Electronic Systems and Programmable Components
Electronic Systems and Programmable Components
AQA GCSE D&T requires understanding of basic electronic circuits, components, and how programmable devices (such as microcontrollers) are used in modern products. You need to know component functions, circuit construction, and how to apply electronics in design contexts.
Electronic Components
Electronic components are categorised by their function within a system.
Input Components (Sensors and Switches):
| Component | Function | Symbol Description |
|---|---|---|
| Switch (toggle, push, slide, tilt) | Manually opens/closes a circuit | Break in line with connection |
| LDR (Light Dependent Resistor) | Resistance decreases as light intensity increases | Resistor with arrows pointing in |
| Thermistor (NTC) | Resistance decreases as temperature increases | Resistor with line through it |
| Potentiometer | Variable resistor — user adjusts resistance manually | Resistor with arrow (wiper) |
| Microphone | Converts sound waves to electrical signals | — |
| Piezoelectric sensor | Generates voltage when mechanically stressed | — |
Process Components:
| Component | Function |
|---|---|
| Resistor (fixed) | Limits current flow; measured in ohms (Ω) |
| Capacitor | Stores and releases electrical charge; used in timing circuits |
| Diode | Allows current to flow in one direction only |
| Transistor (NPN) | Acts as an electronic switch — small base current switches on a larger collector current |
| 555 Timer IC | Integrated circuit used for timing pulses (monostable) or continuous oscillation (astable) |
| Microcontroller (e.g. Arduino, PIC, micro:bit) | Programmable chip that reads inputs, processes data, and controls outputs |
Output Components:
| Component | Function |
|---|---|
| LED (Light Emitting Diode) | Emits light when current flows through it; needs a series resistor |
| Buzzer / speaker | Converts electrical signals to sound |
| Motor (DC) | Converts electrical energy to rotary motion |
| Solenoid | Converts electrical energy to linear motion (push/pull) |
| Relay | Electromagnetic switch — small current controls a larger current circuit |
Circuit Fundamentals
Ohm's Law: V = I × R
- V = Voltage (volts, V) — the "push" driving current around a circuit
- I = Current (amps, A) — the rate of flow of charge
- R = Resistance (ohms, Ω) — opposition to current flow
Series circuits:
- Components connected end-to-end in a single path
- Total resistance = R1 + R2 + R3...
- Current is the same through all components
- Voltage is shared between components
Parallel circuits:
- Components connected across each other, providing multiple paths
- Total resistance is less than the smallest individual resistance
- Voltage is the same across all branches
- Current splits between branches
Calculating LED Resistor Value
When connecting an LED, you must include a current-limiting resistor to prevent burnout.
R = (Supply Voltage − LED Forward Voltage) ÷ LED Current
Example: 9V supply, red LED (forward voltage 2V, current 20mA):
R = (9 − 2) ÷ 0.02 = 350Ω → use the next standard value up: 390Ω
Programmable Components
Microcontrollers are the most important programmable components in GCSE D&T. They are small computers on a single chip that can be programmed to read inputs and control outputs.
Advantages of microcontrollers:
- Can perform complex logic and decision-making
- Easily reprogrammed to change behaviour without rewiring
- Compact size, low cost, low power
- Can control multiple outputs from multiple inputs simultaneously
- Enable smart, responsive products
Common microcontrollers for GCSE:
- Arduino — open-source, C++ programming, wide sensor support
- BBC micro:bit — block-based or Python programming, built-in sensors
- PIC — commonly referenced in exam specifications
- Raspberry Pi Pico — MicroPython, more processing power
Programming Concepts
You should understand basic programming concepts used with microcontrollers:
- Sequence — instructions executed one after another in order
- Selection (IF/ELSE) — decisions based on conditions (e.g. IF temperature > 30 THEN turn on fan)
- Iteration (loops) — repeating instructions (e.g. WHILE button pressed, flash LED)
- Variables — stored values that can change (e.g. counter, temperature reading)
Flowchart representation is commonly used in exams to describe microcontroller programs. Use standard symbols: oval (start/end), rectangle (process), diamond (decision), parallelogram (input/output).
Practical Applications
| Product | Input | Process | Output |
|---|---|---|---|
| Automatic night light | LDR detects darkness | Microcontroller compares light level to threshold | LED switches on |
| Greenhouse ventilation | Thermistor detects high temp | Microcontroller activates when temp > set point | Motor opens vent |
| Intruder alarm | PIR sensor detects motion | 555 timer triggers monostable pulse | Buzzer sounds for set time |
| Smart thermostat | Thermistor + user input | Microcontroller with feedback loop | Heater on/off, display updates |
Printed Circuit Boards (PCBs)
PCBs provide a permanent, reliable platform for electronic circuits:
- Single-sided — copper tracks on one side only (simple circuits)
- Double-sided — tracks on both sides with through-hole connections
- Surface mount (SMD) — miniature components soldered directly to the surface (used in phones, laptops)
PCB manufacture: design in CAD → print onto copper-clad board → etch unwanted copper → drill holes → solder components.
Exam Tips
- Draw circuit diagrams using correct symbols — marks are lost for incorrect or missing symbols
- Always show resistor calculations with the formula and working
- When describing a microcontroller system, name specific components at each stage (not just "sensor" — say "LDR" or "thermistor")
- For programming questions, use flowcharts with correct symbols and clear logic
- Know the difference between series and parallel circuits and when each is appropriate
- If asked to choose between a dedicated circuit (e.g. 555 timer) and a microcontroller, discuss flexibility vs simplicity
Key Definitions
- Microcontroller: A small programmable computer on a single integrated circuit, capable of reading inputs and controlling outputs
- Ohm's Law: The relationship V = I × R, linking voltage, current and resistance
- PCB: A board with conductive copper tracks that connects electronic components without loose wiring
- Transistor: A semiconductor device used as an electronic switch or amplifier
- Integrated circuit (IC): A miniaturised circuit containing multiple components on a single chip