Design of low cost, open-source prototype plant growth chambers for evaluating crop suitability for space environments

Controlled environment growth chambers for evaluating growing media and crop suitability are costly and complex systems making research into these fields prohibitive for citizen science or small research groups. With a renewed interest in space exploration and research into crop growth in space, a pair of prototype open-source benchtop growth chambers with the same internal dimensions as that of the Advanced Plant Habitat on the International Space Station have been developed. The growth dimensions are 40×40×40 cm with a media tray insert of dimension 5×40×40 cm. The chambers have two channels of LED lighting, with five white light units and four full spectrum LED units that use passive cooling and can be independently tuned using potentiometers. Temperature and humidity are not controlled by the chambers since chambers are expected to be placed in an environment where these factors are in an acceptable range for crop growth. A Raspberry Pi 4 is used for logging of environmental factors and control of irrigation events. A GrovePi+ header is used on the RPi for ease of adding and removing sensors. The growth chambers have a temperature and humidity combined sensor (AM2302), a light sensor (TSL2561) which monitors light intensity only (lux) and a pair of analog capacitive moisture sensors which control irrigation events using a threshold media moisture level. A 5 V pump is controlled through a relay connected to the RPi and this irrigates the media using a dripper based irrigation ladder. A digital camera is also connected to the RPi to capture photos of plant growth from above. Each growth chamber costs ~GBP900 (USD1200) and a pair have been constructed such that factors between chambers can be changed and plant growth compared