Applications of Electronics · SHS3 Physics

Lesson notes

Learning Objectives

Indicator: 3.3.4.LI.1 - Design a darkness detector.

By the end of the lesson, learners can:

Explain the function of each component in a darkness detector circuit (light-dependent resistor, transistor, variable resistor, and relay or LED).
Design a complete darkness detector circuit using a solar panel or LDR, showing correct component placement and connections.
Predict what happens to the output (LED on or off) when light intensity on the sensor increases or decreases, giving reasons based on the behaviour of the components.
Construct a working darkness detector on a breadboard from a circuit diagram in small groups.
Evaluate their own and peers’ designs, identifying at least one improvement that could make the detector more sensitive or reliable.

The lesson builds directly on learners’ knowledge of transistors (PNP and NPN amplifiers) from Week 14 and prepares them for the battery charger design in Week 16, which also uses sensing and switching principles.

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Curriculum details

Strand: Electric Field, Magnetic Field and Electronics (Strand 3)
Sub-strand: Applications of Electronics (3.4)
Content standard: 3.3.4.CS.3 - Demonstrate knowledge and understanding of darkness detector circuit. 3.3.4.LO.3 Using a solar panel explain how a darkness detector works.
Indicator: 3.3.4.LI.1 - Design a darkness detector.
Suggested placement: Semester 2, Week 15 (Week 35 of the year)
Our suggestion, laid out in curriculum order across three terms of twelve weeks. NaCCA does not fix the week, so follow your school's scheme of learning.
Curriculum reference: NaCCA curriculum document, p. 195

Exemplars (from the NaCCA curriculum)

Collaborative learning: Using simulations and multimedia, let learners watch a video/simulation of how a darkness detector is built.
Foster an inclusive and respectful classroom culture and address bias in teaching materials and examples.
Assessment (3.3.4.AS.1). The document marks these depth-of-knowledge levels for this indicator: Level 4 Extended critical thinking and reasoning.
Teaching and Learning Resources:
- Audio-visuals
- Internet
- Projectors
- YouTube
- Reference books
- Flash cards
- Field trips or visits