Automatic irrigation sounds simple: a pump runs on a timer, water comes, done. That is true — as long as all variables remain constant. Pot size, substrate quantity, plant size, growth phase, temperature. In practice, all of these change, and a timer system is too dumb to keep up.
The Growix system solves this with weight-based logic: the plant itself says when it needs water — via its weight.
Substrate basics — soil, coco or hydro?
| Substrate | Water retention | Error tolerance | Irrigation interval |
|---|---|---|---|
| Soil (high quality) | High | High | 1–2× daily |
| Coco coir | Medium | Medium | 2–4× daily |
| Coco + perlite (70/30) | Medium-low | Medium | 2–5× daily |
| Pure perlite | Very low | Low | Multiple times daily |
The Growix Core is optimised for soil and coco-based substrates — in a fabric pot with a catch tray underneath. The combination of good water retention and drainage makes the weight-based control particularly stable.
The load cell — heart of the irrigation system
A load cell is a strain gauge-based force sensor that measures electrical resistance changes under weight load. In combination with the HX711 amplifier IC, it delivers a digital weight measurement with a resolution of ±1–5 g.
Calibration — without it, everything is worthless
Calibration means: place a known weight on the cell, note the raw value, calculate the conversion factor. In practice this has several pitfalls:
- Temperature influence: Load cells drift at temperature changes of 0.1–0.5 g/°C. The Growix incorporates the current temperature into each measurement and applies a compensation factor.
- Creep behaviour: Under constant load, some cells show slow creep. The wet weight after watering should only be saved as a reference value after 5–10 minutes.
- Overload protection: The maximum load of a 5 kg cell is mechanically approx. 150% of the rated value — with a fully watered 10L pot plus plant, the correct cell size must be selected.
Pump types compared
| Type | Advantages | Disadvantages |
|---|---|---|
| Submersible pump | Cheap, high flow rate | Hard to dose precisely, always wet |
| Peristaltic pump | Precisely dosable, dry-run capable | Slower, more expensive |
| Diaphragm pump | Self-priming, robust | Loud, pulsating flow |
The Growix system uses a small submersible pump in the 4L quick-release tank, controlled via MOSFET with PWM. The short pump duration (6–10 seconds per cycle) and subsequent waiting for drainage makes the lack of dosing precision irrelevant — the weight after watering is the correction mechanism, not the pump itself.
The 4L quick-release tank
The water tank holds 4 litres — deliberately sized this way. Too large means: less frequent refilling, but higher weight and missing feedback on water consumption.
- 4 litres is sufficient for 3–5 days at average consumption (vegetative phase) or 1–2 days (late flower)
- Quick-release: tank is removable without tools — pull down, fill, insert
- Water level sensor warns via touch UI when tank falls below 20%
The irrigation logic in Growix OS
The logic is simple: do not water by time, but by weight loss.
- Save reference weight after the last watering (5 minutes after pump off)
- Measure current weight every 30 minutes
- When threshold is exceeded (configurable per phase) → pump on for 8 seconds
- Wait 10 minutes (drainage), save new wet weight as reference
- If weight does not increase → empty tank alarm