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This dissertation is mainly to design a digital controller, mainly to accurately control the LED intensity to improve the current light source control for plant growth. This system has constant current output, the highest output current is 1A, through the program and hardware to improve the output current resolution to 1:1000, making the current output more stable and linear. This system uses the RS-485 communication method to integrate with the human-machine interface, making the setting and operation more convenient and user-friendly. The digital circuit control board mentioned in this dissertation contains 18 groups of outputs, which can be used to set 18 groups of different light intensity to achieve precise control of individual channels of light. The system has a time scheduling function. The default 24 steps scheduling can be used to set the different light intensity and other parameters through the human-machine interface so that users can make different settings according to different needs. In addition to the Human Machine Interface control, this system can also be controlled by a remote interface, which can be set via a computer or mobile APP, making it more convenient to use. In addition to the built-in fuse for the first level protection, the digital circuit control board mentioned in this dissertation also contains many safety designs on the software, such as excessive temperature protection, automatic light load reduction, high and low-value alarms, trigger buzzer, etc. Those safety measures make it safer in use. At the end of this dissertation, it provides the result about installing the digital controller on a constant temperature and humidity plant growth chamber, growing different plants, such as Arabidopsis, lettuce, etc., because of the addition of LED light sources, compares the plants grown in this growth chamber than the plants grown in the outdoor conditions, the growth efficiency increased by about 10%. Compared with the general PWM controller, the result of this dissertation, add RS-485 communication, which makes its output more stable, increases the anti-interference ability, and improves the resolution to 1:1000 so that users can grow plants according to their own needs by high efficiency of the intensity of the light source conveniently.
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