Key term
CCEA A-Level Technology and Design 8900
Material Selection and Wood
Metals
Plastics
Composite and Emerging Materials
Processing Materials
Product Analysis and Design Communication
Design for Manufacture, Quality and Safety
Electronic Control SystemsOption A
Topic overviewControl systems, feedback and electronics safetyResistors, Ohm's law and power ratingsCapacitors and RC timingPotential dividers, sensors and comparatorsSwitches, pull-up and pull-down resistorsOutput devices and LEDsTransistors, Darlington pairs and thyristorsLogic gates, truth tables and flip-flops555 monostable and astable timers
Microelectronic Control SystemsOption A
Topic overviewMicrocontroller systems, ADCs and DACsStrain gauges and bridge circuitsOptical switches, encoded discs and Schmitt triggersOp-amp amplifiers and gainZener diodes and voltage regulatorsKarnaugh maps and binary countersSeven-segment, LCD and dot matrix displaysPIC flowcharts and programmingDC motors, stepper motors and driver circuits
Mechanical and Pneumatic ComponentsOption B
Topic overviewOpen and closed loop mechanical and pneumatic controlSafe working with compressed air and mechanismsLevers, linkages and momentsGear types and gear trainsPulleys, belts, chains and shaft fixingsCams, cranks and converting motionCompressed air supply and pneumatic valvesCylinders, shuttle valves, restrictors and reservoirsPneumatic circuits for logic, timing and speed control
Mechanical and Pneumatic SystemsOption B
Topic overviewHydraulics, system limitations and plant safetyTorque, work, power and air consumptionVacuum handling, proximity sensors and 5/3 valvesSequential and cascade pneumatic circuitsCam profiles and follower displacement diagramsGear geometry, pulley blocks and ratchetsToggles, treadles, shafts and couplingsFriction, brakes and clutchesBearings, lubrication and seals
Designing and Manufacturing ProductsOption C
Topic overviewResearch, questionnaires and specificationsIdea generation, critiques and computer simulationManufacturing planning and product evaluationCFRP, GRP, Kevlar and tungsten carbideSmart materials, nanotechnology and biophotovoltaicsIsometric, perspective and assembly drawingLaminating, steam bending, cutting and printing processesRisk assessment and product safety lawScales of production, JIT and cell productionQuality assurance, ISO 9001 and continuous improvementDesign influences and intellectual property rights
Product Design in Industry and SocietyOption C
Topic overviewLife-cycle environmental impact and climate changeThe 6Rs, waste and environmental legislationSustainable metals, plastics and degradable polymersProduct life cycles, consumer types and relaunchesCAD, CAM, 3D scanning and quick-change mouldingMarket pull, technology push and market strategyPrice, place and promotionJigs, fixtures and ICT in quality controlDesign for maintenance, inclusion and scale productionRendering, typography and presentationDyson, Baylis, Memphis and Apple
Product Development
Product and System Design and Manufacture
Microelectronic Control Systems
DC motors, stepper motors and driver circuits
- 3 things to know
- A2 1
Overview
DC motor characteristics and speed control, stepper motors with worked step and speed calculations, holding torque, driver ICs such as the ULN2803, H-bridges and motor supplies.
What you need to know
Answer each one before you reveal it.
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Key term
How can a PIC control the speed of a DC motor?
Key term
How does a stepper motor move?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Describe the main characteristics of a DC motor.
Model answer
A DC motor turns continuously at high speed, and its speed falls as the load rises. The motor usually needs a gearbox to give useful torque.
- 2
How can a PIC control the speed of a DC motor?
Model answer
The PIC switches the motor on and off rapidly, varying the mark/space ratio. A higher ratio gives a higher average voltage and a faster motor.
- 3
How does a stepper motor move?
Model answer
A stepper motor turns in fixed angular steps as its coils are energised in sequence. The sequence run backwards turns the motor the other way.
- 4
A stepper motor has a step angle of 1.8°. How many steps make one revolution?
Model answer
One revolution takes 200 steps. 360° ÷ 1.8° = 200 steps.
- 5
A 1.8° stepper motor must turn a shaft through 90°. How many steps are needed?
Model answer
The motor needs 50 steps. 90° ÷ 1.8° = 50 steps.
- 6
A 200-step motor receives 100 steps per second. Calculate its speed in rpm.
Model answer
The motor turns at 30 rpm. 100 ÷ 200 = 0.5 revolutions per second, and 0.5 × 60 = 30 rpm.
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