Soil Moisture Sensor Module Kit with 5-Pin DuPont Cable

Specifications

• Operating Voltage: 3.3V - 5V DC.

• Output Mode:

  • Analogue (AO): Real-time moisture value (0-1023 on Arduino).

  • Digital (DO): High/Low trigger (Threshold adjustable via Blue Potentiometer).

• Probe Material: Nickel-Plated PCB (Resistive).

• Comparator Chip: LM393.

• Cable Length: ~20cm (5-Pin Ribbon).

• Current Draw: < 20mA.

Compatibility & Platform Support

• Arduino (Uno/Nano/Mega): Directly Compatible.

• ESP32 / ESP8266: Compatible. Works perfectly at 3.3V. Remember that the analogue reading range will be 0-4095 (12-bit) on ESP32.

• Raspberry Pi: ⚠️ Digital Only. The Pi can read the D0 trigger directly. For Analog readings, you need an external ADC chip (MCP3008).

Key Applications & Projects

• Automatic Plant Waterer: Trigger a relay and water pump when moisture drops below 30%.

• Vacation Garden Monitor: Send an alert to your phone (via ESP8266) if your plants need water while you are traveling.

• Science Fair Biology: Data log soil moisture retention rates of different soil types (Clay vs. Sand).

• Smart Pot: An LED ring that turns Red when the plant is thirsty and Green when happy.

Virtual Technician: Wiring & Safety ⚠️

• VCC: Connect to 3.3V or 5V.

• GND: Connect to Ground.

• D0: Digital Output (0/1).

• A0: Analogue Output (Voltage).

• Corrosion Warning: ⚠️ This is a resistive sensor. If you leave it powered ON 24/7 in wet soil, the metal probes will corrode (electrolysis) within a few weeks.

  • The Fix: Do not power it constantly! Connect the VCC pin to a Digital Pin on your Arduino. In your code, turn the sensor ON, take a reading (10ms), and turn it OFF immediately. This extends the lifespan from weeks to years.

Accessories

• Included in the Package:

  • 1 x Soil Moisture Probe (Fork)

  • 1 x LM393 Comparator Module

  • 1 x 5-Pin Female-to-Female DuPont Cable

• Required Accessories (Not Included):

  • Controller: Arduino Uno.

  • Actuator: 5V Relay + Water Pump (if building a watering system).

Frequently Asked Questions (FAQ)

• Why does the sensor stop working after a few weeks? It is likely due to electrolysis corrosion. Constant DC current eats away the metal traces in wet soil. To fix this, only power the sensor ON for the split second you take a reading, then turn it OFF.
• What is the included "5-pin wire" used for? Two pins connect the Probe to the Driver Module. The remaining three pins connect the Module (VCC, GND, Output) to your Arduino.
• Is this sensor waterproof? The Probe (Fork) is waterproof and meant to be buried. The Electronic Module (Blue Board) is NOT waterproof. Keep the electronics in a dry box.
• How do I calibrate the values? Read the sensor in dry air (Record as 'Dry Value') and then in a cup of water (Record as 'Wet Value'). Use the map() function in Arduino to convert these to 0-100%.
• What is the blue potentiometer knob for? It adjusts the Digital Threshold. If you are using the D0 pin, this knob sets the moisture level at which the output switches from LOW to HIGH.
• Can I use it with a 3.7V LiPo battery? Yes, the module works reliably down to roughly 3.3V.
• Is Capacitive better than Resistive? Yes. Capacitive sensors (like our v1.2 model) do not have exposed metal electrodes, so they don't corrode. This resistive one is cheaper and better for education/prototyping.
• Can I extend the wires if my plant is far away? Yes, but analog signals degrade over long distances. Use shielded cable if going over 1 meter, or place the microcontroller closer to the plant.
• Does it measure air humidity? No. It measures electrical conductivity, which requires a medium like soil or water. Use a DHT11 for air humidity.
• Why do I get high readings when dry and low when wet? This is standard inverse logic. Dry soil = High Resistance = High Voltage. Wet soil = Low Resistance = Low Voltage. You can flip this in your code: value = 1023 - analogRead(A0).
• Can I use this to detect water leaks on the floor? Yes! If you place the probe tips on the floor, it will detect water puddles instantly (circuit closes).
• What happens if I touch the probes with my hand? Your skin has moisture and salt, so the sensor will trigger. This is a good way to test if it's working before putting it in soil.
• Is the probe safe for food (Hydroponics)? The PCB is lead-free (usually), but the nickel plating will dissolve over time. We do not recommend using this specific resistive sensor for food crops. Use a non-contact or food-grade sensor instead.
• Do I need a library to use this? No. It uses standard digitalRead() or analogRead(). No special library is required.
• Does soil type affect the reading? Yes. Sandy soil drains faster and conducts less than clay soil. You must recalibrate if you move the sensor to a different pot.
• How deep should I bury it? Ideally, bury it to the root level of your plant (usually 2-3 inches deep). Do not bury the plastic connector at the top of the probe.
• Can I connect multiple sensors to one Arduino? Yes. You can use multiple Analog pins (A0, A1, A2...) for as many sensors as you have pins.
• Why is the "Power" LED on but "Signal" LED off? The Signal LED only turns on when the Digital Output is triggered (i.e., when soil is dry/wet depending on pot setting).
• What is the current consumption? Very low, typically under 20mA.
• Can I use it with NodeMCU/ESP8266? Yes. Just remember NodeMCU has only one Analog pin (A0). If you need more sensors, you need a multiplexer.