Arduino Automatic Watering System

In this Instructables guide I will show you how to make your own - Arduino -automatic watering system for your "desk" flower (or plant). The whole procedure is very easy and you can complete this guide in about 30 min.

The goal is to automatically watered the plant when the soil moisture decreases, so we will use one "soil hygrometer" sensor for this measurement. For watering, we will use one small air-pump motor that will blowing air into the bottle from one small pipe! The pressure will throw the water from the other pipe to our plant.

I used the Adafruit Trinket Pro board for my system but if you want you can also use the Arduino uno, Arduino Pro mini or Arduino nano board.

So, let's get started!

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Step 1: What You Will Need

For this project you will need:

  • Adafruit Trinket Pro (or any other Arduino Board)
  • Soil hygrometer module (FC-28)
  • Air pump motor (i used 6V AM-265)
  • Pipe (you will need two small pieces)
  • NPN TR 2222A
  • Diode (e.g. IN4001)
  • Small/Tiny breadboard
  • Some breadboard wires

You will also need a hot melt glue gun to make sure that the bottle is airtight from the pipe holes.

You can buy them from, good prices and free shipping.

Step 2: The Pipes and the Bottle

Follow the steps below:

  • Make two holes in the cap of the bottle.
  • Take two pipe pieces
  • Now see the first image above, one pipe must be on the top of the bottle (this pipe will be connected to the air pump motor). Use some hot melt glue on both sides of cap.
  • The other pipe must be on the bottom of the bottle (this pipe will throw the water to our plant / see the second image above). Again, use some hot melt glue on both sides of cap.

Now make sure that the bottle is airtight, if you blow air (use your mouth) from the pipe (small one) you must see the water gets out from the other one.

The watering system is ready. Now lets make it automatic with the Arduino and the soil hygrometer module.

Step 3: The Circuit

The connections are pretty easy, watch the above image with the breadboard circuit schematic.

Useful notes:

Soil hygrometer module:

  • Vcc - 5V
  • GND - GND
  • AO - A0
  • DO - not connected

NPN Tr 2222A:

  • 1st pin - GND
  • 2nd pin - 9
  • 3rd pin - Motor negative pin (-)


  • Anode pin - Motor negative pin (-)
  • Cathode pin - Motor positive pin (+)

Step 4: The Code

Here's the code, embedded using Codebender!

Try downloading the Codebender plugin and clicking on the "Run on Arduino" button to program your Arduino board with this sketch. And that's it, you've programmed your Arduino board directly from your browser! It's really amazing.

Read the comments to understand how it works. If you want you can make your correction by clicking the "Edit" button, try for example to change the percentage that will activate the watering system from 20% to 50%.

Step 5: Well Done!

Now you have your own Arduino automatic watering system for your small plant or flower! Keep in mind that it will also need a sunlight to grow up, so place it near a window. Of course don't forget to refill your bottle with water after some days ;)

For more Arduino tutorials and cool projects you can visit our web page:

I would like to see photos of your plants!
I hope you liked this, let me know in the comments below.

Robotics Contest 2016

Runner Up in the
Robotics Contest 2016

Urban Farming Contest

Runner Up in the
Urban Farming Contest

2 People Made This Project!


  • Instrument Contest

    Instrument Contest
  • Make it Glow Contest

    Make it Glow Contest
  • STEM Contest

    STEM Contest

12 Discussions


6 months ago

the sensor is going to be electrolysis in the soil and ruining it by chemically unwanted ions.
in scale of weeks, the sensor stop working and plants will die.
use two pen graphite as buried sensor, it is chemically inactive and wont corrode over time
also this type of moisture sensing has an inherent drift which wont last more than couple of months and that is exactly for the electrolysis of the moist soil.
with respect it is useless
do not bother yourself with.


2 years ago

We have an Arduino UNO board and we don't know if the code will work. Can Anybody help us???

1 reply

Reply 2 years ago

It will work with any Arduino, I used Arduino Uno to build mine.


3 years ago

You guys are just to awesome on this site.I don't have an Arduino YET,but I have gotten the motivation needed to buy one immediately and to attempt being like you guys.This is so far the BEST website I have ever registered to.


3 years ago

Very nice! I will be using this to keep my bonsai watered while im away from home. However, I was wondering if you could comment on the longevity of the hygrometer, as I plan on using this to maintain a plant over the span of 2-3 months and have heard most hygrometers dont like being kept in soil for prolonged periods.

1 reply

Reply 3 years ago

I don't know... but I think that this varies depending the sensor and the quality of it. But thank you for comment because I didn't know that they have limited lifespan.


3 years ago

I love it! I mean, I've seen quite a few projects here, but when looking at things and thinking what I can actually use, yours is the best one yet :) I'm just a sucker for things you can actually use around the house.

1 reply