design of an automatic irrigation control system

given by:

OYEDIRAN TOBILOBA JOSEPH

10CK011291

Electrical and Electronics Engineering

Friday 10th April, 2015

1. INTRODUCTION

2. AIM AND OBJECTIVES

3. METHODOLOGY

4. SYSTEM DESIGN

5. RECOMMENDATIONS

6. QUESTIONS AND ANSWERS

WHY THIS PROJECT ? ?

Humans always had to be involved. Someone has to be present, either continuously or intermittently. Such time could be used for something else!

A lot of water is wasted in the process as there is no way to ensure that the water actually get to the roots of the crops. There is not even enough water in the world for humans yet!

Design an irrigation system that can

autonomously control the irrigation process

and conserve water while at it.

• Develop a sensor to determine when irrigation is necessary

• Develop a control circuit (the brain of the system)

• Develop a pumping and delivery channel for the irrigation water

• Develop a power supply unit for the system

A moisture sensor was constructed to model the electrical resistance of the soil;

A regulated 12 volts power supply unit was constructed to power the system;

The control circuit was implemented using operational amplifier and timer;

And the pumping subsystem consisting of a submersible low-noise micro water pump was constructed using a small dc-operated motor.

Power Supply Unit

Step down transformer : turns ratio 16:1; 15V output

Diode bridge

Filtering capacitor : 2200uF

Voltage regulator: LM7812 ; 12V output

Noise cancelling capacitors : 0.1uF

Unit output 12V = control circuit supply voltage = pump’s driving voltage

Moisture sensing

Modelling soil electrical resistance

Inverse relationship between soil moisture content and electrical resistance

Calibration indicated 100kilo ohms as the sensor’s dry point for most soil samples.

Sharp sensitivity

Specs: probes’ length = 6cm

separating distance = 4cm

totally dry soil resistance = 1-2 mega ohms

The Control Circuit

15.0

8.0

2.5

5.0

3.0

1.5

12.0

7.5

2.0

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

40 50 60 70 80 90 100 110

Irrigationtime

(seconds)

Level of soil dryness (%)

Graph of irrigation time against percentage of soil dryness

clay soil

sandy soil

loamy soil

For the large scale implementation of this project:

a more powerful motor should be used;

the control circuit be implemented using amicrocontroller in order to accommodate morethan one sensor;

where homogenous irrigation is needed andthe crops cover every part of the area, the dripmeans of irrigation should be modified into asprinkling system

where there is possibility of presence of wateraround where the control box is located, themode of power supply should be implementedusing detachable, rechargeable batteries.