Question 1
Which of the following groups contains only electronic components mentioned in the study material?
Strand 3 · Vigour Behind Life
General Science Year 1 Learner Material, Section 7: Basic Electronics
Hello learner, have you ever visited a radio, television or computer repair shop?
What are some of the electronic components you remember from your JHS basic electronics lessons?
This section will equip you with an understanding of household electronic devices, their electronic component composition, the uses of these components, and the ability to design a basic amplifier. You will therefore be introduced to household electronic devices such as old/spoilt/abandoned televisions, radios, microwaves, and refrigerators, where available or watch videos about their internal electronic components. You will explore and be introduced to the internal electronic components of the devices like resistors, capacitors, transistors, diodes, and integrated circuits. You will also be guided to design a basic amplifier using electronic components.
At the end of the section, you will be able to Explain the uses of electronic components in household electronic devices and amplifiers.
KEY IDEAS
• Electronics: This is a branch of physics that deals with the emission, behaviour, and effects of electrons. Electronics is concerned with the design of circuits using transistors and microchips, and with the behaviour and movement of electrons in a semiconductor, conductor, vacuum, or gas.
• Circuit: A circuit is a closed loop or pathway through which electric current flows.
Overview of Electronics
In simple terms, electronics involves manipulating electrical signals to perform specific functions or tasks. It covers many areas, including designing, developing, and manufacturing electronic devices and systems.
Electronics have transformed our lives with the use of smartphones, computers, televisions, kitchen appliances, and medical equipment. Some common components of electronic devices include resistors, capacitors, transistors, and integrated circuits, which are combined to create complex electronic systems.
These systems can perform amplification, signal processing, data storage, communication, and control tasks. Electronics is a continuously evolving field with regular advancements and innovations.
Let us now discuss the unique functions of the electronic components in any electronic device.
Electronic Components and Their Uses
Activity 7.1: Electronic components Fill in the table below with any information that you recall from JHS about the electrical components listed.
After you have filled out as much as you can, watch the video linked below to help you fill out the rest of the table.
https://www.youtube.com/watch?v=XfQs-PQaC_E
Table 7.1: Electronic components, their symbols and functions Electronic Component Circuit Symbol Function Resistor Electronic Component Circuit Symbol Function Capacitor Diodes Transistors Inductors Light-emitting diodes (LEDs)
Activity 7.2: Some common examples of household electronic devices Having gone through the electronic components, let us remind ourselves that examples of household electronic devices are televisions, refrigerators and washing machines. Discuss with your friend and add to the list.
Consider which of the above-named circuit components may make up the circuitry for the household appliances you have identified. For example, would you expect to find a resistor inside a washing machine? How about an LED? In a pair or group, make a concept map of your thoughts.
If possible, find an old/broken electrical appliance and take it apart to investigate the components inside it.
Now, let us discuss the design of circuits involving transistors and switches.
Designing Circuits Involving Transistors and
Switches A circuit is a closed loop or pathway through which electric current flows. It consists of components like resistors, capacitors, inductors, and power sources connected by conductive wires or traces on a circuit board. Complete the following
activity in a group.
Activity 7.3: Experiment on how to build an LED circuit Aim: To build an LED circuit Apparatus: Breadboard, LED (Light Emitting Diode), resistor (330 Ohms or appropriate value for the LED), 9V battery and battery clip (or a suitable power supply, connecting wires (jumper wires), multimeter (optional, for testing), switch (optional, to control the LED) Procedures:
1. Place the breadboard on a flat surface for easy component insertion.
2. Place the LED on the breadboard with the positive anode (longer leg) in one row and the negative cathode (shorter leg) in another row.
3. Connect one end of the resistor to the same row as the anode of the LED.
4. Connect the other end of the resistor to an empty row.
5. Attach the battery clip to the 9V battery.
6. Connect the red wire (positive) from the battery clip to the row with the free end of the resistor.
7. Connect the black wire (negative) from the battery clip to the row with the cathode of the LED.
8. Insert the switch into the breadboard.
9. Connect one terminal of the switch to the row with the free end of the resistor.
10. Connect the other terminal of the switch to the row with the red wire from the battery clip.
11. Double-check all connections.
12. Connect the battery clip to the 9V battery.
13. If using a switch, toggle it to the “on” position.
14. Observe the LED lighting up, indicating a successful circuit.
NB: if the LED doesn’t light up:
a. Check all connections for loose wires.
b. Ensure the LED is correctly oriented (anode to positive, cathode to negative).
c. Verify the resistor value is appropriate for the LED and power supply.
d. Use a multimeter to check for continuity and correct voltage levels.
Activity 7.4: Experiment on how to build an electrical circuit Observe the image in Fig. 7.1 (note that the reference/link below shows the image as an animation) and carefully complete the experiment that follows.
Fig. 7.1: Light dependent resistors.
https://www.technologystudent.com/elec_flsh/ldrsensor1.gif Aim: To build a light-dependent resistor circuit.
Apparatus: Breadboard, LDR (light-dependent resistor), 10k Ohm resistor, LED, 330 Ohm resistor, 9V battery and battery clip, jumper wires.
Procedures:
1. Connect one end of the LDR to the battery’s positive terminal.
2. Connect the other end of the LDR to one end of the 10k Ohm resistor.
3. Connect the other end of the 10k Ohm resistor to the battery’s negative terminal.
4. Connect the junction of the LDR and the 10k Ohm resistor to the base of an NPN transistor (if using).
5. Connect the transistor emitter to the battery’s negative terminal.
6. Connect the collector of the transistor to one end of the 330 Ohm resistor.
7. Connect the other end of the 330 Ohm resistor to the anode (positive terminal) of the LED.
8. Connect the cathode (negative terminal) of the LED to the negative terminal of the battery.
9. The LED should light up when the ambient light levels fall below a certain threshold.
10. Discuss with your group a useful application of this circuit in day-to-day life.
Method of Building an Amplifier
Having looked at the systematic ways of circuit design, let us discuss ways by which you can build an amplifier.
An amplifier is a device that increases the strength (amplitude) of a signal or sound. It takes a weak input signal and produces a stronger output signal, usually with the same waveform but a larger amplitude. Amplifiers are essential in various electronic devices such as audio systems, radios, televisions, and telecommunications equipment to boost signals for better transmission.
Now go through the following process as we build an amplifier. Find further information in Annex 7.2.
1. Determine the Amplifier Type
2. Select your Components
3. Design the Amplifier Circuit
4. Calculate Component Values
5. PCB Layout
Audio frequency (AF) Amplifiers
Activity 7.5 : How to build a simple audio amplifier
• Study the image in Figure 7.2.
• Are you able to identify any of the electronic components?
• Share your response with your friend.
Fig. 7.2: Diagram of Audio Frequency Amplifier
Activity 7.6: Experiment on how to Build a Simple Audio Amplifier Apparatus: LM386, 10 μF electrolytic capacitor (2 pieces), 0.047 μF ceramic capacitor (1 piece), 10 Ohm resistor (1 piece), 1k Ohm resistor (1 piece), potentiometer (10k Ohm, for volume control), speaker (8 Ohms, small size), audio input jack (3.5mm stereo jack), battery (9V battery with battery clip), breadboard or PCB (Printed Circuit Board), connecting wires, soldering kit (if using PCB) Procedure:
1. Place the LM386 IC in the middle of the breadboard or PCB for easy wiring.
2. Connect the 9V battery clip to the breadboard or PCB.
3. Connect the positive terminal of the battery clip to pin 6 of the LM386.
4. Connect the negative terminal of the battery clip to the ground rail on the breadboard or PCB.
5. Connect the audio input jack’s ground (sleeve) to the ground rail on the breadboard.
6. Connect the audio input jack’s left or right channel (tip or ring) to one terminal of the 10k Ohm potentiometer.
7. Connect the wiper (middle terminal) of the potentiometer to pin 3 of the LM386.
8. Connect a 10 μF electrolytic capacitor between pin 7 and the ground.
9. Ensure the negative leg of the capacitor goes to the ground.
10. Connect a 10 μF electrolytic capacitor between pin 1 and pin 8 of the LM386 to set the gain to 200. Ensure the negative leg is on pin 1.
11. Connect a 0.047 μF capacitor between pin 5 of the LM386 and one terminal of the 10 Ohms resistor.
12. Connect the other terminal of the 10 Ohm resistor to the speaker’s positive terminal.
13. Connect the negative terminal of the speaker to the ground rail on the breadboard or PCB.
14. Connect a 220 μF capacitor’s positive leg to pin 5 of the LM386 and its negative leg to the junction between the 0.047 μF capacitor and the 10 Ohm resistor.
15. Double-check all connections to ensure they are correct.
16. Attach the 9V battery to the battery clip.
17. Plug an audio source into the input jack and adjust the potentiometer to control the volume.
18. You should hear the amplified audio through the speaker.
NB: The concentration should be on the audio amplifier.
Activity 7.7: Designing your own circuit In a group of no more than 5 learners, design a circuit to meet a need to fulfil a particular function (for example, a circuit that will light up an LED when the temperature exceeds a certain value or a circuit that will smooth the output of an AC signal).
ANNEXES Annex 7.1 – Solutions to some activities
Activity 7.1
Electronic Component Circuit
Symbol Function
Resistor This device restricts the flow of electric current in a circuit, helping to control voltage levels and protect sensitive parts.
Capacitor It stores energy in the form of electrical charge and releases the energy when needed.
They are commonly used for smoothing voltage fluctuations and filtering out noise in power supplies.
Diodes Diodes allow electric current to flow in only one direction and are often used to convert AC (alternating current) to DC (direct current) in power supplies.
Transistors These amplify or switch electronic signals. They are crucial in amplifiers, computers, and various digital devices.
Electronic Component Circuit
Symbol Function
Inductors Inductors store energies in a magnetic field and are commonly used in filters, transformers, and power supplies.
Light-emitting diodes (LEDs) They convert electricity into light. They are extensively used in household electronics for indicators.
Activity 7.2
• Microwave ovens
• Air conditioners
• Vacuum cleaners
• Gaming consoles, etc.
Activity 7.4
This circuit would be used in automatic street lighting.
Annex 7.2 – Further information on Electronic Components How to Design a Circuit Designing circuits involving transistors and switches typically involves several steps. The following is the general outline of the process:
Define the Objective
i. It is important to clearly define the purpose of your circuit, for instance an LED circuit.
ii. Determine what function or task you want the circuit to accomplish.
Fig. 7.3: Circuit diagram of transistor as a switch Circuit Analysis Use the image in Figure 8 as an example to analyse circuits.
i. Identify the components and their connections needed to achieve the desired functionality.
ii. Consider the input and output requirements, power supply, voltage levels, and specific constraints.
Transistor Selection
i. Select the appropriate transistor type (s) for your design based on your circuit analysis. Common types include bipolar junction transistors (BJTs) and field-effect transistors (FETs).
ii. Consider factors such as current handling capacity, voltage ratings, speed, and other specifications relevant to your circuit.
Component Sizing
In component sizing
i. Determine the values of resistors, capacitors, and other components required to bias and drive the transistors properly.
ii. Calculate or choose appropriate component values based on the desired performance and the transistor’s datasheet specifications.
Circuit Simulation
Utilise circuit simulation software such as Linear Technology Spice (LTspice) or Proteus to simulate and validate your circuit’s performance. This can help identify potential issues, optimise component values, and achieve the desired functionality.
Printed circuit board (PCB) Layout If you plan to create a (PCB) for your design, create a layout incorporating the components, their connections, and proper trace routing. Consider factors such as component placement, signal integrity, and thermal considerations.
Prototype and Testing
i. Build a physical prototype of your circuit using the designed PCB or a breadboard.
ii. Test how the circuit function, perform and check whether it is reliable.
iii. Make any necessary adjustments or modifications based on the test results.
Documentation Document your circuit design, including schematics, component values, and any specific design considerations. This documentation will be useful for future reference, troubleshooting, or sharing your design with others Process Of Building An Amplifier Circuit Determine the Amplifier Type Decide on the type of amplifier you want to build, such as a class A, class AB, class D, or a specific audio amplifier design. Each type has its characteristics and applications.
Select your Components Choose the necessary components for your amplifier design. This typically includes transistors (bipolar junction transistors or MOSFETs), resistors, capacitors, and possibly transformers or inductors, depending on the amplifier type. Refer to an amplifier circuit diagram or schematic for component values and specifications.
Design the Amplifier Circuit
Create a circuit diagram or schematic based on the selected amplifier type and component choices. This diagram will illustrate how the components are connected and the flow of signals through the amplifier.
Calculate Component Values
Determine the values of resistors, capacitors, and other components based on the desired performance and the amplifier design specifications. This may involve biasing, gain, stability, and frequency response calculations.
PCB Layout
If you plan to create a printed circuit board (PCB) for your amplifier, design the layout incorporating the components and their connections. Pay attention to proper trace routing, ground planes, and thermal considerations to ensure optimal performance and reliability.
Review Questions 7.1
1. You are assigned to design and build a basic audio amplifier circuit that can amplify a weak audio signal from a microphone to drive a small speaker.
2. Describe the key electronic components you would use in your amplifier circuit and their roles (e.g., transistors, resistors, capacitors).
3. Explain how you would use these components to achieve the desired amplification.
4. What considerations would you take into account regarding power supply requirements and component ratings?
5. Discuss any additional features you might include in your design to improve sound quality or functionality (e.g., tone control, volume control).
Considerations:
• Specify the expected input and output signal levels.
• Describe how you would test and troubleshoot the amplifier circuit once built.
Which of the following groups contains only electronic components mentioned in the study material?
In the LED circuit activity, the longer leg of the LED is the anode. To which terminal of the battery should the anode be connected?
Kojo wants to build a basic audio amplifier that takes a weak signal from a microphone and drives a small speaker. What is the main function of the amplifier?
Which set of components is mentioned in the study material as useful for designing a basic amplifier?
Ama builds the LED circuit and toggles the switch to the “on” position, but the LED does not light. According to the material, which checks should be made first?
Ama Serwaa owns an electronics repair shop at Kejetia Market in Kumasi. A customer brings a spoilt radio for repair. When Ama opens the radio, she finds resistors, capacitors, diodes, transistors, inductors and light-emitting diodes (LEDs) on the circuit board. She explains the work of each component to her apprentice, Kofi, and later tests the repaired radio with a small amplifier that she built herself, so that the loudspeaker produces sound.
Identify any three of the electronic components found in the radio, and state one use of each in a household electronic device.
Explain the use of (i) a capacitor; (ii) an inductor in household electronic devices.
Ama says the amplifier is needed because the signal that arrives from the radio station is very weak. Explain how the transistor, the resistor and the capacitor work together in the amplifier to make the weak signal strong enough to drive the loudspeaker.
Kofi connects an LED directly across the 9 V battery without a resistor in the circuit. The LED gives one bright flash and then goes off for good. Explain why the LED was destroyed, and justify why a resistor of about 330 must be used when building an LED circuit.
The General Science Club of Tamale Senior High School is preparing a public address (PA) system for the school's speech day. The club has a microphone, a loudspeaker, a 9 V battery and a box of electronic components. The table below shows four household electronic devices and some of the electronic components found inside them.
| Household device | Electronic components found inside |
|---|---|
| Radio | resistor, capacitor, diode, transistor, integrated circuit |
| Television | resistor, capacitor, transistor, integrated circuit, LED |
| Refrigerator | resistor, capacitor, inductor, integrated circuit |
| Microwave oven | resistor, capacitor, diode, transistor |
From the table, identify the two electronic components that are found in all four household devices, and state one use of each in a household electronic device.
Explain the use of (i) the diode in the radio; (ii) the inductor in the refrigerator.
When the club switched on the amplifier they had built, the sound from the loudspeaker was distorted and the transistor became very hot. Analyse any two possible causes of this problem and, for each cause, suggest one remedy.
The club wants the amplifier to give clearer sound. Suggest one additional feature they could add to the amplifier and justify your suggestion with two reasons.