Our customer had a newly-constructed greenhouse (plant growth chamber) which required controlled temperature and humidity for optimal plant growth. The customer desired to measure these parameters and control them with standard greenhouse machinery.
To monitor these conditions, vital for plant growth, Radix placed temperature and relative humidity sensors inside and outside of our customer’s plant growth chamber. These sensors were connected to a PLC which displayed parameters on an HMI and allowed operators to set necessary limits.
Because control of relative humidity and temperature must be continuous, Radix built a 2-layer failsafe scheme to give operators hard-wired manual control of the plant growth chamber in case of PLC failure.
Radix connected the operation of water pumps, heaters, hot and cold air fans, screens and vents to a system that allowed temperature and humidity to be controlled automatically or manually by operators.
After successful automation of one plant growth chamber, the customer had Radix integrate two more for a total of 3.
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:
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.
