Design and applications of multichannel photosynthetic photon flux density sensor for artificial lighting

The measurement of plant growth’s light environment is the basis of urban agriculture, such as light-emitting diode plant factories. The photosynthetic photon flux density (PPFD) sensors, which measure the photon flux density of radiation in the spectral interval from 400 to 700 nm, cannot measure the spectral components, including the photon flux density of red light band and the photon flux density of blue light band, the light in these two bands are widely used in plant lighting. Facility agriculture, especially plant factories with artificial lighting, needs these data and their ratios by far, so a type of multichannel PPFD sensor is designed to solve these problems. First, we expound the design principle, circuit, and structure of the sensor, and calibrate the unregulated sensors by a standard PPFD sensor (PQS-1, Holland) under the calibration device constructed by controller based on DMX512 protocol. The test results show that the sensor’s average variance is 0.9956, which approximates the ideal linear response value 1. Meanwhile, we make a black opaque soft plastic anticrosslight sleeve using three-dimensional printing to solve the problem of crosslight on the sidewall of the filter, which let the crosslight error coefficient of the red and blue channels reduced by an order of magnitude and approached 0. Finally, we designed a set of light environment control systems, which can autocontrol the PPFD and light quality ratios, and a set of supplemental lighting systems, which can control the daily light integral, based on the sensors.