Considering different usage scenarios, our products will be provided in different forms. A powerful testing and maintenance solution will further enhance the environmental friendliness and sustainability of this product.

Therefore, providing simple and portable solutions for frontline inspection and maintenance personnel is the focus of the hardware team. Our envisioned device integrates a set of light intensity sensors (RS485 communication), a set of bacterial density monitoring module, a set of temperature and humidity integrated sensors (digital control), and an OLED screen (SPI communication).

All modules with specific functions on the device are controlled by an Arduino microcontroller as the main control computer. This equipment will provide real-time reference data for frontline inspection and maintenance personnel to confirm whether the product's bacterial density, lighting effect, and environmental temperature and humidity meet the standards.

In order to provide more stable and reliable support for the equipment, we have made a PCB. Each module with specific functions will be integrated into the PCB to form a complete system. In this device, we choose the Arduino Nano microcontroller as the main controller.

The Arduino Nano has reduced its size by half compared to the Arduino Uno, eliminating the DC power interface and voltage regulator circuit of the Arduino Uno and adopting a Mini-B standard USB socket.

This processing has earned Arduino Nano the same interface functionality as Arduino Uno: using ATmega328 as the core, with 14 digital I/O ports (including 6 supporting PWM output), 8 analog inputs, and a 16MHz crystal oscillator. The Arduino Nano has therefore become our preferred host computer.

On the PCB, the temperature and humidity sensor inputs digital signals through the digital port D7. The temperature and humidity sensor sends TTL high and low level signals to RXD and TXD pins through the TTL485 module, thereby communicating with Arduino through serial port. The spectral sensor module transmits spectral signals through the I2C function pins, and receives digital signal control and automatic detection through the D8 pin.

In order to understand the luminous effect of the product in specific application scenarios, we use BCE brand B-RS-L30 light intensity sensor. The B-RS-L30 is small in size, lightweight, and stable in operation, meeting the requirements of portable testing and maintenance equipment.

The measurement range of the sensor is 0-200000lm, with a resolution of 0.01lm and a working temperature range of -40 ° C to +80 ° C, suitable for most outdoor scenarios.

The sensor adopts Modbus-RTU communication protocol, which is stable and reliable, suitable for various industrial environments. The four wire interfaces are VCC/GND/RS485-A/RS485-B, which also creates the possibility for expansion.

In order to understand whether the temperature and humidity of the product meet the requirements in specific application scenarios, we use DH11 temperature and humidity sensors.

DH11 is only 12*15.5*5.5mm in size and contains a calibrated digital signal output temperature and humidity composite sensor. The humidity measurement range of the sensor is 20% to 95% RH, and the temperature measurement range is 0-50 degrees Celsius. The long-term stability is ± 0.5% RH/yr, with strong stability, suitable for temperature and humidity measurement in complex environments.

In order to understand whether the bacterial population density of the product meets the requirements in specific application scenarios, we use OD600 as the measurement standard.

Considering that the frequency band of the light emitted by the product itself is also around 600nm, the scheme of directly using the product's 600nm optical density for testing is obviously unreliable.

Our Hardware team has decided to use an indirect method to test bacterial density. The experiment shows that the optical density of the bacterial community at 600nm is a linear function of the bacterial density. Therefore, the optical density of the product at 600nm under different bacterial densities can be measured in advance, which can be used as a reference to estimate the bacterial density of the product at different optical densities at 600nm.

Our equipment uses an AS7341 module and an IR LED as the measurement device. AS7341 is a 11 channel multi-purpose spectral sensor with a size of only 15*19.7*11.5mm, specifically optimized for fluid and reagent analysis. In actual operation, the detection and maintenance personnel only need to press a button named "Genshin Launcher Button" for a long time to know the real-time bacterial density of the product on the OLED screen of the device.

SSD1306 OLED display screen is an ultra-thin, high contrast, and fast response display device using organic light-emitting diode technology. This display screen adopts the SSD1306 controller chip, which has a wide range of applications, including embedded systems, electronic devices, and DIY electronic projects. Compared to traditional liquid crystal displays, SSD1306 OLED using organic light-emitting diode technology has higher contrast, higher clarity, and a wider viewing angle.

Because each pixel is self illuminating and does not require backlighting, it can provide clear images in dark environments and display more information. In addition, the SSD1306 OLED, which provides a resolution of 128 * 64 pixels, can control brightness at the pixel level and can be completely turned off when a certain pixel does not need to be lit.

Therefore, compared to some other display technologies, the SSD1306 OLED display screen has lower power consumption when displaying images, and its low voltage and low power consumption characteristics. Support SPI and I2C communication interfaces, making it easier to integrate with various microcontrollers and microcontrollers.

Note: Due to the Arduino nano controller we used having only 2048 Bytes of sRAM, while OLED used an array of 128 * 64/8=1024 Btyes, which took up half of the sRAM space and prevented the program from burning. Therefore, we modified the driver to reduce the screen area to 64 * 32, so that only 256 Btyes were used in the array.

Visit our hardware on igem gitlab for more details.

The industrial design students in our team designed an ergonomic shell for this set of testing equipment, which makes the product able to be used easily in the mobile scene, meeting the requirements of portability and function.