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Example "PID control"

4.7 Integrate temperature comparison as condition in control program

STEP 7 Basic V10.5

154 Getting Started, 12/2009, A5E02651459-01

4.7 Integrate temperature comparison as condition in control program

Introduction

The following steps will show you how to evaluate the temperature values of the PID

controller and integrate them as condition for control of the machine. The pasteurization

process is controlled by the following organization blocks:

● Main [OB1]

The program for controlling the machine dependent on the temperature values of the PID

controller is executed in the "Main [OB1]" organization block.

● PID [OB200]

The technological object "PID_Compact" of the PID controller and the simulation block

"PROC_C" are executed in the organization block "PID [OB200]".

Connection between PID controller and control program

The temperature monitoring of the PID controller is integrated as follows into the program of

the organization block "Main [OB1]":

The actual temperature value of the "temperature" tag, which is used as input for the PID

controller, should be read by the program in the organization block "Main (OB1)" and

compared with a minimum and maximum value.

● If the actual temperature value is between a minimum value of 73°C and a maximum

value of 77°C (setpoint +/- 2°C), the conveyor will be driven.

● If the minimum value of 73°C has not been reached yet or the maximum value of 77°C

has been exceeded, the "conveyor_drive_ON_OFF" tag will be reset.

Requirements

● The organization block "Main [OB1]" is open.

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Siemens v1.0 Manual de servicio Pagina 154