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Leveraging Remote IO for Indoor Vertical Farming

Remote IO for Vertical Farming
Posted in Allen Bradley PLC, Manufacturing Automation and Intelligence, PLC Programming, Specialty Machinery

Summary

Most modern PLCs, with or without the uses of removable modules, offer a lot of communication methods, including digital, analog, RS-232, RS-485, Modbus, Ethernet IP, and CAN, to name a few. These various communication schemes enable PLCs to communicate with a lot of field devices. However, it’s not always cost-effective or reliable to run individual wires long distances to each field device.

Remote IO allows for some IO that would be done by the PLC to be moved closer to the field devices. This replaces many individual signal wires with one more robust communication cables. This single cable reduces the susceptibility of the system to noise and allows for fault detection to narrow down and single out problems and wire breaks.

DMC worked with an indoor vertical farming company to commission a system that used several remote IO modules, all controlled from one central PLC. Each remote IO rack was placed in its panel and passed inputs and outputs between the central PLC and those panel's devices.

Solution

DMC worked with the client to program and commission 13 POINT IO modules and 16 Turck IO blocks, along with several VFDs that all feed back into one Allen Bradley Control Logix 5580 PLC. Connecting each remote IO module to the PLC via ethernet enables DMC to start the commissioning process as soon as the first remote IO blocks are installed and significantly decreases the time the project would take, as DMC works in parallel with electricians during the construction process. Using only one PLC also proved a central point of communication both for downloading changes to the code and for SCADA integration using Ignition.

The system has several separate zones, many of which are nearly identical. Within the PLC, each zone was given an independent program that was called by a continuous main task. Giving each zone independent programs not only allowed DMC to copy large sections of identical code between zones but also reduced the number of IO points in each zone to a manageable number of points relevant only to that zone’s IO.

Some of the IO locations are in humid environments or places where water might splash on panels; some of the remote IO modules required a higher IP (ingress protection) rating. Using Turck remote IO blocks equipped with M12 connectors allowed for this while still providing a full range of diagnostic information back to the Allen Bradley PLC. In other locations, Allen Bradley POINT IO modules were selected for their wide range of IO capabilities and ease of expansion. This choice proved invaluable as some zones as new IO was added to accommodate new actuators and sensors.

Overall, the system combined Allen Bradley POINT IO, Turck remote IO modules, an Allen Bradley Control Logix 5580 Controller, and Ignition, all to provide one seamless and flexible system.  The uses of Remote IO can significantly help increase the reliability and flexibility of a system. Increased flexibility and reliability enables customers to have greater confidence in their system’s accuracy while planning for successful expansion in the future.

DMC has continued working with this client on the development and commissioning of their HVAC control system to regulate building temperature and humidity. 

Learn more about DMC's PLC Programming and HMI/SCADA Expertise and Services. 

Customer Benefits

  • Scalability – One PLC can be used to control many remote IO modules, spread out over a large area, using only Ethernet cables.
  • Modular Architecture – Each remote IO module, as well as its corresponding PLC code, are separated into zones making it easy to duplicate or remove individual zones without affecting the rest of the system.
  • Centralized PLC – Using one central PLC makes it easy to monitor the entire system from SCADA, and to update in the future.
  • Time and Material Savings –Locating remote IO closer to the field devices, reduces the number of individual wires that need to run long distances, saving both wiring and time.

Technologies