A drying room only works if the humidity inside it stays where you set it. Walk into a date packing house in July, a seed shed after harvest, or a herb curing room at the end of a long day, and you will find the same scene: someone is squinting at a wall-mounted hygrometer, deciding whether to open a vent, switch on a heater, or just hope. Every hour. Every shift.
That manual loop is what loses batches. A humidity spike at 3 a.m. that nobody saw. A heater that was supposed to run for two hours and ran for eight. Product that hit the customer at the wrong moisture content and got rejected. The fix is not a fancier hygrometer. The fix is an IoT controller that runs the loop continuously, in the background, and tells you when something is off.
This guide explains how that system is built, what each component does, and how to put it together for dates, seeds, herbs, or any other crop that needs a controlled moisture environment.
Why Drying Rooms Need Automated Humidity Control
The argument for automation is not about saving operator time, though it does that. The argument is about three failure modes that manual control cannot prevent.
Overshoot. A worker checks the room, sees RH climbing, switches on the exhaust fan, and walks out. Forty minutes later the fan is still running and the room is now ten percent below target. The product is being over-dried. Repeat this every shift and product quality drifts away from spec batch by batch.
Silent failure. The hygrometer is on the wrong wall. The heater is undersized. The night crew did not log the reading. Nobody notices for two days. By the time someone walks in and smells mould, the batch is gone.
No audit trail. Buyers want documentation. GlobalG.A.P., HACCP, organic certification, kosher and halal inspectors, food safety auditors. They all ask the same question: “Show me the humidity log for that batch.” A manual clipboard does not satisfy the modern version of that question.
A controller that reads the sensor every minute, switches the actuators inside a tight hysteresis band, logs every event to the cloud, and pages you when something is wrong, eliminates all three failure modes. It does not replace the operator. It frees the operator to spend the day doing work that needs human judgement.
The Four Components of a Drying Room Control System
Strip away the brand names and every automated drying room contains the same four pieces.
1. The Humidity (and Temperature) Sensor
The sensor sits inside the room and reports the current relative humidity, usually paired with temperature. Two numbers, updated every few seconds, are the input to everything that follows.
We use the SHT30 Temperature and Humidity Sensor for almost every indoor humidity control job. It measures 0-100% RH at ±2% accuracy and -40 to +125°C at ±0.3°C, responds in under eight seconds, has a long-term drift below 0.25% RH per year, and outputs a digital I2C signal that the Omni Genesis Controller reads natively. Optional IP67 housing makes it survive dusty drying rooms and warm date conditioning chambers.
Where you mount the sensor matters as much as which sensor you use. Common mistakes:
- Too close to the supply air or fan. The sensor reads the conditioned air, not the room’s actual state. The controller thinks the room is dry while the product is still wet.
- Too close to the product surface. The sensor reads the microclimate of a single tray, not the room.
- Direct sun or radiant heat. Temperature reading goes high, RH goes artificially low, the system stops dehumidifying.
For most drying rooms, mount the sensor at chest height, away from any vent or heater, in the middle of the room or above the central aisle. For very large rooms (more than about 80 m²), use two or three sensors at different zones and average them, or run separate setpoints per zone.
2. The IoT Controller
The controller is the brain. It reads the sensor, applies the control logic (setpoint, hysteresis, time-of-day rules), decides which relays to switch, logs every event, and sends data to the cloud.
The Omni Genesis Controller was built for this kind of multi-sensor, multi-output job. It has 4 modular ports that auto-detect across I2C, Analog, Digital, 1-Wire, RS-485, Modbus, and SDI-12, so the same controller can read the SHT30 humidity sensor, an additional temperature probe, a CO₂ sensor, or any other measurement you decide to add later. It runs on dual 18650 batteries with solar charging (6-32 V DC) and sleeps at under 30 µA, so off-grid drying sheds and remote conditioning rooms are practical. Wi-Fi and Bluetooth are built in. Cellular (4G/LTE) is an optional module for sites without a local network.
Genesis drives relay outputs that switch the actuators in the room. Each relay can be assigned its own setpoint, its own hysteresis band, and its own time-of-day or interlock rule, so a single controller can run a coordinated three-actuator loop without needing a separate PLC.
3. The Relays and Actuators
A relay is the bridge between the controller’s low-voltage signal and the high-voltage device that actually moves air or adds heat. The actuator is whatever the relay switches: an exhaust fan, a heater, a dehumidifier, a misting system, a vent damper.
In a drying room, the typical actuator set is:
- Exhaust fan. When indoor RH is higher than outdoor RH, blowing room air out and pulling drier outdoor air in is the simplest way to lower humidity when conditions allow. Most useful in dry climates, at night when outdoor RH drops, or in seasons when the outdoor ambient is favourable.
- Heater. Heating the room raises the saturation point and drops RH without removing any water from the air. Useful in cold and humid climates where outdoor air is no help. Pair with a small fresh-air intake so you do not just recirculate moist air.
- Dehumidifier (refrigerant or desiccant). Removes water from the air directly. Most expensive to run but works in any climate. Mandatory for sealed rooms where outdoor exchange is not possible.
The Genesis controller does not care which actuator is on which relay. You wire them, label them in the dashboard, give each a setpoint and a hysteresis band, and the controller drives them according to the rules you set.
4. The Cloud Dashboard
The dashboard is where the system stops being a thermostat and becomes a tool. The features that earn their place in practice:
- Live readings per room. RH and temperature, refreshed continuously.
- Setpoint and hysteresis configuration per room and per actuator. Change a setpoint from your phone, no climbing a ladder to a wall-mounted unit.
- Event log. Every actuator state change, every reading outside band, every alert. Permanent record.
- Alerts. SMS, email, or webhook when RH stays outside band for longer than a threshold, when a sensor goes offline, or when an actuator fails to respond (the RH does not move after the relay closes).
- Historical graphs. Daily, weekly, monthly trends per room. The graphs catch slow drifts (a heater starting to degrade, a sensor starting to drift) long before they become a failed batch.
Without the dashboard, the controller is just a fancy humidistat. With the dashboard, it is the operations record.
How the Control Loop Actually Works
The control logic in a drying room is simpler than it sounds, but two details matter enough to spell out.
Setpoint. The target RH. For dates entering conditioning, this is often 60-70% RH for soft varieties, 50-60% for semi-dry. For seeds being dried for storage, the target is the RH that puts the seed at 8-12% moisture content at room temperature (varies by species). For herbs, typically 50-55% RH during the active drying phase, dropping to 40-45% for finishing. The right setpoint for your product comes from your agronomist, your buyer’s spec, or a moisture content chart for the crop.
Hysteresis. The “dead band” around the setpoint. If the setpoint is 55% RH with a 4% hysteresis band, the controller switches the exhaust fan on at 57% RH and off at 53% RH. Without hysteresis, the relay would chatter on and off every few seconds as RH bounces around the setpoint, wearing out the relay and the actuator. A 2-5% RH hysteresis is standard for humidity control.
The full loop, per minute:
- The SHT30 sensor reports current RH (and temperature) to the Genesis controller.
- The controller compares RH against each actuator’s setpoint and hysteresis band.
- If RH is above the upper threshold, the controller closes the exhaust fan relay (or heater relay, or dehumidifier relay, depending on which is assigned).
- The actuator runs until RH drops back below the lower threshold, then the relay opens.
- Every reading and every relay event is logged locally and synced to the cloud on the next telemetry interval (typically every 1-5 minutes for active control, longer for monitoring-only rooms).
- If RH stays above the band for longer than a configured alert window, the system pages whoever owns the room.
A single Genesis controller can run three or four independent loops like this, one per actuator, all from the same humidity sensor. That is how you get coordinated control without a separate PLC.
Application Examples
The same controller, same sensor, same relay setup runs across very different crops. The setpoints change.
Date Conditioning Rooms
Israeli date packing houses run conditioning rooms where freshly-picked dates rest for several days to reach a target moisture content. Soft varieties like Medjool need higher RH (65-75%) and gentler conditions to keep the texture and skin intact. Semi-dry varieties like Deglet Nour need lower RH (50-60%) to finish drying. The conditioning rooms are typically large (50-500 m²), well-insulated, and run a combination of dehumidifier + circulation fan, sometimes with a small heater for cold mornings. Genesis with one SHT30 per zone, three relays per Genesis, handles a full conditioning room with no extra hardware.
Seed Drying Sheds
Seed harvesters dry seed down from field moisture (often 18-25%) to storage moisture (8-12% for most field crops). The drying process needs to be slow enough that the seed does not crack or lose germination viability, which means a gentle setpoint and patient hysteresis rather than aggressive dehumidification. Seed sheds are often outdoors or in partial shelter, where the Genesis solar + battery + cellular configuration is the natural fit. One sensor and one or two relays per room is usually enough.
Herb and Spice Drying
Cut herbs (mint, oregano, thyme, basil) dry quickly but lose colour and aroma if pushed too hard. Typical drying-phase RH is 50-55% with continuous gentle airflow. The bottleneck is usually circulation, not raw drying capacity. A two-relay setup (exhaust fan for daytime, circulation fan continuous) gives much better leaf quality than a single high-capacity dehumidifier blasting the room.
Hay and Forage Storage
Bales going into storage need to be below 15% moisture or they will heat up and risk spontaneous combustion. Monitoring is more critical than active drying here, because once the bale is on the stack you cannot easily intervene. Genesis as a monitoring-and-alert role, with RH and temperature sensors throughout the stack and a clear alert escalation, is the right shape of system.
Generic “Climate Room”
Anywhere a crop, ingredient, or finished product needs to sit at a specific RH for a specific time, the same hardware applies. The controller does not care about the crop. It cares about the setpoint.
Wiring and Installation Notes
A few practical points that prevent the most common install problems.
- Run the sensor on a shielded cable. I2C is fine over the short distances inside a typical drying room (under 3-5 metres), but use shielded cable and keep it away from any power lines. For longer runs, use the SHT30 in its RS-485 housed variant or add an I2C-to-RS-485 bridge.
- Use externally rated relay modules for high-current loads. A dehumidifier or a 3-phase fan motor draws more current than a small board-level relay can handle. Use proper contactors or solid-state relays rated for the actuator’s inrush current. The Genesis drives the contactor coil; the contactor drives the load.
- Add a manual override. Every actuator should have a manual switch in addition to the controller-driven relay. When you need to test, troubleshoot, or override during a controller outage, you do not want to be re-flashing firmware. This is also a requirement under most food-safety auditing schemes.
- Power the controller separately from the actuators. A spike from a contactor coil should not reach the controller. Use a separate fused circuit, ideally with surge protection, and ground the controller properly.
- Mount the controller in a dry corner of the room or just outside. IP65 means it survives splashes and dust, not continuous condensation. A small junction box mounted on the cool side of the wall is the ideal home for the Genesis.
Where to Start
If you run a drying or conditioning room today on manual checks and a mechanical humidistat, the practical first step is to instrument the most critical room. The one where a missed batch costs the most.
A starter system for a single room is one SHT30 sensor, one Omni Genesis Controller, and the contactor or solid-state relay set you already have for the existing fan and heater. Wire the contactor coil to a Genesis relay output, configure the setpoint in the dashboard, and the room is running automated within an afternoon.
Once the first room proves out, expanding to a second and third is incremental: another sensor, another controller (or extra relays on the same controller if the rooms are close), same dashboard. The cloud platform scales without re-architecting.
The hardware is modular, the protocol set covers any humidity or temperature sensor on the market, and the same Genesis controller that runs a drying room also runs an irrigation valve, a silo level alert, or a fish-pond DO loop. You build the room you need today, and the system grows with you.