Photoelectric Leaf Area Measuring Instrument Based On MCU

The leaves of green plants are the carrier of photosynthesis,the media of transpiration,one of the most important standards for measuring the growth state and and yield prediction.Thus leaf area measuring has already became one of new agricultural research technologies.this technology has already achieve certain development at home and abroad at present.But there still exist some performance deficiency, and the majority of measuring instruments are high in price.Aiming at these problems,this thesis takeing universal SCM as core of the system,combineing optical circuit with SCM system,utilize the photoresistance and its peripheral circuit to realize converting the corresponding optical signals to electric signals,after A/D transforming,through sending the signals to SCM,and displaying leaf area on LCD to realize a measuring instrument which is based on SCM. It realize real-time processing and displaying the leaf area signals as well,the main content of this study and results as follows:(1) select STC89C52SCM as core of the system,by debugging the compiled C program in SCM programming software Keil to realize the real-time displaying of leaf areas.(2) Optical design of the system select the high-power led as light source,the optical signal go through the optical path which is consist by two light rays convergeing convex lens,the type of Cds photoresistance convert the converging optical signal to the changes of its resistance,then convert the changes of its resistance to the changing voltage signals by the bleeder circuit.(3) the signal processing circuit will amplify and filter the weak voltage signal,amplifying circuit take three-level design,the first level select instrumental amplifier AD620 to realize flexible control of voltage gain,the second level select operational amplifier OP07 to process the reverse amplification.The last level is based on OP07 to realize the function of reverse voltage following and low-pass filtering,providing stable voltage signal for the follow-up circuit.(4) fit the leaf areas and related voltage signals using MATLAB7.0,to gain corresponding relation between the leaf areas and voltage values,analyse correlation and residuals of the unary linear curve,to prove its rationality.(5) peripheral circuit which is based on SCM realize the function of digitalize analog signals and input the to SCM,compile C program of A/D transformation,curve fitting,LCD display,finally realize the real-time display of the corresponding leaf area value on LCD screen.