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B-3

Ladder Logic (LAD) for S7-300 and S7-400

C79000-G7076-C504-02

B.2 Bit Logic Instructions

Figure B-1 shows a conveyor belt that can be activated electrically. There are

two push button switches at the beginning of the belt: S1 for START and S2

for STOP. There are also two push button switches at the end of the belt: S3

for START and S4 for STOP. It it possible to start or stop the belt from either

end. Also, sensor S5 stops the belt when an item on the belt reaches the end.

You can write a program to control the conveyor belt shown in Figure B-1

using symbols that represent the various components of the conveyor system.

If you choose this method, you need to make a symbol table to correlate the

symbols you choose with absolute values (see Table B-1). You define the

symbols in the symbol table (see /231/ User Manual).

Table B-1 Elements of Symbolic Programming for Conveyor Belt System

System Component

Absolute

Address

Symbol Symbol Table

Push Button Start Switch I 1.1 S1 I 1.1 S1

Push Button Stop Switch I 1.2 S2 I 1.2 S2

Push Button Start Switch I 1.3 S3 I 1.3 S3

Push Button Stop Switch I 1.4 S4 I 1.4 S4

Sensor I 1.5 S5 I 1.5 S5

Motor Q 4.0 MOTOR_ON Q 4.0 MOTOR_ON

MOTOR_ON

` Start

` Stop

` Start

` Stop

Sensor S5

Figure B-1 Conveyor Belt System

Controlling a

Conveyor Belt

Symbolic

Programming

Programming Examples

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