ELECTRICAL CONTROL SYSTEMS 1

Transcription

1 ELECTRICAL CONTROL SYSTEMS 1 LEARNING ACTIVITY PACKET CONTROL LOGIC BB703-XB01UEN

2 LEARNING ACTIVITY PACKET 1 CONTROL LOGIC INTRODUCTION This LAP and the ones that follow cover the electrical controls that are used with automated machines. Specifically, a type of control called electrical relay control. This type of control uses electrical components that are wired together to form the logic that determines the sequence of the machine s operations. This LAP begins by covering the basic relay logic control elements and the basics of reading ladder diagrams. ITEMS NEEDED Amatrol Supplied 1 90-EC1A Applied Electrical Control Learning System School Supplied 1 Compressed Air Supply FIRST EDITION, LAP 1, REV. A 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 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 LOGIC ELEMENTS (AND, OR) OBJECTIVE 1 Describe the function of relay control logic circuits OBJECTIVE 2 List the six elements of control logic OBJECTIVE 3 Describe the function of AND logic and give an application SKILL 1 Connect and operate an AND logic control circuit OBJECTIVE 4 Describe the function of OR logic and give an application SKILL 2 Connect and operate an OR logic control circuit SEGMENT 2 LOGIC ELEMENTS (NOT, NOR, NAND) OBJECTIVE 5 Describe the function of NOT logic and give an application SKILL 3 Connect and operate a NOT logic control circuit OBJECTIVE 6 Describe the function of NOR logic and give an application SKILL 4 Connect and operate a NOR logic control circuit OBJECTIVE 7 Describe the function of NAND logic and give an application SKILL 5 Connect and operate a NAND logic control circuit OBJECTIVE 8 Describe the function of MEMORY logic and give an application SEGMENT 3 LADDER DIAGRAMS OBJECTIVE 9 Describe the function of a ladder diagram OBJECTIVE 10 Describe the function of the four components of a ladder diagram Activity 1 Identify the four basic components of a ladder diagram OBJECTIVE 11 Explain fi ve rules of drawing a ladder diagram SKILL 6 Read and interpret the operation of a circuit given a ladder diagram SKILL 7 Connect and operate a logic circuit given a ladder diagram SKILL 8 Design a ladder diagram using one or more logic elements SEGMENT 4 ELECTRO-PNEUMATIC SOLENOID VALVES OBJECTIVE 12 Describe the function of a solenoid-operated fl uid power valve OBJECTIVE 13 Describe the function of a power diagram SKILL 9 Connect and operate a circuit using a solenoid valve given a ladder diagram SKILL 10 Design a control circuit in a ladder diagram format to operate a solenoid valve 3

4 SEGMENT 1 LOGIC ELEMENTS (AND, OR) OBJECTIVE 1 DESCRIBE THE FUNCTION OF RELAY CONTROL LOGIC CIRCUITS All automated machines use some type of controller that acts as the brain for the machine. One of the functions a controller performs is to control the sequence of steps in the machine s operation by turning outputs on and off as necessary. One example of a type of controller that can perform this sequence of steps is a relay-based control logic circuit. This type of controller uses switches as input devices and devices called relays that function as the brains. A relay is a special type of switch. These devices can be wired together in various combinations to create the sequence of operations. OBJECTIVE 2 LIST THE SIX ELEMENTS OF CONTROL LOGIC There are six ways input switches and relay switches can be connected in a circuit. These are called logic elements. Logic elements are simple, but they form the basic building blocks to create very complex sequences. The six elements of control logic are: AND OR NOT NOR NAND MEMORY 4

5 OBJECTIVE 3 DESCRIBE THE FUNCTION OF AND LOGIC AND GIVE AN APPLICATION An AND logic circuit is made of two normally open (N.O.) switches wired in series. The term series means that the components are connected so that electricity must flow through the first component before it can flow through the next one. Both of the switches must be closed to energize the output (lamp), as shown in figure 1. OUTPUT OFF OUTPUT ON BOTH SWITCHES BOTH SWITCHES OPEN CLOSED 1PB 2PB LAMP LAMP 1PB 2PB Figure 1. Basic AND Logic Circuit An application of an AND logic circuit is a two-hand circuit. This circuit requires that both hands must be used to start the machine by having each hand press a separate pushbutton at the same time. The purpose is to protect the operator from getting a hand caught in the machine during its operation. The machine will stop if either hand is removed from one of the start pushbuttons. Figure 1 does not show a complete two-hand circuit. The connection of an OSHA approved two-hand circuit has additional components to ensure the safety of the operator. 5

6 AND logic is often used in machines where it is important to keep both hands clear of the machine. In a shearing press like the one shown in figure 2, the controls are usually designed with two start buttons, which have to be pressed at the same time to start the operation. This action ensures that neither hand is in the machine. CYLINDER 2 CYLINDER 1 Figure 2. Shearing Press 6

7 SKILL 1 CONNECT AND OPERATE AN AND LOGIC CONTROL CIRCUIT Procedure Overview In this procedure, you will connect and operate an AND logic control circuit to control an indicator lamp. You will also learn how to set up the model 90-EC1A Applied Electrical Control system. 1. Perform the following substeps to set up the Amatrol model 90-EC1A Applied Electrical Control trainer. A. Position yourself in front of the trainer, as shown in figure 3. Figure 3. The 90-EC1A Applied Electrical Control System 7

8 The system is divided into two sections. The left side of the system is the control side, as shown in figure 4. It consists of switches, relays, and other devices used to form the control logic. PUSHBUTTONS SELECTOR SWITCH RELAYS INDICATOR LAMPS TIME DELAY RELAY Figure 4. Control Section The right side of the system is the power side, as shown in figure 5. It consists of cylinders, solenoids, and other output devices that are controlled by the control side components. CONTROL POWER 90-EC1A 2LS LIMIT SWITCHES CYLINDER #1 1- SOL DIRECTIONAL CONTROL VALVE 1LS 4LS SOLENOIDS CYLINDER #2 CYLINDERS 2- SOL DIRECTIONAL CONTROL VALVE 3LS MOTOR M1 AIR SUPPLY CONNECTOR Figure 5. Power Section 8

9 B. Make sure the main power circuit breaker, as shown in figure 6, is off. C. Remove any plug-in test leads (wires) from the system. These test leads will be used later to connect logic circuits. D. Plug the power cord into an available electrical outlet, as also shown in figure 6. MAIN POWER CIRCUIT BREAKER TO ELECTICAL OUTLET Figure 6. Power Cord Connection to System 2. Connect the AND logic circuit, as shown in figure 7. Figure 7. Basic AND Logic Circuit 9

10 The procedure to connect a test lead to a jack on the front panel of the system is shown in figure 8. DIRECTION TO PUSH TO INSERT LEAD PANEL JACK Figure 8. Connecting a Test Lead to the Panel 3. Turn on the main power circuit breaker. 4. Perform the following substeps to operate the control logic circuit. A. Press and hold the pushbutton labeled 1PB and observe the lamp. Lamp Status (On/Off) You should notice that the light did not come on because AND logic requires both pushbuttons to be pressed to energize the output device. B. Release 1PB. C. Press and hold the pushbutton labeled 2PB and observe the lamp. Lamp Status (On/Off) The light should still be off because AND logic requires both pushbuttons to be pressed. D. Now press and hold 1PB again while continuing to press 2PB. Observe the lamp. Lamp Status (On/Off) The light should come on, because both 1PB and 2PB are closed to complete the circuit path. E. Release either 1PB or 2PB. The light will go off. F. Release the other pushbutton. 5. Perform the following substeps to shut down the system. A. Turn off the main power circuit breaker. B. Remove the test leads. 10

11 OBJECTIVE 4 DESCRIBE THE FUNCTION OF OR LOGIC AND GIVE AN APPLICATION An OR logic circuit is formed by two normally open (N.O.) switches wired in parallel. The term parallel means that the components are connected so that the flow of electricity can branch through one component or the other. With OR logic, either one of the switches can be activated to energize the output (lamp), as shown in figure 9. 2PB PRESSED OUTPUT ON 1PB PRESSED OUTPUT ON START 1PB LAMP START 1PB LAMP 2PB LAMP ON 2PB LAMP ON REMOTE START REMOTE START Figure 9. Basic OR Logic Circuit A common application of OR logic is found on machines that use remote start/ stop stations. If a machine has two remote start/stop stations, pressing the start button on either station will start the machine. 11

12 SKILL 2 CONNECT AND OPERATE AN OR LOGIC CONTROL CIRCUIT Procedure Overview In this procedure, you will connect a circuit using OR logic to provide a remote start pushbutton to turn on the output device. The output device for this procedure will be an indicator lamp. 1. Perform the following substeps to set up the system. A. Make sure the main power circuit breaker is off. B. Remove any test leads on the front panel. 2. Connect the OR logic circuit as shown in figure 10. Figure 10. Basic OR Logic Circuit 12

13 The two pushbuttons are wired in parallel in an OR logic circuit. To connect this circuit the leads must be stacked, as shown in figure 11. PANEL JACK Figure 11. Stacking the Connections 3. Supply power to the system by plugging in the power cord, if necessary, and turning on the main power circuit breaker. 4. Perform the following substeps to operate the control logic circuit. A. Press and hold pushbutton 1PB to energize the output device and observe the indicator lamp. Lamp Status (On/Off) The light should come on because OR logic requires only one pushbutton to be pressed. B. Release 1PB and observe the lamp. Lamp Status (On/Off) The light should now be off. C. Press and hold pushbutton 2PB and observe the lamp. Lamp Status (On/Off) The light should come on because once again only one pushbutton is required to be pressed when OR logic is used. D. Release 2PB and observe the lamp. Lamp Status (On/Off) The light will once again be off. 5. Perform the following substeps to shut down the system. A. Turn off the main power circuit breaker. B. Remove the test leads. 13

14 SEGMENT 1 SELF REVIEW 1. are the input devices that send messages to the relaybased control logic circuit. 2. There are elements of control logic. 3. A(n) logic circuit consists of two N.O. pushbutton switches wired in series. 4. A(n) logic circuit is formed by two N.O. pushbutton switches wired in parallel. 5. A common application of logic is a shearing press. 6. A common application of logic is two remote Start/Stop stations. 14

15 SEGMENT 2 LOGIC ELEMENTS (NOT, NOR, NAND) OBJECTIVE 5 DESCRIBE THE FUNCTION OF NOT LOGIC AND GIVE AN APPLICATION NOT logic is formed by the use of a single normally closed (N.C.) switch. The output lamp is on when the input switch is NOT activated. Likewise, when the input switch is activated (e.g. pressed), the output is NOT on, as shown in figure 12. OUTPUT ON OUTPUT OFF (NOT ON) LAMP 2PB LAMP Figure 12. NOT Logic Is Formed by a Single Normally Closed Input Switch 15

16 A common use of NOT logic is the stop pushbutton. It is a standard practice to use a normally closed pushbutton switch to stop a machine, like the CNC lathe shown in figure 13. When the stop pushbutton is activated, it opens the circuit and de-energizes the output device. In the case of the CNC machine, the stop pushbutton de-energizes the drive motors. EMERGENCY STOP BUTTON Figure 13. CNC Lathe with Emergency Stop Pushbutton 16

17 SKILL 3 CONNECT AND OPERATE A NOT LOGIC CONTROL CIRCUIT Procedure Overview In this procedure, you will connect an electrical control circuit using NOT logic with a normally closed switch to provide a stop button. 1. Perform the following substeps to set up the system. A. Make sure the main power circuit breaker is off. B. Remove any test leads on the front panel. 2. Connect the circuit shown in figure 14. Figure 14. Basic NOT Logic Circuit 3. Supply power to the system by plugging in the power cord, if necessary, and turning on the main power circuit breaker. The light should come on when the main power circuit breaker is turned on because the input switch is normally closed. The electricity can flow through the switch without it being pressed. 17

18 4. Perform the following substeps to operate the control logic circuit. A. Press and hold 1PB and observe the lamp. Lamp Status (On/Off) The light should go off because NOT logic is used to block the flow of electricity in a circuit when a pushbutton is pressed. B. Release 1PB and observe the lamp. Lamp Status (On/Off) The light should come back on because releasing the pushbutton allows the switch to return to its normal position (closed). This action completes the circuit and allows electricity to flow to the light. 5. Perform the following steps to shut down the system. A. Turn off the main power circuit breaker. B. Remove the test leads. OBJECTIVE 6 DESCRIBE THE FUNCTION OF NOR LOGIC AND GIVE AN APPLICATION NOR logic is made of two or more normally closed (N.C.) switches wired in series with the output. The output is energized when neither input switch A nor input switch B is activated, as shown in figure STOP A STOP B LAMP Figure 15. Circuits with Multiple Stop Pushbuttons Use NOR Logic NOR logic is often used to provide multiple stop pushbuttons in a control circuit. These multiple stop pushbuttons provide safer operation because they can be placed at several locations around the machine. One common example of this is on the assembly line of an automobile plant. Any of the workers can stop the line at any time. 18

19 SKILL 4 CONNECT AND OPERATE A NOR LOGIC CONTROL CIRCUIT Procedure Overview In this procedure, you will connect a control circuit using NOR logic to provide a remote stop pushbutton. 1. Perform the following substeps to set up the system. A. Make sure the main power circuit breaker is off. B. Remove any test leads on the front panel. 2. Connect the circuit shown in figure 16. Figure 16. Basic NOR Logic Circuit 19

20 3. Supply power to the system by plugging in the power cord, if necessary, and turning on the main power circuit breaker. You have connected two normally closed switches in series. Therefore, the light should come on when the main power circuit breaker is turned on. 4. Perform the following substeps to operate the control logic circuit. A. Press and hold 1PB and observe the lamp. Lamp Status (On/Off) The light should go off because NOR logic requires only one pushbutton to be pressed to open the circuit path. B. Release 1PB and observe the lamp. Lamp Status (On/Off) The light should come back on. C. Press and hold 2PB and observe the lamp. Lamp Status (On/Off) The light should go back off again because only one pushbutton has to be pressed to open the circuit path in NOR logic. D. Release 2PB and observe the lamp. Lamp Status (On/Off) The light should come back on. 5. Perform the following substeps to shut down the system. A. Turn off the main power circuit breaker. B. Remove the test leads. 20

21 OBJECTIVE 7 DESCRIBE THE FUNCTION OF NAND LOGIC AND GIVE AN APPLICATION NAND logic consists of two or more normally closed (N.C.) input switches wired in parallel with the output. The output in this circuit will stay on until all input switches are activated, as shown in figure PB LAMP 2PB 3PB Figure 17. Normally Closed Switches in Parallel Must All Be Actuated to Turn Off the Output A common application of NAND logic is the interior light circuit in a car, like the one shown in figure 18. Figure 18. NAND Logic Circuit Controlling the Interior Light Each door on a car has a switch connected to the interior light. When the doors are open, the switches are not being activated and the light is on. Closing a door will activate one switch, but the light will continue to stay on because all the doors must be closed before the light will go off. 21

22 SKILL 5 CONNECT AND OPERATE A NAND LOGIC CONTROL CIRCUIT Procedure Overview In this procedure, you will connect a control circuit using NAND logic to simulate the interior light of a car. 1. Perform the following substeps to set up the system. A. Make sure the main power circuit breaker is off. B. Remove any test leads on the front panel. 2. Connect the circuit shown in figure 19. Figure 19. Basic NAND Circuit 22

23 3. Supply power to the system by plugging in the power cord, if necessary, and turning on the main power circuit breaker. NOTE The light should come on when you turn on the main power circuit breaker because you have connected two normally closed switches in parallel which provides the path for the flow of electricity to the output device. 4. Perform the following substeps to operate the control logic circuit. A. Press and hold 1PB and observe the lamp. Lamp Status (On/Off) This simulates closing one of the doors on a car. The light should remain on because NAND logic requires that all pushbuttons must be pressed to block the flow of electricity in a circuit. Pushbutton 2PB is providing a path for the electricity to flow around switch 1PB, which is now open. B. Press and hold 2PB while continuing to press 1PB. Observe the lamp. This simulates closing all the car s doors. Lamp Status (On/Off) The light should go out because NAND logic blocks the flow of electricity in a circuit when all the pushbuttons are pressed. C. Release the pushbuttons. The light will come back on as the electrical path is restored. 5. Perform the following substeps to shut down the system. A. Turn off the main power circuit breaker. B. Remove the test leads. 23

24 OBJECTIVE 8 DESCRIBE THE FUNCTION OF MEMORY LOGIC AND GIVE AN APPLICATION Memory logic is used to keep an output energized after the input signal that turned it on has been removed. The device used to perform the memory logic function in electrical control circuits is called a control relay. The control relay is a very important device, because it allows logic circuits to perform machine sequences. You will learn how it does this and how it works in a later LAP. A common application of memory logic is in electric motor control. A magnetic motor starter, like the one shown in figure 20, uses memory logic to allow the operator to start a motor by momentarily pressing a start button and then releasing it. The memory circuit will continue to feed electricity to the motor even though the start button is no longer activated. Therefore, the operator does not need to continue to hold the start button closed. MAGNETIC MOTOR STARTER OVERLOAD RELAY Figure 20. Magnetic Motor Starter 24

25 SEGMENT 2 SELF REVIEW 1. NOT circuits use switch contacts to perform their operations. 2. A control is the device used to perform the memory function in an electrical logic circuit. 3. A stop button switch uses contacts. 4. A remote stop pushbutton is created with a(n) logic element. 5. A common application of logic is the interior light circuit on a car. 25

26 SEGMENT 3 LADDER DIAGRAMS OBJECTIVE 9 DESCRIBE THE FUNCTION OF A LADDER DIAGRAM A ladder diagram is a type of schematic diagram that represents electrical control circuits in a way that makes them easier to read. This type of diagram arranges the electrical wires in orderly rows like rungs on a ladder with components located on each of these rungs. A basic ladder diagram is shown in figure 21. RUNG 1 L1 1 1PB R L2 RUNG 2 2PB G Figure 21. Ladder Diagram Schematic 26

27 OBJECTIVE 10 DESCRIBE THE FUNCTION OF THE FOUR COMPONENTS OF A LADDER DIAGRAM The four components of a ladder diagram represent the four basic components of an electrical circuit, as shown in figure 22. Power Supply Input Device Output Device Conductors RUNG 1 L1 1 POWER SUPPLY (+) 1PB CONDUCTOR (WIRES) POWER SUPPLY (-) R L2 INPUT DEVICE (POWER BUTTON SWITCH) OUTPUT DEVICE (INDICATOR LAMP) Figure 22. Basic Components of a Ladder Diagram Power Supply All electrical circuits must have a power supply to allow the control logic circuit to energize the output devices. The power supply in a ladder diagram is represented by the two vertical lines on each side. The vertical line on the left is the hot or positive side of the power supply and is usually labeled L1. The vertical line on the right is the ground or negative side of the power supply and is usually labeled L2. These two vertical lines form the side rails of the ladder. Input Device All input devices, such as switches, are used to perform the logic functions that control the outputs. Input devices are always connected between the positive side of the power supply (L1) and the output devices. They are represented by a variety of symbols depending on the device. Output Device Output devices are the components that cause the machine to perform its operation. Output devices are always located on the right side of ladder diagram. They are connected directly to the negative side of the power supply (L2). 27

28 Conductors Conductors are the electrical wires that connect the control circuit. They form the rungs of the ladder and connect the components located on these rungs. Activity 1. Identify the Four Basic Components of a Ladder Diagram Procedure Overview In this activity, you will learn about the function of the ladder diagram components and the locations of these devices on the 90-EC1A. The control section on the 90-EC1A is designed to match the ladder diagram design. This will allow you to more easily see how to connect the circuits using ladder diagrams. 1. Locate the Power Supply Connections L1 and L2 on the 90-EC1A system, as shown in figure 23. The power supply connections on the system are labeled L1 and L2, just like on the ladder diagram. (INPUT) PUSHBUTTONS (INPUT) SELECTOR SWITCH L1 (OUTPUT) INDICATOR LAMPS (OUTPUT) SOLENOIDS (OUTPUT) MOTOR L2 Figure 23. Control Section of the 90-EC1A System 28

29 2. Locate the Input Devices on the 90-EC1A system as shown in figure 23. The input switches on the 90-EC1A use the same symbols as are used in ladder diagrams. 3. Locate the Output Device Symbols on the 90-EC1A system, as shown in figure 23. The output device symbols on the 90-EC1A are the same as the symbols used in a ladder diagram. 4. Locate the Conductors on the 90-EC1A system. In the case of the 90-EC1A, the conductors are the test leads. You will use these test leads to connect the control circuits according to the given ladder diagrams. The ladder diagram symbols of the components that you have used so far are shown in figure 24. PUSHBUTTON NORMALLY OPEN CONTACTS 1PB PUSHBUTTON NORMALLY CLOSED CONTACTS 2PB SELECTOR SWITCH THREE POSITION 1SS INDICATOR LAMP DENOTES COLOR R CONTACTS Figure 24. Ladder Diagram Symbols 5. Locate the symbols of the input devices shown in figure 24 on the control section of the 90-EC1A system. The pushbutton with the normally open contacts symbol, shown in figure 24, represents that the pushbutton must be pressed down to close a circuit. The pushbutton with the normally closed contact, shown in figure 24, represents that the pushbutton must be pressed down to open a circuit. 29

30 The selector switch symbol shown represents the multiple positions that may be used to control its contacts. By switching to the left-hand position, the lower contacts are closed. By selecting the right-hand position, the upper contacts are closed. By switching to the center position, all contacts are open. The indicator lamp symbol shown may have a letter to represent the color of the lens. NOTE The component symbols used in ladder diagrams are often slightly different than the symbols used in electrical schematic diagrams. OBJECTIVE 11 EXPLAIN FIVE RULES OF DRAWING A LADDER DIAGRAM Five basic rules you should follow when drawing or interpreting ladder diagrams are: All Components Labeled - Each component in a ladder diagram should be labeled with its function (e.g. start) and an abbreviation identifying what it is (e.g. 1PB), as figure 25 shows. All Conductors (wires) Numbered - The wires connecting the components should be numbered left to right and top to bottom. Notice that L1 and L2 are both numbered.any wires that are connected to L1 or L2 will all have the same numbers. All of the conductors connected to L1 will be numbered 1. All conductors connected to L2 will be numbered 2. Also, conductors that are joined together directly will have the same numbers. All Rungs Numbered - A rung is considered any horizontal level where conductors in the circuit run. 30

31 L1 START 1PB 1 3 RUNG 1 START 2PB 1 RUNG 2 START 4PB 1 RUNG 3 STOP L2 3PB R 5 G 2 INPUT DEVICES AND LOGIC OUTPUT DEVICES Figure 25. Structure of a Ladder Diagram Control Devices Only - A ladder diagram shows only control devices such as switches, solenoids, and relays. It does not show power devices such as valves, motors, and cylinders. These are shown on a separate diagram called a power diagram. Only One Load Per Rung - A load is an output device such as an indicator lamp. Loads should never be wired in series on the same rung. They should be wired in parallel on different rungs as shown in figure 26. INCORRECT CORRECT RUNG 1 L1 1PB R G L2 RUNG 1 L1 1PB R L2 RUNG 2 G Figure 26. Wiring of Multiple Loads The ladder diagram method helps you to more easily read the operation of the circuit because it unravels the lines and allows the diagram to be read in an orderly fashion. By looking at the closed/open status of the inputs on the left side of a rung of a ladder diagram, you can determine whether the output on the right side is on or off. Each rung usually contains a single output device. If the ladder diagram is used to perform a sequence of steps, the rungs are normally arranged so that the outputs are located from top to bottom in the order in which they are energized. 31

32 SKILL 6 READ AND INTERPRET THE OPERATION OF A CIRCUIT GIVEN A LADDER DIAGRAM Procedure Overview In this procedure, you will use a ladder diagram to determine the operation of a control circuit. 1. Look at the ladder diagram in figure 27. The best method for reading a ladder diagram, whether you want to construct a circuit or simply determine the sequence of operation, is to start at the upper left on the first rung. Then, work your way across that rung before moving down to the next rung. Always work from left to right. Use the information about reading a ladder diagram from the previous objective to determine the operation of the circuit. L1 L2 1PB RUNG R RUNG 2 1 2PB G 2 Figure 27. Ladder Diagram Schematic 2. Determine the status of the red lamp if 1PB is pressed. Red Lamp Status (On/Off) The red lamp will be on because pressing 1PB completes the circuit between L1 and L2, allowing current to flow through the red lamp. 3. Determine the status of the green lamp if 1PB is pressed. Green Lamp Status (On/Off) The green lamp will also be on because pressing 1PB completes the circuit between L1 and L2, allowing current to pass through the green indicator. 32

33 4. Repeat steps 2 and 3 to test 2PB. Red Lamp Status (On/Off) Green Lamp Status (On/Off) Both should again be on because the circuit paths are completed between L1 and L2 through the lamps. 5. Perform the following substeps to determine the operation of a circuit using the ladder diagram shown in figure 28. L1 1PB L2 2PB RUNG R RUNG 2 G 2 Figure 28. Ladder Diagram A. Determine the status of the red lamp if 1PB is pressed. Red Lamp Status (On/Off) B. Determine the status of the green lamp if 1PB is pressed. Green Lamp Status (On/Off) C. Determine the status of the red and green lamps if 1PB is pressed and held and 2PB is also pressed. Red Lamp Status (On/Off) Green Lamp Status (On/Off) 33

34 SKILL 7 CONNECT AND OPERATE A LOGIC CIRCUIT GIVEN A LADDER DIAGRAM Procedure Overview In this procedure, you will connect a circuit using a ladder diagram as a reference. To begin, you will be given a step-by-step example. Then you will do it without assistance. 1. Perform the following substeps to set up the system. A. Make sure the main power circuit breaker is off. B. Remove any test leads on the front panel. 2. Perform the following substeps to connect the circuit shown in figure 29. Remember, read a ladder diagram from left to right, top to bottom. LADDER DIAGRAM PICTORIAL DIAGRAM L1 1PB 2PB L R 2 G 2 Figure 29. Test Circuit A. Connect a lead wire from L1 to one side of the N.O. contacts of 1PB. This is the conductor labeled as 1 on the ladder diagram. This is the first component in the upper left part of the ladder diagram. 34

35 B. Connect a lead wire from the other side of the N.O. contacts of 1PB to one side of the N.O. contacts of 2PB. This is the next connection that needs to be made as you move across the first rung. This is the conductor labeled as 3. C. Connect a lead wire from the other side of the N.O. contacts of 2PB to the connector for the red indicator lamp. This is the conductor labeled as 4. D. Connect a lead wire from the red indicator lamp to L2. This is the conductor labeled as 2. This completes the connections for rung 1. E. Connect a lead wire from the right side of the N.O. contacts of 2PB to the green indicator lamp connector. This puts the green indicator lamp in parallel with the red lamp. F. Connect a lead wire from the green indicator lamp to L2. This is rung 2 of the ladder diagram. 3. Turn on the main power circuit breaker. 4. Perform the following substeps to operate the control logic circuit. A. Press and hold 1PB and observe the lamps. Lamp 1 Status (On/Off) Lamp 2 Status (On/Off) Neither should be on because, even though 1PB is closed, 2PB is still open. The switches are connected in AND logic. B. Release 1PB and observe the lamps. Lamp 1 Status (On/Off) Lamp 2 Status (On/Off) The lamps should be off because the circuit is open. C. Press and hold 1PB. Then press 2PB. Observe the lamps. Lamp 1 Status (On/Off) Lamp 2 Status (On/Off) Both lamps should be on because the circuit to both lamps is still complete. Both 1PB and 2PB are closed. D. Release 2PB and observe the lamps. Lamp 1 Status (On/Off) Lamp 2 Status (On/Off) Both lamps should go off. The circuit is again open. 35

36 5. Now connect and test the circuit shown in figure 27. This time you only have the ladder diagram to use as a reference. Be sure to turn off the main power circuit breaker before changing the circuit. 6. Connect and test the circuit shown in figure 28 to further develop your skill in reading ladder diagrams. 7. Perform the following substeps to shut down the system. A. Turn off the main power circuit breaker. B. Remove the test leads. SKILL 8 DESIGN A LADDER DIAGRAM USING ONE OR MORE LOGIC ELEMENTS Procedure Overview In this procedure, you will design a ladder diagram to perform a specific function using one or more control logic elements. You will then connect and test the circuit based on your ladder diagram. 1. Design a control logic circuit to perform the following functions. Draw your circuit on a separate piece of paper. Functions The green light will be on when the power supply is connected to the system. Placing selector switch 1SS in the right-hand position (closed) and pressing 1PB will turn on the red indicator lamp. Pressing 2PB will turn off the green indicator lamp. 2. Connect the circuit you designed in step Supply power to the system by turning on the main power circuit breaker. 4. Perform the following substeps to test the circuit which you designed. A. Check to see if the green indicator lamp comes on when the power supply is connected. B. Place the selector switch in the right hand position. Press and hold 1PB and observe the red lamp. Red Lamp Status (On/Off) The red indicator light should come on. Placing the selector switch in the right-hand position and pressing 1PB should close the circuit to the red indicator lamp. 36

37 C. Release 1PB and observe the red lamp. Red Lamp Status (On/Off) The red indicator lamp should be off. D. Press and hold 2PB and observe the green lamp. Green Lamp Status (On/Off) The green indicator lamp should go off. Pushbutton 2PB should open the circuit to the green indicator lamp. E. Release 2PB and observe the green lamp. Green Lamp Status (On/Off) 5. Perform the following substeps to shut down the system. A. Turn off the main power circuit breaker. B. Remove the test leads. 37

38 SEGMENT 3 SELF REVIEW 1. diagrams are used to represent electrical control circuits in a way that makes them easy to read. 2. There are basic components of a ladder diagram. 3. The power supply in a ladder diagram is represented by two lines. 4. are always connected between the positive side and the output devices of the power supply. 5. Output devices are always located on the side of a ladder diagram. 6. are the electrical wires that connect the control circuit. 7. All horizontal levels, called, should be numbered in a ladder diagram. 8. Each rung should contain a single device. 9. Outputs should never be wired in. 10. Wires that are connected directly together in a control circuit are given the same. 38

39 SEGMENT 4 ELECTRO-PNEUMATIC SOLENOID VALVES OBJECTIVE 12 DESCRIBE THE FUNCTION OF A SOLENOID-OPERATED FLUID POWER VALVE Solenoid-operated fluid power directional control valves provide the means by which electrical circuits can control the operation of pneumatic or hydraulic systems. These types of valves use a solenoid, as shown in figure 30, to shift the valve spool. When electricity is applied to the solenoid coil, the valve spool shifts causing the fluid (oil or air) to flow through the valve and change the direction of motion of the actuator. When electricity is removed from the solenoid coil, a spring causes the valve to shift back to its original position SOLENOID Figure 30. Solenoid-Operated Directional Control Valve Used on the Amatrol 90- EC1A System 39

40 OBJECTIVE 13 DESCRIBE THE FUNCTION OF A POWER DIAGRAM While a ladder diagram shows the electrical connections needed to wire a control circuit, it does not show the connections of the hoses or wires that connect the valve to a cylinder, motor, or other power device. Therefore, an additional diagram is needed to show the connections for the power devices. This diagram is called a power diagram. An example of a power diagram is shown in figure 31. Here, a solenoid valve controls a cylinder. LADDER DIAGRAM POWER DIAGRAM L1 L2 P 1 1PB 1-SOL EXTEND 1-SOL SAME WIRE NUMBERS AS ON POWER DIAGRAM WIRES FROM CONTROL CIRCUIT 2 3 A B CYLINDER Figure 31. Ladder Diagram and Power Diagram The symbol of the valve used in a power diagram will depend on the type of valve being used. The valve shown in figure 31 is the same as those used on the Amatrol 90-EC1A. Notice the dashed lines labeled 2 and 3 shown in the power diagram of figure 31. These lines represent the electrical wires going to the solenoid. These lines are labeled to match the numbers used in the ladder diagram. The solenoid shown in the power diagram and the solenoid shown in the ladder diagram are the same device. A ladder diagram shows the logic of the circuit. It allows you to determine what signals are being sent from the control circuit to the power devices. However, without the power diagram to show the connections of the power devices, it would be impossible to tell what type of output action will result. For example, in figure 31 the power diagram illustrates what happens when the solenoid is turned on. In this case, the cylinder extends. If a power device is connected to a control circuit, the ladder diagram should be accompanied by a power diagram. 40

41 SKILL 9 CONNECT AND OPERATE A CIRCUIT USING A SOLENOID VALVE GIVEN A LADDER DIAGRAM Procedure Overview In this procedure, you will connect and operate a control circuit that will control a solenoid valve. The valve will be connected to a cylinder. 1. Perform the following substeps to set up the system. A. Make sure the main power circuit breaker is off. B. Remove any test leads on the front panel. 2. Perform the following substeps to connect the air supply to the system. A. Attach the female quick connect from your air supply to the male air supply connector on the 90-EC1A. The male air supply connector is located at the bottom right-hand corner, as shown in figure 32. A typical air supply system, also shown in figure 32, will have a shutoff valve, a pressure regulator, and a connection for an air hose. If you are using a different system or need help adjusting the air pressure, ask your instructor for help. NOTE You may not have access to the pressure regulator for your air supply. SHUTOFF VALVE REGULATOR TO ELECTRICAL OUTLET HOSE CONNECTION PRESSURE GAGE AIR SUPPLY CONNECTION Figure 32. Air Supply Connection 41

42 B. Adjust the pressure of the air supply to 50 psig/345 kpa. NOTE This system is rated at 100 psig/ 690 kpa maximum pressure. Do not exceed 100 psig/ 690 kpa when using this panel. 3. Connect the circuit shown in figure 33. The pictorial connections are shown alongside the ladder diagram to help you. Notice that one side of the solenoid is preconnected to L2. LADDER DIAGRAM PICTORIAL DIAGRAM L1 1PB 1-SOL L2 Figure 33. Test Circuit 42

43 The solenoid coil is represented in the ladder diagram of figure 33 by the symbol shown in figure 34. As shown, the solenoid coil has two electrical leads and is located in the circuit as an output device just like a lamp. SOLENOID SYMBOL COIL ELECTRICAL LEADS Figure 34. Solenoid Coil Symbol 4. Turn on the main power circuit breaker. 5. Perform the following substeps to operate the control logic circuit. At this point, electricity has not yet been supplied to the solenoid. Therefore, it will have no effect on the cylinder because no air is allowed to flow to the cylinder. This is shown in figure 35. LADDER DIAGRAM SOLENOID OFF L1 1PB 1-SOL L2 SOLENOID VALVE EXHAUST SUPPLY SOURCE Figure 35. Solenoid Off 43

44 A. Press and hold 1PB and observe cylinder 1. Cylinder 1 Status (Extend/Retract) Cylinder 1 should extend because electricity flows from L1 to the solenoid 1-SOL. The solenoid shifts the valve that operates cylinder 1, as shown in figure 36. Now air flows to the cylinder and causes the cylinder to extend. SOLENOID ON LADDER DIAGRAM EXTEND L1 1PB PRESSED 1PB 1-SOL L2 VALVE SHIFTED EXHAUST POWER SOURCE Figure 36. Solenoid On/Valve Shifted/Cylinder Extends 44

45 B. Release 1PB and observe cylinder 1. Cylinder 1 Status (Extend/Retract) The cylinder should now retract. The solenoid is off. A spring causes the valve to shift back to its original position, causing the cylinder to retract, as shown in figure 37. SOLENOID OFF RETRACT Figure 37. Solenoid Off Again/Valve Returns/Cylinder Retracts 6. Repeat step 5 several more times to become more familiar with the operation of a solenoid-operated pneumatic valve. 7. Connect and test the circuit shown in figure 38. Be sure to turn off the main power circuit breaker before changing the circuit. Pressing 1PB should cause only cylinder 1 to extend. Pressing 2PB should cause only cylinder 2 to extend. L1 1PB RUNG SOL 2 L2 RUNG 2 1 2PB 4 2-SOL 2 Figure 38. Test Circuit 45

46 8. Connect and test the circuit shown in figure 39. Pressing 1PB should cause both cylinders to extend at the same time. LADDER DIAGRAM L1 1PB 1-SOL L2 2-SOL Figure 39. Test Circuit 9. Perform the following substeps to shut down the system. A. Turn off the main power circuit breaker. B. Remove the test leads. 46

47 SKILL 10 DESIGN A CONTROL CIRCUIT IN A LADDER DIAGRAM FORMAT TO OPERATE A SOLENOID VALVE Procedure Overview In this procedure, you will design a circuit to control two solenoid valves. 1. Design a control logic circuit that will perform the following functions. Extend cylinder 1 when 1PB is pressed. Extend cylinder 2 when 2PB is pressed and the selector switch 1SS is in the left-hand position. Draw your circuit on a separate piece of paper. 2. Perform the following substeps to set up the system. A. Make sure the main power circuit breaker is off. B. Remove any test leads on the front panel. 3. Perform the following substeps to connect the air supply to the system. A. Check to make sure the air supply is connected to your system. B. Adjust the pressure gauge on the air supply to 50 psig/345 kpa. 4. Connect the circuit you designed in step Turn on the main power circuit breaker. 6. Perform the following substeps to test the circuit that you designed. A. Press and hold 1PB and observe cylinder 1. Cylinder 1 Status (Extend/Retract) Cylinder 1 should extend because pressing 1PB closed the circuit and allowed current to flow to the solenoid. The solenoid shifts the valve and caused air to flow to the cylinder to extend it. B. Release 1PB and observe cylinder 1. Cylinder 1 Status (Extend/Retract) Cylinder 1 will retract because the solenoid is off. This causes the valve to return to its normal position. C. Place the selector switch 1SS in the left-hand position. Press and hold 2PB and observe cylinder 2. Cylinder 2 Status (Extend/Retract) Cylinder 2 should extend because the selector switch in the left-hand position (closed) and pressing 2PB will close the circuit to the solenoid. 47

48 7. Have your instructor observe your circuit in operation. This is part of your skills assessment. 8. Perform the following substeps to shut down the system. A. Turn off the main power circuit breaker. B. Remove the test leads. C. Turn the air supply off by either turning off the shutoff valve or reducing the regulator pressure to minimum. 9. Place a copy of your circuit design in your portfolio. 48

49 SEGMENT 4 SELF REVIEW 1. Solenoid-operated directional control provide the means by which electrical circuits can control the operation of pneumatic or hydraulic systems. 2. A(n) diagram shows the connections for the power devices. 3. When the on a solenoid-operated directional control valve is activated, the valve shifts causing a change of flow direction. 4. The electrical connections on a power diagram and those on the ladder diagram should be numbered (the same/differently). 5. A(n) causes the valve to shift when the valve s solenoid is turned off. 6. devices are never represented in a control diagram. 49