Sunlight multiband photon flux density detection based on PFD calculation model

The sunlight provides essential light and temperature for photosynthesis in protected cultivation. Sunlight is one of the important plant living environment factors in facility agriculture. Most of the existing light detecting equipment are used to detect the whole band of Photosynthetic Available Radiatio (PAR), which is unable to meet the demand of modern photosynthesis research. In order to solve the problem, a function model between single-band spectral Photon Flux Density (PFD) and solar altitude was established through experiments. Based on the model, a sunlight multiband PFD detecting device was designed, which was using a PAR sensor as the detecting node and microcontroller as the core part. This device can detect the PFD of different bands in PAR by using a single sensor. Meanwhile, detecting band can be set by using keyboard according to the characteristic of spectrum absorption of different plants. The secure digital memory card (SD card) was used in the device to store data. Results of the field test showed that determination coefficients of the device testing red and blue PFD with standard value were 0.986 and 0.993 respectively. The device with little relative error and high reliability could be applied in facility light detecting.