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.

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Ordering & Quality

Photo	Mfr. Part #	Company	Description	Package	PDF	Qty
	LM3S9B90-IQC80-C5	Company:Texas Instruments	Remark:IC MCU 32BIT 256KB FLASH 100LQFP	Package:LQFP-100	LM3S9B90-IQC80-C5  Datasheet	In Stock:2320 Inquiry	Inquiry
	MR27V1602ETN	Company:OKI	Remark:	Package:TSOP	MR27V1602ETN  Datasheet	In Stock:721 Inquiry	Inquiry
	MMA2204KEGR2	Company:Freescale Semiconductor - NXP	Remark:ACCELEROMETER 112.5G ANAL 16SOIC	Package:16-SOIC (0.295", 7.50mm Width)	MMA2204KEGR2  Datasheet	In Stock:1330 Inquiry	Inquiry
	RHC2512FT150R	Company:Stackpole Electronics	Remark:RES SMD 150 OHM 1% 2W 2512	Package:2512 (6432 Metric)	RHC2512FT150R  Datasheet	In Stock:19360 Inquiry	Inquiry
	PM8110	Company:QUALCOMM	Remark:power-supply-charger-ic-chip-PM8110	Package:BGA	PM8110  Datasheet	In Stock:1833 Inquiry	Inquiry
	MCF5206ECAB40	Company:Freescale Semiconductor - NXP	Remark:IC MCU 32BIT 160QFP	Package:QFP160	MCF5206ECAB40  Datasheet	In Stock:1276 Inquiry	Inquiry
	MC68332GCEH20	Company:NXP / Freescale	Remark:IC MCU 32BIT 132PQFP	Package:132-BQFP Bumpered	MC68332GCEH20  Datasheet	In Stock:2569 Inquiry	Inquiry
	S9S12G128F0CLH	Company:NXP	Remark:IC MCU 16BIT 128KB FLASH 64LQFP	Package:64-LQFP	S9S12G128F0CLH  Datasheet	In Stock:5046 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
	BCM5221KPB	Company:Broadcom Limited	Remark:Ethernet ICs 10/100Base TX/FX Mini-PH Tra	Package:BGA	BCM5221KPB  Datasheet	In Stock:975 Inquiry	Inquiry