Open-Source Photosynthetically Active Radiation Sensor for Enhanced Agricultural and Agrivoltaics Monitoring

Photosynthetically active radiation (PAR) is crucial for plant growth, influencing photosynthesis efficiency and crop yield. The increasing adoption of controlled-environment agriculture (CEA) necessitates precise PAR monitoring. Commercial PAR sensors are expensive, however, limiting their accessibility. Recent research has explored low-cost alternatives using multi-channel spectral sensors like AS7341 and AS7265. This study develops the electronics for an AS7341-based open-source, cost-effective (~US$50) PAR sensor validated across a broad PPFD range and conditions, ensuring reliability and ease of replication. It uses relatively simple multi-linear regression, that offers real-time applications without energy intensive machine learning. The developed sensor is calibrated against the industry-standard Apogee SQ-500SS PAR sensor in four distinct farming environments: i) horizontal grow lights , ii) vertical agrotunnel lighting, iii) agrivoltaics, and iv) in greenhouses. A mean error ranging from 1-5% indicates its suitability for controlled environment farming and continuous data logging. The open-source hardware design and systematic installation guidelines enable users to replicate, calibrate, and integrate the sensor with minimal background in electronics and optics.