Structure automate et types de cartes [ Tuto programmation automate Siemens S7 #1 ]

Overview

This tutorial introduces the core structure of Siemens PLCs (example: Siemens S7-300) and explains how inputs/outputs and program execution are organized.

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1) PLC Architecture (Hardware)

• CPU as the “brain”

  • The PLC program is loaded into the CPU and then executed.
  • The CPU reads inputs and manages outputs (both digital and analog).

• Digital input cards

  • Used with devices such as pushbuttons, sensors, limit switches, contacts.

• Analog input cards

  • For proportional signals (example mentioned: 0–10V-type signals).
  • Thermocouple is also mentioned, but the exact ranges/values are unclear in the provided subtitles.

• Digital outputs

  • Drive devices like relays, contactors, solenoid valves, etc.

• Analog outputs

  • For proportional/analog actuators (again, 0–10V-type outputs are mentioned).

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2) Input/Output Card Wiring & Variants

• Always consult the technical documentation

  • Wiring and terminal assignments depend on the specific card/module.
  • The tutorial emphasizes that correct connection often involves plus 24V and a common/ground reference, depending on the card.

• Example card types

  • 16-input digital input cards that can directly accept AC voltages
    • Example use case: interfacing 220V equipment to a PLC.
  • Relay output card
    • A wiring diagram is referenced as being available in the card documentation.

• PNP vs NPN input concept (very important)

  • PNP
    • Sensors/modules send +24V
    • Common is likely 0V (depending on the convention used).
  • NPN
    • Sensors/modules send 0V
    • Common is likely +24V (depending on the convention used).

• PNP vs NPN also applies to outputs

  • PNP/NPN output modules have different “common” levels:
    • One common at 0V
    • The other common at 24V

Recommendation: double-check whether the module is PNP or NPN so it matches your field sensors—especially because certain standards used in the US/UK can differ.

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3) Programming Terminology (German vs English Addressing)

• Siemens mnemonics historically come from German, but there’s an option for English-style conventions.

• Digital inputs

  • Referred to using “i” (with the NPN convention noted).

• Digital outputs

  • Terminology differs in the “English vs German” explanation (the subtitles mention avoiding confusion related to “0” vs similar concepts).

• Analog addressing in later tutorials

  • The instructor states that they will use English standard addressing for analog in subsequent material.
  • Analog proportional signals are described using specific addressing symbols/variables (subtitles mix German/English, but the key idea is that analog proportional signals have distinct addressing notations such as symbols/variables like “p” and “w”).

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4) Addressing Structure: Grouping into Bytes/Bits

• Inputs and outputs are grouped into sets of eight:

  • 1 byte = 8 bits

• Bit numbering

  • Starts at 0, and runs 0 through 7 (not from 1).

• Addressing example concept

  • Select an input/output group (a byte),
  • then select a bit within that byte to define a specific signal.

This same “byte + bit” idea applies to:

• digital input groups
• digital output groups

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5) PLC Program Execution Model (Read/Cycle Concept)

• The tutorial introduces cyclic execution:

  • The PLC uses an OB block (OB1) as the organizing routine (described with a metaphor like “maestro/conductor”).
  • It also discusses Function Blocks (FC) / structured program parts.
    • Example: FC1 for a motor
    • Example: FC2 for signaling (e.g., lights/beacons)

• Execution order

  • Scanning is described as from top to bottom and left to right.

• Cycle idea

  1. PLC captures an input image (a snapshot of input states)
  2. runs logic based on that snapshot
  3. then updates outputs
     • switching digital outputs
     • updating analog output values

• Timing

  • The scan is described as very fast and deterministic.
  • A rough figure is mentioned (subtitles unclear): approximately ~5 to 15 ms (timing details are not fully clear).

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Tutorials / Series Context

• This is Video #1 in a series of PLC programming tutorials.
• Follow-ups are promised, including:
  • a detailed explanation of the read cycle
  • more structured programming modules

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Main Speakers / Sources

• The instructor speaking (host/creator of the “Industrial Technology / Technique Industrie” tutorials).
• Mentions Siemens S7-300 (example PLC).
• Also references compatible/alternative card brands (e.g., FIPA is mentioned), but the primary source is the tutorial creator/instructor.