Siemens 020-011 User Manual
Industry Sector, IA&DT
SCE Training Curriculum
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TIA Portal Module 020-011, Edition 04/2014
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SCE_EN _020-011_R1404_Startup Programming with SIMATIC S7-1500
5.
What is a PLC and what are PLCs used for?
5.1
What does the term PLC mean?
PLC is the abbreviation for Programmable Logic Controller. This describes a device that controls a
process (for example, a printing press for printing newspapers, a filling system for filling cement into
bags, a press for pressing plastic parts, etc.).
These actions are carried out corresponding to the instructions of a program that is located in the
device’s memory.
bags, a press for pressing plastic parts, etc.).
These actions are carried out corresponding to the instructions of a program that is located in the
device’s memory.
5.2
How does the PLC control the process?
The PLC controls the process as follows: so-called actuators are wired with a control voltage of -for
example- 24V by means of PLC connections called outputs. This allows for motors being switched on
and off, valves opened and closed, and lamps switched on and off.
M
M
0V
24V
The PLC outputs control the actuators
through switching the control voltage!
PLC
Machine
Program with
instructions
Memory
Program loaded in the
PLC’s memory…
Speicher der SPS......
.... controls the
machine
PLC
Outputs
Lamp is lit
Lamp is not lit