5. Smart and Adaptive Intermittent Illumination Control System

This was a team project when I was an undergraduate student and it was funded by NUAA University Undergraduate Innovation Fund Project.

Team members: Peng Chen, Muyun Cao

Abstract:

To overcome the shortcomings of the existing supplemental lighting that the supplemental light duration and strength are unadjustable, and the full-spectrum is underused by photosynthesis, the presented system introduces the MSP430 SCM to replace continuous supplemental lighting with intermittent supplemental lighting on the ground of the theory that photoreaction is faster than the dark reaction in the photosynthesis[1], so as to avoid waste of photoreaction products, and inhibit dark reaction. Light sensing circuit is used to detect the environment’s current illumination; the duty ratio is adjusted to generate light supplements intermittently to make the light up to the illumination optimal for plant growth; the high-intensity LED light clusters with a 5:1 red-blue ratio are used to replace the traditional supplemental lighting for efficient spectral absorption. The system is innovative, efficient, and energy-saving, and can be widely used in greenhouses, shelters and families.

Basic idea:

Based on the theory that photoreaction is faster than the dark reaction in the photosynthesis, we designed a smart and adaptive system to control the illumination intermittently according to different light conditions. There are two improvement in our system. The first one is the addition supply light is automatic adjustable according to different natural light intensity. The second one is the addition supply light is intermittently. Intermittent light is better for most plant growing which has been proven.

Hardware design:

The system's hardware diagram is shown in Fig 1. The low-power consumption MSP430 chip from TI is used as the main control module. The light sampling module with photoresistor as its core component is used to detect the illumination situation of the current environment. Then, the MSP 430 is used for analysis and processing the data. After that, it will generate the control signals to control the LED array module that provides strong supplemental lighting.

Fig 1. The Hardware System Diagram

Software design:

C was used for the system's programming. The coding part was not so difficult, and the idea was simple. By using a timer, we controlled the MSP 430 to receive the data from the ADC in fixed time points. After getting this data, the microcontroller analyzed the illuminance situation of outside environment by comparing the data with the stored data in the devices. After this kind of processing, the microcontroller would know how much additional light should be given by the LED supplemental lighting model and would generate the correct control signals to it. The workflow diagram is as following:

Fig 2 Software Workflow

Experiment results and analysis:

Two sets of comparison experiments have been done to verify our work. Tomato seedlings and melon seedlings were selected. After searching and calculating, we put each plant's information into the database. The main information includes the plant's light saturation point. Of course, when the illuminance situation of outside environment is stronger than the plant's light saturation point, no additional supplyment light is needed.

The gif figure 3 shows the experiment result of tomato seedlings. In the sun-facing room, plants on the left were fed with interminttent light supplements based on a 50% duty ratio, and plants on the right are fed with continuous light supplements. The gif picture included 6 static pictures for each one. The static pictures were taken every three days during 15 days' experiment after germination.

From the experiment results, we could found that plant fed with our smart and adaptive intermittent illuminance system grew better than those fed with continuous light supplements.

Meaning of this system:

There are mainly two purposes of this project. The first one is the positive growing improvement for plants. The second one is saving energy. Let's do a calucation.

We assume a target space of 1m*1m*1m, electricity charges of 0.6yuan per KWH, and a month of 30 days. Each LED cluster has a power of 1.5w; continuous lighting for one month consumes electricity energies of 1.08 KWH. Six clusters are needed, so the electricity bills will total 3.888 yuan. The costs of MSP430, ADC and LCD total 100 yuan. Six Piranha LED clusters of 48 beads each cost 120 yuan altogether. The costs of chassis, power switches, wires, PCB and bracket totals 50 yuan. The total cost is 274 yuan. Mass production can bring the device’s unit cost to below 200 yuan. Therefore, while costing less than the traditional non-LED supplemental lighting, the device incurs only half as large electricity bills as that with the ordinary LED supplemental lighting. More savings will be achieved with longer length of usage.

Achievements of this project:

1. A journal paper:

"Smart Adaptive Intermittent Illumination Control System Based On MSP430" have been accepted for publication in the Journal of Modern Electronics Technique (ISSN:1004-373x)

2. A utility model patent:

"Smart Adaptive Intermittent Illumination Control System" No. CN 202998561 U

Google patent link:http://www.google.com/patents/CN202998561U?cl=en&hl=zh-CN