CBLM_Prepare, Make Changes on Electrical, Electronic Schematics and Drawings

JZGMSAT TESDA IV

Prepare/Interpret Technical Drawing

Version No.: 2 Date: August 12, 2009 By: Glenn F. Salandanan of 21

PREPARING/MAKING CHANGES ON ELECTRICAL/ ELECTRONIC SCHEMATICS

AND DRAWINGS

This is the first of the modular series produced by the Jacobo Z. Gonzales Memorial School of Arts and Trades –

Technical Education and Skills Development Authority Region IV-A

ACHIEVING COMPETENCE IN

PREPARING/INTERPRETING TECHNICAL DRAWING

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TABLE OF CONTENTS Content Page Number

I. LEARNING GUIDE OVERVIEW ........................................................................ 3

II. HOW TO USE THIS GUIDE ............................................................................... 4

III. LEARNING ACTIVITIES ..................................................................................... 5

IV. INFORMATION SHEET 1: SYMBOLS FOR ELECTRONIC/

ELECTRICAL DIAGRAMS ..................................................................................6

INFORMATION SHEET 2: TYPES OF ELECTRONIC/

ELECTRICAL DIAGRAMS ................................................................................11

INFORMATION SHEET 3: LINE CONVENTIONS AND LETTERING ..............14

V. SELF CHECK 1 ................................................................................................ 10

SELF-CHECK 2 ................................................................................................ 13

VI. ACTIVITY SHEET NO. 1: .................................................................................17

VII. ANSWER KEYS .......................................................................................... 19-20

VIII. RECORD OF COMPETENCE .......................................................................... 21

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LEARNING GUIDE OVERVIEW

Because of the complexity of the modern electronics, a considerable number of graphic symbols have been developed for describing the connections and functions of such circuits and systems.

Students who have a basic course in electricity/ electronics will find it easier to understand and make electrical or electronic drawings. This learning material will introduce electrical and electronic symbols, wiring diagrams and circuit diagrams.

In this learning material, the students should be able to apply the line conventions and symbols in drawing different electrical/ electronic diagrams.

Competencies will be demonstrated by completing the job sheet and the unit test with a minimum score of 75 percent.

OBJECTIVES When you have successfully completed the learning activities in this

material, you will be able to: 1. Know the line conventions used in electronic/ electrical

diagrams; 2. Prepare different electronic/ electrical diagrams correctly; 3. Apply correct line thickness and lettering in drawing electronic/

electrical diagrams; and, 4. Layout the diagram with proper spacing between components

for notes and reference information. CONTENTS This learning material includes the following:

1. Standard Symbols 2. Kinds/Types of Electrical/Electronic Diagrams 3. Line Conventions and Lettering 4. Symbols and Layouts 5. Drawing Schematic Diagrams

PRE-REQUISITES The completion of this learning material requires you to have a basic

understanding of: If you are unfamiliar with any of the above concepts, work on________ before working on this learning guide.

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HOW TO USE THIS LEARNING GUIDE This Learning Guide will lead you through a series of activities which will require you to work at your own pace. These activities will ask you to complete associated learning and practice activities in order to gain the knowledge and skills you need to achieve the learning objectives stated earlier. Refer to Learning Activity Page to know the sequence of learning tasks to undergo and the appropriate resources to use in each task. This page will serve as your road map towards the achievement of objectives. Read the information sheets. This will give you an understanding of the work, and why things are done the way they are. Complete the activities as directed in the activity/practice sheets. These will test your knowledge and give you practice of doing the tasks involved. Performance criteria for assessing practical exercise are shown to guide you in undertaking the practical exercises. Always be aware of safety requirements highlighted in this material. Ask for clearance in using some tools and equipment. Should you require some assistance and clarification, consult your trainer or facilitator. They should be available anytime you need them. Answer self-checks found in each section of the learning guide. Do not write anything on this learning guide; provide separate sheets for your answers. Self-checks will let you know how you are going. To know how you fared with self checks, review the answer keys found at the end of the learning guide. When you had completed all the tasks required in this learning guide, an assessment exercise will be given to evaluate if you are already competent with the specified learning outcomes in and ready for the next task. .If you feel ready for the assessment, consult the facilitator. A record of competency is provided on the last page to reflect how much of the required assessment criteria have been met. You may already have some or most of the knowledge and skills covered in this learner’s guide. Talk to your trainer about having them formally recognized. If you have qualification or certificate of competence from previous training, show it to your trainer. If the skills you acquired are still current and relevant to the unit of competency they may become part of the evidence you can present for Recognition of Prior Learning (RPL). If you are not sure about the accuracy of your skills, discuss it with your trainer.

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LEARNING ACTIVITIES

In order to accomplish the objectives stated in this leaning guide, you must perform the learning steps below. Beside each step are the resources or special instructions you will use to accomplish the corresponding activity.

LEARNING STEPS RESOURCES/SPECIFIC INSTRUCTIONS

1. Student will ask the instructor of the

materials to be used

2. Read: Information Sheet No. 1

3. Answer: Self Check 1


5. Answer: Self Check 2


7. Perform: Activity Sheet No. 1

8. Submit activity to Trainer for

Assessment

1. Instructor will provide the learning materials in Preparing/making Changes on Electrical/Electronic Schematics and Drawings

2. Information Sheet No 1: Symbols for

Electronic/electrical Diagram

3. Self Check No. 1: Symbols for

Electronic/electrical Diagram

4. Information Sheet No. 2: Electronic/

Electrical Diagram

5. Self Check No. 2: Electronic/

Electrical Diagram

6. Information Sheet No. 3: Lines

Conventions and Lettering

7. Activity Sheet No. 1: Drawing and

Making Changes on Schematic

Diagram

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INFORMATION SHEET NO: 1

SYMBOLS FOR ELECTRONIC/ ELECTRICAL

DIAGRAMS

We use graphic symbols on electrical and electronic diagrams to show the components and workings in a circuit. Graphic symbols for electrical engineering are a shorthand way to show through drawings how a circuit works or how the parts of the circuit are connected. A graphic symbol shows what a part in the circuit does. Drafters use graphic symbols on single-line (one-line) diagrams, on schematic diagrams, or on connection or wiring diagrams. You can relate graphic symbols with parts lists, descriptions, or instructions by marking the symbols.

Figure 1. Graphic symbols for electrical and electronics diagrams

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Figure 1. Graphic symbols for electrical and electronics diagrams (cont.)

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SELF- CHECK NO. 1 Check your mastery in symbols for electrical/electronic diagrams by completing the tasks below.

I. IDENTIFICATION. Identify the symbol for electrical/electronic diagrams by writing the name of the component on the space provided.

1. ____________________

6. ___________________

2. ___________________ 7. __________________

3. ___________________ 8. __________________

4. ___________________ 9. __________________

5. ___________________ 10. ___________________

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INFORMATION SHEET NO. 2:

TYPES OF ELECTRONIC/ ELECTRICAL DIAGRAMS

There are many kinds of electrical/electronic diagrams. Each kind of diagram suits its purpose. 1. Single-line (One-line) diagram. This diagram shows, using single-lines and graphic symbols, the course of an electric circuit and the parts of the circuit.

Figure 2. A complete single-flow diagram for an AM-FM stereo unit

2. Schematic (Elementary) Diagram. This diagram shows, using graphic symbols, the ways a circuit is connected and what the circuit does. The schematic does not have to show the size or shape of the parts of the circuit. It does not have to show where the parts of the circuit actually are.

Figure 3. Schematic Diagram 3. Connection or Wiring Diagram. This diagram shows how the components of a circuit are connected. It may cover connections inside or outside the components. It has as much detail as is needed to make or trace connections. The connection diagram usually shows how a component looks and where it is placed.

Figure 4. Installation assembly drawing

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4. Interconnection diagram. This is a kind of connection or wiring diagram that shows only connections outside the component. An interconnection diagram shows connection between components. The connections inside the component are usually left out.

Figure 5. Interconnection Diagram 5. Layout diagram – This diagram is a pictorial of how the electronic circuit actually looks. These drawings show the actual layout of the components on the circuit board. This provides a two-dimensional drawing, usually looking down from the top, detailing the components in their location. Shown in Figure 6 is the schematic for a circuit and the same circuit drawn in pictorial or layout format for comparison. Normally the pictorial layout would be accompanied by a parts list.

A. Schematic Diagram

B. Layout Diagram C. Layout, component side Figure 6. Schematic and layout diagram of a pulsing third brake light

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SELF-CHECK NO. 2 Check your mastery in symbols for electrical/electronic diagrams by completing the tasks below.

I. IDENTIFICATION. Identify the kind of electrical/electronic diagram shown below by writing your answer on the space provided.

1. _________________________

2. _________________________

3. _________________________

4. _________________________

5. _________________________

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INFORMATION SHEET NO. 3:

A. LINE CONVENTIONS AND LETTERING

As in any drawings intended for reproduction, line thicknesses and letter sizes should be selected according to the amount of reduction or enlargement involved so that legibility will not be adversely affected.

ANSI recommends a line of medium thickness for general use on electrical diagrams. A thin line may be used for brackets, leader lines, etc. To emphasize special features such as main signal paths, a thicker line may be used to provide the desired contrast. For recommended line thickness, refer to illustration below.

Line conventions for electrical diagrams are shown on Figure 1.

FOR GENERAL USE MEDIUM

MECHANICAL CONNECTION, SHIELDING AND FUTURE CIRCUIT LINE

MEDUIM

BRACKET-CONNECTING DASH LINE MEDUIM

USE OF THIS LINE THICKNESSES OPTIONAL

BRACKETS, LEADER LINES, ETC. THIN

BOUNDARY OF MECHANICAL GROUPING THIN

FOR EMPHASIS THICK

Figure 7. Line conventions for electrical diagrams

B. SYMBOLS AND LAYOUTS The Symbol can be drawn any size needed. However, its size must fit in with the rest of the drawing. Keep in mind whether the drawing will be made larger or smaller. For most electrical diagrams meant to be used for manufacturing, or for use in a smaller form, draw symbols about 1.5 times the size of those shown in American National Standard (see learning material in Identify Interpret Different Electrical/Electronic Diagrams). C. LAYOUT FOR ELECTRICAL DIAGRAMS Layout electrical diagrams so that the main parts are easily seen. The parts of the diagrams should have spaced between them. This is so that there will be an even balance

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between blank spaces and lines. Allow enough blank area around symbols so that notes or reference information will not be crowded. Avoid larger spaces, however. Only allow large spaces if circuits will be added later. D. DRAWING SCHEMATIC DIAGRAMS

Source: Paul Horowitz and Winfield Hill, The Art of Electronics 2nd Edition

A well-drawn schematic makes it easy to understand how a circuit works and aids in troubleshooting; a poor schematic only creates confusion. By keeping a few rules and suggestions in mind, you can draw a good schematic in no more time than it takes to draw a poor one. In this appendix we dispense advice of three varieties: general principles, rules, and hints. We have also drawn some real knee-slappers to illustrate habits to avoid.

General Principles

1. Schematics should be unambiguous. Therefore, pin numbers, parts values, polarities, etc., should be clearly labeled to avoid confusion.

2. A good schematic makes circuit functions clear. Therefore, keep functional areas distinct; don't be afraid to leave blank areas on the page, and don't try to fill the page. There are conventional ways to draw functional subunits; for instance, don't draw a differential amplifier as in Figure 8, because the function won't be easily recognized. Likewise, flip-flops are usually drawn with clock and inputs on the left, set and clear on top and bottom, and outputs on the right.

Figure 8. Placement of power rails and conventions for device alignment (examples of

what not to do)

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Rules

1. Wires connecting are indicated by a heavy black dot; wires crossing, but not connecting, have no dot.

2. Four wires must not connect at a point 3. Always use the same symbol for the same device. 4. Wires and components are aligned horizontally or vertically, unless there's a good

reason to do otherwise. 5. Label pin numbers on the outside of a symbol, signal names on the inside. 6. All parts should have values or types indicated; it's best to give all parts a label,

example, R7 or IC3.

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ACTIVITY SHEET NO. 1

Drawing and Making Changes on Schematic Diagram

A. Objectives: After completing the activity you should be able to:

1. Draw schematic diagram; and,

2. Make changes on electronic diagram

B. Tools and Materials: A4 size drawing paper T-square Eraser Drawing pencil (HB)

Triangles (30ºx60º, 45ºx45º) D. Procedure:

1. Before starting your work, you must read thoroughly the precautions stated below and apply it to your drawing.

2. Study the schematic diagram drawn in freehand. 3. Estimate the size of your drawing. Make sure that the schematic diagram is placed in

the center of the drawing paper. 4. Layout the diagram with proper spacing between components for notes and

reference information.

An illustration showing ``awful'' schematics of a circuit which violates nearly every rule

and is almost impossible to understand.

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PROBLEM:

E. Precautions:

1. Identify parts immediately adjacent to the symbol, forming a distinct group giving symbol, label, and type or value.

2. In general, signals go from left to right; don't be strict about this, though, if clarity is sacrificed.

3. Put positive supply voltages at the top of the page, negative at the bottom. Thus, npn transistors will usually have their emitter at the bottom, whereas pnp's will have their emitter topmost.

4. Don't attempt to bring all wires around to the supply rails, or to a common ground wire. Instead, use the ground symbol(s) and labels like +Vcc to indicate those voltages where needed.

5. It is helpful to bring leads away from components a short distance before making connections or jogs.

6. Leave some space around circuit symbols. 7. Use small rectangles, ovals, or circles to

indicate card-edge connections, connector pins, etc. Be consistent.

8. The signal path through switches should be clear.

9. Power supply connections are normally assumed for op-amps and logic devices.

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ANSWER KEY NO. 1

Check your answer with the answer key below. If you fail to get it right, refer back to corresponding resources until you make it perfect.

1. Amplifier, general

2. Rectifier, bridge type

3. Transformer

4. Fuse, general

5. Capacitor, polarized

6. Switch, single throw, single pole

7. Antenna, general

8. PNP type transistor

9. Speaker

10. Resistor, general

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ANSWER KEY NO. 2

Check your answer with the answer key below. If you fail to get it right, refer back to corresponding resources until you make it perfect.

1. Single-line Diagram

2. Layout

3. Interconnection Diagram

4. Connection or Wiring Diagram

5. Schematic Diagram

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RECORD OF COMPETENCE Below are your assessment ratings: ASSESSMENT /PERFORMANCE

CRITERIA

YES NO

1. Electrical/ Electronic schematic drawn and correctly identified

2. Correct drawing identified, equipment selected and used in accordance with job requirements

CBLM_Prepare, Make Changes on Electrical, Electronic Schematics and Drawings

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