Automatic Plant Watering System
Water plants only when the soil is dry, using a moisture sensor, relay and small pump.
Overview
A soil probe reads how wet the pot is. When the reading crosses a dry threshold, the board switches a relay, which switches the pump. Teaches analog reading, relay driving and separating pump power from board power.
Build Steps
Read the sensor
Wire the probe to 5 V, ground and an analog pin. Note the reading in air and in water for your dry and wet thresholds.
Set thresholds
Switch the relay on after a few dry readings and off once wet. The gap stops chattering.
Wire relay and pump
Put the relay's common terminal in series with the pump's positive lead. Keep the pump on its own supply and share ground.
Test a full cycle
Place the probe away from the pot wall, aim the outlet and run a dry-to-wet cycle before fine-tuning.
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