HydroBot: Nutrient Film Technique

Continuous Flow or Nutrient Film Technique (NFT) hydroponic systems use a shallow stream (or film) of water recirculating through a channel to deliver nutrients directly to the plant roots. The stream is shallow enough that the uppermost roots laying in the channel are exposed to air, providing the plant with access to lots of oxygen in addition to all the water it needs. To control the depth of the water stream, NTF systems use channels sloped at 1:30 or 1:40 (around 1.5 degrees). For most plants, the optimal flow rate in each channel is 1-2 L/m, and a maximum length of 10-15 meters is recommended to avoid nutrient depletion at the end of the channel. Because NFT style systems rely on a pump for nutrient and water delivery, there is no protection against power outage or system malfunctions. Plants will quickly die if the pump stops running for more than a few hours. NFT systems are best suited for leafy plants, due to the restricted channels which would not be adequate for the massive root structures necessary for most fruiting plants.

NFT Hydroponic System

NFT systems typically consist of plant-filled channels and a water reservoir with a re-circulation pump. The pump caries water from the reservoir up to the top of the channels, where it runs down past the plant roots and drains back into the reservoir. An artificial light is required if adequate sunlight is not available, and air movement from wind or a fan keeps the plants stimulated. Aeration is also important to keep up the dissolved oxygen content of the water, and can be provided by an air stone and bubbler.

NFT system using Hydrobot

HydroBot modules can be used to monitor and control an NFT hydroponic system:

HydroBot RelayDrive module installed in an NFT hydroponic system

• AirSense monitors air temperature, humidity, and pressure, and ambient light level, to track changes in the environmental growing conditions.
• RelayDrive monitors water flow rate and controls the light, pump, bubbler, fan, heater, and fill and drain solenoids to regulate growing cycles.
• WaterSense monitors water level and temperature to maintain the water reservoir.
• The Master Control computer manages communication, scheduling, and logging to the database.

NFT style hydroponic growing is very effective at producing leafy plants and can easily be scaled down to a small herb garden or up to a large commercial crop of lettuce. No matter what size garden you have, HydroBot’s modular and flexible design can be easily adapted and scaled to meet your needs.

HydroBot is an open-source hardware and software project. All source can be found in the HydroBot repository, and more posts about the project can be found here on the Protofusion Blog.

Original artwork by Kayla Curtis.

About Matthew Reed

Matthew is a computer engineer who enjoys designing hardware for embedded control systems. His hobbies include photography, gardening, coffee, and anything DIY.