Workbook Section

Part 1 Introduction

Connect the circuit so that lamp L1 will light when switch S1 is closed.

Connect the circuit so that lamp L1 will light when either switch S1 or S2 is closed

Connect the circuit so that, when switch S1 is in position A. lamp L1 will light ,and when the switch S1 is in position B, switch S2 must be closed to light lamp L1.

Connect the circuit so that both switches S1 and S2 must be in the same position to light lamp L1, either switch can be used to turn the lamp on or off.

Connect the circuit so that lamp L1 will light when switch S1 is closed with either switch S2 or S3 closed.

Connect the circuit so that switches S1 or S2 and S3 or S4 must be closed to light lamp L1.

Connect the circuit so that both switches S1 and S2 must be closed to light lamp L1.

Connect the circuit so that, when switch S1 is in position A, lamp L1 will light , and when switch S1 is in position B, lamp L2 will light.

Ladder and Wiring Diagrams Part 2 Ladder and Wiring Diagrams

Ladder and Wiring Diagrams In the fields of electrical engineering and construction, electrical ladder diagrams are a fundamental concept that everyone should have at least a basic understanding of. At first glance, reading ladder diagrams can be difficult, but this lab will provide a step-by-step explanation of the different components, notations and elements in ladder diagrams. You’ll understand how the different elements of the ladder diagram represent components of an electrical circuit - and how to make this circuit drawing a reality.  

Ladder Diagram Ladder diagram – a diagram that uses single lines and graphic symbols to indicate the path and components of an electrical circuit. Ladder diagrams are symbolic representations of complete circuits or systems created during the design phase. their role is to make the circuit easier to understand. They are called “ladder” diagrams because they resemble a ladder (Figure 1), with two vertical rails (supply power) and as many “rungs” (horizontal lines).  

Ladder Diagram   Figure 1

Ladder Diagrams Ladder diagrams are used when information about a circuit is required but detail of the actual wire connections and operation of the circuit are not. Ladder diagram is a diagram that shows the logic of an electrical circuit or system using standard symbols. (Figure 2) Ladder diagram is used to show the relationship between circuits and their components but not the actual location of the components. Ladder diagrams provide a fast, easy understanding of the connections and use of components.  

Ladder Diagrams   Figure 2

Wiring Diagrams Wiring diagrams, or layouts, illustrate the physical connections, or wiring, between components. They are crucial to the assembly of the circuit or system (Figure 3). Wiring (connection) diagram – a diagram that shows the connection of an installation or its component devices or parts. Wiring diagrams show, as closely as possible, the actual location of each component in a circuit, including the control circuit and the power circuit.  

Wiring Diagrams   Figure 3

READING SCHEMATIC DIAGRAMS Part 3 READING SCHEMATIC DIAGRAMS

READING SCHEMATIC DIAGRAMS To read a schematic diagram, a few rules must first be learned. Commit the following rales to memory: Reading a schematic diagram is like reading a book. It is read from left to right and from top to bottom. Electrical symbols are always shown in their off or de-energized position. Relay contact symbols are shown with the same numbers or letters that are used to designate the relay coil. All contact symbols that have the same number or letter as a coil are controlled by that coil regardless of where in the circuit they are located. When a relay is energized, or turned on, all its contacts change position. If a contact is shown as normally open, it will close when the coil is energized. If the contact is shown normally closed, it will open when the coil is turned on. There must be a complete circuit before current can flow through a component.  

READING SCHEMATIC DIAGRAMS Components used to provide a function of stop are generally wired normally closed and con­nected in series. (Figure 1) illustrates this con­cept. Both switches A and B are normally closed and connected in series. If either switch is opened, connection to the lamp will be broken and current will stop flowing in the circuit.   Figure 1

READING SCHEMATIC DIAGRAMS Components used to provide the function of start are generally wired normally open and con­nected in parallel. In (Figure 2) switches A and B are normally open and connected in parallel with each other. If either switch is closed, a current path will be provided for the lamp and it will turn on.   Figure 2

READING SCHEMATIC DIAGRAMS The circuit to be discussed is a basic control circuit used throughout industry. (Figure 3) shows a start-stop push button circuit. Notice in this schematic that there is no com­plete circuit to M motor starter coil because of the open start push button and open M auxiliary con­tacts. There is also no connection to the motor be­cause of the open-M load contacts.   Figure 3

READING SCHEMATIC DIAGRAMS When the start button is pushed, a path for current flow is provided to the M-motor starter coil. When the M coil energizes, both M contacts close, (Figure 4). The small auxiliary contact provides a continued current path to the motor starter coil when the start button is released and returns to its open position. The large M load contact closes and provides a complete circuit to the motor and the motor begins to run. The motor will continue to operate in this manner as long as the M coil remains energized.   Figure 4

Developing Wiring Diagrams Part 4 Developing Wiring Diagrams

Developing Wiring Diagrams In this exercise, two schematic diagrams are dis­ cussed, including their operation and development into wiring diagrams. Understanding the process of developing a wiring dia­gram from a schematic is a great advan­tage when troubleshooting electric circuits.  

 Developing circuit 1  The first circuit discussed is shown in figure 1. In this circuit, a fan motor is controlled by relay FR (Fan Relay). The circuit is so designed that a switch can be used to turn the circuit completely off, operate the fan manually, or permit the fan to be operated automatically by a thermostat. Figure 1

 Developing circuit 1  If the control switch is moved to the “MAN” position as shown in figure 2, a complete circuit is provided to the fan relay coil. Then the relay energizes, FR contact closes and connects the motor to the line. This setting permits the fan to be operated at any-time, regardless of the condition of the thermostat. Figure 2

 Developing circuit 1  If the control switch is moved to the “AUTO" position as shown in figure 3, the fan will be controlled by the action of the thermostat. When the temperature increases to a predetermined level, the thermostat contact will close. This completes a circuit to FR coil. When coil FR energizes, the FR contact closes and connects the fan motor to the line. When the temperature decreases sufficiently, the thermostat contact opens and breaks the circuit to FR coil. Figure 3

Any time a component is gone through, the number will change.  Developing circuit 1  This schematic will now be developed into a wiring diagram. To aid in the connection of this circuit, a simple numbering system will be used. To use this numbering system, the following rules will be followed: All components connected to the same line will receive the same number. Any time a component is gone through, the number will change. A set of numbers can be used only once.

 Developing circuit 1  Applying the numbering system to circuit 1 will develop the diagram in figure 4. Figure 4

 Developing circuit 1  After that we draw the components of the circuit, and write the numbers on each component, figure 5. Figure 5

 Developing circuit 1  Notice that numbers have been placed beside certain components. These numbers corre­spond to the numbers in the schematic. For ex­ample, the fuse in the schematic is shown with a l on one side and a 2 on the other side. The fuse in the wiring diagram is shown with a 1 on one side and a 2 on the other side.   Now that the component parts have been num­bered with the same numbers as those used on the schematic, connection can be made easily and quickly. To connect the circuit., connect all the like numbers. For example, all the number Is will con­nect together, all the number 2s will connect to­gether, and so forth. The connected circuit is shown in figure 6.

 Developing circuit 1  Figure 6

Develop the wiring diagram for the schematic  Developing circuit 2  Develop the wiring diagram for the schematic diagram for circuit #2 shown in figure 7, using the numbering system. Figure 7