CHAPTER TWO

2.0                                       LITERATURE REVIEW

2.1          REVIEW OF DIFFERENT TYPES OF WATER SENSOR

There are different types of water sensor that are used as water level measurement sensors included robust ceramic pressure sensors, shaft encoders, acoustical sensor, and the visual reference staff gages. Stevens still offers the low-powered, mechanical chart recorders for a long-term uninterrupted, real-time chart of water level [8].

PRESSURE SENSOR

Pressure sensors are submerged at a fixed level under the water surface. The pressure sensor measures the equivalent hydrostatic pressure of the water above the senor diaphragm. It is like weighing the water.

Applications:

·         Ground water level monitoring

·         Ground water slug testing

Advantages of Pressure Sensors in water level measurements:

·         Out put can be analog or digital depending on model

·         Smaller diameter stilling well or pipe can be used for installation.

·         A low profile installation site can be achieved using pressure sensors with internal data logging.

·         Easy to install, maintain and calibrate.

Limitations of Pressure sensors in water level measurements:

·         Typically subject to long-term drift and variations with temperatures. However, they are in the water where the temperature is usually fairly stable, so the temperature concern may not be too high. It is good idea to check calibration every 6 months.

·         Fouling or corrosion with direct exposure to the water can affect the readings.

·         Models are available in a broad pressure range that needs to be known at time of purchases.

·         Some models require breather tube in the cable to reference to atmospheric pressure for best accuracy.

·         Some models have a sensor head that can be easily damage to human touch or other objects touch.

ENCODERS FLOAT

Stevens carries a number of encoders, potentiometers, linear variable differential transformers, and synchro that are used in liquid level measurement applications. These devices are float-operated sensors that utilize a float and counter-weight attached to a line placed around the Shaft Encoder’s pulley. As the liquid level changes the float moves up or down, moving the pulley. The shaft encoder turns the angular position of the pulley and shaft into an electronic water level signal that can be logged by an attached data logger.

SHAFT ENCODERS

A shaft encoder is an electro-mechanical device used to convert the angular position of a shaft or axle to an analog or digital electrical signal. These devices are used in many applications including liquid level measurement. Part of the mechanical aspect of this device for level measurement utilizes a float and counter-weight attached to a line or tape placed around a pulley attached to the encoder’s shaft.

As the level changes, the float moves up and down and, thereby, rotating the pulley and the attached shaft – generating an electronic wave form for both rotating direction and amount. By converting shaft rotation into electronic signals, encoders are used to electronically monitor the position of a rotating shaft. There are two main types of encoders for liquid level measurements are absolute and incremental.

Advantages of Float-operated sensors for water level measurements:

·         Since many older sites were designed for mechanical float operated measurement, encoders are easily adapted to existing float gear and gaging system.

·         Float-operated systems are easy to understand and troubleshoot.

·         Most encoders offer good temperature stability.

·         Various electronic technologies can be used including digital incremental and digital absolute (encoders); analog absolute (potentiometers and Linear variable differential transformers); or digital absolute (synchros).

·         Float is protected in a stilling well and sensor is not in direct contact with the water. Therefore the risk of damage is low from debris flow or fouling.

·         Highly accurate with large sized floats.

Limitations of Float-operating sensors in water level measurement:

·         Requires a stilling well to assure stability and reliability of the float-operating system.

·         Rapid changes in water level may result in the cable / tape line becoming disengaged from the float-operating sensor’s pulley.

NON-CONTACT WATER SENSOR

Both ultrasonic and sonic level instruments operate on the basic principle of using sound waves to determine fluid level. The frequency range for ultrasonic methods is ~20-200 kHz, and sonic types use a frequency of 10 kHz. a transducer directs sound waves downward in bursts onto the surface of the water. Echoes of these waves return to the transducer, which performs calculations to convert the distance of wave travel into a measure of level. For practical applications of this method, you must consider a number of factors.

Applications:

Ultrasonic Sensors are frequently used in:

·         Water level measurement with the sensor attached to a bridge or structure directly over the water.

·         For flood applications to avoid damage from debris flow

Advantages of ultra sonic sensors for water level measurement:

·         Non-contact sensor allows for easy installation on a bridge or structure over the water.

·         Non-contact sensor reduces the problem of sensor fouling or corrosion. Also potential damage from debris is reduced.

Limitations of ultra sonic sensors for water level measurement:

·         The speed of sound through air varies with the air’s temperature. The transducer may contain a temperature sensor to compensate for changes in operating temperature. However, this only takes into account the temperature at the sensor, which may be different as the sound wave approaches the water

·         Debris, extreme turbulence or wave action of the water can cause fluctuating readings. Use of a damping adjustment in the instrument or a response delay may help overcome this problem.

·         Maximum distance to the water level surface is typically 30 feet or less.

·         Limited usage in shallow streams or in streams with very high velocities with minimum depth requirements.

·         Very high concentrations of fine sediment in suspension can scatter and absorb the sonic pulse, preventing reflection of a detectable echo.

·         Ultrasonic typically require more power than other water level sensors.

·         Build-up on the sensor head, even simple condensation, can cause problems with the sensors operation.

CONTACT METER

Contact meter is an ideal device for quick, portable measurement of bore holes, wells, reservoirs, and other applications where liquid level depth is needed. The probe is simply feed down and when it reaches liquid the light on the front of the unit illuminates. Depth can then be read from the easy-to-read white tape.

STAFF GAGE

The Staff Gage provides a quick and easy visual indicator of water level. Made with a durable baked-on porcelain enamel finish on a metal plate. Stevens was the company who originally designed and introduced the staff gage measurement styles used by the water resource market.

Stevens is one of the leading designers and providers of custom staff gages. Customer staff gages are for large size, slopes or flow measurements or for other unique mounting angles that a site may require for a easy visual measurement. Contact Stevens with your custom staff gauge requirements.

BUBBLER SYSTEMS

Bubbler systems are hydrostatic pressure sensors that are ideally suited for accurate liquid and water level measurement, especially in industrial process systems.

2.2                                HISTORICAL BACKGROUND OF ARDUINO

The Arduino is developed in 2005. The Arduino microcontroller was initially created as an educational platform for a class project at the Interaction Design Institute Ivrea in Milan (Italy) in 2005. It derived from a previous work of the Wiring microcontroller designed by Hernando Barragan in 2004. From the beginning, the Arduino board was developed to attract artists and designers. The Wiring microcontroller was created by Hernando Barragan to be used for parsing data to electronic devices. His aim was that it could be used by nontechnical people who only had basic experience with using computers. He first of all wanted it to be used as a prototyping tool. Since he needed help to create an easy software tool to programmed the board he engaged Casey Reas and Massimo Banzi as his assistants. Reas created the visual programming language for the prototyping tool.

2.3                                           DEVELOPMENT OF ARDUINO

The computer, commonly defined as a tool for processing, storing, and displaying information, arose from a long line of analog devices used for effective counting and calculation, ranging from the simple abacus (first invented in Sumeria around 2300 BC), to Napier’s Bones (conceived in 1617, and the precursor to the slide rule), to BlaisePascal’s gear-based mechanical calculator (1645).The development of the computer accelerated during the 1940’s, spurred on largely by the highly industrialized nature of military production in World War II.The 1960’s marked a significant evolutionary leap for computing, due to the development of solid state computers (such as the IBM 1401), which used transistors for processing operations, and magnetic core memory for storage. The invention of integrated circuits in 1959 by Jack Kilby, which enabled transistors and circuits to be fused onto small chips of semiconducting materials (such as silicon), allowed further miniaturization of computer components. Another important development during this decade was the advent of high-level computer programming languages that were written in symbolic language, making computer code somewhat easier to read and learn than previous machine languages. COBOL and FORTRAN were the main languages introduced during this period. The microprocessor was introduced in 1970. The microprocessor essentially miniaturized all hardware components of a computers central processing unit to fit onto a single, tiny integrated circuit, now more popularly known as a microchip. The microchip also became the main driving component of microcontrollers (such as the Arduino), which generally consist of a microchip, memory storage hardware, and input/ output hardware for sensors.

2.4                                    OVERVIEW OF ULTRASONIC SENSOR

Ultrasonic sensors are great tools to measure distance without actual contact and used at several places like water level measurement, distance measurement etc. This is an efficient way to measure small distances precisely. In this project we have used an Ultrasonic Sensor, and it is reviewed as below:

Ultrasonic sensors are used around the world, indoors and outdoors in the harshest conditions, for a variety of applications. Our ultrasonic sensors, made with piezoelectric crystals, use high frequency sound waves to resonate a desired frequency and convert electric energy into acoustic energy, and vice versa. Sound waves are transmitted to and reflected from the target back to the transducer. Targets can have any reflective form, even round. Certain variables, such as target surface angle, changes in temperature and humidity, and reflective surface roughness, can affect the operation of the sensors.

2.6   ULTRASONIC DISTANCE SENSOR WORKINGS

The Ultrasonic Sensor sends out a high-frequency sound pulse and then times how long it takes for the echo of the sound to reflect back. The sensor has 2 openings on its front. One opening transmits ultrasonic waves, (like a tiny speaker), the other receives them, (like a tiny microphone).

The speed of sound is approximately 341 meters (1100 feet) per second in air. The ultrasonic sensor uses this information along with the time difference between sending and receiving the sound pulse to determine the distance to an object. It uses the following mathematical equation:

Distance = Time x Speed of Sound divided by 2

Time = the time between when an ultrasonic wave is transmitted and when it is received
You divide this number by 2 because the sound wave has to travel to the object and back.

2.6  REVIEW OF THE RELATED STUDY

The literature review contains the brief discussion of some recent works of water automation for water pump controller system through android application.

M. M. Raykar (2015) presented a model which can collect water expense from a customer and detect the leakage in the water distribution system. The advantage of this model is that it can reduce the periodic tours of providers to each physical location to read each meter. Another advantage is that the bill of water usage can give based on the near real-time expense from the previous expense. Detecting leak supports to save water resources and energy and also reduce the cost.

S. Gowri (2015) proposes a water monitoring system by using an automatic overflow control circuit unit. The proposal is designed from the perspective of monitoring the flow of water into the tanks automatically and from the perspective of setting as per the user demands using a Mobile Application. The advantages of the system are the conservation of water resource, reduction of the manual attempt, and time to time changes over the situation of water storage with the help of sensors.

A basic model of the android application is proposed by S. Paul (2015) which states that water pumps can be switched ON and OFF with the assistance of radio transmitters and Wi-Fi router. The wastage of water and the wastage of electricity can be avoided by this system. Users can check the water level of the tank  and turn the pump ON and OFF from remotely using the android application.

Observing the water level with the help of the ultrasonic sensor was reviewed by A. Nikam (2017). This system helps to conserve water and keep track of water usage and inform the users in situations of abuse of water. It assists the users to check the water level in the water tank. Moreover, users are capable to observe their water usage using the android application. Also, using the android application can avoid the wastage of water by cutting off the water supply.

A new architecture proposes for remote control of agricultural devices  by S. S. Patil (2012). This paper proposes the automation system with the latest electronic technology using  microcontroller and bluetooth device. The project works automatically and hence reduces the human effort. This system provides the reminder to the user so that their irrigation activity can take place on time. From the advantage of android application, farmers are capable to manage the water pump and irrigation process remotely.

A model of variable rate microcontroller based automated irrigation system has been proposed by Jia Uddin (2012). Solar power has used as the only source of power to control the entire process. Without visiting the agricultural land, farmers can find the information about the moisture level. Farmers can control the water pump based on the moisture level by sending a message from his/her cellular phone. Even when the farmers are away, the automated irrigation system always confirms the exact level of water in the agricultural lands.

Paper was discusses by P. P. Karande (2012) on automated systems based on the Android application which monitors the water pump and checks the water level in the agricultural land. Automated irrigation system leads farmers to apply the right amount of water at the right time and turn the water pump ON and OFF without using labor. It is capable to crop performance by ensuring adequate water when needed. It also helps to save time and reduce human errors by adjusting available soil moisture levels which increases their net profits.