What does the Edexcel Systems and mechanisms module cover?

It covers the input-process-output model and electronic components (sensors such as LDRs and thermistors, resistors, capacitors, diodes, LEDs, transistors and relays) with Ohm's law; digital logic (gates and truth tables) and programmable control with microcontrollers and PICs; mechanical devices and the four types of motion with levers, linkages, cams and followers; and gear trains and pulley systems with gear ratio, velocity ratio and mechanical advantage.

Which calculations come up most?

The LED series resistor (subtract the LED forward voltage from the supply, then divide by the current) using Ohm's law $V = IR$; the lever law (effort times effort arm equals load times load arm) and mechanical advantage; and gear and velocity ratios (driven over driver) with output speed equal to input speed divided by the ratio. Compound gear trains multiply the stage ratios. Practise these until automatic.

What is the difference between a logic gate and a microcontroller?

A logic gate (NOT, AND, OR, NAND, NOR) is a fixed component giving an output from its inputs, and a truth table lists every case. A microcontroller (a PIC is one family) is a programmable chip that reads inputs, processes them with a stored program and controls outputs. One microcontroller can replace many fixed components, and its behaviour is changed by reprogramming rather than rewiring.

How is this module examined?

Component 1 mixes calculation and explanation: sizing an LED resistor or a gear or lever system, completing or applying a truth table, mapping a product onto the input-process-output model with named components, and explaining the advantages of microcontrollers or the speed-torque trade-off of gearing. AO4 (technical knowledge) and the maths-in-context marks both feature heavily here.

How should I revise Systems and mechanisms?

Drill the LED resistor, lever, gear and velocity-ratio calculations separately until they are automatic. Learn the function of each electronic component and how to place them in the input-process-output model. Learn the logic gates and their truth tables, and the advantages of programmable control. For mechanisms, learn the four motions, the three lever classes, and how cams and gears change motion, speed and force.

EnglandProduct Design and Technologies

Edexcel A-Level Product Design Systems and mechanisms: a complete overview of electronics, logic, mechanisms and gear calculations

A deep-dive Edexcel A-Level Product Design guide to Systems and mechanisms. Covers electronic systems and components with Ohm's law, logic gates and microcontrollers, mechanical devices and types of motion, and gear, pulley and lever calculations, with the worked methods Edexcel repeats.

Generated by Claude Opus 4.817 min read9DT0Updated 2026-06-02

Reviewed by: AI editorial process; not yet individually human-reviewed

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What this module actually demands
Electronics and control
Mechanisms and gear calculations
How this module is examined
Check your knowledge

What this module actually demands

Systems and mechanisms is the most calculation-heavy technical module. It asks you to build electronic systems from input, process and output components, apply logic and programmable control, and analyse mechanical devices that change motion, speed and force. The examiners reward correct calculation method (clearly shown working) alongside accurate component and mechanism knowledge.

This guide walks through the topics in order and sets out the exam patterns Edexcel repeats. Each topic has a matching dot-point page with practice; this overview ties them together.

Electronics and control

Electronic systems and components use the input-process-output model: sensors (LDR, thermistor) and switches as inputs, resistors, capacitors, transistors and ICs as the process, and LEDs, buzzers and motors (often switched by a relay) as outputs, with Ohm's law $V = IR$ sizing the components. Programmable and logic systems cover the logic gates and truth tables, combining gates to make decisions, and microcontrollers and PICs that read inputs and drive outputs from a stored program, with the advantages of programmable over fixed control.

Mechanisms and gear calculations

Mechanical devices and motion cover the four types of motion, the three classes of lever with the lever law, linkages that change direction or magnitude, and cams and followers that convert rotary to reciprocating motion. Gears, pulleys and mechanical advantage cover gear trains and belt drives, the gear ratio and velocity ratio, how gearing trades speed for torque, compound gear trains, and mechanical advantage and efficiency.

How this module is examined

A typical Edexcel profile for Systems and mechanisms:

Electronic calculation. Size an LED series resistor or find a resistance with Ohm's law.
Logic. Complete or apply a truth table; choose AND or OR for a requirement.
Mechanisms. Apply the lever law; identify motion types and lever classes.
Gearing. Calculate gear or velocity ratio and output speed, and explain the speed-torque trade-off.

Check your knowledge

A mix of recall and calculation questions covering the module. Attempt them under timed conditions, then check against the solutions.

A $6$ V supply drives an LED needing $2.0$ V at $20$ mA. Find the series resistor. (2 marks)
State the output of an AND gate when its inputs are 1 and 1, and when they are 1 and 0. (2 marks)
State the four types of motion. (2 marks)
A wheelbarrow load of $500$ N acts $0.30$ m from the wheel; the handles are $1.2$ m from the wheel. Find the effort. (2 marks)
A $16$ -tooth driver gear meshes with a $48$ -tooth gear. State the gear ratio and what happens to output speed. (2 marks)
Give one advantage of a microcontroller over fixed logic circuits. (1 mark)

Sources & how we know this

Pearson Edexcel A-Level Design and Technology: Product Design (9DT0) specification — Pearson Edexcel (2017)