Automatic Plant Watering / Irrigation System for <$5

One thing we never seem to get right is when to water plants. We either overfeed them or forget them. In either case, they die quickly.

As part of my many home automation endeavors I wanted to build an automatic plant watering system. The basic idea was: a water pump in a glass of water, a moisture sensor and whenever the soil the moisture sensor is measuring is dry, the water pump provides water until the soil is wet.

Read on for how to make this a reality for <$5.

A kit like this one: https://www.aliexpress.com/item/4001096063867.html?spm=a2g0s.9042311.0.0.66e74c4dDfCE0X or the separate components.

First, I used the USB cable that came with the kit to provide power (you can use another way of getting 5V of power). Ignore the inverter in the image, you don't need it.

These are the connections:

• Moisture sensor: connect to two pin side of breakout board. Does not matter which way
• Moisture sensor breakout board:
  • VCC –> +5V
  • GND –> GND
  • D0 (digital output) –> IN on Relay

• Relay:
  • VCC –> +5V
  • GND –> GND
  • IN - D0 of sensor breakout board
  • COM –> +5V
  • NC –> Red wire of water pump
• Water pump:
  • Black –> GND
  • Red –> NC of Relay

That's it! Enjoy!