The way to make and design a PLC project
Do the whole process of a PLC project.
1, familiar with the process and good environment
2, design a control scheme is safe and reliable.
3, draw the electrical control principle diagram
4, to determine a good material, make the material list
5, write a PLC program, monitor screen, the design of PLC cabinet wiring
diagram, and at the same time, making the PLC cabinet
6 Party A, communication, construction site
7, site commissioning, and improve the process control plan
8, organization of Party of acceptance of the project
The principles of PLC design
The performance index of 1, the maximum to meet the object of
For the specific control functions and control system, design personnel in
the design, it should be in-depth field investigation, data collection, work
closely with designers of mechanical part and the actual operation personnel,
electrical control scheme together, cooperative solutions to various problems in
the design process will appear in the.
2, to ensure the safety and reliability of the control system
The electric control system is the lifeline of the reliability of electric
control system, safe and reliable work, cannot long production run. Especially
in order to improve the quality and quantity of products, to ensure the
application of production safety as the goal, must be put in the first place and
reliability, redundant control system
3, to the simple control system
To meet the requirements of the control and guarantee the reliable work,
should strive to simple configuration of the control system. Only a simple
control system is economic, practical, easy to use and maintenance easy to
do.
4, keep an appropriate margin
Considering the expansion of the scale of production, improve the
production process, increase the control task, and convenient maintenance needs,
to make full use of characteristics of PLC is easy to extend, in the selection
of the capacity of PLC (including the number, frame number, slot capacity of I /
O memory, etc.), should be an appropriate margin.
The basic steps for PLC design
In the design of PLC control system, despite the different object and
design task, design the content may involve many aspects, but also need a large
number of field input and output devices, connected, but the basic content
should include the following aspects:
1, a clear design and technical conditions
Design and technical conditions to design task book format, in the design
task book, should make clear the design requirements, constraints and control
mode. Therefore, the design task is to design the entire system on the basis
of.
2, determine the user input devices and output devices
The user input, output device is composed of PLC control system, in
addition to outside the PLC controller as the hardware itself, is designed and
the software model based on. Therefore, to clarify the type of input device
(such as a control button, switch, switch, sensor, protection device, sensor and
so on) and the number of type, output devices (such as signal light, contactors,
relays and other executive components) and the number of the output load, and a
drive motor (such as preparation, electromagnetic valve etc.). And carries on
the classification, summary.
3, the choice of PLC models
PLC is a core component of the control system, choose the correct,
reasonable models for technical and economic performance of the whole system
plays an important role in the.
The selection of PLC should include the choice of models, memory capacity,
the choice of I / O template selection
4, the distribution of I / O address, I / O wiring diagram drawing
Based on the analysis of user input, output devices, the classification and
sorting, I / O address allocation accordingly, then draw the I / O wiring
diagram. So far, the basic completion of the hardware design of PLC control
system
5, the design of control program
According to the model and the choice of the control task and the I / O
wiring diagram, ladder diagram language commonly used control program design of
the system. Application software is designed to ensure the operation of the
control program, the system is safe and reliable, must go through repeated
testing and debugging, to satisfy the control requirements.Design of non standard equipment
6, when necessary
In the selection of equipment, should try to use standard equipment. If
there is no standard equipment available, may also need to design, control
cabinet, operation table simulation display and other non - standard
equipment.
7, prepare technical document control system
In the design of the task is completed, to technical documentation system.
Technical documents shall include the design specification, user manual, I / O
wiring diagram and control procedures (such as the trapezoidal chart
etc.).
The selection of PLC
Select the appropriate type of PLC is a crucial step in the design. At
present, domestic and foreign manufacturers PLC PLC has hundreds of varieties,
the performance of different characteristics, the price is not the same.
Therefore, in the design, first, according to the principle of unified model to
consider, as far as possible to consider using PLC the use of the same series is
with the enterprise, in order to learn and master, ease of maintenance, spare
parts commonality, and can reduce the investment program. On this basis, but
also give full consideration to the following factors, in order to select the
best type of PLC:
The number and nature of the 1, I / O devices
In the choice of PLC, input, output the first response to the requirements
of the system have a detailed understanding, namely input how many, how much
output, which is a switch (or digital), which are analog, to digital output
should also be aware of the nature of the load, to select the appropriate output
(relay type, transistor type, triac type). In determining the size of the PLC
machine control, consider a certain margin, in order to adapt to the change of
system function and process, generally by 10 ~ 15% margin to consider. In
addition, but also consider the structure of PLC, and analyze with I / O points,
decided to choose the integral and modular PLC.
In determining the number and nature of input and output of the PLC, can
further determine the type and quantity of various I / O templates. Switch I / O
template specification 4, 8, 16, 32, 64, the number of multi template, the
average price of each point is relatively low. To switch the external wiring
mode of I / O templates can be divided into isolated and exchange points, each
point of the average price of high isolation type. If the signal does not need
to be isolated between the meeting point, should choose I / O templates. In the
integrated PLC, each I / O terminals are isolated and the meeting point of the
points, in order to meet the need of input / output devices of different voltage
levels.
2, the function of PLC
According to the control process and control characteristics of the system,
determine the PLC machine function. Each series of different specifications of
the machine has the function of PLC is not exactly the same. Such as some small
PLC, only the switch quantity logic control functions, and do not have the data
processing and analog processing function. When a system for position control,
temperature control, PID control and closed-loop control, consideration should
be given to the template PLC, I / O module and the choice of the special
function of the corresponding, otherwise the algorithm design of PLC ladder
diagram programming, on the one hand, on the other hand also takes up a lot of
procedures space.
In addition, consideration should also be given to the computing speed of
PLC, especially when the use of analog quantity control and high speed counter
function, it should be the maximum operating frequency of PLC machine can meet
the requirement of.
3, the user program memory capacity
Determine the user program memory capacity of PLC, PLC application design
and selection is an indispensable link in the. Generally speaking, the user
program memory capacity and memory utilization, switch I / O, the total number
of analog I / O points and designer of the programming level.
Simple estimation formula: words = (memory switch I / O points and O points
of analog I / X 16) X 10
Type: each analog channel (or I / O) is 16 I / O switch. On the basis of
this, consider the left margin of 20 to 25%. For the more complicated process,
should be appropriate to increase the capacity of memory, or, when the control
is more complex, the amount of data processing, there may be insufficient memory
problems.
