How to use PLC instead of relay - Electronic enthusiasts net

the programmable controller is PLC, widely used in the control system. Lack of programmable controller, the control system as a lack of soul. For programmable controller, small make up part. To enhance understanding of the programmable controller, this article explores why PLC instead of relay control technology. Programmable controller is if you are interested in, might as well continue reading.

in the field of industrial automation, programmable controller ( PLC） As the automatic control on the basis of the equipment for most automation system, at the same time also to the industrial control has brought the unprecedented change particularly. The use of PLC industrial control system compared with the traditional industrial control system with relay, precision and efficiency in the operation, control, and so on each aspect has incomparable advantages. Although in the industrial control system used in the relay control equipment will not be completely eliminated, but because of the emergence of PLC has changed the industrial control design ideas of the designer.

a, the disadvantages of current control relay

today relay has been applied to the family and industrial control fields. Their products have higher reliability than ever before. However, this is also will bring some problems. Like most control relay are long-term wear and fatigue under the working conditions, easy to damage. And relay contact is easy to produce arc, even will fuse together to produce wrong operation, serious consequences. Moreover, over the use of a concrete containing hundreds of relay device, the control box will be large and bulky. In under the condition of full load transport, large relay will produce a lot of heat and noise, but also consume a lot of electricity. And relay control system must be manual wiring, installation, if there is a simple modification, also need to spend a lot of time and manpower and material resources to restructuring, installation and debugging.

2, advantages, characteristics and function of the programmable controller

is famous for its small volume by powerful programmable controller, it not only can easily complete the order logic, motion control, timing control, counting control, digital computing, data processing, and other functions, and can be established through input/output interface and all kinds of production machinery digital and analog link, so as to realize the automatic control of the production process. Especially now, due to the advent of the era of information, network, expanded the function of PLC, make it has a strong network communication ability, which is more widely used in many industries.

1, the sequence control

sequence control is the most basic, the most widely used field of PLC. The so-called sequence control, it is in the order process, under the action of control signal, makes the production process of various actuators automatically according to the order. Because it also has a flexible programming design, high speed, high reliability, the advantages of low cost, easy to maintain, so in the realization of single machine control, more machines control, production process control can completely replace the traditional relay contactor control system. It is mainly according to the operation button, limit switches and other site to command signal and sensor signal, control the corresponding mechanical parts for operation, so as to achieve the automatic production line control. Typically used in the automatic control of elevator and the line of electromagnetic logging, open and close automatically, the order of the belt conveyor starting, etc. For example, my factory is the use of raw materials mixing system of PLC sequence control function.

2, closed-loop process control

in the past for process control of analog hardware circuit composed of analog PID regulator is used to realize the open and closed loop control. Now can adopt PLC control system, choose the analog quantity control module, its function performed by the software, the precision of the system is determined by digits, not affected by the components, higher reliability, easy to realize complex control and advanced control method, can control multiple control circuit and the control parameters at the same time. Such as the temperature, flow rate, pressure and velocity in the process of production, etc.

3, motor position control

PLC can support of nc machine tool control and management, in mechanical processing industry, programmable controller and computer numerical control ( CNC） Together to complete machine motor position control, its function is to accept input device input information processing, the processing and calculation, a corresponding pulse to drive, through the stepper motor or servo motor, make machine tools according to the predetermined orbit, to complete the multiaxial servo motor control. Now used to control the centerless grinding block cutting, stamping, complex components, such as touch hobbing cutting applications.