Design And Implementation Of An Intelligent Desktop Lighting System

With the development of modern electronic technology and control technology,all kinds of low power consumption microchip with high performance are manufactured continuously,and various intelligent consumer electronics are designed and produced.As the improvement of living level,the people pay more attention to their health.During the last decades,myopia in the youth is on the increase,so eyes health is very important.A key factor of myopia is the poor illumination,so it is very worthwhile to design and fabricated an intelligent desktop lighting system.In this thesis,using microchip STC12C5A60S2 as control core,a multifunctional desktop lighting system is designed with 2835-type cold and warm white LED chip.The system consists of voltage stabilizing circuit,driving circuit,control button module,photosensitive feedback module,infrared detection unit,illumination intensity and color temperature adjustment circuit,and OLED display unit.Through the infrared detection,it can detect the existence of the user,and switch on or off.Illumination intensity and color temperature can be manually adjusted by the user.Also,or automatically set according to the internal optimal values.The adjustment range is enough to satisfy normal user.In addition,the system can collect the environment humidity and temperature and the date,and display them on the OLED.It presents a friendly operation interface to the user.In the infrared detection,HC-SR501 sensor can generate a signal and input to the BISS0001 processor,and the latter will output a signal to control the power supply of LED.Illumination intensity and color temperature can be independently adjusted by using the PWM(pulse width modulation)method.When the duty of two PWM signals,which are respectively the control signal for cool white LED and warm white LED,changes proportionally,the system illumination intensity will increase or decrease.When the duty of two PWM signals changes independently,the system color temperature will vary.The color temperature can be set by the user or by the internal optimal values.All the control software is based on the C language,and the Keil software is used to generate the files applied in microchip STC12C5A60S2.In order to evaluate the system performance,TES136 chroma meter is used to test the desktop lighting system at our lab.The results show that intensity of illumination can be adjusted from 250 lx to 400 lx when color temperature is 3800 k,from 150 lx to390lx when color temperature is 3800 k,or range from 200 to 380 lx when color temperature is 4400 K.For each adjustment of intensity of illumination,the colortemperature can nearly keep stable.Also,we can fix the intensity of illumination and adjust the color temperature of the system.The results show that the color temperature can change from 2900 to 5400 K even if the intensity of illumination is set to be 350 lx,300lx or 240 lx.For each adjustment of color temperature,the intensity of illumination is nearly stable and its error is lower than 1%.We also measure the lighting uniformity in the longitudinal and transverse directions of the system.The results show that the lighting is very uniform for the range from-60 to 60 cm in the longitudinal direction and from-40 to 40 cm in the transverse direction.