Design of LED aquarium lighting device based on single chip microcomputer control

1 Introduction

The protagonists of ecological aquarium are fish and aquatic plants, and visual appreciation is its main function. Lighting is one of the three major technical issues that need to be solved first.

Commonly used aquarium lighting sources include fluorescent lamps, mercury lamps, halogen tungsten lamps, etc., but their emission spectra do not match the selective absorption spectra of aquatic organisms. When used to supplement light for aquatic plants and animals, they have poor targeting, low light efficiency, high energy consumption, and a large amount of heat that affects the water temperature. Light-emitting diodes (LEDs) are considered to be the main and more ideal artificial aquatic plant and animal light sources in the future due to their high efficiency, multicolor, narrow band, direct current, good color rendering, energy saving, and environmental protection. However, the LED aquarium light sources currently on the market have problems such as prefabricated and solidified spectra and intensity, non-adjustable, poor color rendering, and static, which cannot meet the dynamic needs of aquatic plants and animals for the spectrum. Therefore, intelligent LED aquarium light sources have become the focus of scientific research.

2 Design Principles

2.1 Selective absorption of light bands by the growth and development of ornamental aquatic plants

Plants evolve, grow, and mature under full-spectrum natural light. Within the visible light range of the solar spectrum, the light bands between 690 ~ 780nm, 580 ~ 690nm, and 350 ~ 530nm are the strongest physiological activity bands, which are consistent with the five main plant photobiochemical reaction spectra of chlorophyll absorption, photosynthetic efficiency, phototropism, red light induction of light construction, and long-wave red light induction (see Figure 1). The chlorophyll of green aquatic plants has a strong absorption capacity for red and blue light, and the lutein and carotene in red aquatic plants have a strong absorption capacity for green and blue spectra.

Figure 1 Action spectra of five main plant photobiochemical reactions

2.2 Effect of light quality on the growth of aquatic animals.

As an important ecological factor in nature, light has a significant impact on animal behavior. Different light intensities, photoperiods, and spectral components have certain effects on animal predation rates, metabolism, growth, and reproduction. In general, ornamental fish are not very adaptable to short-wavelength light environments. As the wavelength increases, the growth rate of fish also gradually increases.

2.3 Effects of photoperiod on the growth of aquatic organisms

The strong light period of natural sunlight is about 10:00 ~ 15:00, and the exposure time is about 5 ~ 6h. Considering that the intensity of artificial light is not as strong as sunlight, it is recommended that the aquarium light source should be used for 6 to 8 hours of strong light, and in a segmented lighting manner: "10% light × 1h-80% light × 6h-20% light × 1h". That is, the light intensity should be in the lighting period of "weak → medium → strong → medium → weak", and the power timer should be used to control the time of turning on and off the lights, so that the light can meet the light cycle of aquatic growth.

3 Design of LED combination light source for aquarium lighting

The LED aquarium lighting device based on single-chip microcomputer control mainly includes two aspects of design: hardware design and software design. The hardware design mainly includes three parts: LED combination lamps, LED drivers and circuit control systems (see Figure 2 for the structural block diagram). The LED combination lamps are composed of main light modules and viewing modules. LED adopts step-down constant current drive mode. The circuit control system is used to realize the automatic regulation of light color, light intensity, irradiation period and duration. The software design adopts modular programming ideas, and is written in C language based on the flexible combination and regulation method of the spectrum. It is organically integrated with the hardware, and the main controller is controlled by the keyboard and GSM network to realize the function of providing the full simulation spectrum required by aquatic plants and animals.

Figure 2 Structural diagram of LED aquarium lighting source

3.1 LED combination lamps

3.1.1 Lighting structure design

Based on the fact that aquatic plants and animals selectively absorb light, the main spectrum radiation area of ​​the "LED aquarium lighting source" is determined. Breaking through the technical defects of traditional point and line light sources, the LED combination lamp adopts a modular design, consisting of 1 main light bar (3W 4 blue, 6 white, 2 red LEDs) and 1 moonlight light bar (1W 4 blue, 3 red, 2 green, 1 yellow, 1 three-primary color LED) (see Figure 3). Each lamp bead is equipped with a 30° focusing cap, combined with nano reflective strips on both sides, so that the light is concentrated in the aquarium to the greatest extent. Since the lamp is a point light, the ripples on the water surface reflect shadows, which can simulate the sparkling effect of nature.

Figure 3 Schematic diagram of LED lamp strip

3.1.2 Heat dissipation and waterproof design of lamps

The cooling system of LED aquarium lamps is composed of active cooling (aluminum substrate coated with infrared high-radiation material, aluminum side-tooth cooling lamp trough) and passive cooling (axial-flow fan, circulating water cooling). The PCB aluminum substrate is painted with waterproof paint after welding, and a high-transmittance acrylic baffle is installed under the lamp group. The structural diagram is shown in Figure 4. It solves the heat dissipation and waterproofing problems of high-power LED lamps, making the LED combination light source more efficient, energy-saving and environmentally friendly.

1—Acrylic glass; 2—Light box; 3—LED lamp beads; 4—Aluminum-based PCB board;

5—Aluminum side-tooth heat dissipation lamp trough; 6—Circulating water radiator;

7—circuit board; 8—light box cover; 9—fan

Figure 4 Schematic diagram of the structure of LED combination lamp

3.2 Driving circuit design

The SN3352 chip is used to design the LED drive circuit using a step-down constant current drive method. The SN3352 chip has an input voltage range of 6V to 40V, an output current of up to 750mA, and an output power of up to 30W. It integrates a temperature compensation circuit and has overheat protection and temperature compensation functions. The chip switching and dimming functions are realized through PWM pulse width modulation technology. The circuit schematic diagram of a primitive is shown in Figure 5.

Figure 5 LED module drive circuit

3.3 Circuit control system design

3.3.1 Controller circuit design

The main controller is based on STC89C54RD + MCU, and consists of MCU circuit, I/O interface drive circuit, system parameter storage circuit, key circuit, LCD display circuit, GSM remote control circuit and LED drive control circuit. The MCU is written with C language program, which is used to adjust and set the LED drive current intensity, working frequency and pulse width to meet the demand for flexible spectrum adjustment; the MCU circuit is connected to the LED constant current drive circuit, key circuit, LCD display interface circuit, GSM remote control circuit and data storage circuit through I/O interface and serial data interface. Each block is organically combined, each performs its duties and cooperates in coordination.

3.3.2 Design of GSM remote control system

Based on the OEM board, the serial port is used to communicate with the C89C54 microcontroller. The GSM remote control system includes a microcontroller system chip, a clock chip, a watchdog chip, a GSM interface, a storage chip, and a driver chip (see Figure 6). This system can transmit the user's command information to the microcontroller via SMS, and then remotely control the on and off of the LED lamps and the color of the light. It has the characteristics of simple structure, high reliability, and low cost.

Figure 6 GSM remote control system structure diagram

3.4 System software design

The system software is solidified in the chip of the single-chip microcomputer, adopts modular program design (see Figure 7 for the flow chart), and is written in C language. It mainly includes human-machine interface (keyboard scanning module, LCD driver module, GSM remote control module), LED control module (LED driver circuit module, LED lamp head module), and parameter storage module. Each module has its own function, and the main program coordinates the dependencies of each module to complete the required light quality, light intensity, timing control and other settings, in order to achieve the goal of friendly operation interface, ideal control effect and highly stable system.

Figure 7 Program design flow chart

3.5 Machine design and production

The intelligent LED aquarium lighting system consists of a main control box, LED combination lamps and ultraviolet sterilization lamps. During the production process, we strictly follow the ideas of scientific layout, rigorous structure, pragmatic and concise. In the early stage of production, we designed a variety of prototype models. After many demonstrations, we determined the final design structure and made it strictly in accordance with the mechanical production standards (see Figure 8 for the prototype).

Figure 8 Intelligent LED aquarium lighting source prototype

4 Photoelectric characteristics of LED aquarium lighting sources

4.1 Brightness test of aquarium lighting source

At 5m in front of the aquarium lighting source, the CX-2A imaging brightness meter was used to test the brightness distribution of the aquarium lighting source in four irradiation modes (see Figure 9). The test shows that the spatial distribution of light intensity determines the arrangement interval of the LED tubes of various colors when designing the combined lamp and the irradiation distance when filling the light. The brightness of LEDs at the same distance is different due to different power and light color, which can simulate the sparkling effect.

Figure 9 LED combination lamp brightness

4.2 Spectrum test of aquarium lighting source

The LED combination lamp designed in this study is composed of high-power red, blue, white and green LEDs. The emission spectrum measured by the PMS-50 spectrum analysis system is shown in Figure 10.

Figure 10 LED mixed color spectrum

5 Conclusion

"Intelligent LED aquarium lighting source" is made of high-brightness, high-power white, blue, red, green, and yellow LEDs. It adopts a modular design concept. The LED lamp consists of a main light bar and a moonlight light bar. Based on the single-chip microcomputer, the light color, light intensity, irradiation time, and time period are automatically adjustable, which meets the selective absorption of light by aquatic plants and animals and people's visual appreciation requirements, and at the same time solves the stress response of fish to light. In the design, the humanities and environmental protection concepts are fully applied to achieve energy-saving and high efficiency of the light source. This is the active exploration of pushing LED into new areas. It is believed that the "intelligent LED light source" will bring huge social and economic benefits through scientific research and promotion and application in large-scale aquatic plant variety breeding, artificial breeding, ornamental fish factory breeding, aquarium gardening, aquarium special supplementary light source, and special aquariums.