AC/DC ELECTRICAL SYSTEMS

Transcription

1 AC/DC ELECTRICAL SYSTEMS LEARNING ACTIVITY PACKET BASIC ELECTRICAL CIRCUITS BB227-BC01UEN

2 LEARNING ACTIVITY PACKET 1 BASIC ELECTRICAL CIRCUITS INTRODUCTION Electricity is used to perform tasks related to almost everything we do. This learning system will explore the fundamental concepts of electricity used in many applications, especially control systems. The specific skills discussed in this learning system will enable the learner to perform basic electrical projects at home and on the job. These skills will also be applied in many other units including programmable controllers, electrical motor control, and electro-fluidpower. This LAP will discuss how a basic electrical circuit works by setting up a number of circuits using the various components in the Amatrol T7017 AC/DC Electrical Learning System. This will also help in becoming more familiar with the operation of the trainer that will be used. ITEMS NEEDED Amatrol Supplied 1 T7017 AC/DC Electrical Learning System FIRST EDITION, LAP 1, REV. B Amatrol, AMNET, CIMSOFT, MCL, MINI-CIM, IST, ITC, VEST, and Technovate are trademarks or registered trademarks of Amatrol, Inc. All other brand and product names are trademarks or registered trademarks of their respective companies. Copyright 2013, 2012 by AMATROL, INC. All rights Reserved. No part of this publication may be reproduced, translated, or transmitted in any form or by any means, electronic, optical, mechanical, or magnetic, including but not limited to photographing, photocopying, recording or any information storage and retrieval system, without written permission of the copyright owner. Amatrol,Inc., 2400 Centennial Blvd., Jeffersonville, IN USA, Ph , FAX

3 TABLE OF CONTENTS SEGMENT 1 FUNDAMENTALS OF ELECTRICITY OBJECTIVE 1 Defi ne electricity and give an application OBJECTIVE 2 Describe the two types of electrical current and give an application of each OBJECTIVE 3 Describe the function and operation of a circuit tester SKILL 1 Use an AC tester to check a wall outlet for electricity SEGMENT 2 ELECTRICAL CIRCUIT COMPONENTS OBJECTIVE 4 Describe the function of the four basic components of an electrical circuit OBJECTIVE 5 Describe the operation of two types of power supplies and give their schematic symbols OBJECTIVE 6 Describe the function of an electrical schematic SKILL 2 Connect and operate a power supply SEGMENT 3 MANUAL INPUT DEVICES OBJECTIVE 7 Describe the operation of a manual switch OBJECTIVE 8 Describe the operation of N.O. and N.C. contacts and give their schematic symbols OBJECTIVE 9 Describe the function of three types of manual switch operators and give an application of each OBJECTIVE 10 Describe the operation of three types of manual switch operators and give their schematic symbols SKILL 3 Connect and operate a circuit using three types of manual switches SEGMENT 4 OUTPUT DEVICES OBJECTIVE 11 Describe the function of fi ve types of electrical output devices and give an application of each OBJECTIVE 12 Describe the operation of fi ve types of electrical output devices and give their schematic symbols SKILL 4 Connect and operate an electrical circuit with a resistor SKILL 5 Connect and operate an electrical circuit with a buzzer SKILL 6 Connect and operate an electrical circuit with a solenoid SKILL 7 Connect and operate an electrical circuit with a motor 3

4 SEGMENT 1 FUNDAMENTALS OF ELECTRICITY OBJECTIVE 1 DEFINE ELECTRICITY AND GIVE AN APPLICATION Electricity is defined as the flow of electrons in a conductor. Electrons are very small, negatively charged particles which exist in every kind of matter. This flow of electrons, also called current, can deliver energy to a point of use. Electricity is used for a wide range of applications including: Lighting Heating/cooling Machine motion (electric motor) Controls (televisions, radios, computers, etc.) Figure 1. Electrically-Powered Manufacturing System 4

5 OBJECTIVE 2 DESCRIBE THE TWO TYPES OF ELECTRICAL CURRENT AND GIVE AN APPLICATION OF EACH There are two types of electrical current: Direct Current Alternating Current Direct Current Direct current (DC) electricity flows in only one direction, as shown in figure 2. Using the conventional theory of current flow, the power supply creates flow from the highest potential (positive terminal) to the lowest potential (negative terminal). Many times the power supply provides both the lowest and highest potential points. In figure 2, the power supply pushes the electrons through the conductor and also provides a place for the electrons to return. Any path that allows the electrons to leave the power supply and return to the power supply is called a circuit. (HIGHEST POTENTIAL) POSITIVE TERMINAL CONVENTIONAL DIRECTION OF CURRENT FLOW POWER SUPPLY + - PUSH (LOWEST POTENTIAL) NEGATIVE TERMINAL LOAD CONDUCTOR Figure 2. Direct Current (DC) Current Flow A battery is a common source of DC current. Many portable devices operate on DC current from batteries. Examples include devices such as flashlights, portable radios, cellular phones, and even laptop computers. Another source of DC current is a DC power supply, which is an electronic circuit that converts AC current from your wall outlet into DC current. A common use of DC current sourced from a DC power supply is in a personal computer. 5

6 Alternating Current Alternating current (AC) flows alternately in one direction and then in the other (cycles). This happens because the power supply pushes in one direction for one-half of a cycle. It then pushes in the other direction during the other half of a cycle, as shown in figure 3. NOTE The AC electricity produced in the United States cycles 60 times per second. FIRST HALF OF A CYCLE SECOND HALF OF A CYCLE POWER SUPPLY PUSH POWER SUPPLY PUSH CURRENT FLOW CONDUCTOR CONDUCTOR Figure 3. Alternating Current (AC) Current Flow Most of the electrical power produced in the world is AC. One reason for this is that it is easier to transmit over long distances. Another reason is that AC can be easily changed (transformed) to DC. AC electricity is used at home, school, and work. The wall outlets at home are a source of AC for your television set, stereo, microwave, computer, and other appliances. 6

7 OBJECTIVE 3 DESCRIBE THE FUNCTION AND OPERATION OF A CIRCUIT TESTER A circuit tester determines if electricity is present in a circuit. As shown in figure 4, the tester has a tiny neon bulb that glows when current flows through it. The current flows through the test leads and passes through the neon bulb. An example of its use is to test a wall outlet for the presence of AC electricity. When the leads of the tester are inserted into the outlet, one in the right slot and the other in the left slot, the neon light should be lit if there is AC electricity present. NEON LIGHT FOR TESTING CRICUITS WALL OUTLET TEST LEADS CIRCUIT TESTER HOW TO USE A CIRCUIT TESTER Figure 4. A Common Circuit Tester Shown with 120 VAC Outlet 7

8 SKILL 1 USE AN AC TESTER TO CHECK A WALL OUTLET FOR ELECTRICITY Procedure Overview In this procedure, you will test a wall outlet for the presence of AC current using a circuit tester. The procedure is shown using a 120 VAC 60 Hz circuit. If your voltage is different, the procedure will still be performed in the same manner. CAUTION Two basic safety rules to remember when working around electricity are: 1. Avoid touching bare wires or component leads when the power is on. 2. Make sure the power is off before installing, removing, or replacing components in a circuit. Electricity does many good things for us, like provide power for our favorite devices. However, it can also be very dangerous. We don t need to fear electricity, but we do need to have a healthy respect for it. It only takes a small amount of current to cause a severe shock or even death. 1. Locate an electrical wall outlet. CAUTION Do not touch the metal part of the test leads while inserting them into the outlet. 8

9 2. Insert one test lead into the left slot of the outlet and the other test lead into the right slot, as shown in figure 5. If your voltage is different than 120 VAC, your receptacle will look different than the one shown. Figure 5. A Common Circuit Tester on 120 V Outlet 3. Observe if the indicator light is on. Indicator Light Status (On / Off) It should be on. 4. Now, carefully remove one of the test leads from the outlet. The indicator light should now be off because you have broken the path for current to flow through the indicator light. Whenever a circuit does not provide a complete path for current to flow through, the circuit is said to be open. 5. Now, carefully insert the test lead back into the slot. The indicator light should be on again. You have completed the path for current to flow through the light. The circuit is now closed. 6. Carefully remove both leads from the outlet and store the circuit tester. 9

10 SEGMENT 1 SELF REVIEW 1. is the flow of electrons in a conductor. 2. delivers electrical power to the point of use. 3. A device that creates electrical current is called a(n). 4. The flow of electricity in only one direction is called current. 5. A common source of DC is a(n). 6. The flow of electrons in one direction and then the other direction is called current. 7. The output from an electrical wall outlet is current. 8. A(n) uses a tiny neon bulb that glows when current flows through it. 10

11 SEGMENT 2 ELECTRICAL CIRCUIT COMPONENTS OBJECTIVE 4 DESCRIBE THE FUNCTION OF THE FOUR BASIC COMPONENTS OF AN ELECTRICAL CIRCUIT An electrical circuit includes the components necessary to deliver the electricity to the point of use for an application. The four basic components of an electrical circuit, as shown in figure 6, are: Power supply - This device supplies the energy needed to create an electrical current. Input device - This is the part that allows you to control when the current will flow in a circuit. A common input device is a switch. Output device - This component produces a desired output. It is also referred to as a load. A common output device is a lamp. Conductor - This is the part that connects all the components and allows current to flow. Copper wire is most often used. (POWER SUPPLY) BATTERY CONDUCTOR (OUTPUT DEVICE) INDICATOR LAMP (INPUT DEVICE) SWITCH Figure 6. The Four Basic Components of an Electrical Circuit You will learn more about each of these components as you progress through the rest of this LAP. 11

12 OBJECTIVE 5 DESCRIBE THE OPERATION OF TWO TYPES OF POWER SUPPLIES AND GIVE THEIR SCHEMATIC SYMBOLS Power supplies are used in electrical systems to modify the power supplied from the power company (e.g. from the wall socket) to a form that is needed for the application. One feature power supplies are usually designed to do is provide a constant current or constant voltage output. This is called regulation. A constant current supply provides the same current level regardless of the demand placed on it by the load. However, the voltage varies according to the size of the load. The applications of a constant current supply are limited. They are most often used to supply a specific current in process control circuits, where a constant current level is critical to the operation. Constant voltage power supplies are more widely used. They maintain a constant voltage output, regardless of the load. Here, the current varies instead of the voltage. Constant voltage supplies come in various forms and can produce AC or DC voltage. Sometimes they even produce both. The T7017 power supply provides both constant voltage AC and DC outputs. 12

13 Another type of constant voltage DC power supply is a battery. A battery depends on a chemical reaction to produce electricity. It doesn t require an external source of power. However, most constant voltage supplies, like the one shown in figure 7, require an external AC power source. CONNECTION TO AC POWER SOURCE Figure 7. Constant Voltage Power Supply In addition to regulating voltage or current, power supplies perform other functions as well. These include reducing voltage levels, changing AC to DC, and providing overcurrent protection. Figure 8 shows the order in which these functions are performed in the power supply s circuit. INCOMING VOLTAGE ELECTRICAL POWER SUPPLY STAGE 1 STAGE 2 STAGE 3 STAGE 4 CONVERTED OUTPUT VOLTAGE CHANGES VOLTAGE LEVEL CONVERTS INCOMING POWER FROM AC TO DC REGULATES OUTPUT OVERCURRENT PROTECTION Figure 8. Stages of an Electrical Power Supply 13

14 Figure 9 shows the schematic symbols for a constant voltage AC power supply and a constant voltage DC power supply. + - DC POWER SUPPLY AC POWER SUPPLY Figure 9. Schematic Symbols for a DC Power Supply and an AC Power Supply OBJECTIVE 6 DESCRIBE THE FUNCTION OF AN ELECTRICAL SCHEMATIC Electrical diagrams show how the components in a circuit are connected so that we can understand what the circuit does and how it works. So far the diagrams used have been pictorial, where actual pictures are used. While pictorials allow us to easily see how the devices look, they become very time consuming to draw and hard to read, especially as circuits become more complex. Instead, electrical schematic diagrams are used. The electrical schematic diagram is a form of visual shorthand where each component is represented by a standard symbol. A schematic diagram represents the components in a circuit and how they are connected. However, schematic diagrams do not show physical connections. Many schematic diagrams even show certain electrical parameters such as voltage, current, and resistance values that can be measured at specific points. This is helpful when you are trying to find a problem in a circuit. As you progress, you will learn the schematic symbols for each component you use. Figure 10 gives an example of a schematic diagram of the basic circuit from figure 6. + DC POWER SUPPLY SWITCH LAMP Figure 10. Electrical Schematic Diagram of a Basic Electrical Circuit 14

15 SKILL 2 CONNECT AND OPERATE A POWER SUPPLY Procedure Overview In this procedure, you will first identify the components of the T7017 AC/ DC Electrical System. You will then connect and operate its power supply. 1. Position yourself in front of the Model T7017 AC/DC Electrical System shown in figure 11. POWER CORD Figure 11. The Model T7017 AC/DC Electrical System 2. Locate the Power Cord. This cord plugs into a wall outlet to supply electricity to the trainer. 15

16 3. Perform the following substeps to locate the various control panel components on the T7017 AC/DC Electrical System, as shown in figure 12. MAIN POWER INDICATOR AC/DC SELECTOR SWITCH ANALOG VOLTMETER DISPLAY MAIN POWER SWITCH CIRCUIT BREAKER AC INDICATOR LIGHT POWER SUPPLY OUTPUT TERMINALS DC INDICATOR LIGHT VOLTMETER TEST LEAD TERMINALS Figure 12. Control Panel of the T7017 AC/DC Electrical System A. Locate the Main Power Switch. This switch turns the power on or off for the entire trainer. Up is the on position. Down is the off position. B. Locate the Main Power Indicator light. This light will be lit when the power cord is plugged in and the main power switch is in the on position. The light will not be lit if the main power switch is in the off position or if the power cord is not plugged into a wall outlet. C. Locate the Circuit Breaker. The circuit breaker is a protection device that protects the trainer from the effects of excessive amounts of current. You will learn more about the function of a circuit breaker later. D. Locate the AC/DC Selector Switch. This switch allows you to select which type of current (direct current or alternating current) is supplied at the terminals. If the switch is in the lefthand position, AC is selected. If the switch is in the right-hand position, DC is selected. E. Locate the AC Indicator Light. This light will be lit when the AC/DC selector switch is in the left-hand (AC) position and the main power is on. 16

17 F. Locate the DC Indicator Light. This light will be lit when the AC/DC selector switch is in the right-hand (DC) position and the main power is on. G. Locate the Power Supply Output Terminals. The output terminals provide a source of either alternating current or direct current. The type of current supplied and the function of the separate terminals will depend on the setting of the AC/DC selector switch. If DC is selected, the right-hand terminal is the positive terminal. This will be the point from which the current is pushed through whatever circuit is connected to the power supply. The left-hand terminal is the negative (return) terminal for the positive terminal if 24 volts is needed. The center terminal is the return terminal for the positive terminal if 12 volts is needed. This is shown in figure 13. SOURCE SELECT AC DC (-) 24V 12V 12V (-) (+) GROUND Figure 13. Positive, Negative, and Ground Terminals for the DC Supply The center terminal is actually a special return point called a ground. A ground is usually a common return point for many different circuits. You will learn more about a ground later. If AC is selected, the polarity of the terminals is not a factor since the current flow is continuously changing directions. Connecting to the right terminal and the left terminal will provide 24 volts. Connecting to either the left or right terminal and the center terminal will provide 12 volts. H. Locate the Analog Voltmeter Display. A voltmeter is an electrical measurement device. You will learn more about this later. 17

18 I. Locate the Voltmeter Test Lead Terminals, as identified in figure 13. The test leads for the voltmeter are connected here. The test leads are used to perform the measurements. 4. Locate the various component modules. The components are listed below and shown in figure 14. REF. DESCRIPTION QTY. A. Buzzer Module 1 B. Capacitor Module 2 C. Circuit Breaker Module 1 D. Magnetic Compass Module 1 E. Fan Module 1 F. Rheostat Module 1 G. Fuse Module 1 H. DPDT Knife Switch Module 1 I. Lamp Module 3 J. Pushbutton Switch Module 1 K. Transformer Module 1 L. Relay Module 1 M. Selector Switch Module 1 N. Solenoid Module 1 O. Resistor Module 10 Ohm 1 P. Resistor Module 25 Ohm 2 Q. Transformer Load Module 1 A. B. B. C. D. E. F. G. H. I. I. I. J. K. L. M. N. O. P. P. Q. Figure 14. Component Modules for the T

19 5. Locate the connection wires and test equipment included with the T7017, as listed below and shown in figure 15. REF. DESCRIPTION QTY. R. Test Lead Pair, 1 Red/1 Black 1 S. Digital Handheld Multimeter 1 T. Neon Circuit Tester 1 U. Patch Cord-Spade to Spade 10 V. Patch Cord-Spade to Banana 4 R. S. U. T. V. Figure 15. T7017 Instruments and Connectors NOTE If any of these components are not present, notify your instructor. 19

20 6. Perform the following substeps to connect the power supply. A. Make sure the main power switch on the front panel of your trainer is in the OFF position. B. Carefully plug the main power cord attached to the back of the trainer into an available wall outlet. Be sure not to touch the metal prongs on the plug when you insert the plug into the outlet. C. Observe the power supply output terminals just below the AC-DC selector switch. You can get different output values (24 or 12) from the terminals as indicated on the panel. These values are available for AC or DC output. 7. Perform the following substeps to operate the power supply. A. Make sure the circuit breaker is in the on (right) position. B. Turn on the main power switch. The main power indicator lamp should be on. If it is not, turn the main power switch OFF and check to make sure you power cord is properly inserted into the wall outlet. Then, turn it back on again. C. Place the AC/DC selector switch in the DC position. The indicator light above DC should be on. D. Place the AC/DC selector switch in the AC position. The indicator light above AC should be on. 8. Perform the following substeps to shut down the power supply. A. Turn off the main power switch. All indicator lights should go out. B. Make sure there are no wires connected to the power supply output terminals. 20

21 SEGMENT 2 SELF REVIEW 1. A common input device is a(n). 2. An output device is also called a(n). 3. A(n) connects all of the components in an electrical circuit. 4. Electrical diagrams are forms of visual shorthand where each component is represented by a standard symbol. 5. A constant power supply maintains the same output voltage regardless of the load connected to it. 6. A battery depends on a(n) reaction to product electricity. 21

22 SEGMENT 3 MANUAL INPUT DEVICES OBJECTIVE 7 DESCRIBE THE OPERATION OF A MANUAL SWITCH A circuit is said to be closed if there is a complete path for current to flow from the positive terminal to the negative terminal. Figure 16 shows a closed circuit. The path for the current flow is complete so electricity flows through the lamp. BATTERY CONDUCTOR WIRE LAMP (ON) CURRENT FLOW Figure 16. A Closed Circuit 22

23 If the path is broken in some way, the circuit is said to be open. Figure 17 shows an open circuit where the current path has been broken. The current flow is stopped and the lamp is not on. BATTERY CONDUCTOR (WIRE) BROKEN PATH LAMP (OFF) Figure 17. An Open Circuit A simple method for opening and closing a circuit is to use a switch. When the switch is closed, the circuit is closed and electricity flows, as shown in figure 18. When the switch is open the circuit is also open. CLOSED CIRCUIT OPEN CIRCUIT CURRENT FLOWS (CLOSED) SWITCH INDICATOR LAMP (OPEN) SWITCH Figure 18. Closed and Open Circuits Using a Switch 23

24 The two main components of a manual switch are the: Operator - This component causes the switch to activate. Contacts - This component will open or close the circuit when the operator is activated. KNIFE SWITCH OPERATOR CONTACTS Figure 19. Components of a Manual Switch Switches are commonly used in electrical circuits to control when the power is supplied to an output device such as a light or a machine. With a switch, you can safely start and stop the current flow. OBJECTIVE 8 DESCRIBE THE OPERATION OF N.O. AND N.C. CONTACTS AND GIVE THEIR SCHEMATIC SYMBOLS Switches use two types of contacts: Normally Open(N.O.) - These contacts are open until acted upon by the operator. Normally Closed(N.C.) - These contacts are closed until acted upon by the operator. The schematic symbol for each type is shown in figure 20. NORMALLY OPEN NORMALLY CLOSED Figure 20. N.O. and N.C. Contact Symbols 24

25 OBJECTIVE 9 DESCRIBE THE FUNCTION OF THREE TYPES OF MANUAL SWITCH OPERATORS AND GIVE AN APPLICATION OF EACH The two basic categories of switch operators are: Manually operated - The operator is activated by a person. Automatically operated - The operator is activated by a machine or other device. There are several types of manually operated switches used in electrical circuits. These switches are even named for their operator. Three of them are: Knife switch Pushbutton switch Selector switch The function of the operator on any manual switch is to allow you to manually change the states of the contacts of the switch. However, the way in which each operator does this differs, as you will see in the next objective. The applications of the different switches also varies. A knife switch is often used in applications where a visual confirmation of the switch s state is important. A common application is the main disconnect switch for incoming power to a large machine, like the one shown in figure 21. DISCONNECT SWITCH Figure 21. Knife Switch Used as Main Disconnect Pushbutton and selector switches are often used on machine control panels. Pushbutton switches are frequently used to start and stop a machine operation. Selector switches are often used to change machine modes (automatic to manual or forward to reverse). 25

26 OBJECTIVE 10 DESCRIBE THE OPERATION OF THREE TYPES OF MANUAL SWITCH OPERATORS AND GIVE THEIR SCHEMATIC SYMBOLS Knife Switch A knife switch, as shown in figure 22, consists of a lever (operator) that conducts current and one or more sets of contacts. When the lever makes contact with both contacts, the switch is considered closed and allows electricity to conduct through the circuit. When the lever does not make contact with both contacts, the switch and the circuit are open. Figure 22 also shows the schematic symbols for a knife switch with one set of contacts, single-pole double-throw (SPDT) and the schematic symbol for a doublepole double-throw (DPDT) knife switch. Don t worry about what a pole or a throw is, you will learn this later. KNIFE SWITCH SCHEMATIC SYMBOL SPDT SWITCH DPDT SWITCH Figure 22. A Knife Switch and its Schematic Symbols 26

27 Pushbutton Switch A pushbutton switch consists of a pushbutton-type operator and one or more sets of contacts, as shown in figure 23. Pushing the operator causes the contacts to be opened or closed depending on the normal state. Most pushbuttons have a set of normally open (N.O.) contacts and a set of normally closed (N.C.) contacts. PUSHBUTTON OPERATOR NORMALLY CLOSED CONTACTS NORMALLY OPEN CONTACTS Figure 23. The Construction of a Pushbutton Switch Figure 24 shows the schematic symbol of a normally open pushbutton switch and a normally closed pushbutton switch. NORMALLY OPEN CONTACTS NORMALLY CLOSED CONTACTS 1PB 1PB Figure 24. Schematic Symbols for a Pushbutton Switch 27

28 Selector Switch A selector switch is much like a pushbutton in its design, as shown in figure 25. However, instead of pushing a button, you rotate a knob. A selector switch knob may be designed to stay in a selected position or may have a momentary action like the pushbutton switch. OPERATOR NORMALLY CLOSED CONTACTS NORMALLY OPEN CONTACTS Figure 25. The Construction of a Selector Switch Figure 26 shows the symbols for a selector switch with normally open contacts and normally closed contacts. NORMALLY OPEN CONTACTS NORMALLY CLOSED CONTACTS Figure 26. Schematic Symbols for a Selector Switch 28

29 SKILL 3 CONNECT AND OPERATE A CIRCUIT USING THREE TYPES OF MANUAL SWITCHES Procedure Overview In this procedure, you will connect three types of manual switches in an electrical circuit and use them to control a lamp. 1. Position yourself in front of the T Perform the following substeps to prepare the power supply. A. Make sure the main power switch is in the OFF position. B. Place the AC-DC selector switch in the DC position. C. Make sure there are no wires connected to the output terminals of the power supply. 3. Connect the circuit shown in figure 27. Make sure that the knife position is as shown. Figure 28 shows how to connect the wires to the terminals. SOURCE SELECT SCHEMATIC AC DC + 12V - 24V 12V + 12V SWITCH MODULE LAMP MODULE Figure 27. A Circuit with a Knife Switch and a Lamp Notice in figure 27 the schematic symbol of a lamp. 29

30 TERMINAL POST SPADE CONNECTOR WIRE SCREW DOWN TO SECURE CONNECTION SPADE CONNECTOR INSERT WIRE Figure 28. How to Connect the Wires to the Terminals on the Model T7017 Electrical System 4. Perform the following substeps to operate the circuit. A. Turn on the main power switch. B. Close the knife switch and observe the lamp s status. Lamp status (On/Off) The lamp should be on (lighted). C. Open the knife switch and observe the lamp s status. Lamp status (On/Off) The lamp should be off. D. Repeat closing and opening the switch a few more times to become more familiar with it s operation. A knife switch is a very basic manually operated switch. The main power disconnect switch on a residential or commercial electrical panel is usually a knife switch. The knife switch with the T7017 is a double-pole double-throw (DPDT) switch, which means that it has two sets of contacts. It is basically the same as having two separate switches in one. 5. Now close the knife switch in the other direction and observe the status of the lamp. Lamp Status (On/Off) The lamp should not be on even though the contacts are closed. This is because the lamp is not connected to this set of contacts and they do not affect the lamp. 30

31 6. Turn off the main power switch. All indicator lights should go out. 7. Disconnect all wires from the components and the power supply terminals. 8. Connect the circuit represented by the schematic diagram in figure 29. SOURCE SELECT SCHEMATIC AC DC + 24V 12V 12V - + PUSHBUTTON SWITCH 12V LAMP PUSHBUTTON SWITCH MODULE LAMP MODULE Figure 29. A Schematic Diagram and Pictorial of a Circuit with a Pushbutton Switch and a Lamp 9. Perform the following substeps to operate the circuit. A. Turn on the main power switch. B. Press and hold the pushbutton switch and observe the lamp. Lamp status (On/Off) The lamp should now be on. C. Release the pushbutton and observe the lamp. Lamp status (On/Off) The lamp should be out. D. Repeat pressing and releasing the pushbutton a few more times to familiarize yourself with it s operation. 10. Turn off the main power switch. 11. Disconnect the wires connected to the components and the power supply output terminals. 31

32 12. Connect the circuit represented by the schematic diagram in figure 30. SOURCE SELECT SCHEMATIC AC DC + 24V 12V 12V - + SELECTOR SWITCH 12V LAMP SELECTOR SWITCH MODULE LAMP MODULE Figure 30. Schematic Diagram and Pictorial of a Circuit with a Selector Switch and a Lamp 13. Perform the following substeps to operate the circuit. A. Make sure the selector switch knob is rotated to the left and turn on the main power switch. B. Rotate the selector switch to the right and observe the lamp. Lamp status (On/Off) The lamp should now be on. C. Rotate the selector switch in the other direction and observe the lamp. Lamp status (On/Off) The lamp should go off. D. Repeat energizing and de-energizing the selector switch a few more times to familiarize yourself with it s operation. Another type of selector switch is the one on the front panel of your training unit. This switch is used to turn the main power on and off. Another just like it is used to select between AC or DC output. These are instrumentquality selector switches. They have a different appearance but operate the same as their industrial counterparts. 14. Perform the following substeps to turn off and secure the power supply. A. Turn off the main power switch. B. Disconnect any wires or components that may be connected to the power supply output terminals and store them. 32

33 SEGMENT 3 SELF REVIEW 1. A simple method for opening and closing a circuit is to use a(n). 2. The two main components of a switch are the and the contacts. 3. The two basic categories of electrical switches are manual and. 4. If the path is broken in some way, the circuit is said to be. 5. A(n) makes a manually-operated switch momentary. 33

34 SEGMENT 4 OUTPUT DEVICES OBJECTIVE 11 DESCRIBE THE FUNCTION OF FIVE TYPES OF ELECTRICAL OUTPUT DEVICES AND GIVE AN APPLICATION OF EACH There are many types of electrical output devices that can be used in an electrical circuit. We are going to consider five types: Lamp - A lamp or indicator light gives off light when electrical current flows through its resistive (usually wire) element. They are used on many pieces of equipment to indicate a certain state of operation. They can indicate when the power is on, that a certain action is being performed, or can alert you to a possible danger or problem. Resistor - A resistor limits the flow of electrical current. It is one of the most commonly used components in an electrical circuit. Resistors are often used with motors to suppress the surge of current and allow the current to the motor to be gradually increased. Many electronic devices use resistors as internal components to control voltages and current. 34

35 LAMP RESISTOR BUZZER SOLENOID MOTOR Figure 31. Output Devices Buzzer - A buzzer is a type of output device that produces sound. Buzzers are used in doorbells and alarm systems. Solenoid - A solenoid produces linear mechanical motion from electrical energy. Solenoids are used to operate flippers in pinball machines, operate fluid power valves and turn motors on and off. Motor - A motor is the output device that produces rotary mechanical motion. You see many examples of motors each day. A fan, for example, uses a motor to turn the blades. 35

36 OBJECTIVE 12 DESCRIBE THE OPERATION OF FIVE TYPES OF ELECTRICAL OUTPUT DEVICES AND GIVE THEIR SCHEMATIC SYMBOLS The schematic symbols for the five output devices just discussed are shown in figure 33, along with a picture of each device. The operation of each is described as follows: Lamp - A lamp contains a resistive element inside a glass bulb. The bulb is filled with a gas. When current flows through the element, the element heats up and excites the gas. This produces the light that we see. Resistor - A resistor is made of a material that does not allow current to easily flow through it. The most common material used to make resistors is carbon. Resistors come in a wide range of values. Buzzer - When electricity is applied to a buzzer, it causes a vibration to occur inside the buzzer s housing. This vibration is what causes the buzzing noise. Solenoid - The solenoid has an armature or plunger that moves in a linear motion when electrical current is applied to its electrical coil, as shown in figure 32. SOLENOID DEENERGIZED SOLENOID ENERGIZED ARMATURE (PLUNGER) "C" FRAME WIRE COIL PLUNGER MOVEMENT MAGNETIC FLUX Figure 32. Construction and Operation of a Solenoid Motor - When electricity is applied to a motor, a magnetic field is set up inside it. This magnetic field causes a shaft inside the motor to start rotating. Whatever is attached to the shaft also rotates. 36

37 LAMP DEVICE ELECTRIC OUTPUT DEVICES SCHEMATIC SYMBOL RESISTOR BUZZER SOLENOID MOTOR M Figure 33. Output Devices and their Schematic Symbols 37

38 SKILL 4 CONNECT AND OPERATE AN ELECTRICAL CIRCUIT WITH A RESISTOR Procedure Overview In this procedure, you will connect a resistor in an electrical circuit and use a pushbutton switch to control the current flow to it. You should also note that when current is applied to the resistor, the resistor body becomes hot. 1. Perform the following substeps to connect the power supply. A. Make sure the main power switch is OFF. B. Place the AC-DC selector switch in the DC position. C. Make sure there are no wires connected to the power supply terminals. 2. Connect the circuit shown in the schematic diagram in figure 34. SOURCE SELECT SCHEMATIC AC DC + 24V 12V 12V - + SELECTOR SWITCH 12V RESISTOR 25 SELECTOR SWITCH MODULE 25 RESISTOR OHM MODULE Figure 34. A Schematic Diagram and Pictorial of a Circuit with a Selector Switch and a Resistor 38

39 3. Perform the following substeps to operate the circuit. A. Turn on the main power switch. B. Face the operator of the selector switch and make sure it is turned to the left-hand position. This position will put the contacts in their normal state (open). C. Change the position of the selector switch selector knob to the right-hand position. This will cause the contacts to close. D. Put your hand close to the resistor body. CAUTION Do not physically touch the resistor body. It gets very hot and can burn you. Resistor status (Hot/Cool) It should get hot. When electrical current flows through a resistor it gives off heat. For most circuits, this heat is carried away by a fan or some type of cooling system. However, this concept can be applied for applications where heat is the desired output. The heating elements used on electric ranges or electric hot water heaters are basically resistors. E. Return the selector switch to the left-hand position and wait about 30 seconds. Then check the resistor again. Resistor status (Hot/Cool) The resistor body should be cool. NOTE This is the same basic operation as turning on and off a heater. F. Repeat energizing the selector switch and feeling the resistor body to familiarize yourself with the operation. 4. Perform the following substeps to turn off and secure the power supply. A. Turn off the main power switch. B. Disconnect any wires or components that may be connected to the power supply output terminals and store them. 39

40 SKILL 5 CONNECT AND OPERATE AN ELECTRICAL CIRCUIT WITH A BUZZER Procedure Overview In this procedure, you will connect a buzzer in an electrical circuit and use a pushbutton switch to control it. 1. Perform the following substeps to connect the power supply. A. Make sure the main power switch is OFF. B. Place the AC-DC selector switch in the DC position. C. Make sure there are no wires connected to the power supply terminals. 2. Connect the circuit shown in the schematic diagram in figure 35. Be sure to observe the polarity of the buzzer when you connect it. SOURCE SELECT SCHEMATIC AC DC + 24V 12V 12V - + PUSHBUTTON SWITCH 12V + BUZZER - PUSHBUTTON SWITCH MODULE + - BUZZER MODULE Figure 35. A Schematic Diagram and Pictorial of a Circuit with a Pushbutton Switch and a Buzzer 40

41 3. Perform the following substeps to operate the circuit. A. Turn on the main power switch. B. Press and hold the pushbutton switch and listen. Buzzer status (Sounding/Not Sounding) The buzzer should sound. C. Release the pushbutton switch and listen. Buzzer status (Sounding/Not Sounding) The buzzer should stop. This is like pushing a doorbell button. D. Repeat pressing and releasing the pushbutton switch a few more times. 4. Perform the following substeps to turn off and secure the power supply. A. Turn off the main power switch. B. Disconnect any wires and components that may be connected to the power supply output terminals and store them. 41

42 SKILL 6 CONNECT AND OPERATE AN ELECTRICAL CIRCUIT WITH A SOLENOID Procedure Overview In this procedure, you will connect a solenoid in an electrical circuit and control it using a pushbutton switch. 1. Perform the following substeps to connect the power supply. A. Make sure the main power switch is OFF. B. Place the AC-DC selector switch in the DC position. C. Make sure there are no wires connected to the power supply terminals. 2. Connect the circuit shown in the schematic diagram in figure 36. SOURCE SELECT SCHEMATIC AC DC + 24V 12V 12V - + PUSHBUTTON SWITCH 12V SOLENOID PUSHBUTTON SWITCH MODULE SOLENOID MODULE Figure 36. A Schematic Diagram and Pictorial of a Circuit with a Pushbutton Switch and a Solenoid 3. Perform the following substeps to operate the circuit. A. Turn on the main power switch. B. Insert the armature of the solenoid barely into the solenoid. C. Push and hold the pushbutton switch and observe the armature. Armature status (In/Out) The armature should be pulled inside the solenoid or retracted. D. Release the pushbutton switch and pull the armature out. E. Repeat steps C and D a few more times. 42

43 4. Perform the following substeps to turn off and secure the power supply. A. Turn off the main power switch. B. Disconnect any wires and components that may be connected to the power supply output terminals and store them. SKILL 7 CONNECT AND OPERATE AN ELECTRICAL CIRCUIT WITH A MOTOR Procedure Overview In this procedure, you will connect and operate the motor of a fan and use a selector switch to control it. 1. Perform the following substeps to connect the power supply. A. Make sure the main power switch is OFF. B. Place the AC-DC selector switch in the DC position. C. Make sure there are no wires connected to the power supply terminals. 2. Connect the circuit shown in the schematic diagram in figure 37. Be sure to observe the polarity of the fan motor when you connect it. SOURCE SELECT SCHEMATIC AC DC + 24V 12V 12V - + SELECTOR SWITCH 12V + - M SELECTOR SWITCH MODULE + FAN MODULE - Figure 37. A Schematic Diagram and Pictorial of a Circuit with a Selector Switch and a Motor 43

44 3. Perform the following substeps to operate the circuit. A. Make sure the selector knob is to the left and turn on the main power switch. B. Rotate the selector switch in the circuit and observe the fan. Fan status (Blowing/Not Blowing) The fan should start blowing. C. Rotate the selector switch back to the left and observe the fan. Fan status (Blowing/Not Blowing) The fan should stop blowing. This is basically how your fan at home works. D. Repeat energizing and releasing the selector switch a few more times to familiarize yourself with the operation. 4. Perform the following substeps to turn off and secure the power supply. A. Turn off the main power switch. B. Unplug the main power cord from the wall outlet. C. Disconnect any wires and components that may be connected to the power supply output terminals and store them. 44

45 SEGMENT 4 SELF REVIEW 1. A(n) is an output device that gives off light. 2. A(n) produces mechanical linear motion. 3. A resistor will give off. 4. A buzzer will give off. 5. A motor is an output device that produces mechanical motion. 45