plc What is the role of the power module

plc generally have small internal switching power supply, the output voltage is used for their own chips, components and external sensor power supply module , a large current can also give small executive power components, such as solenoid valve relays, etc.
plc cpu host power supply is limited, if you add the expansion unit, or peripheral unit. When using host power beyond its rated value, then you need the power module.

Input Module plc's shortcomings

input module plc Disadvantages: module mechanism to bring safety hazard
1, the intercept system calls.
2, modify the output symbol table.
3, by modifying the system calls the plc temperature module themselves hidden.
4, redirect file operations.
5, modify the file owner.
6, plc controller suppliers processes.
7, the executable file redirection.
8, calling sys_socketcall by modifying the system, making the system after receiving the specified data packet open the back door
9, TTY hijacking.
10 virus.

Definition of the PLC

There are many definitions PLC. International Electrotechnical Commission (IEC) is the definition of the PLC: Programmable Logic Controller is a digital electronic computing operating programmable logic controller system, designed for applications in industrial environments. It uses a programmable memory, used in its internal storage to perform logical, sequential control, timing, counting and arithmetic operations such as operating instructions, and through digital and analog inputs and outputs, control types machinery or production processes. Programmable logic controller and related equipment, all with industrial control systems should be easy to form a whole, to expand the principles of the design of its functions. The mid-1980s to the 1990s, is the fastest growing PLC period, the annual growth rate has been maintained at 30 to 40 percent. During this period, PLC capability in handling analog and digital computing power, man-machine interface capabilities and network capabilities have been greatly improved, PLC gradually entering the field of process control, in some applications in the field of process control to replace the dominant DCS systems. PLC has the versatility, ease of use, wide adaptation, can be * high anti-jamming

plc power supply module

capability, programming and simple. PLC in the industrial automation and control especially in order to control the position, in the foreseeable future, can not be replaced.

Role of input and output modules

Fire alarm, the alarm controller output module plc needs to start linkage external control devices such as smoke control valve, sending valve, fire shutter doors, fans, alarm, etc., and to accept the action device answer.
Output modules connected to the bus loop controller can be installed in the vicinity of the control device can also be installed in the floor inside the terminal block. Electronic writing code, you can live encoding. Ji-output control logic output modules can be completed according to the project situation programming. When the controller receives the alarm signal to the detector, based on pre-programmed into the program, the controller will be linked via the bus control signal to theplc analog output module, the output module needs to start linkage firefighting equipment; action after the device will accept a signal answer.

The main job of the output module plc

SCM can be used to direct the development of control systems, but very demanding for the developer (not the general level capable of ) , long development cycles, high costs ( for some large decency you need to Nanda plc power supply module  do a little experiment , a printed circuit board requires a considerable the cost , you can say you use the emulator to develop experimental board , but I have to tell you , do you just verify the feasibility of hardware and software , does not mean that can be used in industrial control systems, industrial control systems because Immunity requirements for very high stability first , rather than the performance of the first , so you must constantly  Nanda plc input output modules test the circuit board design , improvement ) when you solve these problems, you will find that you have done a PLC , of course, If you need to use someone else can easily use the software you'll need a set , so you may not need to tell others about your circuit ( you can not tell anyone ) .
       Many people feel very mysterious PLC , PLC is actually very simple , in addition to its internal CPU speed , the Nanda Programmable Output Module  other functions not as common microcontroller . PLC usually uses 16 or 32-bit CPU, serial communication with the outside world with a channel or two , and has an internal timer can , to improve the reliability plus a watchdog timer is enough .