The current prototype operates on an Ebb and Flow (Media-based) Aquaponics system, which requires a tidal mechanism to periodically raise and lower the water level. This process is crucial for oxygenating the roots and facilitating the filtration of nutrients in the plant tank.
The current prototype system is powered by Home Assistant with ESPHome running on a local Raspberry Pi . The main challenges faced by the current system include:
- not a standalone system (Raspberrypi + Station Controller)
- no option for easy remote monitoring of the system (NAT, DNS)
- missing control options (regular self-calibration, failsafe mode)
The current prototype remains on the following setup.
| Category | Component | Description | Type |
|---|---|---|---|
| Plant Tank | 1x Falling Tide Pump | Pumps from plants to fish | SSR 220V - PIO |
| 1x Water Level Top (PTT) | Sense if the max. volume is reached | Replaced by Fuel Gauge Sensor | |
| 1x Water Level Bottom (PTB) | Sense if the max. volume is reached | Replaced by Fuel Gauge Sensor | |
| 1x Growing LED (optional) | Basic AC Control, no dimming | SSR 220V - PIO | |
| 1x Water Temperature Sensor | Measure water temperature | 1-Wire: DS18B20 | |
| Fish Tank | 1x Rising Tide Pump | Pumps from fish to plant | SSR 220V - PIO |
| 1x Flow Meter (optional) | Turbine based | Interrupt PCTN² | |
| 1x Aquarium Heater (optional) | Heat the water | SSR 220V - PIO | |
| 1x Air Pump | 220V - NC/Always ON | ||
| Accessory | 1x Gas sensor (Optional) | For Air Monitoring | BME680 |
| 1x OLED Display (Optional) | For User Interface | ||
| 2x Buttons (Optional) | For User Interface |
The core goals of this software development phase are:
- Create the Edward Controller, which is responsible for maintaining optimal conditions conducive to the health of aquatic life and plant growth.
- Design a User Interface that assists users in configuring their stations and managing basic settings with ease.
- Facilitate remote connectivity through the IoT Integrator, enabling access and control over the internet.
- Design a digital twin for virtual testing the system – Testing on a real station.
The Edward Controller's main function is to oversee the plant tank's automated tidal process. The software is engineered for reliability, crafted to maintain functionality in the face of technical challenges such as power outages and sensor errors. Operational scenarios are meticulously detailed within a truth table and in the analysis of Worst-Case Scenarios.
Syphon
Due to the falling pump's elevated position above the fish tank's outlet, a natural siphon effect occurs, which allows the circuit to continue draining even when the pump is not powered. This siphon effect could present a problem if it coincides with the pump's rising cycle, as it would exacerbate the drainage and potentially trap the system in a continuous loop and cause timeout errors. To mitigate this, the duration of the low tide must be sufficiently long to ensure that the siphoning ceases before the next cycle begins. The necessary duration of this delay is variable, as the duration of the siphon effect is dependent on the height difference between the bottom water level sensor and the drainage pump exit.
Input Processing
The inputs received from the water level sensors require filtering and debouncing. This approach is designed to stabilize the readings and avoid false triggers that could result from wavegenerated perturbations.
Plants Illumination
The system's lighting is managed by a straightforward scheduling mechanism, which automates the grow lights, toggling them on and off as programmed. Although the current iteration lacks the functionality to adjust light intensity, the timing of the grow light is synchronized with the natural patterns of sunrise and sunset. This synchronization provides the essential dark periods that plants require for their rest and recovery during the nigh.
Safety Mechansim
| Situation | Result | Severity | Worst-Case Scenario Prevention |
|---|---|---|---|
| Total drainage of the fish tank | Dead fish | High | Position rising pump above the min. water level. Limit operation time of the rising pump. |
| Tank Overflow | Flooding the environment | High | Install an overspill safeguard in the plant tank. Ensure fish tank capacity equals total water supplied. |
| Not synced time | Stressed plants due to excessive light | High | Synchronize system clock accurately (consider location-based settings). |
| Dryness in the plant tank | Stressed and dry plants | Medium | System can endure temporary dryness. |
| Power Failure | Fish suffocation | High | Implement a heartbeat signal for regular checks. Automate system reboot when cycling stops. |
| Internet Failure | No remote control and telemetry | Low | Queue commands until connectivity is restored. Have a secondary access point as a fallback. |
| Pump Failure | Nutrient imbalance | Middle | System can tolerate short-term pump failure. |
| Hacker Attack | Compromised system | High | Hardcoded vital function. Enable safety mechanisms to prevent unauthorized use. |
| Overheat | Dead Fish | High | 2 layers of safety (Edward control & Thermostat). |
Flow Meter (Optional)
The integrated flow meter is essential for providing precise volume measurements during the rising tide phase. It accurately gauges the total water capacity of the plant tank. As plant roots grow and biomass increases, a natural reduction in the apparent water capacity of the tank is expected. Therefore, a decrease in measured volume over time can be indicative of healthy plant growth. For routine monitoring, the flow meter serves as a diagnostic tool, offering straightforward feedback—either confirming successful tank filling (OK) or detecting issues (NOK). This feedback is crucial as it works with the water level sensors, providing a secondary verification method to ensure that water-related sensors are functioning properly.
Water Heater (Optional)
Aquarium heaters are typically equipped with built-in thermal controls, so no special operations are required for this setup beyond the ability to turn the heater on or off. For optimal functionality, it is crucial that the heater's operational state persists through a power outage. The water heater should operate within a defined temperature range for safety and efficiency. If the water temperature falls below the minimum threshold, indicating that the heater may not be functioning properly, the user should receive a notification. Conversely, if the temperature exceeds the maximum limit, suggesting excessive heating, the system should automatically turn off the heater and alert the user to this condition.
During the current development phase, the system has been designed to manage tidal controls through four distinct operational modes:
- Calibration: Adjusts and sets the baseline parameters for tidal operations. Normally occurs on first start and on demand.
- Automatic Tidal: Executes water level adjustments based on predefined settings without user intervention.
- Manual: Allows users to directly control tidal settings for maintenance.
- Faulty: Stops the related process (tidal or heating) as a safety measure.
The diagram illustrates the transitions between modes, which are governed by three types of triggers:
- Time-Out Based: The system automatically shifts modes after a certain time without receiving commands or if a process takes too long.
- User Command: The user manually initiates a mode change.
- Process Control: The system's internal processes dictate the shift from one mode to another, typically for calibration or error handling. The transitions detailed in the state machine, with their respective triggers, are designed to be flexible. The primary objective is to establish safety measures through restrictions that govern the switch from one operating phase to another.
This mode measures the total water displacement (Vinitial). It is a critical process that allows for the assessment of water movement and ensures that all system components are functioning correctly. During this process, time out values are obtained for the later automatic monitoring:
- Rising time = Bottom-Middle + Middle-Top
- Falling time = Top-Middle + Middle-Bottom If in any case a pumping operation reaches the timer of maximum duration (hardcoded), the system will trigger a faulty system. During rising tide, the flow meter can calculate the total water displacement.
User Defined Tidal Height (Optional)
This development objective ensures that the water displacement during a rising tide is adjustable. Consequently, the limit of the TOP state is no longer bound by the level sensor but is instead determined by the adjusted rising time or by using a flow meter. Due to the siphon effect, the BOTTOM level cannot be adjusted since it will always drain to the lowest point. Implementing this feature for automatic tidal requires more complex scheduling and will remain functional as long as the plant level sensors stay in the same position. If the sensors are moved, a complete calibration cycle will be necessary.
Automatic Tide Cycle
This elementary process loops in an endless cycle of high and low tides in the plant tank. Users can define the settings of the tide (High-Low Tide Duration & User- Defined Tidal Height). Doing so, the duration of a complete tide cycle is defined by: " Total Tide Duration = Rising Time + Duration High Tide + Falling Time +
Duration Low Tide In terms of state system and monitoring, the following truth table provides a comprehensive overview:
| PTB | PTT | Level | Direction | Next State | Action/Comment | Issue |
|---|---|---|---|---|---|---|
| 0 | 0 | Bottom | Rising | MIDDLE | Pump & Timer Control | 0 |
| Falling | WAIT→MIDDLE | Tide done (Wait) | 0 | |||
| 0 | 1 | DC | DC | DC | Check Sensor Water | 1 |
| 1 | 0 | Middle | Rising | TOP | Pump & Timer Control | 0 |
| Falling | BOTTOM | Pump & Timer Control | 0 | |||
| 1 | 1 | Top | Rising | WAIT→MIDDLE | Tide done (Wait) | 0 |
| Falling | MIDDLE | Pump & Timer Control | 0 |
DC : Don’t care - ISSUE: 2 – no operation (faulty) / 1 – critical sensor situation (automatic) / 0 – no restriction (automatic)
External perturbation
This occurs when a state change in the water level sensors (PTB,PTT) during a no-pumping phase. This abnormal sensor behavior (indicating a fault) can also result from an unexpected water loss or gain of the plant tank.
A faulty sensor should be detected during the rising phase by checking the flow meter and timer’s benchmarks. Even when the sensors are not functioning (critical sensor situation), if previously calibrated accurately, it can continue to operate using the flow meter for the rising tide and a pre-set timer for the falling tide.
To utilize the siphon effect, a long low tide timer is employed. This issue should be resolved once maintenance occurs, with a complete calibration cycle required to reset the system. This situation should be addressed swiftly as the absence of overfill protection and the potential for the pump to run dry could compromise system integrity. Therefore, the user should be notified about the reduced safety mechanism.
Error management is further supported by timeout counters for different operational phases. Transition durations are critically evaluated against two types of limits:
- Variable values derived from calibration cycle mode.
- Hard-coded values serve as an additional layer of security (especially during calibration and manual operation).
Should either set of limits be reached, the system is programmed to either transition into a faulty state or operate with reduced functionality, alerting to a critical sensor situation:
| Direction | Level | Transition | Flow Meter | Issue |
|---|---|---|---|---|
| Rising | Bottom | Bottom→Middle | OK | Faulty PTB Sensor (or water-leak) → 1 |
| NOK | Faulty rising pump or not enough water → 2 | |||
| Rising | Middle | Middle→Top | OK | Faulty PTT Sensor (or water leak) → 1 |
| NOK | Faulty rising pump or not enough water → 2 | |||
| Falling | Top | Top→Middle | DC | Wait if Top→Bottom (only PTT faulty) → 1 |
| else (Faulty falling pump, clogged circuit) → 2 | ||||
| Falling | Middle | Middle→Bottom | DC | If Top→Middle before (only PTB faulty) → 1 |
| else (risk of overfill at next rising) → 2 |
DC : Don’t care - ISSUE: 2 – no operation (faulty) / 1 – critical sensor situation (automatic) / 0 – no restriction (automatic)
Manual Mode
In Manual Mode, users are granted direct control over the pumps through both the User Interface and remote access. However, this mode does not allow the user to bypass any of the safety features established in the Automatic Tidal Mode.
| Control | Description |
|---|---|
| Fill Plant Tank | Fills the plant tank to capacity and maintains the water level. |
| Drain Plant Tank | Empties the plant tank completely and maintains this state. |
| Pause Cycle | Halts all pumping actions, preserving the current water level. |
| Fast Cycle | Turn rising-falling pump on. |
| Force Calibration | Execute a complete calibration cycle (→ automatic tidal) |
| Switch Light | Toggles the current state of the grow light on or off. |
| Switch Heater | Toggles the current state of the aquarium heater on or off. |
The return to Automatic Tidal Mode should be triggered based on time-out or user interaction. At that moment, the system should remember it water's level state to properly restart.
Faulty Mode
Faulty Mode is activated exclusively in response to a critical system issue that typically requires manual intervention for resolution. This may involve tasks such as repairing a sensor or readjusting water levels. When in Faulty Mode, the system enters an Overwrite state, where only pumping commands are accessible through the local GUI.
To ensure the system exits Faulty Mode correctly, specific procedures must be followed. These procedures typically involve verifying the resolution of the issue, calibration parameters and reestablishing normal operational mode.
Monitoring Values
State Machine
| Mode | Actions and Options |
|---|---|
| Manual Mode: | Fill Plant Tank - Drain Plant Tank - Pause Cycle - Fast Cycle - Force Calibration - Switch Light - Switch Heater |
| State Machine | Calibration - Automatic Manual - Faulty |
| Issue | 0 OK - 1 Critical - 2 Faulty |
| Latest Log Entry | Time & Date Action (e.g., "22.12.23 7h04 Rising Tide...") |
Duration
| Category | Specification | Notes |
|---|---|---|
| Station ID - Name | Generate ID (from chip) and set name for identification | |
| Version | Firmware Version | |
| Time | Hours and Minutes and Sunset-Sunrise / No Set | |
| High Tide Duration | By User in Minutes (limit by Max. High Tide Duration) | |
| Low Tide Duration | By User in Minutes (limit by Max. Low Tide Duration) | |
| Critical Tide Duration | Equals Max. Low Tide Duration (for max. siphon effect during issue) | |
| Bottom→Middle | By measuring1 (limit by Max. Bottom-Middle Duration) in Seconds | |
| Middle→Top | By measuring1 (limit by Max. Middle-Top Duration) in Seconds | |
| Top→Middle | By measuring1 (limit by Max. Top-Middle Duration) in Seconds | |
| Middle→Bottom | By measuring1 (limit by Max. Middle-Bottom Duration) in Seconds | |
| Manual→Automatic Mode | By User in Minutes (limit by Max. Manual Mode Duration) | |
| Growing Lights | By User in Minutes (limit by Max. Light per 24h) | Optional |
| Usage pump, lights | By counting operating hours counter (Reset per device GUI) |
System Related
| Name | Units |
|---|---|
| Capacity Plant Tank | Liters measured by the flow meter during calibration |
| Current Volume | Liters estimated based on time (falling tide) or rising tide (flow meter) |
| Level Direction | Bottom-Middle-Top |
| Water Temperature | Heating switch on off based on min and max temperature range |
| Heater Pump Output | Falling ON OFF Rising ON OFF |
| Digital State Input | PTB ON OFF / PTT ON OFF / Flow Meter |
| Tidal Height | If user-defined height in % or Liters (not mandatory) |
| Flow Meter | OK (>1/minute) - NOK |
| Ambient Air Quality | Readings from BME680 (°H, %C, kPa-CO2) |
While the current focus is on establishing core functionalities, more advanced monitoring capabilities, such as pH level tracking and the option to export data in CSV format, are planned for a later phase of development. These features will primarily be cloud-based to leverage enhanced data processing and storage capabilities.
However, if integrating historical temperature data proves straightforward, this enhancement could be included in the current development phase. The aim would be to provide users with daily and monthly views of temperature data etc., including minimum and maximum values recorded over these periods. This feature would enhance user experience and provide valuable insights into the system's performance for predictive maintenance.
This interface will be designed as a web page hosted on a local web server, functioning independently without requiring external internet connectivity. This design choice allows users to conveniently update and configure various hardware components of the system, such as pumps and sensors.
If a faulty state occurs, the user can override the timers and sensors and operate the machine without any safety mechanism.
The control functionalities provided will be consistent with those described in the Tidal Control's Manual Mode. Additionally, the interface will facilitate basic operations, including time synchronization. The attached images serve as preliminary sketches, providing an initial visual concept of what the interface might look like and how it might operate.
On first startup, a local access point for Wi-Fi connection should be provided. Doing so, the user sets up necessary settings through a web page interface. Therefore, this user interface should be always available regardless of the current state.
For remote access capabilities, the system is designed to support data exchange and basic control operations/settings through a potential platform like Thingsboard. This choice enables efficient device management, data collection, processing, and visualization, facilitating integration while also aiming to reduce costs.
Key features will include data telemetry and the possibility of implementing Over- The-Air (OTA) updates to ensure the system remains up-to-date and secure. All connections will be safeguarded to protect user data from unauthorized access. The remote interface will offer the same command capabilities as found in Manual Mode. Additionally, crucial parameters, such as tide definitions, will be configurable through this interface, providing administrators with comprehensive remote control over their different stations. In a later development phase, this data should be integrated in a user-friendly application providing maintenance reminders and push notifications.
"This specification document not only outlines technical propositions but also remains open to alternative approaches in development. To ensure efficiency and maintainability, the programming strategy should incorporate the following principles:
- Avoiding large blocks of nested if-else statements in favor of concise and effective routines.
- Adopting a C++ programming approach to benefit from structured and object-oriented programming, which encourages the creation of reusable and modular code.
- Ensuring robustness and scalability to support future enhancements, such as intensity management for grow lights and the inclusion of additional control options.
- Structuring the development into divided milestones to reduce complexity." As mentioned earlier, specific functionalities and variables, including pinouts and duration settings, may be hard-coded during this phase of development for simplicity and efficiency. Concerning the state machine and various critical levels, there is a potential for errors. We welcome any corrections or suggestions for improvement in these areas. Flexibility for improvement and adaptation of the described processes is crucial. For programming inspiration, a list of potential libraries is attached to this document. For testing, a working prototype can be made available, or a remote laboratory setup with a webcam can be used. However, a more modern approach might involve implementing a digital twin. This would allow for thorough testing of all different states and scenarios without the complications of physical hardware.