CHAPTER 4:SOLENOID

SOLENOID

4.1 INTRODUCTION OF SOLENOOID

The general principle of the solenoid action is very important in machine control.Solenoid is an electromechanical device.Electrical enery is used to magnetically cause mechanical movement.

4.2 PRINCIPLE OPERATION OF SOLENOID

    A solenoid is a coil with an iron core and moveable iron plunger.When the coil is energized, the plunger is attracted by the coil.It “pulls in” ,and this motion can be used to activate another mechanism.

The solenoid shown in figure4.2(a),is used in many electrically activated devices such as valves, locks, punches and marking machines.

Solenoid is made up of three basic parts

a)     Frame

b)    Plunger

c)     Coil

The frame and plunger are made up of laminations of high-grade silicon steel.The coi is wound of an insulated copper conductor.Solenoids for alternating current use are now available as oil-immersed types.Heat dissipation and wear conditions are improved with this design.

4.3 SYMBOL OF A SOLENOID

Below is a symbol of a solenoid.

Figure 4.3:Standard symbol of a solenoid.

4.4 TYPES OF SOLENOID

There are many kinds of solenoids.Figure 4.4,shows one type of solenoid in industrial use.

Figure 4.4:Plug in,oil immersed of solenoid.

4.5 BASIC FUNTION OF SOLENOID CONTROL CIRCUIT

Operating the START push-button switch close the circuit to the coil of relay ICR as shown in figure 4.5(a).The coil is now energized. Relay contact 1CR-1 as shown below then close, interlocking around the START push-button switch.Contact 1CR-2 closes, energizing selenoid A.The circuit can be de-energized by operating the REVERSE push-button switch.

     In figure 4.5(b),a time-delayed relay is added.Operating the START push button switch closes the circuit to the coil of relay 1CR.The coil is now energized Contact 1CR-1 closes,interlocking around the START push button switch.Contact 1CR-2 closes, energizing solenoid 1A.Contact 1CR-3 close, energizing the coil of timing relay 1TR.After a time relay, as set on the timing realay ,the timing constant contact closes,energizing solenoid 1B.The circuit can be de-energized by operating the REVERSE push -button switch.Note that if for some reason the REVERSE push button switch is operate before the tim eset on the timing relay expires, solenoid 1B will not be energized , as the timing relay coil will be de-energized.With the relay coil de-energizing,the timing contact remains in the normal open condition.

4.6 APPLICATION OF SOLENOIDS

Solenoids are used to control fluid flow in hydraulic or pneumatic system.Solenoids are also applied in many electrically activated devices such as valves, locks, punches and marking machines.

CHAPTER 3: RELAY

RELAY

3.1 INTRODUCTION OF RELAYS

The relay is an electromagnetically device.The relay offers a simple ON/OFF switching action and response to a control signal.

3.2 RELAY PRINCIPLE

     The electrical relay offers a simple ON/OFF switching action in response to a control signal.Figure 3.2 illustrates the principle.When a current flows through the coil of wire a magnetic field is produced.This pulls a movable arm that forces the contact to open or close.This might then be used to supply a current to a motor or perhaps an electric heater in a temperature control system.

     Time-delay relays are control relays that have a delayed switching action.The time delay is usually adjustable and can be initiated when a current flows through the relay coil or when it ceases to f;ow through the coil.

3.3 APPLICATION OF RELAYS IN INDUSTRIES

     Relays are used in the control of fluid power valves and in many machine sequence controls such as boring,drilling,milling and grinding operations.

3.4 SYMBOL OF RELAYS

Below is the common electrical symbols of relay based on the function of relay.

3.5 SPECIFICATION OF RELAY

 

      The standard voltage for relay used in machine control is 120 volt.The coils on electro-mechanical devices such as relay,contactors and motor starter are designed so as not to drop out(de-energize) until the voltage drops to minimum of 85% of the rated voltage.The relay coil also will not pick up (energize)until the voltage rises to 85% of the rated voltage.This voltage level is set by the National Electrical Manufacturer Association (NEMA).

3.6 RELAYS AND SWITCH LOGIC CIRCUIT

       Relays are widely applied in electromagnetic devices.Figure 3.6(a) and 3.6(b) shows a typical relays appearance.When the relay is not energized,the spring keeps the armature away from the coil.This produces an air gap and the main contact presses against the normally closed contact.’When the relay is energized,the armature is attracted and moves toward the coil.This eliminates the air gap and the main contact touches the normally open contact and completes that circuit.The circuit with normally closed contact is opened.The relay acts as a single -pole double-throw switch.Many different contact arrangement are possible.

 

 

     

     Relays require a given current for pull-in.Once they pull-in,less current is require to hold them in the closed position.This is because the air gap is eliminated when the armature pulls in.The air has quite a bit more reluctance than the iron circuit and eliminating it means that less emf is required to overcome the spring tension.

   The switch logic circuit application in relay (Figure 3.6(c) shows a relay with (NO contacts).One contact is used as an interlock around the START push button.Thus, a interlock circuit is a path provided for electrical energy to the load after the initial path has been opened.The second relay contact is used to energize a light.Remember that when a relay coil is energized,the NO contacts close.The circuit can be DE-energized by operating the STOP push-button switch.                             

                  

                 

                                                                                             

CHAPTER 1: INTRODUCTION OF MECHATRONIC DEVICES

INTRODUCTION OF MECHATRONIC DEVICES

1.1 INTRODUCTION OF MECHATRONIC

Mechatronic is a term coined by Japanese to descried the integration of mechanical and electronic engineering.More specifically,it refers to multidisciplinary approach to product and manufacturing system design.It represents the next generation machines, robots and smart mechanisms for carrying out work in a variety of environments-predominantly factory automation and home automation Ashlen in figure 1.1(a).

Figure 1.1(a):Domains of mechatronics

     As a discipline mechatronic encompasses electronics enhancing mechanics (to provide high levels of precision and capabilities). Some examples where mechanics has been enhanced by electronics are numerically controlled machines tools which cut metal automatically,industrial robots and automatic bank tellers.The products where electronics replaces mechanics include digital watches,calculator or other.

    However,the products that really blur the distinction between electronics and mechanics are machines and robots driven by numerical control.Japan is the first country in the world to have mastered the NC machines technology and as a result the Japanese machine tool industry has flourished.This is because the Japanese have mastered mechanics,the vision of precision mechanics and electronics in design ,engineering and manufacturing, which are popularly depict by the Japanese.

1.2 SCOPE OF MECHATRONICS

    Since the 1970s ,there has been a dramatic change in the technology of these products, mainly an increasing content of electric and electronic systems integrated with the mechanical parts of the products, mechatronic.Example of products which have already moved to mechanization technology from simple mechanical products are :

a)   Machine tools incorporating computer numerical control (CNC),electronic servo drives,electronic measuring systems ,precision mechanical parts such as ball screws,anti friction guide ways and each other.

b)  Electronic watches incorporating fine mechanical parts and sophisticated electronic circuits.

c)   Electronic consumer products _washing machines,electronic cooking appliances ,fax ,plain paper copiers and others.

    In the last twenty years, the production technology has seen the introduction of high precision measuring instruments such as electronic gauges and measuring instruments ,in process gauge and quality control instruments,laser measuring systems and others to ensure high dimensional accuracies, as well increased productivity on the shop floor.

In the domain of factory automation, mechanics has had far reaching effects in manufacturing and will gain even importance in future .Major constituents of factory

automation include CNC machines,robots,automation systems and computer integration of all function of manufacturing.Proper application, utilization and maintenance of these high technology products and systems is an important aspect that enhances the productivity and quality of products manufactured by the customers.To ensure correct selection of equipment, an accurate estimation of the techno-economics of various manufacturing systems,developments in the high technology machines and equipment are studied in detail.Also,proper maintenance of various mechatronic elements, diagnostics can increase the life of the various mechatronic elements,which in turn will enhance the life of the product or system.

Such inputs in mechatronics can be best given by the manufacturers og hi-tech machines and manufacturing systems. In fact, the machine tool manufacturers are now being called upon to offer a total manufacturing for solution in production, by the customers, rather than supply of just the stand –alone machines.this trend is already evident in many of the advanced countries.Evidently, the design and manufacturing of future products will involve a combination of precision mechanical and electronic systems and mechatronics will form the core of all activities in products and production technology.

1.3 TYPES OF MECHATRONIC DEVIES

In this module ,we will discuss a several types of mechatronic devices which is used such as switches, relay, solenoid, power diode, power  transistor,thyristor,gate controller switches ,rectifier,chopper, transducer and others.These types of devices will be discussed in module by unit in this module.