Introduction
In order to better detect and degrade microplastics, our team designed Spetex. Our equipment can use the special color reaction of microplastics with colloidal gold to detect the concentration of microplastics and better degrade microplastics.
In order to ensure economical and convenient design, the design of our hardware has a high degree of unity with the wet experiment team. The overall design aims to provide a convenient environment for the detection and degradation of microplastics. And the whole device design logic is reasonable, the production cost is about 570.1 $, easy to be copied. The whole device is expected to provide design ideas for the industrial treatment of microplastics in the future.
Structural Overview
1.Frames and containers
In order to make it a complete installation, we designed the fixed frame and container. Our entire structure is crafted in Autodesk Fusion.
The fixed frame and container are manufactured using CNC machining technology, and the use of high transparency acrylic sheets as materials makes it easier to display the internal structure and ensure the correct recognition of the color response by the color sensor.
The frame structure and the corresponding reaction container are processed in blocks and pasted with professional acrylic glue. The various circuit hardware modules involved are fixed with 2-6mm diameter copper columns and nuts.
2.Circuit
In the circuit part, we have realized the basic functions of the control system, power supply system, transmission system, heating system, stirring system, detection system, display system, and ultraviolet sterilization system, and have electrically connected each system.
System Composition
1. Control System
The control system adopts Arduino UNO R3 development board based on ATmega328p and Arduino Mega2560 development board based on ATmega2560. The Arduino UNO R3 development board is used to control the heating system and detection system, and the Arduino Mega2560 development board is used for the direct-plug connection of the display. Serial communication is adopted between the two development boards.
2. Power Supply System
In the power supply system, we use the switching power supply to convert 220V AC to 24V DC, and then use the LM2596 DC-DC three-way DC step-down to reduce the 24V DC to 12V, 8V and 5V DC. Among them, the heating system, stirring system and transmission system use 24V DC power supply, the ultraviolet sterilization system uses 12V DC power supply, and the control system relay and other sensor components use 5V DC power supply. In addition, there is a LED lamp with 8V direct current and rated power of 10W for filling light, and after testing, the LED filling light effect under this voltage is the most suitable.
3. Transmission System
In the transmission system, three 24V DC powered solenoid valves are respectively applied to the connection between the bacterial liquid container and the reaction container, the connection between the microplastic solution and the reaction container, and the connection between the reaction container and the discharge pipe. The use of electromagnetic valves effectively replaces the role of water pumps and can better control the flow rate. The discharge pipe is a transparent PU water pipe, which is connected to the solenoid valve with a straight joint. The solenoid valve is controlled by three of the four relays, the relay control voltage input port is DC 5V, the control port is connected with three capacitive touch modules, and the switch of the three solenoid valves can be controlled at will. The high level is DC 5V, the output port NO is connected to 24V DC, the COM is connected to the positive electrode of the solenoid valve, and the NC is grounded.
4. Heating System
The heating system consists of a 24V DC powered heating plate, which is placed under the reaction vessel and is padded with \thermal soft silicone gasket. The heating temperature can be up to 110℃, which can fully reach the optimal reaction temperature and the temperature rises rapidly. The heating sheet is driven by a high-power driving module, and the control system Arduino UNO R3 controls the IO port for heating output, which can maintain the temperature at the optimum temperature required by the reaction.
5. Stirring System
The stirring system is a 24V DC powered stirring motor with a blade length of 28mm and a rod length of 60mm, which is placed in the liquid of the reaction vessel. The presence of a stirring system allows the reaction to proceed completely and fully. The stirring motor is controlled by one of the four relays, the control port is connected with a KAN-28 button switch, its high level is 5V DC, the output port NO is connected to 24V DC, COM is connected to the positive electrode of the stirring motor, and NC is grounded.
6. Detecting System
The detection system is composed of DS18B20 temperature sensor, PH sensor and TCS34725 color recognition sensor. The DS18B20 temperature probe and PH measuring electrode are placed in the liquid of the reaction container, and the TCS34725 color recognition sensor is fixed on the attached container of the microplastic liquid container, which can measure the RGB value of the color reaction after the combination of microplastic and colloidal gold in real time, and can calculate the microplastic liquid concentration in real time after artificial data fitting. In order to better receive the RGB value of the color, an LED white light is placed at the bottom of the included container to fill the light. And placing an LED white light at the bottom of the microplastic liquid container allows a better view of the state of the microplastic.
7. Display System
The Display system is a 3.5-inch Arduino Display-Mega2560 display, which supports the Arduino Mega2560 in line. The display is fixed in front of the device, above the switching power supply. The display displays the temperature, PH value and microplastic concentration detected by the detection system in real time through the serial communication between the Arduino UNO R3 development board and the Arduino Mega2560 development board.
8.Ultraviolet Sterilization System
The UV sterilization system is an ozone-free UV lamp, powered by 12V DC and controlled by KAN-28 button switch. The lamp tube is placed along the entire path of the reaction vessel and pipe. The system can effectively prevent accidental leakage of engineered bacteria in the device and ensure biosafety.
Programming
We use Arduino IDE to program the Arduino UNO R3 development board and Arduino Mega2560 development board in the control system.
1.Arduino UNO R3 Development Board
The program in the Arduino UNO R3 development board includes the temperature sensor to measure the temperature and output it in the serial port, the PH sensor to measure the PH value and output it in the serial port, the analog port to control the output of the heating system, the color recognition sensor to measure the RGB value and output the calculated microplastic liquid concentration in the serial port. We can adjust the temperature by changing the set value. When the PH value deviates, we can also add the corresponding buffer to adjust it in time. Measuring the concentration of microplastics in a sample will also allow us to better treat contaminated water from the corresponding source.
2.Arduino Mega2560 Development Board
The program in the Arduino Mega2560 development board includes receiving the value of the serial port output of the Arduino UNO R3 development board and displaying it in real time on the display screen through the in-line connection. In addition, we also wrote the boot screen of our team name and project name.
Sensor detection
Under the effect of the above sensors, we successfully measured the RGB color response in the experiment. We used MATLAB2022a software to quasi-merge the three values of RGB and the concentration and found that there was an obvious linear relationship. After that, we carry out multivariate linear fitting to these three values and concentrations, and get very satisfactory results.
After getting the fitting results, we burned the resulting formula on the Arduino UNO R3 development board to calculate the concentration of the microplastic sample in real time.
Prototype Presentation
How does Spetex work?
Future of Spetex
We know that our equipment leaves a lot to be desired, such as the accuracy and standardization of the design.
Equipment safety is also where we need to improve, ultraviolet sterilization should be controlled remotely under more reasonable circumstances. In addition, we also need to consider other ways to ensure safety.
We use a large number of hardware modules for the sake of convenience, and as mentioned at the beginning, we hope that our equipment can provide design ideas for the future industrial treatment of microplastics.