Melsec FX5 to Encoder Interconnection


In connection to the application, which involves the interconnection between a Kuebler encoder and a Melsec iQ-F PLC – the following applies;

There should be two methods in how to establish such a connection:

Method 1: Bus communication

  1. Ethernet based communication. The recommended communication protocol would be CC-Link IE Field Basic and Modbus TCP
  2. Serial based communication (RS-422\RS485). The recommended communication protocol would be Modbus RTU.
  3. If none of these communication protocols can be used with your application – due to the encoder protocol limitation – then a custom protocol is to be written.
  4. Upon correct communication setup and successful communication establishment – function blocks is to be used to extract the encoder data. (copy-and-paste does not apply)


More information can be attained as follows:

  • Ethernet communication HERE
  • Serial communication HERE

Method 2: IO connection

  1. This method utilizes pulse trains being read into the FX5 High-speed input (digital discrete pulse trains).
  2. The first few inputs of the FX5 PLC can accommodate 200khz pulses. The rest can accommodate 10Khz pulses.
  3. Upon successful connection of the signals, the PLC configuration needs to configured correctly.
  4. From there special function blocks are to be used to enable certain functions in the PLC program (EI and HIOEN).
  5. Finally, the PLC program is to be built – which will utilize these pulse trains being read for your application. (Each application will be different.
  6. It is imperative that the IO signals from the encoder is to be confirmed FIRST – before it can be picked up by the PLC. (plug-and-play does not apply)


More information can be attained as follows:

  •                 Positioning Control HERE
  •                 Startup Manual HERE (High-speed Inputs)


Some additional information resources…

As for Online training requirements – the following are applicable:

  • Adroit’s Online GX Works3 and FX5 PLC training HERE (finish the questionnaire and email it to us for certificate) (training manual downloaded HERE).
  • Mitsubishi FA EMEA e-Training courses HERE

The latest versions of the software can be downloaded HERE. It is free and no registration required for the downloads. (it is recommended that you keep your software consistently updated.)

As for technical online support – the following two websites are applicable. It must be pointed out that users are required the create an account through registration – however registration is free, quick and easy.

  • The Adroit MyMitsubishi Support site is found HERE.
  • Mitsubishi FA EMEA Common Platform HERE.
  • Mitsubishi FA EMEA e-Manual Tool HERE or HERE (this tool is a mega helpful for both portable and online use. Ensure to keep it periodically updated.) (both of these sites are recommended to be registered to)

For Selection\Sizing tools of the Mitsubishi FA equipment – the following links apply:

Older PLCs:

  • Melsec Q-series: (Modular) HERE
  • Melsec L-Series: (Hybrid) HERE
  • Melsec FX-Series (Compact) HERE

Latest PLCs:

  • Melsec iQ-F Series: HERE
  • Melsec iQ-R Series: HERE



In Conclusion…

A takeaway point – these applications are not a matter of wire, configure, program and run. Troubleshooting and faultfinding is a major factor in such applications. (implementation is only half the work).

                (The answer for such custom interfacing is not pre-existing – and needs to be worked on and arrived at. Trial-error and testing is to be expected.)