Design And Construction Of A Proximity Sensor

ABSTRACT

Proximity sensor detects the presence of nearby objects without any physical contact. Examples of proximity sensor usage include detecting an out-of-paper condition in a printer or a mobile phone screen that dims to save battery life when placed near a face.

Proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation, and looks for changes in the field or return signal. The object being sensed is often referred to as the proximity sensor’s target.

Their operating principle is based on a high frequency oscillator that creates a field in the close surroundings of the sensing surface. The presence of a metallic object (inductive) or any material (capacitive) in the operating area causes a change of the oscillation amplitude. The rise or fall of such oscillation is identified by a threshold circuit that changes the output state of the sensor. The operating distance of the sensor depends on the actuator’s shape and size and is strictly linked to the nature of the material. This study is aimed at building an inductive type of proximity sensor.

 TABLE OF CONTENT

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

• BACKGROUND OF THE STUDY
• STATEMENT OF PROBLEM
• AIM AND OBJECTIVES
• SCOPE OF THE RESEARCH
• SIGNIFICANCE OF THE STUDY
• JUSTIFICATION OF THE STUDY
• STUDY LIMITATIONS/DELIMITATION

CHAPTER TWO

• LITERATURE REVIEW
  • INTRODUCTION
  • REVIEW OF THE STUDY
  • REVIEW OF RELATED STUDIES
  • REVIEW OF DIFFERENT TYPES OF PROXIMITY SENSORS
  • PROPOSED SYSTEM

CHAPTER THREE

• CONSTRUCTION
  • BLOCK DIAGRAM
  • PROXIMITY SENSOR CIRCUIT SCHEMATIC
  • SYSTEM OPERATION
  • CIRCUIT DESCRIPTION
  • DESCRIPTION OF COMPONENTS USED

CHAPTER FOUR

• RESULT ANALYSIS
  • INSTALLATION OF THE COMPLETED DESIGN
  • CONSTRUCTION PROCEDURE AND TESTING
  • CASING AND PACKAGING
  • ASSEMBLING OF SECTIONS
  • TESTING OF SYSTEM OPERATION
  • PROBLEM ENCOUNTERED

CHAPTER FIVE

5.1      CONCLUSION

5.2      RECOMMENDATION

5.3      REFERENCES

 CHAPTER ONE

1.1                                               BACKGROUND OF STUDY

Sensors are devices used to provide information on the presence or absence of an object. It measures the closeness of body to obstacles (both animate and inanimate) that may not be visible to the driver or that the driver may yet not have realized (NEMA, 2013).

Previous researcher has discussed the proximity issue in construction including injury and fatality statistics of collisions between construction equipment and workers. Because construction projects often involve many repetitive tasks, construction workers can experience decreased awareness and loss of focus (Pratt et al. 2001, Teizer et al. 2010). Construction equipment operator visibility, specifically operator blind spots, can be a major factor in contact collisions between construction equipment and ground workers (Fullerton et al. 2009). A real-time proximity detection and warning system is needed on construction jobsites to           warn equipment operators of hazardous proximity situations.

Proximity Detection Sensors detect and measure and detect the presence of an object or person with making contact.  The proximity detection devices offer a wide range of performance, and compensates for ambient light, allowing it to operate in environments ranging from bright sunlight to dark rooms. The wide dynamic range allows operation in short-distance detection applications behind dark glass, such as cell phones. Proximity Detection Sensors can be used for a mechanical switch replacement or to sense human gesturing.

A proximity sensor detects the presence of nearby objects without any physical contact.

A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for instance), and looks for changes in the field or return signal. The object being sensed is often referred to as the proximity sensor’s target. Different proximity sensor targets demand different sensors. For example, a capacitive or photoelectric sensor might be suitable for a plastic target; an inductive proximity sensor always requires a metal target.

The maximum distance that this sensor can detect is defined “nominal range”. Some sensors have adjustments of the nominal range or means to report a graduated detection distance.

Proximity sensors can have a high reliability and long functional life because of the absence of mechanical parts and lack of physical contact between sensor and the sensed object.

Proximity sensors are commonly used on smart-phones to detect (and skip) accidental touch-screen taps when held to the ear during a call. They are also used in machine vibration monitoring to measure the variation in distance between a shaft and its support bearing. This is common in large steam turbines, compressors, and motors that use sleeve-type bearings.

Historitical Background of Proximity Detector

In 1958—exactly 50 years ago—the proximity switch was invented in a Mannheim laboratory owned by Pepperl+Fuchs. What was originally conceived as a customer-specific solution for an intrinsically safe current circuit in the chemical industry, has since become the universally recognized industry standard for non-contact switching.

The proximity switch is one of the oldest electronic components in automation. It has been continuously reinvented over the years to keep pace with ever-changing requirements.

Fifty years ago, when Walter Pepperl and his colleague Wilfried Gehl were commissioned by BASF to find an alternative to mechanical contacts, they had no idea that they would set a milestone in the development of automation technology. The challenge was to develop a robust component that would operate reliably after many thousands of switching cycles at very low switching currents, in the corrosive atmosphere of a chemical plant.

As trained radio engineers, they knew what happens when a metallic object approaches a coil system. With the bi-polar transistor, which William B. Shockley had invented 10 years earlier, the two engineers had at their disposal a new compact component with which the damping of an oscillating circuit could be easily evaluated and converted into a switching signal. The invention of the proximity switch is consequently an early example of how communications engineering expertise advances automation technology.

In the early years, application of the inductive proximity switch was restricted to the chemical industry, where problems with mechanical contact wear due to the low currents used and the resulting absence of cleansing through contact erosion, were the most severe.

However, in the early 1960s, people began to appreciate the practically unlimited service life of these switches in other automation applications. So it was no surprise when Pepperl+Fuchs introduced an inductive version of the roller lever limit switch on the market in 1968. This device shared mounting compatibility with its mechanical counterpart and had the option of five different positions for the active sensor surface, so that any possible travel direction of the mechanical switch could be replicated.

In those days it was not yet possible to reproduce all the different voltage ranges electronically. Nevertheless, the 60 different versions of proximity switch required as a result could not prevent its success on the market. The absence of wear was a major advantage for the reliability of automation systems.

Ten years later, the next-generation device was presented, which simplified applications. The user could now change the active sensor surface himself and the amplifiers with different voltage ranges could be easily replaced by insertion. This proximity switch design continues to be one of the highest selling, but the development of this technology has resulted in much greater variety.

1.2                                              STATEMENT OF PROBLEM

Devices such as limit switches detect an object by contacting it which can cause low response, abrasion or damage to the object , affect the service life and also subject to environment. To overcome this problem a proximity sensor was built.  Proximity Sensors convert information on the movement or presence of an object into an electrical signal. Proximity Sensors detect an object without touching it, and they therefore do not cause abrasion or damage to the object. Detection takes place with almost no effect from dirt, oil, or water on the object being detected.

1.3                                                   AIM AND OBJECTIVES

The main aim of this work is to build a device that will detect the presence of an object without making physical contact with the object. At the end of this work the following objective shall be achieved:

• A device that converts information on the movement or presence of an object into an electrical signal shall be built.
• The connection and operation of inductive circuit shall be known.
• Operation, application and connection of the device shall also be known.

1.4                                               SCOPE OF THE RESEARCH

Proximity sensor comes in various design voltages and ohms the choice of a particular sensor then depends on its application. The project tends to cover the design of distance sensor inductive circuit to indicated obstacles at close proximity to the device. Their operating principle is based on a coil and oscillator that creates an electromagnetic field in the close surroundings of the sensing surface.

1.5                                           SIGNIFICANCE OF THE STUDY

An advantage with these sensors is that they are capable of detecting both metallic and non-metallic targets whose dielectric constant is more than that of air. They are generally low cost and have good resolution, stability, high speed and low power usage. Proximity sensors detect the presence or absence of an object. Examples of proximity sensor usage include detecting an out-of-paper condition in a printer or a mobile phone screen that dims to save battery life when placed near a face.

Proximity sensors can be used in industrial, automotive and consumer applications.

1.6                                           JUSTIFICATION OF THE STUDY

Proximity sensor was choosing because of its advantages it has over contact making sensors such as:

Proximity Sensors detect an object without touching it, and they therefore do not cause abrasion or damage to the object.

Devices such as limit switches detect an object by contacting it, but Proximity Sensors are able to detect the presence of the object electrically, without having to touch it.

No contacts are used for output, so the Sensor has a longer service life (excluding sensors that use magnets).

Proximity Sensors use semiconductor outputs, so there are no contacts to affect the service life

Unlike optical detection methods, Proximity Sensors are suitable for use in locations where water or oil is used.  Detection takes place with almost no effect from dirt, oil, or water on the object being detected.

1.7                                    STUDY LIMITATIONS/DELIMITATION

The project work deals on the construction of proximity sensor for objects thus the limitation of study could be likened to financial constraint, time consumption and difficulties encountered while getting materials for the design.