What is the systems approach to designing electronic products, and how do block diagrams and feedback work?
The systems approach to designing: the input, process and output model, representing systems with block diagrams, breaking products into sub-systems, the role of programmable components and microcontrollers, and feedback in control systems.
A focused answer to Eduqas GCSE Design and Technology (C600) on the systems approach to designing: the input, process and output model, block diagrams, sub-systems, microcontrollers and feedback in control systems.
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What this dot point is asking
Eduqas C600 expects you to understand the systems approach to designing electronic products: the input, process and output model, how to draw a block diagram, how to break a product into sub-systems, the role of programmable components and microcontrollers, and feedback in control systems. In the written exam this is tested by describing the three blocks for a named product and by Explain questions on the advantages of a microcontroller.
The input, process, output model
Thinking in blocks is powerful because it separates what the product should do from how each part is built. You decide the behaviour (when it gets dark, turn on a light), draw the three blocks, then choose a sensor, a control circuit and an output to fill them.
A block diagram can also show sub-systems: a complex product (an alarm) is broken into smaller systems (a sensor sub-system, a timing sub-system, a sounder sub-system), each designed and tested separately, then connected. This makes a large design manageable.
Programmable components and microcontrollers
Microcontrollers have transformed product design. Instead of building decision-making from many fixed parts (logic gates, timers, counters), a single chip runs software that can be changed. Advantages are a simpler, smaller and cheaper circuit, complex behaviour (timing, counting, decisions) in software, and reprogrammability (update or repurpose the product without rewiring). This is why so many modern products are "smart".
Feedback
Feedback turns an open system into a self-regulating one. A thermostat is the classic example: it senses temperature (input), compares it with a target (process), switches the heater (output), and the resulting temperature change feeds back to the sensor, so the heater cycles on and off to hold the target. Without feedback the system would heat continuously.
Try this
Q1. State which block of a system an LED belongs to. [1 mark]
- Cue. The output (it produces the effect).
Q2. Give one advantage of a programmable microcontroller over fixed components. [1 mark]
- Cue. It replaces many components and can be reprogrammed to change function without rewiring.
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 C600 20183 marksDescribe the three parts of a systems block diagram and give an example of each for an automatic night light.Show worked answer →
A 3-mark question, one mark for each block correctly described with a suitable example.
Input: the part that senses a condition. For a night light, the input is a light sensor (a light-dependent resistor, LDR) that detects darkness.
Process: the part that decides what to do with the input. For a night light, the process is a control circuit or microcontroller that switches the light on when the LDR reads dark.
Output: the part that produces the effect. For a night light, the output is an LED (or lamp) that lights up.
Markers reward the three blocks in order (input senses, process decides, output acts) with a matching example for the night light (LDR, control circuit, LED). Getting the order wrong or giving no example loses marks.
Eduqas C600 20214 marksExplain two advantages of using a programmable microcontroller in an electronic product instead of fixed components.Show worked answer →
A 4-mark Explain wants two developed advantages of a microcontroller.
Advantage 1, fewer components and smaller products. One programmable microcontroller can replace many fixed components (timers, logic gates, counters), so the circuit is simpler, smaller and often cheaper to manufacture.
Advantage 2, reprogrammable and flexible. The same chip can be reprogrammed to change how the product behaves without redesigning or rewiring the circuit, so a product can be updated or a single design reused for several functions.
Other valid points: complex decisions and timing in software, easier to modify during development. Markers reward two developed advantages (replaces many parts; reprogrammable without rewiring). Two bare statements cap the mark at two.
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Sources & how we know this
- WJEC Eduqas GCSE (9-1) Design and Technology (C600) specification — WJEC Eduqas (2017)