paddy samplesextracted from this machine with variabletime for mixing were analysed. After aseries of tests, it was found that a mixingtime of 99 seconds and extraction of 10 gpaddy were sufficient for the preparation ofpaddy samples.

ConclusionA paddy bulk sampling equipment wasdesigned and fabricated for sampling of bulkpaddy in trucks. The equipment workedsatisfactorily when operated manually. Thehardware and software requirements for the6802 Motorola microprocessor basedmodule to function as a stand alonecontroller of the bulk paddy samplingequipment operations were successfullydesigned. In order to automate the operationof the bulk paddy sampler equipment,design improvements on the probetransporter drive, hydraulic layout andfurther development on controller instrumentare required. The motorised paddy mixer forpreparation of uniform and workable size

paddy sample for analysis was alsosuccessfully designed and locally fabricated.

AcknowledgementThe author is very thankful to paddypostharvest research officer, Tuan HajiAbdullah Ali for providing some technicalinformation on development of the bulkpaddy sampling equipment. The author isalso grateful to research assistants Mr.Zulkifli Ahmad and Mr. Arshad AbdulSamad for their assistance in themodification and testing of the equipment.

ReferencesAbdullah, A. (1987). Use of modified light pickup

truck for handling of paddy in Malaysia.Proceeding of an International Workshop onBulk Handling and Storage of Grain inHumid Tropic, ACIAR Proceedings No. 22, p212–5. Kuala Lumpur: ACIAR

Ahmad Robin, W. and Dhiauddin, M. N. (1984).Bulk handling of paddy: A measure toaccelerate delivery of wet grain to dryingcomplex. Proceeding of the 7th ASEANTechnical Seminar on Grain Post HarvestTechnology, p 355–65. Kuala Lumpur:ASEAN Crops Post Harvest Programme

Anon. (1988). Microprocessor, microcontroller andperipheral data. Volume 2. Motorola databook DL139. Data sheets 3-1363-3-1431. US:Motorola

–––– (1989). Motorola high speed CMOS logicdata, DL129 revision 4. US: Motorola.

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Accepted for publication on 22 September 2000

design and fabrication of a bulk paddy sampling …ejtafs.mardi.gov.my/jtafs/28-2/paddy sampling...

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