How it works

A closed loop, not a planter

Most towers give you a place to put plants and leave the water to you. Garden of Eaten is built the other way round: the instrument came first, and the tower and reservoir were drawn around it. Here is what it does between one morning and the next.

Six in the morning: measure

Two industrial probes hang in the reservoir. One reads pH — how acidic the water is. The other reads electrical conductivity, EC, which tracks how much dissolved nutrient is in the water; more salts, more conductivity. The pH probe also reports water temperature, a level sensor reports how full the tank is, and a sensor in the housing reports the air temperature and humidity around the plants. The display refreshes once a second and keeps a chart of the last hour, day, week and month, so you can see the night the temperature dropped or the afternoon the plants drank a litre.

Compare, and refuse to jump

Every reading is compared with a setpoint you can change on the screen. Nothing acts on a single reading: values are median-filtered and the condition has to hold for thirty seconds before a pump turns. A bubble on the probe or a stray reading doses nothing. This is the difference between an instrument and a timer.

Mid-morning: dose, in order

If conductivity has drifted below its setpoint, the controller runs Nutrient A for a measured shot — a geared peristaltic pump turning for a few seconds moves a few millilitres — and then waits. A settle window lets the recirculating water carry the concentrate away from its entry point and mix it through the tank. Only then does Nutrient B run, and it waits again.

The order and the waiting are the chemistry. Nutrient A carries the calcium; Nutrient B carries the phosphate and sulfate. At the strength they come in the bottle, they react on contact and drop out of solution as scale — nutrients the plant can no longer reach, and a crust that closes tubing. Separate bottles, separate pumps, separate tubes, and two entry points 110 mm apart on the lid keep the concentrates from ever meeting undiluted. That separation is in the plumbing, not the instructions.

pH is corrected last. If the water is running alkaline and the nutrients are already in, a short shot of pH Down goes in, followed by a lockout of tens of minutes while it mixes. The controller will not dose acid before nutrients, and will not fire two doses of anything in the same pass.

All day: recirculate

A pump in the reservoir lifts water to the top of the tower. It falls back down through each segment and over the roots, which sit in air with a film of solution on them, and drains into the reservoir to go round again. Roots in air with moving water over them are well oxygenated by construction, which is why a drip tower needs no air stone, and why the stone is not in the box.

Evening: top up

As the plants drink and the day evaporates, the level drops. At the low mark a normally-closed solenoid opens on your water line — reverse-osmosis or tap — and closes at the full mark. If the level sensor ever fails to report full, a run-time limit closes it anyway. Nothing floods.

The interlocks are the feature

What the controller refuses to do matters as much as what it does. It will not dose nutrients below a minimum water level. It will not dose acid until nutrients are in and settled. It caps the volume of nutrient it may add in an hour and the length of every single shot. It will not run the fill valve past a time limit. It holds every automatic dose until the reading has persisted. And when the power fails, the pumps stop and the valve closes, because that is the state they rest in; when the power returns, it resumes on its own.

What is still yours

Refill three bottles. Connect a water line, or top the tank up by hand. Calibrate the two probes roughly once a month — the screen walks you through it with the reference solutions. Rinse the reservoir between crops. Plant things, and eat them.