MINOR PROJECT REPORT AUTOMATIC WEIGHING AND PACKAGING MACHINE CHAPTER 1 INTRODUCTION In Industry weighers & weighing mechanisms are to be very accurate. Without this accuracy, extraction figures are meaningless. Weigher is the necessity either to weigh or to weigh the final products to calculate extraction rate. Low cost automatic weighing machine using latest technology of servo control and Programmable Logic Control (PLC) was designed and developed considering the advantages of electronic weighing and linear motion guide ways moving accuracies. The results of studies carried out for automatic weigher indicated that the equipment could be used as weigher. Statistical analysis indicated that there was no significant difference in mean value of measurements from set weights and measured weights at the 95% probability level. Automatic weighing equipment can be successfully used for weighing and dosing of products into bags, containers in automated production processes. Automatic weighing machine consists of hopper, weigher with hooks arrangements for empty bag & drop hole mechanism. Full open to half open or full close of the gate operates through drop hole mechanism is used to fill the specified quantity of matter into the bag which affects the accuracy of weighing. Continuous DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING Page 1
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
MINOR PROJECT REPORT AUTOMATIC WEIGHING AND PACKAGING MACHINE
CHAPTER 1
INTRODUCTION
In Industry weighers & weighing mechanisms are to be very accurate. Without this accuracy,
extraction figures are meaningless. Weigher is the necessity either to weigh or to weigh the final
products to calculate extraction rate. Low cost automatic weighing machine using latest
technology of servo control and Programmable Logic Control (PLC) was designed and
developed considering the advantages of electronic weighing and linear motion guide ways
moving accuracies. The results of studies carried out for automatic weigher indicated that the
equipment could be used as weigher. Statistical analysis indicated that there was no significant
difference in mean value of measurements from set weights and measured weights at the 95%
probability level. Automatic weighing equipment can be successfully used for weighing and
dosing of products into bags, containers in automated production processes.
Automatic weighing machine consists of hopper, weigher with hooks arrangements for
empty bag & drop hole mechanism. Full open to half open or full close of the gate operates
through drop hole mechanism is used to fill the specified quantity of matter into the bag which
affects the accuracy of weighing. Continuous monitoring of set weight and matter feeding was
absent. Conventional filtering methods employed in dynamic weighing systems have limitation
in improving accuracy and throughput rate .Fluctuations in the bulk density of the raw materials
in volumetric or rotary charger dosing results in alterations in weight. Weighing machines
equipped with platform scales or beam balances with dials do not ensure the required accuracy of
weighing batch materials. Mechanical scales are not reliably precise and their applications in
automatic lines are complicated. Mechanically operated weighers are obsolete and maintenance
oriented. Electronic weighers are sophisticated and calibrate themselves by using built in
calibration procedures and saves the data themselves. Load cells are widely used in a variety of
industrial weighing applications such as wending machines and weighing systems. Load cells
interfaced with integrated electronics convert the weight force to an electric signal and deliver
the output signal to an automation system. Linear motion guide ways accompanied with
precision ball screw can greatly enhance moving accuracy. Hence, considering the advantages of
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERINGPage 1
MINOR PROJECT REPORT AUTOMATIC WEIGHING AND PACKAGING MACHINE
electronic weighing accuracy and linear motion guide ways moving accuracy, the present project
is undertaken to design and develop state of art technology i.e. low cost automatic weighing
machine using latest technology of servo control and Programmable Logic Control (PLC)
concepts.
The equipment works on the basic principle of batch weighing. Working flow diagram is as
shown in the Figure.1. Raw material to be weighed is automatically fed to the weighing hopper
through a quantity regulating servo slide. The movement of the slide is controlled by precision
linear motion guide way assembly which is driven by brushless servo motor. Feeding of the
material from the collection hopper to the weighing hopper is done in coarse and fine feed.
Automatic weighing cycle starts with wide opening of the servo slide followed by weight register
by the load cells. During rapid movement of the servo slide, more quantity of material is passed
to the weighing hopper. As the weight of the weighing hopper is nearing to the set weight, servo
slide moves slowly to provide fine feeding of the grain. As soon as the weight of the material in
the weigher hopper achieves the set value, the servo gate of the storage hopper closes and the
weigh hopper gate opens to discharge the set quantity of material on to a downstream process
line. Micro controller registers and updates the exact quantity of material discharged. When the
weigh hopper becomes empty, weigh hopper gate closes and the storage hopper servo slide
opens for the next weighing cycle.
The below figure shows how the process will go in the project . Firstly the the product which is
to be packed must be check that in what form it is present then the product is to placed in hopper
in bulk.
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERINGPage 2
MINOR PROJECT REPORT AUTOMATIC WEIGHING AND PACKAGING MACHINE
Figure 1.1 Flow chart of process.
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERINGPage 3
MINOR PROJECT REPORT AUTOMATIC WEIGHING AND PACKAGING MACHINE
CHAPTER 2
PROJECT DESCRIPTION
2.1 Shutter
The shutter is made up of iron in which we have use the iron sheet and ball bearings which help
in rotating the sheet according to our requirement . In this the size of the sheet is kept in such a
way that it covers the mouth of hopper from the bottom . The length and breadth of sheet is kept
(9x18 inches). The ball bearing which are used in it are such that when sheet is connected to the
motor used it drives the shutter forward & backward movement . Fig 2.1 sow the real shutter.
Figure 2.1 Closed Shutter
When the shutter moves in forward direction the path beside it left vacant which show that the
process is going on . Fig. 2.2 show the ball bearing & open view of shutter.
Figure 2.2 Opened Shutter
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERINGPage 4
MINOR PROJECT REPORT AUTOMATIC WEIGHING AND PACKAGING MACHINE
2.2 Hopper
A hopper is a large pyramidal shaped container used in industrial processes to hold particulate
matter that has been collected from expelled air. Hoppers are usually installed in groups to allow
for greater collection quantity. They are employed in industrial processes that utilize air pollution
control devices such as dust collectors, electrostatic precipitators, and bag houses/fabric filters.
Steel is the typical material of choice for hopper construction . Hopper walls are insulated in
order to protect the outside environment and personnel from the discarded contents. Oftentimes,
the bottom ¼ - 1/3 of the container is heated to eliminate the possibility of condensation inside
the hopper. The greatest difficulty associated with the removal of dust from the hopper is the
compaction of the ash. Moisture content, particle shape and size, and vibration are all factors that
contribute to the compaction. Typically vibrators are installed on the outer walls of a hopper to
shake and release the dust.
Figure 2.3 Hopper
2.3 LCD interfacing with Load Cell
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERINGPage 5
copper alloys. By bonding strain gages to a precisely machined element, the force applied can be
identified in terms of resistance change. The strain gages, usually four or a multiple of four, are
connected into a Wheatstone bridge configuration in order to convert the very small change in
resistance into a usable electrical signal. Passive components such as resistors and temperature
depending wires are used to compensate and calibrate the bridge output signal.
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERINGPage 8
MINOR PROJECT REPORT AUTOMATIC WEIGHING AND PACKAGING MACHINE
Figure 3.1: Strain gages
3.1.2 Accuracy of load cell
Load cells are ranked, according to their overall performance capabilities into differing accuracy classes. Some of these accuracy classes are related to standards which are used in legal for trade weighing instruments, while other accuracy classes are defined by the individual load cell manufacturer. Depending on the standard and the performance of a particular load cell type, an alphanumeric “accuracy grade” is given to the product. The alpha designate refers to the specific accuracy class, while the numeric part refers to the number of divisions. Revere Transducers manufactures products meeting NTEP, OIML and in-house specifications. These product are designated: Az Products meet the NTEP requirements for class III applications. Bz Products meet the NTEP requirements for class IIIL applications. Cz Products meet the OIML requirements for class III and IIII applications. CC/D3 These are arbitrary in-house classifications for products used in non-trade applications. Note “z” represents the number of divisions
(x1000), i.e. A3, B10, C6, etc.Most weighing systems use load cells where their working or measuring range is well below their rated capacity. In these situations, the values for the load cell utilisation and minimum verification interval (vmin) are important.The minimum verification interval is defined as the smallest value of a quantity (mass) which may be applied to a load cell without exceeding the maximum permissible error. It is specified as Emax/γ, where Emax represents the load cell’s rated capacity and γ represents a value which is specified by the load cell supplier.
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERINGPage 9
MINOR PROJECT REPORT AUTOMATIC WEIGHING AND PACKAGING MACHINE
3.2: Digital Load Cell
Digital load cells are still niche products. They are available as calibrated C3 and C6 cells as well
as uncalibrated types. Typical applications are set-ups with long wires (where the digital signal
transmission is better than analog), when several load cells are processed by one single
controller, e.g. truck scales or in electro-magnetical noisy environments. The advantages can
therefore be concluded as: ƒ Long cable lengths possible without loss in signal strength.
Combination of several load cells processed by a single processor ƒ Reduced sensitivity to EMI
ƒ Good replaceability as intrinsically calibrated cells. In order to get a more detailed picture of
what a digital load cell is or how its concept is like we have a look at its set-up nowadays. As
mentioned in the introduction it basically consists of the load cell itself combined with the
electronics which is a converter and a microcontroller.
Figure3.2: Load cell with analog to digital converter
The signal generated by the strain gages on the load cell are given to the electronics . Here an
A/D converter digitizes the analog signal and feeds the micro- controller or DSP with the A/D
raw count. The controller processes then the raw values, corrects them in terms of linearization,
filtering, hysteresis, etc. and finally puts out the digital signal.
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERINGPage 10
MINOR PROJECT REPORT AUTOMATIC WEIGHING AND PACKAGING MACHINE
Digital load cells are still only used in special applications like truck scales, silo scales, container
scales, etc. In common standard scales like i.e. bench scales or legal for trade scales they are not
used very often.
But exactly in this area there is a lot of benefit in using DLCs, some advantages cannot be
realized by using the analog load cell. The idea of a new possible structure is illustrated in the
following picture:
Figure 3.3: Separation of analog (weighing) part and the digital part
The analog part includes the sensor (load cell) and the electronic. The knowledge about weighing
lies in this part, i.e. construction of a good load cell or to make calibration, temperature
compensation, etc. The output is fully digital signal which delivers the weighing information
already fully calibrated.
The pure digital part on the other hand receives the digital data stream and just handles tasks like
displaying of the weight, recognition of buttons or interface other devices (e.g. network scales).
Also, language or country localization can be done in the software here. To make the digital part
there is not much knowledge about weighing itself needed.
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERINGPage 11
MINOR PROJECT REPORT AUTOMATIC WEIGHING AND PACKAGING MACHINE
3.3 Circuit diagram of Digital Load cell
Figure 3.4: Circuit diagram of load cell
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERINGPage 12
MINOR PROJECT REPORT AUTOMATIC WEIGHING AND PACKAGING MACHINE
3.4 Components of load cell
1. Crytal Oscillator : It is an electronic oscillator circuit that uses the mechanical resonance of
a vibrating crystal of piezoelectric material to create an electrical signal with a very
precise frequency. This frequency is commonly used to keep track of time (as in quartz
wristwatches), to provide a stable clock signal for digital integrated circuits, and to stabilize
frequencies for radio transmitters and receivers. The most common type of piezoelectric
resonator used is the quartz crystal, but other piezoelectric materials including polycrystaline
ceramics are used in similar circuits.
Quartz crystals are manufactured for frequencies from a few tens of kilohertz to tens of
megahertz. More than two billion crystals are manufactured annually. Most are used for
consumer devices such as wristwatches, clocks, radios, computers, and cellphones. Quartz
crystals are also found inside test and measurement equipment, such as
counters, and oscilloscopes.
Figure 3.5:Crystal Oscillator
2. AT89S52: All four ports in the AT89C51 and AT89C52 are bidirectional . Each consists of a latch (Special Function Registers P0 through P3), an output driver, and an input buffer . The
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERINGPage 13
MINOR PROJECT REPORT AUTOMATIC WEIGHING AND PACKAGING MACHINE
output drivers of Ports 0 and 2, and the input buffers of Port 0, are used in accesses to external memory. In this application, Port 0 outputs the low byte of the external memory address, time-multiplexed with the byte being written or read. Port 2 outputs the high byte of the external memory address when the address is 16 bits wide. Otherwise the Port 2 pins continue to emit the P2 SFR content. All the Port 3 pins, and two Port 1 pins (in the AT89C52)are multifunctional . The alternate functions can only be activated if the corresponding bit latch in the port SFR contains a 1. Otherwise the port pin is stuck at 0. It has less complex feature than other microprocessor.
Figure 3.6:Microcontroller
3. DC Motor : A DC motor is a mechanically commutated electric motor powered from direct
current (DC). The stator is stationary in space by definition and therefore so is its current.
The current in the rotor is switched by the commutator to also be stationary in space . This is
how the relative angle between the stator and rotor magnetic flux is maintained near 90
degrees, which generates the maximum torque.
DC motors have a rotating armature winding but non-rotating armature magnetic field and a
static field winding or permanent magnet. Different connections of the field and armature
winding provide different inherent speed/torque regulation characteristics. The speed of a DC
motor can be controlled by changing the voltage applied to the armature or by changing the
field current. The introduction of variable resistance in the armature circuit or field circuit
allowed speed control. Modern DC motors are often controlled by power electronics systems
called DC drives.
The introduction of DC motors to run machinery eliminated the need for local steam or
internal combustion engines, and line shaft drive systems. DC motors can operate directly
from rechargeable batteries, providing the motive power for the first electric vehicles. Today
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERINGPage 14