Abstract: Photosynthetically active photon flux density (PPFD) provided to plants from a grow light may be calculated based on light-canopy distance measurements, intensity measurements around the plants, and a known shape or distribution of light at the measured distance from the grow light. A controller and a method of controlling one or more grow lights can employ closed-loop techniques that repeatedly measure and adjust light until a desired PPFD is achieved and then maintained.

Abstract: A hydroponic system includes a first sensor system that measures one or more characteristics of a nutrient solution, a second sensor system that measures one or more characteristics of an environment of a plant; and a network device including a communication interface to the first sensor system and a communication interface to the second sensor system. The network device may be configured to transmit measurements from the sensor systems through a wireless network to a remote device or database. The network device and the sensor systems may be implemented in a housing that fits within a collar of the hydroponic system. The collar can allow easy replacement of the sensor systems and can electrically isolate the sensor systems.