FDC-IO Module System: Overview and Sample Applications;

PLC System Expansion, Data Acquisition and Ethernet Gateway


Modular IO system from Future Design Controls is an innovative product providing a simple low cost solution for distributed I/O requirements.

The IO system consists of stand-alone Digital and Analog - Input/Output modules communicating on an RS485 two-wire multi-drop network.

The modules communicate using the MODBUS RTU protocol. A 32bit ARM CPU is used in the modules to provide high-speed data processing and fast communications turn around times. Multiple baud rates are selectable from 2400 to 115200 baud. Each module may have an address assigned from 1 to 127 with the Modbus message length limited to 100 consecutive read / write registers. If more registers are required then a new poll group must be added for the next xxx registers.

All IO modules plug directly onto an industry standard DIN rail. All modules have a minimum isolation of 1000VAC rms between the field and logic. Logic is the 12-24VDC power for the module itself and Field is the power, when required, for the actual input or output.

The modules have been equipped with status led’s which are used to indicate the status of the Inputs or outputs. This visual indication assists with fault finding and diagnostics.

PLC I/O Expansion - Sample Application

There are a number of devices such as PLC’s (Programmable Logic Controllers) and HMI (Human machine interface), which have a MODBUS Communications facility available. Many PLC and HMI manufacturers provide Modbus Master and Modbus slave drivers to communicate directly with third party devices using Modbus protocol using different kind of hardware connection.  PLC/HMI can be configured as a MODBUS Master. IO modules are attached to the RS485 network and configured as RTU slaves. The address setting is via dip switches on the IO module itself, configurable from address 1 to 127. The PLC/HMI system use IO modules as remote I/O reducing cabling costs and increasing the I/O capability of the control system.


Data Acquisition - Sample Application

Another use of the IO Modules is for Data Acquisition where a PC (Personal Computer) is connected to the Network. Many SCADA software packages support the MODBUS Master Protocol and can hence retrieve data from Input Modules or send data to Output Modules. The serial port of the PC is connected to an RS232/RS485 Converter, which in turn is connected to the Network.

Future Design Control's FDC-IO_Studio_DAQ software provides an out-of-the-box data acquisition software solution at a very low price. It acquires data from Modbus RTU/Modbus TCP slave devices like the FDC-IO Modules and shows Real time data in the PC in the form of Trends, Bar graphs, Digital values, etc., and stores the data in PC for later archival. For more information download the FDC-IO_Studio_Manual.

Ethernet Connectivity

The IO Modules are designed to communicate via RS485 Modbus serial connection. If application requires Ethernet, Future Design Controls PC-E Protocol Converter provides Serial Modbus to Modbus TCP Ethernet protocol conversion providing an easy & cost effective manner to connect Serial Modbus devices to Ethernet TCP networks; for additional information refer to PC-E sales brochure.



Sample System



Wireless Serial and/or Ethernet Connectivity


For Serial and/or Ethernet Modbus Wireless transmitter - refer to PC-W



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