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D & T Design Lesson

D & T Design Lesson. Technological Areas - Electronics. Sec 3B By: MdmLee Kah Gek. Technological Areas. Electronics. Structures. Mechanisms. Electronics Module. Objectives. Know basic electronics components and its function ( Res, var res, relay, transistor, temp sensor and light sensor)

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D & T Design Lesson

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

  2. Technological Areas Electronics Structures Mechanisms

  3. Electronics Module

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

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

  6. Switches • Samples of switches

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

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

  9. Series and Parallel connections R1 R2 R3 R1 A B P Q Three resistors in series. Total Resistance AB is R2 Two resistors in parallel Total resistance PQ is

  10. 40 KΩ 30 KΩ 6.67 KΩ A B P Q 60 KΩ 30 KΩ 10 KΩ 20 KΩ 40 KΩ Exercise 1: Find the total resistance Q1. Total resistance = R1 + R2 = 30 KΩ + 6.67K Ω = 36.67 k Ω Q2. P Q Total bottom series resistance = 20 K Ω + 40 K Ω = 60 K Ω Total top series resistance = 10 K Ω + 30 K Ω = 40 K Ω

  11. 50K Voltage Divider I V1 R1 Va R2 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. Or Va = IR2

  12. Device A 3V R A B C 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. 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 Voltage divider or potential divider 10 k

  13. 2. Relay • 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

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

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

  16. 5. Light Dependent Resistor (LDR) • 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.

  17. Identify the electronics symbols

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