IoT Based Automated Indoor Vertical Hydroponics Farming Test-Bed -

IoT Based Automated Indoor Vertical Hydroponics Farming Test-Bed

The aim of this work is to design and construct an indoor automatic vertical hydroponic system that does not depend on the outside climate. The designed system is capable to grow common type of crops that can be used as a food source inside homes without the need of large space. A microcontroller was working as a brain of the system, which communicates with different types of sensors to control all the system parameters and to minimize the human intervention. An open internet of things (IoT) platform was used to store and display the system parameters and graphical interface for remote access. The designed system is capable of maintaining healthy growing parameters for the plants with minimal input from the user. The functionality of the overall system was confirmed by evaluating the response from individual system components and monitoring them in the IoT platform. The system was consuming 120.59 and 230.59 kWh respectively without and with air conditioning control during peak summer. This system was circulating around 104 k gallons of nutrient solution monthly however, only 8–10 L water was consumed by the system. So, the user can monitor several parameters without using laboratory instruments, which will allow to control the entire system remotely. Moreover, the system also provides a wide range of information, which could be essential for plant researchers and provides a greater understanding of how the key parameters of hydroponic system correlate with plant growth. The parameters of the system were studied and calculated such as the suitable temperature, light wavelength, pH, EC, and the required amount of water for the system. Finally, the parameters were displayed in Things peak IoT platform web-interface and mobile application to provide easily accessible user interface. User can monitor visualize the parameters and system can send SMS massage in case of pump interruption. The proposed platform can be used both for quantitatively optimizing the setup of the indoor farming and for automating some of the most labor-intensive maintenance activities.

The block diagram of the automated vertical hydroponic system consists of six parts: main power supply, power meter, sensing and control system, vertical hydroponic structure, Wi-Fi module, and online database. All the sensors connected to the vertical hydroponic system can be monitored from the IoT platform on any smart device. There is a power meter module for continuous monitoring the power consumption of the system in order to make the system power efficient and possible for large scale expansion. In any hydroponic system, there are several parameters that should be maintained within certain range, such as pH, electric conductivity (EC), temperature of the surroundings, and water level of the container. An automatic hydroponic system should adjust and maintain these parameters within its suitable value automatically and independently without the requirement of user intervention. Different sensors are connected to the microcontroller to monitor the different parameters of the hydroponic system. A panel electromechanical relay was used to control artificial lights, water pumps and the dosing pumps that were used to add pH and nutrient to the water.

1. NFT structure and essential components

2. Water flow path

3. Nutrition and pH controlling system

4. Internet of Things (IoT) platform

A typical hydroponic system consists of the hydroponic pipes, nutrient container, water pump, artificial lights, nutrient, and pH adjustments’ solutions. The nutrient container, water pump, and artificial lights are selected carefully to assure the highest efficiency of the hydroponic system. This section presents the process of selecting the right size of the nutrient container and the water pumps, the selection of the artificial lights, nutrients, and pH adjustment solutions

Nutrients’ Container

A nutrient container is used to reserve the nutrient solution that would be supplied to the vertical NFT system. Since it is a closed system, all the excess solution would return to it. The ideal container should be made from plastic material, using metal containers is prohibited as they are reactive materials.

Water Pump

Sizing the water pump is very important as selecting the right pump would assure the sufficient amount of water is flowing continuously in the system. For this design, submersible pumps were selected to be used since they suit the small systems that need 1200 of gallons or less. The sizing of the pump was done in three steps. The first step was to calculate the gallons per hour (GPH) that the pump was required to supply to the system, and the second step was to measure the head height of the hydroponic system and the third step was to use the first two information to verify if the pump was suitable using the water pump datasheet.

Artificial Lights

Lighting is essential for the plants as it plays an important role in the photosynthesis process. Plants do not require the full range of light spectrum for growth. They only absorb their needed amount of light in the spectrum. The lights requirement is between 400 and 700 nm which lies within the visible range and it is also known as photosynthetically active radiation (PAR).

Nutrients and pH

There are 17 different types of elements that are important for the complete growth of the plants. In the hydroponic system, these 17 elements were added to the plants as nutrient solution. However, the amount of nutrition must be added within the suitable range for each plant where any incorrect amount added can cause a huge damage to the plants. To confirm the correct range of nutrient amount in the solution, the electrical conductivity (EC) was measured continuously. Furthermore, the amount of pH must be monitored in the nutrient solution as it is considered essential for plants’ growth. The suitable pH range in the hydroponic system is between 5.0 and 7.5. A higher amount of pH in the nutrient solution from the recommended range for the plants leads to a higher chance of nutrient deficiencies, which become toxic to the plants.

Isolation Circuit

The isolation circuit is an important part of the automated vertical hydroponic system. It is used to prevent any unwanted voltage and current interference that can affect the sensor readings.

RTC Circuit

The DS3231 real time clock (RTC) (Arduino, CA, USA) was used to calculate the real time for the system so that the events of decision making (light on/off) can be done according to real clock and it is equipped with a coin cell battery.

Air Conditioner (AC) Controlling Subsystem

It is essential to maintain the temperature in a specific range for the healthy growth of plants in an indoor hydroponic system. Plants require a certain range of temperature, which allows the suitable environments for the plants to grow healthier, and better. The optimal range for temperature is between 19–28 ℃. The system used the data coming from the temperature sensor, and through the infrared (IR) transmitter LED, it can send a signal to the AC to control.

Power Consumption Monitoring Subsystem

The amount of power consumed has to be monitored and controlled to reduce the overall running costs of the system. The power, voltage and current consumed by the system were measured by using the power meter designed and implemented. The power meter has two ports: input and output, where the input of the power meter is connected to 240 V alternative current (AC) source and the output port is connected to the hydroponic system (load). The power meter consists of micro-controller, AC/DC converter (HLK-PM12 (ShenZhen, China)) to power-up the micro-controller (Arduino Nano (Somerville, MA, USA)), a current sensor (ACS712 (Worcester, MA, USA)) and a voltage sensor (ZMPT101B (Guangzhou, China)) to measure the current and the voltage consumption of the loads. All the measured data were sent to the central micro-controller to measure the total power consumption.

Internet of Things (IoT) Platform

Internet of things (IoT) allow the system to be connected to internet to gather and store all the information’s or data collected from the devices through a web server. The user would have the ability to reach this data through a computer or smart phones from any place and any time via the Internet. In this paper all the reading of the sensors such as: pH, EC, water level, humidity, and temperatures sensors along with the power consumptions of the system were sent to web server, through a Wi-Fi-module, ESP8266 (Shanghai, China. The Wi-Fi-module is connected to the microcontroller, where all the data from the sensors were acquired and were sent to an open source IoT platform, Thingspeak. Thingspeak is not only open source, but it also allows MATLAB (The MathWorks, Inc., Natick, MA, USA) based data visualization and algorithm implementation on the acquired data, which has made it as an excellent choice for indoor vertical hydroponic system.  Therefore, to make a cost-effective system with reliable IoT platform facilities Thingspeak based system is a suitable option. Moreover, it allows exporting historical data in CSV format for further analysis, which will help significantly for future machine learning based studies.

Testing of Electronic Sensors

EC and pH Sensor

The EC and pH sensors were tested and calibrated by connecting it to the Arduino Mega (Somerville, MA, USA) microcontroller. The process of calibration was done by following the instruction in the datasheet of the manufacturer. The EC sensor was calibrated using dry, low, and high EC calibration using solutions with different EC level. The pH sensor was calibrated using solutions with different pH level and results were very accurate. EC and pH are important factors to sustain healthy growth of the plants. Furthermore, the pH is controlled by two dosing pumps where pH up or down was added to the nutrient solution to keep the pH in the suitable range for the growing plant.

Water Flow Sensors

Water flow sensor was connected to microcontroller and it was calibrated to measure the flow rate. The water flow sensor was capable of measuring accurately the flow rate utilizing the hall sensor to deliver pulses on water fall and microcontroller was used to count the number of pulses to measure the flow of water. This helps us to measure the volume circulation per day and on average in a month how much fresh water was refilled to maintain the water level correct in the system.

Power Meter Subsystem

The non-contact capacitive water level sensor was continuously reading ‘0’ when it senses there is liquid at the sensor level (22.5 cm height or 37 L of nutrition). However, if the water evaporates or loses due to the consumption of the plants, the water level sensor outputs ‘1’ which triggers ON the fresh water pump until it delivers 2 L of fresh water from the reservoir so that pump does not need to be turned ON frequently. In the testing phase of the system, this operation principle was tested and confirmed its functionality.

Dosing Pumps

In the calibration stage, it was tested that how much solution the dosing pump can deliver per minute. This was done by pumping water from a bottle to another mL labelled bottle by continuously running the dosing pump for one minute. The dosing pumps were not turned ON initially during system initialization rather when the system was running for a while (after first 30 min), the EC and pH level were evaluated and based on that 5 mL of EC and pH up/down were injected in the system in each injection, however after each injection, the system waited for 10 min before next injection as it takes time to stabilize the EC and pH of the system. During this period, the dosing pumps were not activated based on the level of EC and pH. Rather, these quantities were monitored only.

Power Meter Subsystem

During the calibration and testing phase, the power meter subsystem was used to test power consumption of each individual system component so that overall system power consumption can be calculated and verified with the power data provided in system run-time. The power consumption measured by the meter based on their daily operating time. However, the air conditioner which is the most power consuming system was investigated in two different conditions:

(1) in a typical operating condition without AC control module in function and

(2) AC control module operated to keep the temperature within specified range of 19–28 ℃ for the indoor hydroponic system.

Reference:

Chowdhury, M.E., Khandakar, A., Ahmed, S., Al-Khuzaei, F., Hamdalla, J., Haque, F., Reaz, M.B.I., Al Shafei, A. and Al-Emadi, N., 2020. Design, construction and testing of iot based automated indoor vertical hydroponics farming test-bed in qatar. Sensors, 20(19), p.5637.