1. 1 D & T Design Lesson Sec 3B By: MdmLee Kah Gek Technological Areas - Electronics MacPherson Secondary School

2. 2 Technological Areas Structures Mechanisms Electronics

3. 3 Electronics Module

4. 4 Objectives 1.Know basic electronics components and its function ( Res, var res, relay, transistor, temp sensor and light sensor) 2.Learn the electrical symbols. 3. Series and Parallel Circuits

5. 5 Power Supply AC rating ( 230V, 110V, 415V) AC to DC power supply DC to DC power supply Batteries

6. 6 Switches Samples of switches

7. 7  Resist electricity  Used to supply the correct voltage to the various components in an electric circuit. 1. Resistor (fixed and variable) Variable resistor

8. 8 Task 1: Read the resistor value Write down the colour code Check the table State the resistor value

9. 9 Series and Parallel connections R1R1 R1R1 R3R3 R2R2 R2R2 Three resistors in series. Total Resistance AB is AB PQ Two resistors in parallel Total resistance PQ is

10. 10 Exercise 1: Find the total resistance 30 KΩ A B 6.67 KΩ 60 KΩ PQ 40 KΩ Q1. 10 KΩ 30 KΩ 20 KΩ 40 KΩ Q2. Total resistance = R 1 + R 2 = 30 KΩ + 6.67K Ω = 36.67 k Ω P Q Total top series resistance = 10 K Ω + 30 K Ω = 40 K Ω Total bottom series resistance = 20 K Ω + 40 K Ω = 60 K Ω

11. 11 Voltage Divider 50K Voltage can be stepped down from 9 V to 3 V and 6V. By replacing the 10K resistor with a 50K variable resistor, we can vary the stepped down voltage. Va V1V1 R1R1 R2R2 I Or Va = IR 2

12. 12 Exercise 2: a) Device A has a voltage drop of 2 V across it and needs to draw a current of 4 mA. Suggest a suitable value for resistor R. Device A R 3V Voltage across resistor = 3 – 2 V = 1 V V=IR 1 = 0.004R R = 250 Ω b) What is the circuit arrangement below called? If A and C are connected across a 6 V battery, calculate the voltage at B if the variable resistor is set to (i) 5 kΩ (ii) 40 k Ω 10 k A B C Voltage divider or potential divider

13. 13  Electrically operated switch  Coil of wire and a metal lever which changes the position of the switch.  Advantage - permits a low voltage DC circuit to control a completely separate high-power circuit 2. Relay

14. 14  Transistors have many uses including switching, voltage/current regulation, and amplification  Two types NPN and PNP 3. Transistors

15. 15  Decreases as the temperature rises (negative temperature coefficient or ntc thermistor)  Increase in resistance with temperature. (positive temperature coefficient, or ptc thermistor) 4. Temperature Sensors (Thermistor)

16. 16  A LDR varies it resistance according to the amount of light falling on its surface.  Total darkness -1 MOhm  In bright light - a couple of kOhm. 5. Light Dependent Resistor (LDR)

17. 17 Identify the electronics symbols

18. 18