Beginner2–3 h (estimate, plus a few days of observation)7 parts

Smart plant monitor

A soil-moisture sensor, an alert LED and an optional pump switched by a MOSFET.

Overview

A capacitive soil-moisture sensor and a light sensor (LDR) feed the analog inputs. The board converts readings into a calibrated 0–100% moisture value, prints them over Serial, lights an alert LED when the soil is dry, and can optionally run a small 5 V pump for a short, limited burst.

The key skill is calibration: every sensor and soil type reads differently, so you measure "dry" and "wet" yourself.

You will learn

· Analog inputs and the ADC
· Two-point calibration
· Hysteresis so outputs do not chatter
· Switching a motor load with a MOSFET and flyback diode

Parts list

Part (generic)	Qty	Note
Arduino Uno-compatible board (5 V logic)	1
Capacitive soil-moisture sensor module (analog output)	1	Capacitive types corrode far less than bare two-prong probes.
Light-dependent resistor (LDR) and 10 kΩ resistor	1 each
LED and resistor (use the LED resistor simulator to pick it)	1 each
Optional: small 5 V DC submersible pump, logic-level N-MOSFET module or MOSFET + gate resistor, flyback diode, tubing	1 set
Optional: separate 5 V supply for the pump	1
Breadboard and jumper wires	as needed

Generic part names only. Pinouts and logic levels vary between modules of the same type, so check the documentation of the exact module you have.

Tools

· USB cable and the Arduino IDE
· Multimeter
· A cup of dry soil and a cup of watered soil for calibration

Safety

· Keep water away from the board and supply; mount electronics above the pot.
· Low-voltage DC only. Do not switch mains-powered pumps in this project.
· Limit pump run time in code so a stuck sensor cannot flood the pot.

Learn the ideas first

Full build

01Wire and read the moisture sensor
02Two-point calibration (dry and wet)
03Add the light sensor and alert LED
04Hysteresis thresholds
05Optional: MOSFET-switched pump with a run-time limit
06Log a few days of readings

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