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