Short answer: a commercial greenhouse automation system needs more than sensors and a controller. Define the crop and weather basis, measuring points, equipment duties, control sequences, safe states, alarms, operator access and acceptance tests. The system should show what it measured, why it acted and what happens when a sensor, device, network or power source fails.
Write the operating basis before choosing hardware
Record the crop, growth stage, production calendar, target crop-zone temperature and humidity, light strategy, irrigation duty and carbon dioxide policy where used. Add the project weather source, ventilation and cooling limits, heating design condition, utility reliability and operator response time. These inputs determine the points list and control sequence.
Do not ask one sensor to represent the whole greenhouse. Divide the facility into zones based on crop, exposure, equipment and airflow. Show each sensor location on the plan and section. A temperature or humidity sensor belongs near the crop zone, shielded from direct sun, heaters, doors, wet pads and local drafts unless that location is the condition being measured.
| Control layer | Required record | Failure question |
|---|---|---|
| Measurement | Variable, range, accuracy, location, shielding, calibration and update rate | How is a bad or missing reading detected? |
| Decision | Setpoints, deadbands, stages, priorities, delays, weather limits and overrides | Which value or mode is used when data is unavailable? |
| Action | Device duty, command, travel, feedback, interlocks and safe position | How does the system detect that equipment did not respond? |
| Operator response | Alarm text, severity, recipient, escalation, acknowledgement and work instruction | Who can reach the site before crop or equipment risk becomes unacceptable? |
Coordinate temperature, humidity and light
These variables cannot be controlled as independent numbers. Opening vents can lower temperature but change humidity and carbon dioxide. A thermal screen can reduce heat loss but also trap moisture. Supplemental light adds heat and changes the irrigation demand. Fogging or evaporative cooling changes both temperature and humidity and depends on outside air conditions.
Write one sequence for each operating mode, such as cold night, bright winter day, hot dry day, hot humid day, rain, high wind and power recovery. The sequence should state priorities and conditions that block conflicting commands. It should also define when the system leaves normal optimization and enters crop protection or equipment protection.
Specify sensors as maintained instruments
For every sensor, state range, accuracy, repeatability, enclosure, output, cable or network, installation detail and calibration method. Include outdoor temperature, humidity, wind, rain and solar radiation where the sequence uses them. For indoor zones, identify temperature, humidity, light, carbon dioxide, irrigation, substrate or water measurements that are required by the crop and equipment design.
Plan access for cleaning, comparison and replacement. Keep a calibration register with the reference instrument, result, correction, date and next due date. UMass Extension notes that greenhouse thermostats and sensors should be kept clean, checked for accuracy, shielded from sun and located near the plants. A precise controller cannot correct a sensor that is dirty or installed in the wrong place.
Require feedback, interlocks and safe states
A command is not proof of movement. Ask for position feedback on critical vents, screens, valves and drives where the risk justifies it. Use pressure, flow, current or status feedback for pumps, fans and dosing equipment as appropriate. The controller should alarm when the commanded state and measured response disagree.
Define the safe state for loss of power, communication, weather data or a critical sensor. A vent may need a different response during high wind than during heat stress. A pump should not run dry. Heating and ventilation stages should not fight each other because two subcontractors used separate controllers. Record each interlock and test it at commissioning.
Design the data and access boundary
State which data is stored locally, the sampling interval, retention period, export format and backup method. Keep a change log for setpoints, programs, users and software. Assign roles for operators, managers, service technicians and remote support. Remove default accounts and document how access is revoked.
Remote dashboards do not replace local control. Agree which functions continue if the internet or cloud service is unavailable. Keep the latest approved program, controller configuration, network diagram and recovery procedure in the handover package. Test a restore instead of assuming the backup is usable.
Commission normal and failed conditions
First verify labels, wiring, sensor locations, calibration, actuator direction and full travel. Then test each operating sequence with recorded inputs and outputs. Introduce failed sensors, lost communication, power interruption, stuck equipment and high-wind or rain signals. Confirm alarms, escalation, safe states and restart behavior.
Seasonal performance may require deferred tests. If summer cooling or winter heating conditions are unavailable, record the missing condition, temporary evidence, responsible witness, target date and commercial consequence. Handover should include approved drawings, points list, control narrative, alarm matrix, calibration records, user roles, backups, manuals, spares and training.
RFQ inputs for a greenhouse automation system
The quotation should return the points list, equipment interfaces, control narrative, alarm matrix, test plan, licenses, training, service scope and exclusions on the same schedule used for every bidder.
- Site, greenhouse zones, crop stages, production calendar and operator hours.
- Local weather source and target crop-zone conditions by operating mode.
- Equipment schedule with capacity, power, control interface and safe state.
- Sensor points, range, accuracy, location, shielding and calibration method.
- Control narrative with stages, priorities, delays, limits and interlocks.
- Alarm matrix with severity, recipients, escalation and response time.
- Power, panels, surge protection, backup loads, network and offline operation.
- Data retention, exports, user roles, change logs, backups and recovery test.
- Factory checks, field checks, functional tests and deferred seasonal tests.
- Drawings, source files, licenses, manuals, training, spares and service scope.
Use the smart control system overview for available system context. The temperature-control overview covers connected climate equipment. The climate-controlled greenhouse guide covers the wider system design, and the energy-efficient greenhouse guide covers envelope and energy choices. The commercial production greenhouse guide covers facility interfaces and handover, while this article owns automation architecture, sensor quality and commissioning.
Technical references
- UMass Extension: Ventilation for Greenhouses
- UMass Extension: Heating System Efficiency for Greenhouses
Preparing an automation RFQ? Send CFGET the zones, crop duty, equipment schedule, weather basis and required failure response. Ask suppliers to return the same points list, control narrative and test matrix.