1. Relative Humidity and Temperature control with Auto, Manual and Maintenance modes
2. HMI to view indoor and outdoor temperature as well as to enter set points and operate various controls in maintenance mode
3. Online UPS-based system for uninterrupted system control
4. Desk Control Panel with necessary pushbuttons and selector switch for manual controls in case of PLC failure

Our customer required control of temperature and relative humidity. Temperature was to be maintained within 0.5 C of the control point and relative humidity within 3% of the setpoint with programmable high and low limits. Radix achieved this through actuation of ventilation, heaters, hot and cold air fans.

A secondary set of independent high and low temperature alarm set-points were provided for safety. These operated audible alarm in the control panel.

Radix deployed 1 relative humidity and temperature transmitter (SC807) inside the plant growth chamber and another outside to serve as a reference. These were connected to an Allen Bradley Micrologix 1200 Series PLC in a Desktop Control Panel.

To facilitate programming setpoints and viewing status on a plant mimic screen, Radix provided an Allen Bradley PV600+ color touchscreen HMI.

The Radix PLC system controlled the operations of:

2 water pumps

2 heaters

3 cold air fans

2 hot air fans

1 screen

2 vents

in our client’s greenhouse.

To give our client complete flexibility in controlling their system, Radix provide 3 modes of operation: Automatic, Manual and Maintenance. In Automatic mode, the system controlled the equipment detailed above as per predefined setpoints. The user also had the option of using the HMI to manually control individual machines with specific interlocks in Maintenance mode. In case of PLC failure, Manual mode allowed the operator to operate each machine via pushbuttons and selector switches on the control panel.