Catalog

I Essential Differences Between PLC and Microcontrollers

(1) PLCis a mature control system composed of microcontrollers, and is the product of mature and stable microcontroller application system. It has a strong universality.

(2) Microcontrollers can constitute a variety of application systems, and have a wider range of use. As for Microcontrollers, it is only an integrated circuit and can only be applied with other components and software.
(3) From the view of engineering use, it's convenient for the single project or the project with few repetitions to use PLC. Because it has a high success rate, a good reliability. However, the cost is high.

(4) For large scale supporting projects, the adoption of SCM system(Supply Chain Management system) has the advantages of low cost and high efficiency, but it requires considerable research and development strength and industrial experience to make the stytem stable.     

What Is a Supply Chain Management System?    

II Characteristic and Functions of PLC

In essence, PLC is a set of Microcontroller (the range of Microcontroller is wide) system. But PLC also has its characteristic: 

PLC widely uses the ladder diagram to replace the computer language, and has certain advantage to the programming. You can regard the ladder diagram as computer language such as assembly, though they have a different using range. Generally the PLC transform your ladder diagram into C or assembly language(determined by the CPU used by the PLC), and then use the assembly or C to compile into machine code. the PLC only runs machine code. The ladder diagram just makes it easier for the user to use.
As what have said, MCS-51 MCU can also be used for PLC production, but only for 8-bit CPU in some advanced applications, such as a lot of calculation (including floating point operation), embedded systems (now UCOS can also be transplanted to MCS-51), and it;s just a little powerless working, but with DSP can meet the general requirements.In addition, by using trapezoid graph programming, we can convert the trapezoid graph to C51 and compile it with KEIL's C51. We can also find that different types of PLC will choose different CPU, in fact, the PLC is a complete set of single-chip computer system.  

Internal Structure of MCS-51

Of course, you can also use MCU directly to develop control system, but it has quite a high requirement for developers(it's not general level can be competent),like the long development cycle, high cost, and you need to do experiments for some large system.The printed circuit board requires a very high cost, and you could use the emulator or experimental board to replace it, , but it;s just verify the feasibility of hardware and software, and it can't mean that can be used in industrial control system. Because the requirements for industrial control system against interference is very high, and it requires stable first, rather than the first performance, so you have to experiment and improve your circuit board design again and again .When you solve the above problems, you will find that you have made a PLC.

In fact, it is not a mystery to see PLC. PLC is very simple, and the functions of its internal CPU except speed are inferior to the ordinary Microcontroller. Usually, PLC uses 16 or 32 bit CPU, with 1 or 2 serial channels to communicate with the outside world, and a timer can be provided inside. If you want to improve its reliability , you can add a watchdog timer .

PLC Components and Their Functions

In addition, the key technology of PLC lies in the internal solidification of a program that can explain the trapezoidal graph language and the auxiliary communication program. For simple applications, which usually operate as independent controllers, there is no need to exchange information with the outside world, just internal solidification of programs that can interpret the language of the trapezoid diagram.In fact, the main job of designing PLC is to develop program to explain the ladder diagram language. Single chip microcomputer can replace PLC completely now. In the past, due to the weak stability and anti-electromagnetic interference capability compared with PLC, the current single chip has achieved high stability and strong anti-interference capability, which has been replaced in some fields.

You May Also Like:

Some Basic Knowledge of Solid Capacitors

Selection of Residual Current Protector in Charging Pile

PCB Layout Tips and Tricks: The Components and Wires

Common Guide for Selecting Electronic Components

Ordering & Quality

Photo	Mfr. Part #	Company	Description	Package	PDF	Qty
	DSPB56374AE	Company:NXP / Freescale	Remark:IC DSP 24BIT 150MHZ 52-LQFP	Package:52-LQFP	DSPB56374AE  Datasheet	In Stock:10211 Inquiry	Inquiry
	CAP017DG	Company:Power Integrations	Remark:IC CAP DISCHRG 1000V 2500NF 8SO	Package:8-SOIC (0.154", 3.90mm Width)	CAP017DG  Datasheet	In Stock:7450 Inquiry	Inquiry
	MK20DX256VLH7	Company:NXP / Freescale	Remark:IC MCU 32BIT 256KB FLASH 64LQFP	Package:64-LQFP	MK20DX256VLH7  Datasheet	In Stock:5060 Inquiry	Inquiry
	PWR263S-20-3300F	Company:Bourns	Remark:RES SMD 330 OHM 1% 20W D2PAK	Package:TO-263-3, D²Pak (2 Leads + Tab), TO-263AB	PWR263S-20-3300F  Datasheet	In Stock:108 Inquiry	Inquiry
	FC4L110R050FER	Company:Ohmite	Remark:RES SMD 0.05 OHM 5W 4320 WIDE	Package:Wide 4320 (11050 Metric), 2043	FC4L110R050FER  Datasheet	In Stock:481 Inquiry	Inquiry
	1N4148W-7-F	Company:Diodes Incorporated	Remark:DIODE GEN PURP 100V 300MA SOD123	Package:SOD-123	1N4148W-7-F  Datasheet	In Stock:5270000 Inquiry	Inquiry
	K9F4G08UOA-P1BO	Company:SAMSUNG	Remark:4G-bit NAND Flash Memory with spare 128M-bit	Package:	K9F4G08UOA-P1BO  Datasheet	In Stock:5960 Inquiry	Inquiry
	MCF52210CEP66	Company:NXP	Remark:IC MCU 32BIT 64KB FLASH 64QFN	Package:64-VFQFN Exposed Pad	MCF52210CEP66  Datasheet	In Stock:144 Inquiry	Inquiry
	MPC8280VVQLDA	Company:NXP / Freescale	Remark:IC MPU MPC82XX 333MHZ 408TBGA	Package:480-LBGA	MPC8280VVQLDA  Datasheet	In Stock:744 Inquiry	Inquiry
	UPSD3212CV-24U6	Company:STMicroelectronics	Remark:IC MCU 8BIT 80KB FLASH 80TQFP	Package:TQFP80	UPSD3212CV-24U6  Datasheet	In Stock:1200 Inquiry	Inquiry