Learn PLC Under 1 Hours | Siemens S7 1200

Main ideas / lessons conveyed

1) What an S7-1200 PLC is made of (hardware architecture)

The video focuses on Siemens S7-1200 (S7-1200) PLC hardware, especially:

• CPU (example shown: CPU 1214C), including built-in:
  • Digital inputs (DI)
  • Digital outputs (DO)
• Extension IO modules (example mentioned: SM1223 / “SM1 22 3” / similar digital in/out modules)
  • The type/selection of IO modules depends on how many field inputs/outputs are needed.
• Later mention that there are also analog input/output modules, though they’re not covered fully in the opening.

2) Power supply and wiring fundamentals for S7-1200

The PLC system uses a power supply whose purpose is to:

• Convert AC to 24 V DC
• Provide 24 V DC power to the CPU and IO modules

Key wiring steps emphasized:

• On the AC side:
  • Connect Neutral (N) to neutral
  • Connect Live (L) to live
• Safety instruction: make connections only when the power supply is cut off
• On the DC side:
  • Connect 24 V positive to L+ (L positive) (positive terminal on the CPU)
  • Connect 24 V negative to M (negative terminal)
• After powering:
  • The CPU enters RUNNING mode
  • Associated modules show powered/ready indicators

3) Rack / rail mounting and how CPU shares power/data with IO modules

The video describes mounting on a DIN rail / mounting rail (“DNR / metal rail”).

• CPU mounting:
  • Open the mechanical latch
  • Insert/tighten the CPU into the rail
• Key concept (“trick” shown):
  • The CPU provides data and power sharing to attached IO modules via a dedicated port/backplane slot connection on the rail/rack.
• IO expansion:
  • IO modules are inserted “in line” and connect through the same rail interface.

4) Real plant PLC panel example (field-to-PLC concept)

The presenter shows a real PLC panel / rail feed setup in an actual plant.

• Field level:
  • Transmitters/sensing elements (pressure/flow related) provide signals via wiring
• Signal termination and interface:
  • Field signals terminate at terminal blocks (TBs)
  • TB outputs go to PLC IO cards/modules
• Control room/panel components (conceptual examples):
  • Network switch connections to devices like HMI
  • Mentioned safety-related elements (e.g., safety relay, door interlocks, emergency stop)
  • Panel power supply and circuit breakers
    • including 220 VAC passing through breakers before powering the supply
• Simplified wiring-drawing overview:
  • Inputs coming into the PLC (often via 24 V positive and M/negative reference)
  • Outputs going from PLC to actuators/final control elements

5) Programming S7-1200: connecting a laptop and building the first project

Physical connection / cable and protocol

• Programming uses an Ethernet cable
• Laptop connects to the PLC Ethernet port
• (Older Siemens programming cable types for S7-300/S7-400 are mentioned in contrast.)

Software workflow (TIA Portal)

• Open TIA Portal
• Create a new project
• Add a device:
  • Select the CPU type available for S7-1200 / 1500
  • Specifically select CPU 1214C
  • Verify it matches the hardware order number

Hardware configuration (IO modules)

• In TIA Portal, add/confirm IO modules to match the real hardware (digital IO modules are referenced as examples)

IP / network setup (important)

• Ensure the laptop and PLC are on the same subnet
• Example:
  • PLC IP must be known/set
  • Laptop IP might be set to 192.168.0.x
  • Subnet mask: default
  • Do not set the laptop to the same IP as the PLC
• Instruction:
  • If the laptop is not on the correct network/subnet, you cannot communicate with the PLC

First logic example (simple start/stop-like “light/fan”)

• Use:
  • One digital input and one digital output
• Addressing:
  • Inputs: e.g., I0.0 (byte then bit; each byte has 8 bits)
  • Outputs: e.g., Q0.0
• Create ladder/contact-style logic:
  • I0.0 drives Q0.0
  • Named tags like “input one” / “output one” are suggested for clarity

Download & test

• Use Download
• Select the correct interface (video mentions “interface profet”)
• Test via online/simulation view:
  • Switching the selector/input on/off should toggle the output/light accordingly

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Methodology / instruction-style content (detailed bullet points)

A) Hardware wiring: power supply to PLC (S7-1200)

• Safety first
  • Ensure the power supply is cut off before wiring.
• AC side
  • Connect Neutral (N) to neutral
  • Connect Live (L) to live
• Power supply role
  • Convert AC → 24 V DC
• DC side to CPU/modules
  • Connect 24 V positive to terminal labeled L+
  • Connect 24 V negative to terminal labeled M
• Verification after power on
  • Confirm CPU is in RUNNING mode
  • Confirm modules indicate power/ready

B) Rack/rail installation (mounting and module expansion)

• Mount CPU on DIN rail
  • Open latch → insert CPU → close latch
• Connect IO modules in-line
  • Attach IO modules to the rail/backplane slot interface
  • CPU supplies data + power through the rail connection

C) Plant wiring concept (field → TB → PLC inputs)

• Field produces signals via instruments/sensors/transmitters
• Signals terminate at terminal blocks (TBs)
• TB outputs wire into the appropriate PLC input modules/IO cards
• Panel includes networking/control for devices like the HMI

D) Programming workflow in TIA Portal (S7-1200 + Ethernet)

• Physical connection
  • Connect an Ethernet cable from laptop to PLC Ethernet port
• Software workflow
  • Open TIA Portal
  • Create new project
  • Add device/CPU:
    • Select CPU 1214C
    • Verify correct hardware type/order number
  • Confirm/add IO modules under device configuration
• Network setup
  • Find PLC IP (must be known)
  • Set laptop IP to the same subnet
    • Example: 192.168.0.(different number) on the laptop
    • Subnet mask default
• Build program
  • Add Main
  • Simple logic:
    • Normally open input (e.g., I0.0) controlling output (e.g., Q0.0)
  • Optionally name tags for readability
• Download & test
  • Click Download
  • Choose appropriate interface (mentions “Profet”)
  • Use online view to observe I/Q and validate behavior

E) Training on NO/NC momentary push buttons (field wiring + PLC logic)

• NO (Normally Open) momentary
  • Normal state: circuit open
  • Press: circuit closes
  • PLC input becomes ON, output turns ON
• NC (Normally Closed) momentary
  • Normal state: circuit closed
  • Press: circuit opens
  • PLC input becomes OFF, output turns OFF
• 24 V wiring concept
  • NO button
    • Apply 24 V from PLC power to one side
    • Other side goes to the PLC input channel
  • NC button
    • Similar concept using PLC 24 V, but wired to a PLC input channel such that pressing opens the circuit
• Common negative / jumper
  • Use M (negative) common via a jumper to multiple inputs
  • Inputs share common negative; only the positive side/channel changes

F) Demonstrating NC behavior and ladder logic differences

• Using a normally closed contact in ladder logic results in behavior that can be opposite/inverted relative to the raw input hardware state.
• Two approaches shown:
  • Test actual NO/NC operation using hardware indicators
  • Program with NC/NO contacts to match the intended outcome

G) Latching (seal-in) concept + solving “output drops after momentary press”

• Problem described
  • Momentary NO push button causes output only briefly (pulse length)
  • Need the output to stay ON after a short press until a stop condition happens
• Solution
  • Use a feedback (seal-in) path
  • Add a parallel branch where output Q feeds back through a contact (typically using Q0.0 as a normally-open contact) so the circuit stays energized after the input pulse disappears
• Common real issue during first attempt
  • Improper feedback logic can keep the output ON longer than intended
• Proper fix
  • Add a STOP button using NC logic
  • STOP is wired/used so that pressing it breaks the latch (turns output OFF)
• Resulting behavior
  • START (momentary NO) → latches output ON
  • STOP (momentary NC) → unlatches output OFF

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Speakers / sources featured

• Primary speaker/presenter: Unnamed person (multiple segments covering S7-1200 hardware, wiring, TIA Portal programming, and ladder logic)
• Secondary on-screen host/instructor (separate intro segment): Noman from IT and Automation Academy
• Brand/source referenced: Siemens (S7-1200, TIA Portal, and the broader Siemens PLC ecosystem)