YL-69 Soil Hygrometer Humidity & Soil Moisture Detection Sensor Module

wire connection YL-69 Soil Hygrometer Humidity & Soil Moisture Detection Sensor Module The YL-69 Soil Moisture Sensor Module is a practical and affordable solution for measuring soil moisture levels in plant pots, agricultural systems, greenhouse environments, automated irrigation projects, and IoT-based farming applications. The sensor uses a two-prong conductive probe to detect changes in electrical conductivity caused by the amount of moisture present in the soil. The module includes an LM393 comparator and provides dual-output operation, allowing users to obtain a continuously varying analog signal for moisture-level monitoring or a digital ON/OFF signal based on a user-defined moisture threshold. An onboard potentiometer allows the digital trigger level to be adjusted according to the application. Applications The YL-69 is suitable for: Automatic plant watering systems Smart irrigation systems Indoor plant and garden monitoring Greenhouse automation Agricultural soil monitoring IoT-based farming projects Arduino and ESP32 projects Soil moisture alarms Water pump control systems Educational electronics and robotics projects Wire Connection The YL-69 control module normally has four pins: YL-69 Pin Arduino Connection ESP32 Connection Function VCC 5V 3.3V Power supply GND GND GND Ground AO Analog input, e.g. A0 ADC pin, e.g. GPIO34 Variable moisture signal DO Digital pin, e.g. D2 Digital GPIO Moisture threshold signal For ESP32: It is recommended to power the YL-69 module from 3.3V when connecting its AO output directly to an ESP32 ADC input. Do not feed a potentially 5V analog output into an ESP32 GPIO. How It Works When the probe is inserted into soil, the amount of water between the two conductive tracks changes the electrical conductivity of the soil. The module converts this change into an electrical signal. Dry soil: Higher resistance and a different analog output level Wet soil: Lower resistance and a different analog output level AO: Provides a variable signal that can be used to estimate relative soil moisture DO: Provides a digital HIGH/LOW signal when the moisture level crosses the threshold set by the potentiometer Important Note The YL-69 probe is designed for basic soil-moisture sensing and educational or DIY applications. Because the exposed conductive probe can gradually corrode during prolonged use, especially in continuously wet or chemically treated soil, it is recommended to use it for intermittent measurements rather than permanent immersion.