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Soil Moisture Sensor (YL-69 + LM393)

Sensor

Senses moisture by measuring the soil's resistance with a fork probe; the comparator board gives an analog value and a digital output with an adjustable threshold. A resistive probe corrodes when powered all the time, so power it only while measuring.

Specifications

Probe type

Resistive (YL-69)

Supply voltage

3.3 - 5V DC

Output

Analog (AO) + digital (DO)

Comparator

LM393

Threshold adjustment

Trimmer

Digital output

LOW when moisture is above the threshold

Pins

VCC, GND, DO, AO

Shop prices

• RobotzadeIn stock27.00 ₺
• Modül ElektronikIn stock27.59 ₺
• SAMM MarketIn stock30.26 ₺
• Robolink MarketIn stock33.00 ₺
• RobocomboIn stock35.00 ₺
• ElektrovadiIn stock36.07 ₺
• HatfonIn stock36.75 ₺
• MotorobitIn stock37.88 ₺
• HobiDevreIn stock40.32 ₺
• RobotistanIn stock41.81 ₺
• KomponentciIn stock53.12 ₺
• RobotsepetiIn stock60.96 ₺
• Entegre DünyasıIn stock119.22 ₺
• F1 DepoOut of stock36.00 ₺
• Direnc.netOut of stock41.84 ₺

Prices read from the shops' pages on 22 October 2026. Prices and stock may have changed since; check at the shop before you buy.

Projects with this part

• Automatic Plant WateringIntermediate50 minA system that waters a potted plant by itself once the soil dries out: the soil moisture sensor measures moisture as a percentage, and when it drops below 30% the Arduino runs the mini submersible pump for 3 seconds through a relay, waits for the water to soak in, measures again and repeats until moisture passes 50%. The pump runs on three AA batteries of its own; the relay keeps that circuit fully apart from the Arduino. If 5 waterings in a row leave the soil dry, the tank counts as empty and the pump is stopped so it never runs dry. It teaches calibrating a sensor into a percentage, switching a separately powered load with a relay, powering a sensor only while it reads to slow its corrosion, and guarding a system against faults. No extra library needed.Open project