Embedded Systems & IoT · 2023 · completed
Smart Irrigation System
Automated closed-loop precision agricultural system with soil moisture telemetry and relay valves.
01 / Overview
An automated closed-loop irrigation system designed to eliminate water waste and prevent crop root dehydration. Reads soil moisture levels across multiple sensor points, triggers solenoid valves, and streams telemetry data to a local monitoring dashboard.
02 / Problem
Traditional timed irrigation runs regardless of actual soil moisture levels or atmospheric humidity, resulting in severe water waste and risk of crop root rot.
03 / Contribution
Constructed the sensing array, designed transistor relay driver circuits with flyback protection, and programmed hysteresis control logic.
04 / System architecture
Physical + hardware
- Capacitive soil moisture sensors (corrosion resistant)
- Submersible 12V DC water pump and 12V solenoid valves
- Optocoupled relay module with flyback freewheeling diodes
- Microcontroller unit running continuous sensing loop
Firmware + software
- Sensor calibration curve mapping analog voltage readings to volumetric water content percentage
- Hysteresis threshold control algorithm preventing pump rapid cycling (chattering) around trigger boundaries
- Timeout failsafes ensuring pump auto-shuts off if moisture does not rise within 3 minutes (leakage protection)
Signal flowCapacitive sensors -> Analog input ADC pins -> Threshold comparator logic -> Optocoupler -> 12V relay drive -> Pump.
05 / Engineering decisions
- 01Used capacitive moisture sensors rather than resistive probes to prevent metal oxidation and electrode corrosion over prolonged soil immersion.
- 02Built dual-threshold hysteresis (activating pump at <30% moisture and deactivating at >65%) to extend mechanical valve lifespan.
06 / Results + constraints
Observed results
- Maintained consistent root-zone moisture across 30-day testing cycle.
- Reduced total water consumption by an estimated 38% compared to continuous scheduled timer watering.
- Failsafe shutoff successfully prevented dry-run pump damage when water reservoir was depleted.
Current limitations
- Requires periodic soil salinity recalibration for maximum absolute accuracy.
- Off-grid solar charging integration is planned for remote field deployments.