Build a Smart Plant Watering System with a 3V Circuit

A brightly shining LED indicates the need to water a plant

The circuit consumes very little power, operating on a 3V supply

Circuit Diagram

Components:

Device Purpose:

This circuit is designed to signal when a plant requires watering. The LED emits at maximum intensity when the soil within the flower pot is excessively dry; it diminishes progressively as the moisture level within the pot increases, ceasing to operate once the ideal moisture level is attained. This condition is achieved through the adjustment of R3.

Integrated Circuits (ICs) play a crucial role in this circuit. The 4093 is a versatile quad Schmitt-trigger NAND gate integrated circuit. These ICs are commonly used as building blocks in digital logic circuits, offering robust switching characteristics and the ability to generate precise square wave signals. The Schmitt trigger input provides hysteresis, minimizing noise sensitivity and ensuring stable operation. The quad configuration enables the creation of complex digital circuits with multiple inputs and outputs, allowing for versatile control and monitoring functions. The 4093's precise switching behaviour allows for creating reliable square waves.

Circuit Operation:

IC1D generates a square wave oscillation with an approximate 10/90 mark-space ratio. This signal is fed to probe P1, and its inverted version, produced by IC1A, is compared with the signal captured by P2, utilizing the NAND gates within IC1B and IC1C in parallel, thereby driving the LED. When a low resistance exists between the probes due to a high water content in the flower pot, the LED remains off, gradually illuminating as the resistance between the probes increases.

Notes: