Fig。 3。 Communication preconditioning flow

(1)Configure PLC hardware under STEP-5。0 programming software。 Choose the Corresponding functional modules of PLC in the above-mentioned modules , put them into the simulation software orbit in order, and then the program writing tool will arrange the address for each module automatically。 One of communication module 316 #1 (Communication Module # 1 for 332, communication module # 1 for 416)。

(2)Initialize the Communication Module CP340, using module parameters of program tools: select Communication protocol selection in ASCĊ format; set RS485 communication mode as the two-line model。

(3)set the temperature controller communication parameters as follows: 9600 baud, 8 data bytes, no parity, 1 start bit, communications smallest time interval as 3ms。

(4)call communication commands FB2 (RECEIV) and FB3 (SEND) using STEP-5。0 Programming software function modules, the former is used to receive the information which arrives communication module, while the another is used to send read and write commands: set AD, DB_N, DBB_N of FB2 to 316,MW100, MW102; set ADD, DB_N, DBB_N, LEN of FB3, to 316, MW104, MW106, 12。 and set MW100, MW102, MW104, MW106 as the  initial value 100 , 200,0。

(5)Chang the content in temperature controller or Touch Panel set value in the memory of PLC into ASCĊ。

(6)define data block DB100, DB101 。。。 DB131 and DB200, DB201 。。。 DB231。 Make the former block as a buffer to receive data, put data block number (DB_N) into WM100; Make the latter block as a buffer to send data, put data block number (DB_N) into WM104。

Fig。 4。  Cycle to read and write communication flow

D  Host monitor procedures

The local data obtained by the communication module论文网

#1 and #2, as well as digital input modules and analog modules (Thermostat district head measured temperature, frequency converter, DC speed regulator operating status, temperature control browser, converter, DC speed regulator alarm, alarm disconnected, including meters and so on) will be stored in the corresponding data block or a register of PLC, and then will be regularly sent to the host through communication module #3。Communication module # 3 can also receive commands from the host, and then these data will be transmitted to CPU for implementation。 The host monitor procedures are written by MSComm of ActiveX serial communication controller based on VB6。0。Recall the Microsoft Comm Control 6。0 (MSComm) in Engineering components in VB6。0, and set

up their property properly。 When there is serial communication events (send or receive data) occurs, the communication controller will trigger one OnComm case, and then the sent or received data will be processed。 At last ,The received data will be separated and shown in the monitoring program window。

IV。 CONCLUSION

PLC controller plays a good performance and shows high price-performance ratio in the local control。 The extrusion system based on the new theme of this paper has been put into operation。 The Varied-Frequency speed regulator operation control, parameter settings and operating status monitoring ,and control of temperature controller have been carried on by the implementation of PLC。 The theme in this paper will both improve the control accuracy and the quality of products, and also reduces cost, achieving satisfactory results at last。

REFERENCES

[1] SIEMENS SIMATIC S7-300 Programmable Controller System Manual, SIEMENS AG

[2] Lu Lin-Jie。 Principle and application of Programmable Logic Controller。 Tsinghua University Publishing House。2002

[3] Xu Shi-Xu。 System Principle, application and network of Programming Logic Controller, HeFei: Publishing House of University of Science and Technology China, 2000

[4] Siemens Totally integrated Automation: http://www。auto mation。siemens。com/fea/html_00/down_module。htm