PLC Demo System

The PLC demo system aims to demonstrate the complete PLC signal chain. It has four isolated input channels and four isolated output channels. The input channels have 24 bit resolution (using AD8220 IN-AMP + AD7793 Sigma Delta ADC) and each channel can be configured to accept a wide variety of input signals, from 4-20ma current loops to high voltage inputs 0-5, 0-10v, +/-5v, +/-10v. It can also accommodate RTD/TC inputs. The output channels have 16 bit resolution using the AD5422 which features an integrated output driver and built in fault detection and protection. The AD5422 has the following programmable output ranges, 4-20ma, 0-5v, 0-10v, +/-5v, +/-10v. Channel isolation is achieved using the ADuM5401 or ADuM1401. The complete design uses ADI converters, isolation technology, processors and power management products, allowing customers to evaluate the whole signal chain.

PLC_003

Features:

  • Inputs Selectable: 0-20mA, 4-20mA, 0-5V, 0-10V, ±5V, ±10V, RTD, TC
  • Outputs Programmable: 0-20mA, 4-20mA, 0-5V, 0-10V, ±5V, ±10V
  • FOUR ISOLATED 24 BIT ANALOG INPUT CHANNELS
    AD7793 24 Bit Sigma Delta ADC, 40nV Noise
    ADR02 Wide Operating Range, Precision reference
    ADR441 Ultralow Noise Voltage Reference
    AD8220 Instrumentation Amplifier, >80db CMRR
    ADUM5401 iCoupler Digital Isolator with isoPower (up to 500mA)
    ADUM1401 iCoupler Digital Isolator
  • FOUR ISOLATED 16 BIT ANALOG OUTPUT CHANNELS
    AD5422 Single Channel, 16-Bit, Serial Input, Current Source & Voltage Output DAC
    0.01% Typical Total Unadjusted Error (TUE)
    Single Chip Solution
    Output Fault Detection and Protection
  • POWER/INTERFACE/CONTROL
    ADI ARM7 ADUC7027
    ADP3339 High Accuracy Ultralow Iq, LDO
    ADM3251 Isolated Single Channel RS-232 Line Driver/Receiver










System_Level_Design_A

PLC Total Solution Diagram


Documentation:

User Guide:  The UG-181 user guide describes the PLC Demo system. (pdf)

Analog Dialogue:  PLC Evaluation Board Simplifies Design of Industrial Process-Control Systems (pdf)

PLC Demo Schematics and Layout
Please be aware that the PLC Demo board is not available for purchase.

Source Code:

The source code was written for ADUC7027 to perform basic communications with on board data converters. The description of files included are:

  • main.c - Implements data comms between PC and PLC Design Board.
  • plcbios.c - Contains the drivers for ADC/DAC communications.
  • plcbios.h - Header File for PLCBIOS.C/ADUC7027
  • AD7793.h - Header File for AD7793 ADC.

The source code includes a project file for the Keil development environment. An evaluation version of the Keil development environment can be found at https://www.keil.com/demo/eval/arm.htm

Download Source Code (zip)