Automatic Plant Watering System Circuit

If you are one of those people who would like to spend their well-earned summer vacations in the comforts of a hill resort but  worried about your potted companions back home, then a  plant watering system  is what you need. This circuit immediately waters the plant once the soil turns dry. By adding timer circuits and other  components, we can extend the flexibility of this project and make  further improvements such that it operates automatically at duration set by timer.

circuit diagram of automatic plant watering system using 555

Circuit Description of Automatic Plant Watering System: –

The circuit is built around IC555. It also includes pump and other passive components.  As the soil dries up, its resistance increases causing the voltage at pin 2 of IC555 to fall below 1/3 Vcc. This activates the trigger comparator and the output goes high, switching on the pump. The output remains high for the time interval set by VR1  and is given by

Tminutes  = 1.1 R.C/60*106

where R is in ohms and C is in microfarad.


Resistors (all ¼-watt, ± 5% Carbon)
R1  = 1 KΩ

VR1, VR2  = 1 MΩ

C1  = 470 µF/16V

C2  = 0.01 µF

IC1  = NE555

T1  = SL100

D1  = 1N4001

RL1  = 12V, 100Ω Relay