Multi-DIY Humidity Sensor + Irrigating System

Often having a large amount of plants to water becomes a tedious task and having various type of plants requires more attention because each type consumes different amount of water. So my friends and I have decided to implement an automatic watering system based on the soil moisture in a greenhouse as shown in the pictures. We tried this on a plot of land of 20m x 10m

Note that only one soil moisture sensor will not be reliable,so for our mini-project we have used 18 soil moisture sensors and have done an average of all these analog inputs which is a more precise result.

Step 1: Materials Used:

1. Arduino Uno

2. 3 x LM 324 - Quad Op-Amps

3. 1602 LCD Display

4. 26 x 1kΩ, 1/4W Resistors

5. 10 x 330Ω, 1/4W Resistors

6. 3x LED (Green, Red, Yellow)

7. 1 x Push Button

8. 1 x MOC 3041

9. 1 x 4.7kΩ, 1/4W resistor

10.1 x TRIAC BTA 16

11. 1 x DIAC

12. 1 x 100nF,50 V Capacitor

13. 1 x 10kΩ potentiometer

14. Galvanised steel rods

Step 2: Circuit Used:

1. DIY Soil Moisture Sensor

2. Averaging Circuit using Op-Amp (LM324-Quad Operational Amplifiers)

3. Interfacing Water pump with Arduino Uno

4. Hardware connection of LCD display with Arduino Uno

1. DIY Soil Moisture Sensor

2 galvanized steel rods (conductive materials) are placed 3 mm apart from each other. The higher the humidity (amount of water) in the soil the lower will be the resistance between the 2 rods.

2. Averaging Circuit using Op-Amp (LM324-Quad Operational Amplifiers)

3 sensors are placed on 1 op-amp and its output is the average of the 3 potential differences. Thus 3 op-amps can accommodate up to 9 soil moisture sensors and the fourth op-amp is the result of the average of the 9 sensors. For our mini project we have used 2 LM324 to take the average all the 18 soil moisture sensors.

3. Interfacing Water pump with Arduino Uno

Our load is rated 240 V, 50Hz so it can’t be directly connected to the Arduino. The circuit above enables the Pump to interface with the Arduino. An internal circuitry of the MOC 3041 helps us to understand the above circuit.

When the internal LED of the MOC 3041 lights up, it triggers an adjacent opto-triac. This in turns triggers the gate of the TRIAC BTA 16 thus the complete circuit enables the water pump to turn on. TRIAC and DIAC are used as we are dealing with AC current.

4. Hardware connections of LCD Display with Arduino Uno

Step 3: Arduino Code

The following is the code for the watering system. Comments are included in program

Step 4: Testing and Implementing



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    6 Discussions


    2 years ago

    For a moisture sensor I used thin copper tubes available in 12" lengths at Ace Hardware. Attaching wire is easy; just insert bare wire in end of tube and hammer shut. I used mine buried in the lawn to control a sprinkler system. I applied voltage only when making a measurement. Keeping the current flowing continuously can speed up corrosion.

    1 reply

    Reply 2 years ago

    Hi dick55, could you send me more information about the moisture sensor using thin copper?


    2 years ago

    Gada888, you can use any galvanized metal. pieces of old galvanized fencing material, etc. The easiest would be to go to your local builders supply store and ask where the galvanized nails are, then pick a size\length that suits you. 3 to 4 inches long is enough, unless you want to use then with plants with deeper roots, then the nails need to be longer.

    Gamer the nail into a piece of wood, 1/4 to 1/2 deep is enough. Then you can hold the head of the nail over the fire on your stove until is is hit enough to mention solder. You can solder a piece of wire to the nail when it is hot enough. Too hot and you will have to hold that wire there u til the nail cools down enough to let the solder solidify and that could be a while. You can probably get it hot enough holding it in the flame of a candle stick.


    2 years ago

    Nice project,can you please post the link of the steel rod?I wonder how to solder it.i also wonder how to implement one pump to take care of several plant pots?or maybe you used several pumps?


    Thank you for your support. Next step I would like to convert all my DIY Humidity sensors to IoT(Internet of Things) devices so as to reduce the wiring in this project. If you have any ideas to improve this project you're most welcome.