Intelligent Control LED Lighting Device For Hydropnic Plants

In order to solve the food problem of the future population,the plant factory came into being.But light as an important factor in plant growth and development,the development of efficient,pollution-free and suitable for plant growth light source has become a priority among priorities.With the rapid development of LED(Light Emitting Diode),LED has become the main light source of the plant with its energy saving,environmental protection,cold light source and tunable spectrum.With the recent development of red phosphor types and improvement of its stability,differing from traditional way of combining red and blue LED-chips to achieve red-blue light,the paper present a new way to achieve red-blue light: the required red-blue light can be realized on single chip by coating red phosphor mixed with silicone on blue-light LED chip,that is pc-LEDs(phosphor converted LED).(1)In order to get the ideal plant-lighting pc-LEDs devices,this paper adopt conformal phosphor coating,self-adaptive phosphor coating methods to achieve red-blue light,and then carry out junction temperature test,PWM(Pulse-Width Modulation)dimming test,and aging performance on the devices,the results show: The junction temperature with conventional spherical coating is of 90?,while the junction temperature with adaptive coating structure is about 80?;the red and blue photons ratio remain essentially constant under PWM dimming;with the passage of time,red and blue photons ratio attenuates from 5.3,and remain stable at 5.0 after 5000 h.When the ratio of powder to gel is greater than 1:13,the traditional spherical phosphor structure shows inhomogeneity in the spatial distribution of red and blue photons ratio,the central ratio is small while the edge is too large.The structure with adaptive coating structure showed a high degree of uniformity in-60~60 degrees,but because of the reflection of the cup bowl and the fluorescent powder adhered to the cup bowl,the edge area showed inhomogeneity.In order to improve the uniformity of spatial chromaticity distribution,the improved double-crown phosphor coating technique improved the central red-blue photon ratio to a certain extent,but the effect was not obvious,and the edge red-blue photon ratio was still high.(2)In order to obtain a favourable phosphor layer structure that could generate uniform distribution of red and blue photons ratio,with the help of the matlab,thispaper uses Monte Carlo thought to simulate the the photon transport process of the LED:including LED luminous model,absorption and scattering models,random step size and random wavelength acquisition algorithm,phosphor layer discretization and outbound judgment algorithm.And then we establish the parameters of the models by comparing the results of experiments and simulation,where the scattering coefficient is 2.0 mm-1and absorption coefficient is 1.0mm-1.And the defects of the spherical structure are verified on the simulation model.In this paper,we propose a new type of red phosphor layer structure,which is similar to normal distribution.With this structure,the small angle blue photons with forward scattering mechanism are treated by total reflection mechanism and increasing optical path,while the edge-region photons are treated by decreasing the optical path.The new structure is compared with the traditional spherical structure under the ratio of red to blue photons around 6.0,we set the maximum thickness of the structure as2.2mm and the value of ?2 as 0.25 by simulations.Compared with the traditional spherical structure,the variance of the red and blue photon ratio at different angles is reduced from 0.445 to 0.0429,which is decreased by about 90%.The structure has a very high uniformity of red and blue photons distribution.(3)In order to verify the utility of red-blue pc-LEDs devices,the peas were irradiated under self-made lamps with different red and blue photons ratio,the PPFD of every group is 70?mol·m-2·s-1.The results show that the dry weight and stem length of pea seedlings reached the maximum while R/B was 9.3;and the chlorophyll content reached the maximum while R/B was 7.2.