Which PLC? Modbus TCP + Ladder Editor

We're in the process of rolling out a wireless sensor network solution for the ag sector.

(see http://southweb.co.nz/telemetrylayer)

Our solution will map raw I/O to MQTT topics and Modbus registers.

What we haven't got is the ability to define and run control loops - and we don't want to reinvent the wheel or roll our own!

So in an ideal world, we need a simple low cost PLC that:

- has a control loop
- is a Modbus (ideally TCP) slave
- comes with a ladder editor (or supports 3rd party editors)
- has remote support for programming/monitoring (i.e. can update Ladders vs TCP/IP)

I thought this would be a simple request, but am yet to find a suitable device so am throwing it open to the forum.

thx.

Take a look at SoftPLC (http://softplc.com), it is a Linux based software that can be embedded in different hardware (they offer a low-cost Micro version for BeagleBone). There is a toolkit that lets you add your own C/C++ code to run in the PAC as well to tie into your solution very tightly. Can be both/either a Modbus or ModbusTCP slave.

Take a look at Unitronics. http://www.modbus.org/viewcompany.php?id=170

Greetings,

Based on the information you have provided, you may want to consider Triangle Research's embedded Ethernet PLCs. Product selection will be dependent upon the number of I/O you will require for your application.

http://www.eternity-sales.com/tri-plc/tri-plc.htm

If you have any questions, feel free to post, pm or email.

Disclosure - ESI is an authorized distributor for Triangle Research

Some great solutions there. Thanks all! Have been in contact with the guys from SoftPLC and this looks to be the closest fit.

Allen Bradley Micro 820 would work.

About $250 with free software(Connected Components Workbench)

http://ab.rockwellautomation.com/Programmable-Controllers/Micro820

Will talk Modbus TCP or Modbus RTU.

PLC_Open based.