Keep every fermentation tank between its limits

With a maximum and a minimum for each tank and one jacket valve per tank. The yeast turns sugar into alcohol and CO2 and gives off heat, so a fermenting tank warms up by itself. The PLC compares every reading with the limits of that tank:

1. Above the maximum: the PLC opens the jacket valve. Cold glycol flows through the jacket and takes heat out of the wine.
2. Between the limits: the valve keeps its state. An open valve stays open, a closed valve stays closed.
3. At the minimum or below: the PLC closes the valve, and the tank starts to warm up again.

This is control with hysteresis. The case shows it in its screenshots: tank 2 at 20.87 °C keeps its valve open until it reaches its minimum of 18 °C. Because each tank has its own limits, tanks with different wines ferment side by side.

A wide band means few valve operations and slow swings of several degrees. A narrow band holds the wine closer to one temperature, with many more operations of the valve and more starts of the chiller. Set Close the jacket valve at to 1 °C below the maximum and compare the Valve openings column.

Run the Four tanks, four stages scenario and follow each tank in its trend.

The pump, the flow check and the chiller start and stop in a fixed order, so the chiller never runs without a circuit to cool. In this simulator the PLC does it in this order:

1. A jacket valve opens. The PLC starts the glycol pump.
2. The flow switch confirms flow. Without flow in 20 s, the PLC stops the pump and sends a flow alert.
3. The PLC enables the chiller, if it has been off for at least 5 min. That minimum off time protects the compressor from short cycles.
4. The last valve closes. The PLC stops the chiller and keeps the pump on 2 more minutes, so the evaporator does not freeze with still glycol.

A chiller has a cooling capacity. In the example it gives 12 kW of cold for 4 kW of electricity, and one tank at 26 °C with glycol at -2 °C takes about 11 kW through its jacket. Two tanks at once already ask for more than the chiller gives. When several tanks open at the same time, the glycol warms up, every jacket cools less and the tanks stay above their maximum for longer.

Run the All tanks at their peak scenario and watch the glycol supply. A cellar avoids it by sizing the chiller for the peak days, by filling the tanks a few days apart, or by letting the PLC cool the hottest tanks first when the glycol is warm.

An open valve with cold glycol must bring the temperature down. The PLC keeps the temperature at the moment the valve opens. If after 60 min it has not dropped at least 0.3 °C, it sends a valve error alert for that tank.

The check runs only when the glycol is at least 15 °C colder than the wine and the chiller runs. When the whole cellar is at its peak and the glycol is warm, a tank can cool slowly with a good valve. Without that condition, the PLC would blame the valves for a chiller that is too small.

A solenoid valve gives no feedback of its own. To know for sure, fit a valve with a position switch, or a temperature probe on the jacket return. Both need one more input per tank.

Run the Jacket valve stuck scenario, then set Stuck valve check to Off and run it again: the first alert comes only when the wine is already 1 °C over its maximum.

Know that it has failed, and not trust the value. A wired probe here is a Pt100 in a thermowell with a transmitter that gives 0-10 V for -10 to 40 °C. A broken wire reads 0 V, which would look like -10 °C. The PLC treats any signal under 0.2 V or over 9.8 V as a probe fault.

A wireless probe, like the ones in the case, sends a reading every 2 minutes on a battery. Its fault is silence: the PLC marks the probe as failed after 3 missing readings, 6 min. It also warns when a battery runs low, before the probe stops. The M-Duino 42+ has no radio of its own: a gateway or the panel PC receives the wireless probes and writes each reading to the PLC, for example over Modbus TCP, with its time.

With a failed probe, the PLC closes the jacket valve of that tank and sends an alert. It does not know the temperature, so it does not cool blind. The wine keeps fermenting and warming up, which the trend shows as the real temperature. Someone has to check the tank by hand until the probe is replaced. Another choice is to cool on a fixed time cycle until then. It is a decision for the winemaker, not for the program.

Run the Probe and chiller faults scenario with wired probes, then with wireless probes.

1. Where the valve closes

Closing at the minimum, as in the case, gives the fewest valve operations and lets the tank swing across the whole band. Closing 1 °C under the maximum keeps the wine near the top of its band. Choose with the winemaker: the limits are part of the recipe of each wine.

2. When an alert is worth sending

Every tank goes a little over its maximum before its valve opens and the wine starts to cool. An alert at the maximum fires on every cycle, and people learn to ignore it. An alert at 1 °C over the maximum for 30 min fires only when the cooling cannot keep up. Set Temperature alert to At once and count the alerts.

3. Wired or wireless probes

A wired probe gives a reading every scan of the PLC and fails in a way the PLC sees at once. A wireless probe needs no cable to each tank, which helps in a cellar with many tanks, but it reads every 2 minutes, runs on a battery and fails by going silent. The case uses wireless probes over Wi-Fi or LoRa, with batteries that last 2 weeks per charge.

4. Where the logic lives

Keep the limits, the valves and the chiller interlock in the PLC, and the screens, the record and the alerts in the panel PC. If the panel PC stops, the PLC keeps cooling with the last limits. The panel writes new limits to the PLC registers, for example over Modbus TCP, and the PLC checks them before it uses them.

5. Outputs for the valves

The digital outputs of the M-Duino 42+ are optoisolated, 5 to 24 Vdc, with 70 mA at most each. A solenoid valve coil usually needs more. Drive each valve, the pump contactor and the chiller enable through an interface relay with a coil under 70 mA, and fit a suppressor on each valve coil.

This simulator goes with the SI-WINE success story by SIRA, a technology company from Andorra. In SI-WINE, wireless probes inside the tanks report every 2 minutes, an M-Duino 42+ acts on the jacket valves and the cooling machine, and a 7-inch TouchBerry Pi panel PC shows the tanks and sends alerts by email, Telegram or WhatsApp. This simulator zooms into the control of the cold.

Read the SI-WINE wine fermentation success story

The limits of the four tanks come from the screenshot of the case. The tank size, the chiller, the glycol loop, the times and the faults are examples, not data from the winery. The case does not publish how the outputs are wired.

To follow battery radio nodes and a gateway across a site, try the Wireless Sensor Network simulator.

These examples cover the parts of this cellar on Industrial Shields hardware.

• The basics of the analog inputs of an industrial PLC, for the probe transmitters
• Chiller control over Modbus RTU with an M-Duino, when the chiller takes orders by bus
• A Modbus TCP register map for a plant on an M-Duino, for the limits and the states that the panel PC reads and writes
• CSV logging with a live history table on a TouchBerry, for the record every 5 minutes
• Telegram alerts and remote control, for the alerts to the phone

More examples: PLC Solution Library · all simulators.

Example I/O for this cellar

This example uses 5 of the 12 analog inputs, 3 of the 14 optoisolated inputs and 7 of the 10 optoisolated outputs. With 10 bits over 50 °C, one count of a probe is about 0.05 °C. The same M-Duino 42+ covers up to 8 tanks: 8 valves, the pump and the chiller fill its 10 optoisolated outputs, and the alarm beacon moves to an analog/digital output, and 9 probes fit in its analog inputs. The case speaks of up to 32 tanks per control unit, which needs more outputs, for example expansion modules or remote I/O. Check your loads and levels against the M-Duino family datasheet. Full specs: M-Duino 42+ · M-Duino family.