/PLC-Analog-Input-Processing--0-4-20mA

Siemens PLC S7-1200 DC/DC/DC with Signal Generator

"Processing Analog Input, 0/4-20mA" in Industrial Automation Towards Industry 4.0.

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Siemens PLC: SIMATIC S7-1200 Compact PLC, DC/DC/DC

  • CPU 1214C, compact CPU
  • DC/DC/DC
  • Onboard I/O: 14 DI 24 V DC; 10 DO 24 V DC; 2 AI 0-10 V DC
  • Power supply: DC 20.4-28.8V DC
  • Program/data memory 100 KB

Hardware, Software & Wiring Configuration

Hardware

  • Power Supply
    • 1x External Siemens PSU (Input 220VAC 1 Phase, Output 24VDC).
  • CPU
    • 1x Siemens Compact PLC 1200 DC/DC/DC.
  • Digital Input
    • 1x Start Push Button(NO) %I0.1.
    • 1x STOP Push Button (NC) %I0.0.
  • Analog Input
    • channel 0, %IW64.
    • install 500 Ohm resistor parallel with analog input channel 0 (2x250 Ohm, 2W, 1%).
  • Signal Generator
    • 1x Signal Generator to Analog Input Channel 0.
    • only use signal ground (GND) and AIo (output, current).
    • powered by an external USB cable.
    • set the mode on Signal Generator to Voltage (press the mode button to switch between voltage & current).
  • Digital Output
    • 5x 24VDC Lamps %Q0.0 (Blue), %Q0.4 (Red), %Q0.5 (Yellow), %Q0.6 (Green), %Q0.7 (White).
  • Cabling
    • AWG 16 with ferrules.
  • Cabling (color)
    • 220VAC Live: brown, 220VC Neutral: blue.
    • 24VDC+: red, 24VDC common: black.
    • 24VDC Digital Input: white.
    • 24VDC Digital Output: orange.
    • 24VDC Common: black.
    • Analog Input: yellow.
  • PLC Firmware level (updated from base 4.5)
    • 4.6.0. Hardware Configuration change in PLC
  • Utilize Realtime Clock (RTC).
    • through TIA portal, devices & network -> system & clock memory -> enable the use of clock memory byte.
    • download to PLC (hardware configuration). Connectivity
  • Laptop to PLC
    • RJ45.
    • straight cable wiring as Siemens 1200 PLC can autocross on the ethernet cable. Application Software
  • Siemens TIA Portal v17 on Windows 11.

PLC Programming

  • Ladder Diagram (LD) with Function Block (FB).
  • Programming logic.
    • If Start Push Button (NO) is pressed, -> Program is running, and the Start Push Button is latched.
      • on the signal generator, manually use your hand, rotate the button, and the display will indicate 4-20mA.
      • observe that the corresponding output lamps:
        • Red: if the analog signal is between 4-8mA.
        • Yellow: if the analog signal is between 8-12mA.
        • Green: if the analog signal is between 12-16mA.
        • White: if the analog signal is between 16-20mA.
    • 4-20mA analog input from the signal generator is converted by the ADC (within PLC) to 0-27648 (integer).
      • we use NORM_X provided function to normalize this range to 0-100% (real).
      • then, we use SCALE_X provided function to scale the normalized numbers to 4-20mA (real).
    • If the Stop Push Button is pressed, -> Program is stopped.
      • Note that Stop Push Button is NO in the program, but NC in the hardware wiring for safety purposes.