How is a complete electronic system designed as subsystems, built, tested and evaluated for the non-exam assessment?
System design and realisation: the systems approach (input, process, output and power subsystems), block diagrams, systematic testing and fault-finding, evaluation against a specification, and health and safety.
An Eduqas A-Level Electronics answer on system design and realisation for the non-exam assessment: the systems approach of input, process, output and power subsystems, block diagrams, systematic testing and fault-finding, evaluating a build against its design specification, and health and safety in construction.
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What this dot point is asking
Eduqas wants you to apply the systems approach (input, process, output and power subsystems), draw block diagrams, test and fault-find systematically, evaluate a build against its specification, and work safely. This is the method behind the Component 3 extended design-and-realisation non-exam assessment.
The answer
The systems approach and block diagrams
Designing each subsystem
Systematic testing and fault-finding
Evaluation, specification and safety
Examples in context
The systems approach is the backbone of the Eduqas Component 3 non-exam assessment, in which a student designs, builds, tests and evaluates a substantial integrated electronic system that solves a real problem. It is also how professional engineers manage complexity: a product is specified, broken into subsystems, each is designed from standard building blocks (the sensing, processing, output and power topics of this course), and the whole is tested systematically and evaluated against the specification. This dot point ties every earlier module together into a working product.
Try this
Q1. Name the four subsystems of the systems approach to an electronic product. [2 marks]
- Cue. Input (sensing), process (decision), output (actuator), and power.
Q2. State why a system should be tested subsystem by subsystem rather than all at once. [1 mark]
- Cue. It makes faults far easier to locate (you find which block fails).
Q3. State one health and safety consideration when building an electronic system. [1 mark]
- Cue. Use the soldering iron safely (or take care with mains voltages, or wear eye protection when cutting/drilling).
Exam-style practice questions
Practice questions written in the style of WJEC Eduqas exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Eduqas 20206 marksExplain the systems approach to designing an electronic product, using the example of an automatic night light, and draw or describe its block diagram.Show worked answer →
Systems approach (up to 3 marks): a system is broken into subsystems connected as a block diagram: an input (sensing) subsystem, a process (decision) subsystem, an output subsystem, and a power subsystem supplying them all. Designing each block separately and defining the signals between them makes a complex product manageable and testable.
Night-light blocks (up to 3 marks): the input is a light-dependent resistor in a potential divider (sensing the light level); the process is a comparator or microcontroller that decides when it is dark enough; the output is a transistor driving the lamp; and the power subsystem is the supply. The block diagram is: power supply feeding all blocks, and signal flowing LDR divider, comparator/microcontroller, transistor driver, lamp.
Markers reward the input-process-output-power subsystem structure with a block diagram, and the correct night-light blocks (LDR sensing, comparator/microcontroller decision, transistor-driven lamp).
Eduqas 20225 marksDescribe how a student should test and evaluate a built electronic system for the non-exam assessment, and state two health and safety considerations during construction.Show worked answer →
Testing and evaluation (up to 3 marks): test systematically, subsystem by subsystem, checking each block produces the expected output for known inputs before testing the whole system, using a multimeter or oscilloscope to find faults. Then evaluate the finished system against the design specification: does it meet each requirement, how accurate and reliable is it, and what improvements could be made. Record measurements and compare them with the targets.
Health and safety (up to 2 marks): two valid points are using a soldering iron safely (heat-proof surface, fume extraction, return it to its stand), and taking care with mains voltages (isolate and enclose any mains wiring, use a fuse). Other valid points: eye protection when cutting or drilling, and avoiding short circuits that overheat components.
Markers reward systematic subsystem testing with instruments, evaluation against the specification, and two valid health and safety points.
Related dot points
- Microcontroller architecture: the CPU, memory and input/output ports, digital input and output pins, pull-up and pull-down resistors, and the analogue-to-digital converter and PWM peripherals.
An Eduqas A-Level Electronics answer on microcontroller architecture and interfacing: the CPU, memory and input/output ports, digital input and output pins with pull-up and pull-down resistors, and the built-in peripherals (analogue-to-digital converter, PWM, timers) that connect the microcontroller to the real world.
- Assembly language programming: instructions and registers, reading inputs and writing outputs, branching and loops, delays, and the program development cycle (flowchart, code, assemble, test).
An Eduqas A-Level Electronics answer on assembly language programming: instructions and registers, reading input pins and writing to output pins, branching and looping for decisions and repetition, generating delays, and the flowchart-code-assemble-test development cycle required for the non-exam assessment.
- Interfacing a microcontroller: input interfacing (signal conditioning, switch debouncing, the ADC), output interfacing (transistor and MOSFET drivers, relays, motor control with PWM and an H-bridge), and the closed-loop control system.
An Eduqas A-Level Electronics answer on interfacing a microcontroller: conditioning and reading sensor inputs (including switch debouncing and the ADC), driving outputs safely through transistor, MOSFET and relay drivers, controlling motor speed and direction with PWM and an H-bridge, and the structure of a closed-loop control system.
- Mains power supply systems: the transformer, rectifier, reservoir smoothing and regulation stages, ripple voltage, and series and switch-mode regulators.
An Eduqas A-Level Electronics answer on mains power supply systems: the transformer that steps down mains voltage, the bridge rectifier, the reservoir capacitor and ripple, voltage regulation with a Zener or series regulator, and the efficiency advantage of a switch-mode supply.
Sources & how we know this
- Eduqas GCE AS/A Level Electronics specification (A410QS) — WJEC Eduqas (2017)