Botanical Bot: Automated Smart Plant Watering Robot
Build an environmental plant companion robot that monitors soil moisture, displays expressive animated eyes on an OLED screen, and waters plants automatically.
A practical, fun environmental robotics project! Features a corrosion-resistant capacitive soil moisture sensor, an I2C OLED display showing animated digital emotional faces (happy when hydrated, sad when thirsty), and an automated 5V submersible water pump that irrigates the soil when moisture falls below a threshold.
Bill of Materials (BOM) & Components
| Component | Specifications | Qty | Estimated Cost |
|---|---|---|---|
| Capacitive Soil Moisture Sensor V1.2 (Corrosion-Proof) | Analog voltage output (does not corrode like resistive sensors) | 1 | $2.50 |
| 0.96" I2C OLED Display (SSD1306 128x64) | Renders animated expressive eyes and moisture percentage | 1 | $3.50 |
| 5V Mini Submersible Water Pump + Silicone Tubing | 120L/H flow rate, 5V DC operated | 1 | $3.50 |
| 1-Channel 5V Relay Module or TIP120 Transistor | Switches pump power on/off safely | 1 | $1.50 |
| ESP32 DevKit or Arduino Nano | Senses moisture and runs OLED animation loop | 1 | $6.00 |
Electrical & Architecture Summary
Capacitive sensor connects to Analog A0. OLED display connects to I2C (SDA/SCL). Digital Pin D4 triggers relay / transistor module to run the 5V water pump.
Step-by-Step Assembly & Configuration
Sensor Calibration in Dry Soil vs Water
Read raw analog values with sensor in air (0% dry, ~3.0V) and fully submerged in water (100% wet, ~1.2V) to calibrate the mapping formula.
- Map raw ADC values to clean 0% - 100% moisture reading in code.
- Seal top sensor electronics with conformal coating or hot glue to prevent splash damage.
OLED Display UI & Expressive Animations
Draw bitmap facial expressions: blinking cheerful eyes when soil is >50%, crying eyes when <25% moisture.
- Use the `U8g2` or `Adafruit_SSD1306` library for high-speed frame updates.
- Display current moisture % and time since last watering.
Pump Plumbing & Automated Irrigation Logic
Place the submersible pump in a water reservoir bottle, route silicone tubing into the plant pot, and program a 3-second safety pump pulse.
- Implement a 1-hour debounce timer after pumping to allow water to soak into the roots before re-measuring.
- Test automated watering cycle.