PERFORMANCE STANDARDS

• Correct technical drawing is selected according to job requirements.

• Technical drawings are segregated in accordance with the types and kinds of drawings.

What Do You Already Know?

Let us determine how much you already know about identifying different kinds of technical drawings. Take this test.

What Do You Need To Know?

Read Information Sheet 1.1 very well then find out how much you can remember and how much you learned by doing Self-check 1.1.

Information Sheet 1.1

When you purchase a brand new appliance or equipment, it is very important that a diagram is included with the product to insure that there will be a reference material in case the appliance or equipment becomes defective. Shown in Fig. 1-1a is the schematic diagram of a 1-watt stereo audio amplifier, while Fig. 1-1b is its pictorial diagram.

Fig. 1-1a is the schematic diagram of a 1-watt stereo audio amplifier

Pictorial diagram of the 1-watt stereo amplifier.

To produce a quality and marketable electronic diagram, you have to follow the Electronic Drafting Standards which is the process of illustrating various kinds of circuits and wiring systems.

The most common graphical languages used in the illustration of components in circuits and wiring systems are block, schematic, wiring, and pictorial diagrams.

Most symbols that you will encounter in laying out electronic diagrams are accepted as standard, but in some cases some manufacturers modify symbols and practices to suit a particular industrial policy while others use their own symbols to represent unique or special component and devices.

Do you know that electronic symbols and their use in conjunction with recommended drafting practices have been developed through the years, and have been standardized by a number of different organizations? Among these are the American National Standards Institute (ANSI), the Electronics Industries Association (IEA), the Institute of Electrical and Electronics Engineers (IEEE), and the International Electrotechnical Commission (IEC).

Drawing instruments and their uses

Drawing instruments are used in preparing accurate drawings. Quality drawing instruments can produce accurate and good and presentable drawings. Below is a list of some of the most common used drawing instruments and materials in electronic drafting.

1. Drawing board. A smooth board usually rectangular in shape provided with perfectly straight edge which is used as working edge on which the Tsquare is moved while making drawings.

2. T-square. A T-square consists of two parts namely the stock and the blade joined together at right angles to each other by means of screws. The stock is made to slide along the working edge and the blade moves on the drawing board. The working edge of a T-square is used to draw parallel lines, vertical lines or inclined lines at 30 or 60 degrees

3. Drafting machine or drafter. In a drafting machine, the uses and advantages of T-squares, scales, set squares, and protractors are combined. One end of the drafter is clamped at the left top end of the drawing board by a screw provided in the drafter.

4. Set squares. Set squares are generally made from plastic material. They are triangular in shape with one corner, a triangle. A pair of set squares (30o- 60o) and 45o. They are used to draw lines at 30o, 60o and 45o to the vertical or horizontal.

5. Protractor. Protractors are used to mark or measure angles between 0 and 180o. They are semicircular in shape and are made of plastic. Protractors with circular shape are capable of marking and measuring 0 to 360 o are also available in the market.

6. Drawing pencils. The accuracy and appearance of a drawing depends on the quality of pencil used to make drawing. The grade of a pencil lead is marked on the pencil. HB denotes medium grade. Increase in hardness is shown by the value put in front of H such as 2H, 3H, etc. Softer pencils are marked as 2B, 3B, and 4B etc. A pencil marked 3B is softer than 2B and pencil marked 4B is softer than 3B and so on. Beginning of a drawing may be made with H or 2H. For lettering and dimensioning, H or HB pencils are used.

7. A technical pen is a specialized instrument used by an engineer, architect, or drafter to make lines of constant width for architectural, engineering, or technical drawings.

8. Compass. Compass is used for drawing circles and arcs of circles. The compass has two legs hinged at one end. One of the legs has pointed needle fitted at the lower end where as the other end has provision for inserting pencil lead.

9. Drawing pins and clips. These are used to fix the drawing sheet on the drawing board.

10. Electronic templates include symbols for electronic and electrical design that can be traced using a drawing pencil.

Drawing Instruments Activity 1

Drawing Instruments Activity 2

What Do You Need To Know?

Read Information Sheet 1.2 very well then find out how much you can remember and how much you learned by doing Self-check 1.2.

Information Sheet 1.2

Resistor

A resistor is a device with a known value of resistance. Its main function is to reduce voltage and to limit the flow of current in a circuit. This resistance is actually the opposition that a component or material offers to the flow of current.

Resistance may or may not be useful in circuit/s. When too much current passes through a conductor, (solid, liquid, gas through which electrons pass easily) the resistance of the conductor may cause it to become hot. This, in turn, can create a fire hazard or cause the conductor to burn out. In this case, it is not desirable. In other cases, when it is placed intentionally in the circuit, it performs its specific task.

Fixed Resistors

It is a single value resistance, which remains the same under the normal condition. The two common kinds of fixed resistors are carbon resistor and film-type resistor.

Variable Resistor

Variable resistors are used when it is necessary to change the amount of resistance in a circuit. There are two common variable resistors, the potentiometer and rheostat. Generally a potentiometer is generally has carbon resistive element while the rheostat is generally made of resistance wire.

Both devices have a sliding arm that brings into contact with the resistance element. In most variable resistors the arm is attached to the shaft that can be adjusted Element changes.

A potentiometer is commonly used as control device. It can be used to vary the value of voltage applied to a certain circuit such as in the amplifier, television, and different kinds of meter circuit.

Resistor Power Rating

Power rating of resistors changes with their sizes, the bigger the resistor the greater the wattages and the smaller the resistor the lesser the wattage. Different sizes of resistors are shown below which are drawn to the exact proportion.

Capacitor

A capacitor is a device that consists essentially of two conducting surfaces separated by a dielectric material like air, paper, mica, ceramic, glass, or Mylar. It makes it possible to store electric energy. Electrons are detained within a capacitor. This, in effect, is stored electricity. It is known as electrical potential or an electrostatic field. Electrostatic field hold electrons. When the increase of electrons becomes great enough, the electrical potentials are now ready to be discharged.

The component is designed intentionally to have a definite amount of capacitance. This capacitance is a property that exists whenever insulating material permits the storage of electricity. It is measured in Farad (F) micro Farad (μF), nano Farad (nF), and picoFarad (pF).

Characteristics of Capacitor:

1. It can store electric charge even though the voltage source is already disconnected.

2. It can discharge electrical voltages.

Variable capacitors used as tuning capacitor for radio receivers

1. Semiconductor Diodes

2. Bipolar Junction Transistors (BJT)

3. Integrated Circuit (IC)

Electronic Schematic Symbols Activity 1

Electronic Schematic Symbols Activity 2

Electronic Schematic Symbols Activity 3

Electronics Components 1

Electronics Components 2

Match up Electronic Components Activity 1

Match up Electronic Components Activity 2

How Much Have You Learned?

Self-Check 1.2 DIRECTION: Draw the schematic symbol and physical appearance of the following electronic components and give the function(s) of each (Table 1-1). Do this in a separate paper or notebook