Tutorial on Simatic s5 Control System :Practical Programming and Fault Finding

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Very practical stuff for Users of the old but reliable Siemens S5 plc system. This is based on practical experience with s5 in our smelter.


TUTORIAL ON SIMATIC S5 CONTROL SYSTEM: Practical programming and Fault finding BY ARCHIBONG, AKANINYENE INSTRUMENT SUPERVISOR, ALUMINIUM SMELTER PLANT, IKOT ABASI, NIGERIA.TABLE OF CONTENTS 1. CONTROL SYSTEM COMPONENTS 1.1. Introduction 1.2. Inputs 1.3. Outputs 1.4. Flags 1.5. Addressing 2. S5 PROGRAM/ ENVIRONMENT 2.1. Important Terminologies in S5 User program 2.2. Control Logic Operations 2.3. Working in the S5 Environment 3. CODING 3.1. Forms Of Logic Representation 3.2. Examples 3.2.1 Series/ Parallel Connections 3.2.2 Interlocking Contacts 3.2.3 Latching Contacts 3.2.4 Timers

4. TROUBLESHOOTING WITH PROGRAMMER 4.1. Steps in Troubleshooting 4.2. Real life Problems

1. 0 CONTROL SYSTEM COMPONENTSThis module reviews what a skeletal control system looks like and brings to the fore characteristics of inputs, flags, outputs and their addresses as regards Simatic S5 control system. In summary, externals from the controller/ transmitter in the control process are discussed.

1.1 IntroductionIndustrialization has paved way for the need of control systems to ensure enhanced productivity among other reasons. A control system is, literally, any network of elements implemented to replace or minimize human interference in industrialization. Fig. 1 shows the 3 basic components of control system.

Fig. 1




InputsInputs in siemens S5 control system are divided into 2 viz Digital and Analog Inputs. Digital Inputs are generated from mostly 2 sources : Contactor contacts or Controller contacts. These inputs are so called because they can only exist in 2 states (0 or 1). Compared to Analog inputs, these inputs make up about 70% of inputs in most siemens S5 plc stations. Digital input cards exist in different models to receive digital inputs in S5 processes. Digital Inputs are assigned operands with the letter I in the S5 program.

Analog inputs are those gotten from sensors in the field like RTDs, thermocouples, flow meters, rotary encoders amongst many others. In Simatic s5, numeric values read from these sensors are represented in different formats. The following formats will be an interest to us in this paper. KF ---- 16 bit fixed point numbers. KH ------ 32 bit fixed point numbers. KM --------- Binary numbers KG ----------- Floating Point Numbers. Eg 2- 34 Negative values are actually read in the PLC as its 2s complement. Reader can read extensively about the ranges of these formats and examples on how they are used. The important fact , however, is that recognition of these will definitely help in troubleshooting analog signals. Analog cards exist in different models and modes to interface analog inputs with the rest of the PLC station.

1.2 OutputsOutputs are results of logic operations from the CPU. As inputs, they are classed into 2: Digital and analog Outputs. Digital outputs are mostly used to drive contactor loads like pumps while analog outputs may drive a variable (PID) control valve. Digital Outputs are assigned operands with Letter O.

1.3 FlagsFlags are intermediate results from logic operations which are used in the program and are not written to Output Cards. Buttons on Operator panels are usually programmed as flags in Simatic S5 Program. Flag Operands are denoted by F.

1.4 AddressingIt is only logical to give addresses to every input and output in a process for identification purposes. Bit, bytes, Word, Double Word are all concepts used in Simatic s5 operand addressing. Bit: This is the smallest unit of information in the program (1) Byte: This comprises 8 Bits Word: This comprises 16 bits or 2 Bytes

Double Word: This comprises 32 bits or 4 bytes. A 0 or 1 can be completely described by a bit inferring that a digital input or output requires bit addressing. Practically, most digital input/ output cards are made up of 8 terminals resulting in a byte e.g. I 7.0 to I 7.7. Recall in the section on analog inputs, numeric representation was introduced. Analog signals require 16 to 32 bits to be accurately represented e.g. FW 54 (means 54.0 --------- 55.7) will be followed in address by FW 56 and not FW 55. It should be noted that the initial address values depend solely on number of sensors in the process and programmer discretion but consecutive address values depend on type of sensors to be read ( Analog or Digital).

QUESTIONS 1. Input and output Operands are denoted by ---------- and --------------- respectively 2. A byte is equal to --------------- double word 3. Fill in the following 2 consecutive addresses FW 15,----- , --------, 4. 105 in Binary form is ------------- and 105 in 2s complement is --------------5. 2F3A in binary form is --------------6. Floating Point numbers are represented by ---------- while Binary numbers are represented by -----------------7. A contactor contact is normally programmed as ---------------- while a rotary encoder signal is normally programmed as --------------8. -------------- are intermediate results of logic operation and also used as ---------------------9. A process with 24 contact sensors has a beginning address of I 56.0, the last address in its PLC station is I ----------10. An analog output can be used to directly drive a single phase motor. (True or False)

2.0 S5 PROGRAM/ ENVIRONMENTThis module deals with some terminologies, logic operations and usage of the S5 user program. Practical use of the PG is required to complete this module. Reader should become conversant with the S5 programming environment and the basics of logic operations upon mastery of this module. However, external materials should be gleaned if necessary.

2.1 Some important Terminologies in the S5 User ProgramThe following will be defined with respect to Simatic S 5 program

1. Assignment lists: This is a display in the program showing operands and associated descriptive comments for the entire program project. 2. Symbols Table: This is a display in the program describing operands for specific segments of the program 3. Program Block: This is a part of the user program where most of the control logic for the program is coded. It is used for non routine tasks. 4. Function Blocks: This is apart of the user program where coding of routine tasks for the process are done. 5. Cross Reference Tables: This relates a selected operand with different blocks where it is used in the entire program. 6. Interface: This is the connection environment between the PG and the CPU. 7. Comments: These are statements used in the program for descriptive purposes alone and not part of the program. 8. Operators: These are commands that act on operands using specified rules of logic. Examples of Operators are AND, OR, COMPARE, NOT, LOAD, TRANSFER 9. Project: This is the entire program for a specified process. 10. Data blocks: These are areas in the program where process set points, operator panel data, timer values and sensor input values are stored. 11. Program Segments: This is a sub division of a block in a program 12. RLO: Result of Logic operation. 13. Accumulators: These are temporary data storage points in the CPU where data to be processed immediately is Kept

2.2 Control Logic OperationsThe essence of control in industry is to manage a combination of conditions by which the process was created. Logic helps achieve this uniform goal of control. Some control logic operations that are needful for this course are defined below.

AND Operation: This operation ensures that the output of the logic operation is 1 only when its inputs are all 1 OR Operation: This operation ensures that the output of the logic operation is 0 ONLY when its inputs are 0 NOT Operation: This ensures that the output of the logic operation is an inverse of the input COMPARE Operation: This compares two variables ( =, ,, ) and outputs a 1 when the operation conditions are true. LOAD Operation: This calls data from the data block for processing TRANFER Operation: This sends data to the data block after processing TIMER Operation: This times the output triggered by an input based on certain timing conditions. There are basically, 5 types of timers viz On delay, Off delay, Pulse timer, Extended pulse Timer and Stored on Delay Timer. Time values are loaded with the symbol KT. The next section deals on programming timers. SET Operation: This operation gives an output of 1 when ever its input is a pulse edge form 0 to 1. RESET Operation: This operation gives an output of 0 whenever its input is a pulse edge from 0 to 1. There are many other operations but these will suffice. Reader should ensure proper understanding of the mentioned operations as this will aid in troubleshooting faults through program.

2.3 Working in Simatic S5 EnvironmentIn this section, some important operations in the S5 Environment are highlighted. LOADING OF PROGRAM: PROCEDURE I. Copy project number from CPU in the PLC Station.


Open S5 program to its home page from the Windows 95 OS. Click on File, then Project, then load. Press F3, or click select Follow the path : D>ALSCON>FACILITY> COPIED PROGRAM Click on first pop up item in the box on the left of the screen ( it just came up) Press the enter key continually for every dialog box until you return to the home page VERIFICATION OF PROCEDURE

VIII. From Home page; Click on File, then project, then Set IX. Click on Blocks and confirm similarity with chosen program. If not similar, Select block through similar procedure as program load (IV VII) X. Click on Symbols and confirm similarity with chosen program. If not similar, Select associated symbol through similar procedure as program load.( IV VII)

NOTE: If there is sameness amongst your loaded program, symbols, blocks and the program on the CPU, then the program has been adequately loaded else this procedure (I X) should b


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