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Electronics and control systems

Every system has input → process → output, often with feedback.

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  1. PDFElectronics and control systems – Design and Technology notes (ZIMSEC O Level)47.5 KB

Systems

Every system has input → process → output, often with feedback.

Components

  • Input: switches (push, toggle), light-dependent resistor (LDR), thermistor (temperature), moisture sensor.
  • Process: transistor (switch/amplifier), integrated circuits such as the 555 timer, microcontrollers.
  • Output: LED, bulb, buzzer, motor, relay.
  • Power: batteries or solar panels.

Basic electricity

V = I × R. Resistors limit current. An LED needs a series resistor to prevent damage: R = (supply voltage − LED voltage) ÷ current.

Worked example: A 9 V battery lights an LED needing 2 V at 0.02 A. Find the series resistor.

R = (9 − 2) ÷ 0.02 = 350 Ω (use the next standard value, 390 Ω)

Circuit making

Breadboards for testing; stripboard or printed circuit boards (PCBs) for permanent circuits; soldering joins components.

Applications

Automatic night lights (LDR), temperature alarms, soil-moisture alarms for gardens, solar-powered phone chargers.

Exam tip: Always draw circuits with standard symbols and label component values.

Check yourself

  1. Name an input sensor that detects light.
  2. Why does an LED need a resistor in series?
  3. State the three parts of a system.
Show answers
  1. A light-dependent resistor (LDR).
  2. To limit the current so the LED is not damaged.
  3. Input, process and output.
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