Chapter 30: Mechanisms
Linear Motion: Movement in a straight line, like a train on a straight track.
Rotary Motion: Movement around a circle or turning, such as a wheel turning.
Reciprocating Motion: Back-and-forth movement in a straight line, like a jigsaw blade.
Oscillating Motion: Swinging from side to side in an arc, like a swing or pendulum.
Different mechanisms are employed for specific applications:
Screw: Converts rotary motion to linear motion. It's non-reversible, meaning pushing a screw won't turn it. Applications include G-clamps, bench vices, car jacks, and bolt and nut systems.
Spur Gears (straight teeth): Change the speed and direction of rotary motion, with speed determined by the gear ratio. Used in simple machinery, clocks, and watches.
Gear Ratio: Calculated as the number of teeth in the driven gear divided by the number of teeth in the driver gear.
Helical Gears: Have angled teeth, providing smoother and quieter operation than spur gears. Found in gearboxes of cars, vehicles, and machines. They are stronger because multiple teeth engage simultaneously.
Bevel Gears: Change the angle of rotation by 90 degrees and alter speed based on the gear ratio. Applications include hand drills, hand whisks, and differential drives for cars.
Worm Drive: Used for raising heavy loads without slipping or reversing. It's non-reversible, meaning the worm can turn the worm wheel, but not vice-versa. It has a high gear ratio (one full turn of the worm rotates the worm wheel by one tooth). Applications include guitar string tuners, tightening ropes, and reducing the speed of electric motors.
Ratchet and Pawl: Allows movement in only one direction, with the pawl preventing the ratchet gear from slipping back. Used in turnstiles, ratchet spanners, bicycle rear axles, and tensioning clotheslines or sports nets.
Rack and Pinion: A round gear (pinion) moves a toothed bar (rack) in a line, changing rotary motion to linear motion. Applications include car steering and raising heavy loads or drill tables.
Gear Trains and Idler Gears: A gear train involves two or more meshed gears. Idler gears only change the direction of motion and do not affect the speed of the gear train.
Compound Gears: Smaller gears drive larger ones to reduce speed, enabling greater torque and power changes. They consist of a smaller and a larger gear rotating on the same axle.
Gearbox: A set of differently-sized pairs of gears used in cars and machines to change output speeds and direction. A clutch is typically used before the gearbox to engage desired gears by sliding them on their axles.
Chain and Sprocket (Chain Drive): Uses a roller chain to connect two gears (sprockets). They are strong, don't slip easily, and require lubrication. Applications include bicycles, car timing chains, and forklifts.
Caterpillar Tracks: Large plated chains used to drive over rough ground, preventing obstacles from getting stuck or the vehicle from being grounded. Used in military tanks, space exploration vehicles/robots, and bomb disposal robots.
Simple Pulley: A rope or belt passes around a pulley wheel. More pulley wheels increase power. Used for raising heavy loads, sails, and window blinds.
Belt Pulley Drive: Transmits rotary motion using a belt tensioned between two pulley wheels. Lighter, quieter, and cheaper than chains, with no lubrication. Can slip. Used in domestic appliances like washing machines, driers, Hoovers, food processors, sewing machines, and toy cars.
V-Belt Pulley Drive: Uses a V-shaped belt and wheels to prevent the belt from coming off. If a V-belt moves sideways, it tightens. Used in industrial and machine tools, drills, and lathes.
Toothed Belt Pulley Drive: Uses a toothed belt and gears to prevent slipping. Applications include car timing belts and printers.
Poly-Vee Pulley Drive: Uses a wider belt with multiple V shapes for more grip, handling heavier loads. Used in lathes and large industrial machinery.
Variable Speed Pulley Drive: Can change speed by moving the belt to different-sized pairs of pulley wheels. Used in lathe and bench drill speed control.
Cam and Follower: Changes motion from rotary to reciprocating. A cam is an irregular rotating shape, and a follower traces its edge. Used in car engines (camshaft and valves), textile weaving machines, and printing machines.
Camshaft and Valves: A camshaft, consisting of one or more cams attached to the same axle, rotates in sync with the pistons in petrol engines. Valves (on springs) act as cam followers, opening and closing to allow fuel and gases in and out of the combustion chamber.
Crank and Slider: Converts rotary motion to regular reciprocating motion and vice versa. Used in air compressors to create a pumping action.
Quick-Return Mechanism (Peg-and-Slot Mechanism): Creates irregular reciprocating motion where the cutting tool moves faster on the cutting stroke than on the return stroke. Used in shaping machines.
Universal Joint (UJ): Allows a rotating shaft to have a 'bend' or 'hinge' while continuing to rotate. Made from two hinges at 90 degrees. Used in car transmissions to allow wheels to move up and down while connected to the drive shaft, and in farm machinery to connect a drive shaft from a tractor to a moving trailer.
Clutch: Two plates that can be engaged and disengaged to transmit rotation or not, and to gradually match two different speeds using friction. In cars, it disconnects the engine from the gearbox, allowing speed changes and stopping the car with the engine running.
Linkage: A set of connected levers used to transmit linear motion over a distance. A reverse-motion linkage changes a push to a pull (and vice versa).
Parallel Motion Linkage: Used to keep objects parallel. Found in toolboxes to allow storage trays to open out sideways.
Scissors Linkage: A squeezing motion at one end causes the other end to extend out at 90 degrees (and vice versa). Advantageous for lifting platforms as the mechanism doesn't need to be higher than the platform itself. Also used in shaving mirrors.
Toggle Mechanism: A set of linkages where a small applied force creates a larger force. When the middle linkage moves past its midpoint, it locks, making it suitable for clamps. Used in vice grips, toggle clamps, and window latches.
Ball Bearings: Reduce friction between rotating parts using hard steel balls between the inside (axle) and outside (axle support). Used in car wheels, bicycle wheels, and skateboard wheels.
Roller Bearings: Use cylindrical rollers instead of balls. They can support heavier loads and are quieter. Used in machine tools and fans.
Thrust Bearings: Allow one part to rotate on top of another without an axle. Used in rotating bar stools, turntables, turning robots, and roulette wheels.
When selecting and designing with mechanisms, it's noted that mechanisms are often powered by electric motors, and a DPDT switch can reverse the motor's direction.
Here are mechanical solutions for common design problems:
Raise a Load or Platform:
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Rack and Pinion: A motor turns a pinion gear, raising a vertical rack. If a worm drive is used to turn the pinion, the load won't slip back.
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Screw Mechanism plus Scissors Linkage: A motor turns a screw mechanism, pulling the bottom ends of a scissors mechanism closer, causing it to extend vertically.
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Hydraulic Ram and a Linkage: The hydraulic ram extends, raising the object via a linkage.
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Chain Drive: Sprockets turn and raise a chain attached to the platform.
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Simple Pulley: A motor turns a cylinder (via a worm drive) which winds in a cable that runs over a high pulley wheel and is attached to the load.
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Holes and Pegs: For adjustable heights, supporting pegs are placed into holes at different heights.
Make a Turnstile:
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Ratchet and Pawl: The turnstile axle is attached to a ratchet, and the pawl prevents it from turning backward.
Tighten Ropes, Clothes Lines, Sport Nets:
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Ratchet and Pawl: A cylinder is turned by hand or motor to wind up a cable. The cylinder is attached to a ratchet and pawl, preventing it from unwinding.
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Worm Drive: A cable-winding cylinder is turned by a worm drive, preventing it from being reversed or unwound by cable pressure. A worm drive has a high gear ratio.
Move a Robot Arm:
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Worm Drive: A worm drive has a high gear ratio, allowing for small arm movements. The arm won't move when the motor is off.
Rotate a Display:
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Worm Drive: A worm drive has a high gear ratio, creating slow turning speeds from an electric motor.
Open Swing Doors or Sliding Doors:
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Gear Train or Worm Drive: A gear attached to the door axles is turned by an electric motor via a worm drive.
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Rack and Pinion: The rack is attached to the sliding doors. A motor turns the pinion via a worm drive to reduce speed.
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Toothed Pulley Drive: Doors could hang from the straight portion of a toothed pulley belt, powered by a motor and worm drive.
Clamp Items:
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Toggle Mechanism: When moved past its mid-point, it locks, preventing it from being forced open by the clamped item.
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Screw Mechanism: The screw tightens two plates against the item. Used in C-clamps, bench vices, and chucks.
Steer Vehicles:
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Rack and Pinion: The steering wheel turns a pinion gear, moving the rack sideways, which in turn moves the wheels via linkages.
Provide Drive to Wheels:
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Gear Train: A motor or engine turns the wheels via a gear train. Compound gears or a worm drive can reduce electric motor speed.
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Pulley Drive: Wheels can be connected to the motor/engine via a pulley belt drive, with the smaller pulley on the motor side.
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Universal Joint: The motor/engine turns the input shaft of a universal joint. The output shaft rotates the wheel axles via bevel gears, allowing wheels to move up and down on suspensions.
Independent Drive to Each Wheel:
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Multiple Motors: Each wheel can be powered by its own motor.
Reduce Wheel Friction:
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Ball Bearings or Roller Bearings: Wheel axles rotate on the inside of bearings, and the outside is attached to the vehicle body or wheel suspensions. Roller bearings support heavier loads than ball bearings.
Allow a Platform to Rotate Freely:
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Thrust Bearing: The bottom of the thrust bearing is fixed to the housing/casing, and the rotating platform is mounted on top.
Create Reciprocating Motion:
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Crank & Slider: Creates an even reciprocating movement.
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Quick-Return Mechanism: Uses a peg-and-slot mechanism, moving faster in one direction than the return.
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Cam and Follower: Creates regular or irregular reciprocating movement. The follower needs to be kept on the cam using gravity or a spring.
Chapter 31: Electronics
Chapter 31:
1. Electrical Terms
Electricity: Energy caused by the movement of electrons, which are tiny charged particles found in the atoms of all materials
. Current (Amps - A): The amount of electrons flowing from one place to another in a given time. Current is measured by an Ammeter
. Voltage (Volts - V): The driving force that causes electric current to flow, measured between two points by a Voltmeter
. Resistance (Ohms - Ω): How easily electric current flows through a material
. Ohm's Law: Current = Voltage divided by Resistance. For the same voltage, the lower the resistance, the higher the current
. Conductor: Has low resistance to current. Metals are good conductors
. Insulator: Has high resistance to current. Plastics and ceramics are good insulators
. Semiconductor: Has a medium resistance to current. Silicon is a well-known semiconductor used to make devices such as transistors, diodes, and integrated circuits
. Power (Watts - W): The amount of electrical energy transferred per second, calculated by multiplying voltage by current
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2. Types and Sources of Electricity
Alternating Current (AC): Voltage and current continually reverse direction many times a second. Mains electricity (220 Volts AC) is an example, which is dangerous but powerful and loses less energy when transported over long distances
. Direct Current (DC): Voltage remains constant, and current flows in one direction only. Low-voltage DC is used in electronic devices and is safe to touch.
Power Supply: Converts high-voltage AC to low-voltage DC (e.g., phone charger)
. Battery: Supplies a few volts DC, enough to power electronic devices like phones and laptops
. Solar Cell: Converts light energy into low-voltage DC electrical energy
. Fuse: A safety device that "blows" (melts a thin wire) to stop current flow if too much current passes through it
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3. Switches
SPST Toggle Switch (Single-Pole, Single-Throw): A simple on/off switch with two connections. One position closes the circuit, and the other opens it
. Push Button Switch (PTM/PTB): Contains an internal spring and only stays pushed in while held. Push-To-Make (PTM) closes the circuit when pushed, while Push-To-Break (PTB) opens it when pushed
. DPDT Switch (Double-Pole, Double-Throw): Composed of two internal switches operated simultaneously. Each internal switch has one input and two outputs, totaling six connections
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4. Resistors
Fixed Resistors: Limit current flow and are made in fixed values, indicated by colored bands
. Variable Resistors: Their resistance can be changed by turning a knob or screw, ranging from zero ohms to a maximum value written on the component
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5. Capacitors
Store small amounts of electrical charge (electrons)
. Used in timer circuits because they take time to charge
. Some are polarized, meaning they have a positive and negative connection and only work when connected correctly
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6. Diodes, Transistors, and Integrated Circuits
Diode: Allows current to flow in only one direction (polarized). Used in rectifier circuits to convert AC voltage into DC voltage
. Transistor: Can act as an electronic switch or amplify an electrical signal. A small current at the base becomes a larger current flowing from collector to emitter
. Darlington Pair: Consists of two transistors connected so the output of the first becomes the input to the second, providing very high current gain (amplification)
. Integrated Circuit (IC): A complete electronic circuit built into a single piece of semiconductor (e.g., silicon). ICs are smaller, cheaper, and faster than circuits made from individual components and can contain millions of transistors. They are the "brains" of most electronic devices like phones, computers, cars, and washing machines
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7. Light and Sound Output
Bulb: Emits light and heat when current passes through it. Not energy-efficient, and contains a tungsten wire in a vacuum
. Light-Emitting Diode (LED): Energy-efficient, works with low DC voltage, and is polarized. Commonly used as "power on" indicators in circuits
. Buzzer: Emits a fixed sound when activated by a certain voltage
. Bell: A type of buzzer that emits a ringing sound
. Siren: A loud device, typically used in house alarms
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8. Input Sensors
Light-Dependent Resistor (LDR): Resistance is high in darkness and low in light. Used in darkness/light detection circuits
. Thermistor (Heat-Dependent Resistor): Resistance is high in cold and low in heat. Used in heat/cold detection circuits
. Thermocouple: Used to measure temperature. A junction of two different metals generates a voltage between them, which depends on the temperature difference. Used to measure furnace temperatures
. Thermostat: An electronic circuit that keeps a system at a constant temperature. It detects the temperature, compares it against the desired temperature, and turns heating on or off accordingly
. Bimetallic Strip (or Bimetal): Detects temperature by bending. Consists of two strips of different metals (e.g., copper and steel) that expand at different rates when heated, causing the strip to bend and activate a switch (e.g., in a thermostat or fire alarm)
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9. Electromagnetic Devices
Electric Motor: Converts electrical energy into mechanical energy (rotation). Can be AC or DC. The rotation of a DC motor can be reversed by reversing the direction of the current through it
. Solenoid: Contains a coil of wire that creates a magnetic field when current passes through it, attracting a metal bar into the coil. When current is switched off, a spring returns the bar to its original position. Used in electrically-operated door locks and valves
. Relay: An electrically-operated switch that uses a magnetic field to mechanically open and close a separate electrical circuit. A low-voltage DC circuit can be used to control a high-voltage AC circuit (e.g., mains lights, motors, machinery)
. Stepper Motor: Rotates in small, precise steps. A microcomputer sends electrical pulses to different coils to control its rotation. Used in CNC machines and printers. It is an open-loop system (does not use sensors and feedback) and is simpler and less expensive than servo motors
. Servo Motor: Uses a feedback control system to accurately position the motor. An encoder measures the motor's position, and a control unit moves it until the desired position is reached. More accurate, faster, and powerful than a stepper motor, but also more expensive. Used in CNC control of lathes/milling machines, accurate positioning of robot arms, and camera auto-focus
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10. Building Circuits
Breadboards: Used for temporary circuits. Component legs are clicked into holes, and columns and top rows are electrically connected inside. No soldering is needed, and they are reusable
. Copper Stripboard: Component legs are pushed through holes and soldered to copper strips. Strips can be broken to create multiple connections
. Printed Circuit Board (PCB): A custom-made set of holes and copper tracks designed for one specific circuit. Copper tracks are etched from a continuous layer. Used for high-volume production as they are very efficient means of connecting circuits
. Soldering: Used to create good electrical connections between the metal legs of components and the electrical tracks of the PCB or stripboard
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11. Measuring Voltage and Current
Voltmeter: Connect across two points to measure voltage
. Ammeter: Connect in series with a component to measure current
. Multimeter: Can measure both voltage and current
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12. Simple Circuits
A circuit is a loop of components where current can flow, requiring a voltage source like a battery or power supply
. Bulb Circuit: Two bulbs connected in parallel light up when the switch is closed
. LED Circuit: An SPDT switch chooses which LED is turned on
. Simple DC Motor Circuit: The motor turns when the SPST switch is closed
. Variable-Speed DC Motor Circuit: A variable resistor controls the current to the motor, setting its speed
. Reversible DC Motor Circuit (using a DPDT Switch): A DPDT switch can reverse the direction of current through the motor, thereby reversing its rotation
. Reversible Motor Circuit with Limit Switches: Adds two limit switches to a reversible motor circuit to stop the motor when it reaches a desired position (e.g., for an automatically opening/closing door). The limit switches cut off the current in the forward or reverse direction when activated, but close again once the door moves away from the limit position
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13. Three Parts of a Circuit
Circuits generally consist of three parts
Input: Takes in information from the environment (e.g., a switch operated by a person, or a sensor responding to light or heat) and sends an electrical input signal to the process part
. Process: Amplifies or changes the input signal, usually done using transistors or an integrated circuit (IC), and sends a processed signal to the output part. A transistor inverts the signal (high voltage at base causes low voltage at collector)
. Output: Converts the processed electrical signal into another form of energy, such as light, heat, sound, or motion
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14. Sensor Circuits
A sensor circuit detects something changing in the real world and takes an action as a result (e.g., turning on a light when it gets dark, a fan when temperature rises, or turning off a motor when water reaches a certain level)
General Structure: Consists of an input sensor component (e.g., LDR or thermistor), a process section (e.g., transistor or IC), and an output device (e.g., LED, buzzer, or relay to switch on a motor)
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15. Timing Circuits
A timing circuit is a specific type of sensor circuit which uses a capacitor to create a delay
How they work: When the input switch is closed, current flows to the capacitor, charging it up. It takes a certain amount of time for the capacitor to charge to the point where it activates the next part of the circuit (e.g., a transistor), which then turns on the output (e.g., a buzzer or LED)
. The "timing" (delay) of the circuit can be adjusted by changing the size of the capacitor or the value of the resistor in the circuit
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Chapter 32:
Information and Communications Technology (ICT)
ICT is defined as the use of computer-based technologies to capture, process, and transmit information
Computer Hardware
Hardware refers to the physical parts of a system
Types of Computers:
Desktop Computer: Has a separate keyboard, mouse, and screen. Usually includes Ethernet and USB ports for connecting to other devices
. Laptop: A portable computer with a built-in screen, keyboard, trackpad, and Wi-Fi connection. Also typically includes Ethernet and USB ports
. Tablet: A portable, battery-powered computer that uses a touchscreen instead of a keyboard and mouse
. Smartphone: A portable, battery-powered mobile phone that performs many computer functions and is designed for internet use. It includes built-in Wi-Fi and uses a touchscreen
. Custom/Integrated Computers: Computers are integrated into most domestic appliances (e.g., washing machines, dryers, dishwashers) and industrial machinery (e.g., robots, CNC machine tools)
.
Basic Computer Components:
IC/Chip: An integrated circuit, which is a complete electronic circuit built into one small electronic component
. CPU (Central Processing Unit): The "brain" of the computer, responsible for executing software program instructions
. RAM (Random Access Memory): Chips for fast, temporary data storage, used to hold data the computer is currently working on. RAM does not retain data when the power is off; data must be saved to permanent storage
. ROM (Read-Only Memory): Chips that hold permanent, pre-programmed instructions for the computer. New data cannot be written to ROM. ROM stores the initial program run when the computer starts up
. Flash Memory: Chips that retain data even when the power is off, used in devices like USB keys
. Graphics Card: An electronic circuit that performs calculations to draw images on the screen, especially useful for games and movies. It reduces the load on the CPU, making the computer faster
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Input/Output Devices:
Input Devices: Get information into a computer (e.g., keyboard, mouse, trackpad)
. Output Devices: Take information out of a computer in a human- or machine-understandable form (e.g., screen, speaker, printer, robot arm)
. Internal & External Devices: Internal devices are built inside the computer casing, while external devices are outside the main casing
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Storage Devices: Store information permanently as digital data and can be internal or external
. Types of Storage: Magnetic disks, flash memory, or optical disks
. Hard Disks: Magnetic storage devices
. USB Memory Sticks/Keys, SD Cards: Use flash memory
. DVD and CD Disks: Optical storage, using lasers to read and write information
. CD (Compact Disk): Read-only optical storage with a capacity of 700MB
. DVD (Digital Versatile Disk): Read-only with a capacity of 8GB
. CD-R and DVD-R: Recordable optical disks that can be written to only once
. CD-RW and DVD-RW: Recordable optical disks that can be written to multiple times
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Data Storage Measurement: Measured in megabytes (MB), gigabytes (GB), and terabytes (TB)
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Touchscreen: A touch-sensitive screen that functions as both an input and an output device. It replaces the need for a keyboard and mouse, making it ideal for portable devices like smartphones and tablets. Touchscreens use LCD (liquid crystal display) technology, where pixels change color and brightness. Surfaces are made from impact and scratch-resistant glass, with sensors underneath reacting to finger pressure. They allow easy zooming but can get smudged and may be difficult for elderly and visually-impaired people to use
. Peripherals: Devices not required for the basic functioning of the computer but provide additional services (e.g., printers, cameras, optical disk players, additional screens, external storage)
. USB (Universal Serial Bus): A standardized way to connect external devices to a computer using a cable (e.g., keyboards, printers, cameras, external hard drives)
. USB Keys/Memory Sticks: Portable external storage devices using flash memory chips with a built-in USB connector
. Printer: Converts digital data from a computer into print on paper
. Scanner: Scans a paper page and sends it as image data to a computer
. 3D Printer: Physically builds plastic objects from computer data
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Computer Software
Software is the set of instructions (programs) that a computer carries out
Operating System (OS): Controls all computer hardware and allows other software programs to run. Common desktop OSs include Windows, Linux, and Mac OSX; smartphone OSs include iOS and Android. Most use a graphical user interface (GUI) with a desktop or home screen containing icons to run programs
. Office Software: Collections of software for common office tasks like email, word processing, spreadsheets, and presentations (e.g., Microsoft Office)
. Desktop Publishing Software: Allows users to design and layout visual and graphical communications such as books, brochures, posters, and web pages
. Mobile Apps: Software programs (applications) run on mobile devices to carry out specific tasks like email, navigation, messaging, banking, music, and social media
. Cloud Computing: Running computer programs on internet servers instead of on your own computer. Requires only an internet browser to access (e.g., Dropbox, Google Drive, Google Docs)
. CAD (Computer-Aided Design) Software: Used to create accurate technical drawings of products for design and manufacture. Also used to design and test (simulate) electronic circuits (e.g., SolidWorks, AutoCAD)
. CNC Machine Programs: Created on a computer and downloaded to CNC-controlled machine tools (e.g., lathes, milling machines) to control cutting tools and workpieces automatically for complex machining tasks
. Computer Simulation: Testing the operation of a product or program on a computer before actual use. Uses computer graphics to show potential outcomes and check for errors or dangerous situations (e.g., simulating CNC machine programs or electronic circuits)
. Virus: A malicious program that attaches itself to another program or file to gain computer access. Viruses can delete files, access accounts, steal data, block access, send unwanted messages, and spread to other programs, documents, and computers via email and other messages
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Computer Networks
A computer network is a set of interconnected computers and related devices that can communicate with each other
Local Area Network (LAN): A set of interconnected computers and devices within a small area (e.g., office, home). Devices usually connect via Ethernet cable or Wi-Fi. A LAN typically contains shared devices like printers, data storage servers, and email servers accessible by any computer on the network
. Wide Area Network (WAN): A set of computers connected across a large area (e.g., between different buildings, towns, or countries). WANs connect via specialist telecommunications cables or satellite and can be private or shared
. Internet: The largest computer network globally, a network of interconnected LANs and WANs. Each computer on the internet has its own IP (internet protocol) address
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Wireless Technology
Wireless technology allows devices to communicate without physical wires, using radio or infrared waves
Wi-Fi: A wireless technology using radio waves that allows computers and devices to detect and communicate over a short range. Devices can connect wirelessly to the internet via a Wi-Fi router connected to an ISP.
Bluetooth: Uses short-range radio technology to send information between smartphones and other devices, and to connect wireless microphones and speakers
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Accessing the Internet
ISP (Internet Service Provider): A company that provides customers with internet access, which can be delivered through telephone lines, TV cables, fiber-optic cables, satellite, or microwave
. World-Wide Web (WWW): The collection of all web pages and related resources on the internet. Web pages are written in HTML, link using URLs (Uniform Resource Locator), and are accessed via HTTP (Hypertext Transfer Protocol)
. Browser: A software program used to access and view webpages (e.g., Google Chrome, Firefox, Safari, Microsoft Edge)
. Search Engine: A cloud software program that searches for web pages on the internet based on entered keywords (e.g., Google Search)
. Uploading: Transferring files from your computer to a web server or other computer hosted on the internet
. Downloading: Transferring files from a web server or other internet computer to your computer's local disk
. Firewall: A security program that checks attempted network access coming through a computer network, allowing connections only from trusted computers
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Computer Applications
Communications: Computers enable modern communications like mobile phones, internet messaging, social media, internet video, TV, and radio. Specialist peripherals like high-quality microphones and webcams are used for internet video conferencing (e.g., Skype, Facetime)
. Navigation and Maps: GPS (Global Positioning System) uses Earth-orbiting satellites to beam radio signals, allowing GPS-enabled devices (e.g., smartphones) to calculate their location. GPS is used by navigation software like Google Maps
. Entertainment: Computers are used for reading, listening to music, and watching videos. Video and audio files are streamed over the internet, meaning they play as they are being transferred without waiting for a full download. Devices have better picture quality with graphics cards and high-definition screens
. Education and Research: The world-wide web offers vast information for learning and research. People collaborate online to share knowledge, and numerous online courses and tutorials are available.
Chapter 33: Pneumatics and Hydraulics
Basic PrinciplesPneumatics uses pressurized air to create movement.
Hydraulics uses oil to create movement.
Basic Pneumatic Circuit
A compressor draws air from the atmosphere and pressurizes it into a reservoir. The air is then piped from the reservoir through a control valve to a single-acting cylinder. When the valve is "on," the pressurized air extends the cylinder rod. When the valve is "off," a spring within the cylinder returns the rod, and the exhaust air is vented.
Basic Hydraulic Circuit
Hydraulic circuits are similar to pneumatic ones, but they use oil, which must be piped back to the reservoir. A key difference is that a double-acting cylinder (or ram) can be pushed in both directions by the pumped oil.
Advantages and Applications
Pneumatic Systems (Air)
Advantages:
-
Extremely fast operation.
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Clean, making them suitable for food processing.
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Reliable.
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Cheap.
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Can be used in hazardous environments.
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Easily automatable and available in small sizes.
Disadvantages:
-
Not as powerful as hydraulics.
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Not suitable for lifting heavy loads because air can be compressed.
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Slower than hydraulics.
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Difficult to control the speed of movement.
Applications:
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Food processing.
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Assembly line operations (pushing items, assembling objects, screwing bolts).
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Opening and closing doors on buses and trains.
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Road drills and dentist drills.
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Wheel and tire-changing equipment.
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Paint spraying.
Hydraulic Systems (Oil)
Advantages:
-
Very powerful, capable of lifting heavy loads because liquids are incompressible.
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A small input force can be converted to a large output force using a large-diameter cylinder.
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The speed of movement of hydraulic rams can be precisely controlled by managing the oil flow rate.
Disadvantages:
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Dirtier, as oil may leak.
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More complex circuits due to the requirement for oil return.
Applications: Used where large force is required:
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Diggers and farm machinery.
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Lifting platforms.
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Punching and pressing sheet materials.
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Car brakes.
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Car jacks.
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Robots designed for heavy items.
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Forging of metals.
Comparison with Electro-Mechanical Systems
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Pneumatic systems are simpler, cheaper, and more reliable than electro-mechanical systems for relatively simple movements.
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Electro-mechanical systems offer greater positional accuracy (due to stepper and servo motors) and are more energy-efficient than pneumatic or hydraulic systems.
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Hydraulic systems are more powerful than electro-mechanical systems.
Pneumatic and Hydraulic Components
Actuators
Actuators are devices that create movement. Hydraulic cylinders are often referred to as hydraulic rams.
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Single-Acting Cylinder: Has one input port. Air or oil moves the piston and connecting rod in one direction (typically out of the cylinder). The piston returns to its starting position via a spring or external force.
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Double-Acting Cylinder: Has two input ports. Air or oil into port 1 moves the piston and rod out, while air or oil into port 2 moves the piston and rod back in.
Power Sources
These components provide the pumped oil or pressurized air for the circuit.
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Compressor (Pneumatic): Takes in surrounding air, compresses it to the required pressure using an electric motor, and fills reservoirs to drive pneumatic circuits. Also used independently for inflating tires or cleaning products.
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Hydraulic Pump: Pumps oil through a hydraulic system, driven by an electric motor. It uses internal interlocking gears to move the oil and prevent backflow.
Other Components
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Reservoir: A tank that stores compressed air or hydraulic oil. It takes time to fill initially and often has a pressure regulator at its output.
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Pressure Regulator: Maintains constant air or oil pressure in a circuit. It has a gauge and a knob for adjustment. If pressure becomes too high, air or oil is vented to relieve it.
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Non-Return Valve: Allows air or oil to flow in only one direction.
-
Throttle Valve / Flow Control Valve: Regulates the speed of air or oil flow. A one-way flow control valve restricts speed in one direction only. Throttle valves are simple restrictive devices, while flow control valves can compensate for pressure drops to maintain constant speed.
-
Shuttle Valve: A non-return valve that combines two inputs into one output. Either input can flow to the output (but not simultaneously), and flow from one input cannot go back into the other.
Directional Control Valves (HL)
These valves act like switches, directing air or oil between different pathways.
-
3-Port, 2-Way (3/2) Directional Control Valve: Commonly used to control a single-acting cylinder.
Port: A connection to a valve.
Way: A selectable position of the valve, drawn as a box with lines indicating port connections.
Example Application (Controlling a Single-Acting Cylinder):
-
Valve port 1 is connected to a compressed air reservoir.
-
Valve port 3 is connected to the single-acting cylinder.
-
Valve port 2 is vented to the atmosphere.
Position 1 (Button Down, Cylinder Out):
Pressing the push-button causes air to flow through the top valve way. Pressurized air goes to the cylinder, pushing out the piston and rod, compressing the return spring.
Position 2 (Button Up, Cylinder In):
Releasing the push-button selects the bottom valve way connections. The cylinder's return spring pushes the cylinder back to its rest position. Exhaust air from the cylinder is pushed out through the valve to the atmosphere, and pressurized air from the reservoir is blocked from reaching the cylinder.
Chapter 34: Robotics
AutomationAutomation involves using machines to perform tasks previously done by humans. Examples include robots, machine tools, computers, and smartphones. Automation allows work to be done faster, more accurately, and at a lower cost than by humans alone.
Example of Automation in a Factory:
-
Computers track parts, send programs to machines, and manage testing stations, as well as finances, supplies, and sales.
-
Conveyor belts and robots move items.
-
CNC machine tools perform automated machining (e.g., turning, milling).
-
Robots assemble parts, weld, and spray paint.
Robots
A robot is a computer-controlled machine that performs actions typically carried out by a person.
Robot Features:
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Usually have arm-like parts.
-
Can have a fixed base or be on wheels or tracks.
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Typically have a gripper at the end of the arm.
-
Use sensors to detect the physical location of parts.
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Employ stepper motors or servo motors for accurate arm positioning.
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May also use hydraulic rams for movement.
-
Controlled by an internal or external computer.
-
Can also be directly controlled by a person using levers or switches on a handheld unit.
Robot Movement (HL - Higher Level)
Degrees of Freedom:
The number of axes through which a robot arm can move.
-
Robot axes can be linear (straight line) or rotary (twisting).
-
A Cartesian robot moves along three linear axes (X, Y, and Z), thus having three degrees of freedom. These robots are suited for accurate pick-and-place tasks like populating printed circuit boards.
-
A robotic arm can have six or more axes, mostly rotary, similar to a human arm. Robotic arms are well-suited for spraying and welding operations.
Working Envelope:
The volume of space within which a robot arm can operate.
-
For safety, humans must remain outside the robot's working envelope.
Robot Drive and Control Systems (HL)
Electro-Mechanical Drives:
-
Most robots are driven and controlled by electro-mechanical systems, which combine electric motors, mechanisms, and computers.
-
Mechanisms like worm drives, rack-and-pinion, and linkages translate motor rotation into robot part movement.
Hydraulics & Pneumatics:
-
Robot arm movement can also be driven by hydraulic or pneumatic systems, which are also under computer control.
Open-Loop Control with Stepper Motors:
-
An open-loop control system does not detect or provide feedback on the robot's position to the computer for correction.
-
Stepper motors are used in such systems because they can be rotated by a small, exact amount by sending specific electrical pulses.
Closed-Loop Control with Servo Motors:
-
A closed-loop system continuously measures the position of the motor or arm using a sensor.
-
This data is fed back to the computer, which continually adjusts the motors until the actual position matches the desired position.
-
Servo motors are employed in these systems as they are faster than stepper motors or DC motors.
Sensors
Robots use sensors to "see," "hear," "touch," or measure objects in their surroundings.
-
360° or movable cameras, or laser/ultrasound distance-measuring sensors are used to locate objects.
-
Pressure-sensitive pads on grippers are used to hold objects without damaging them.
-
Sensors send data back to the control unit, which then instructs the robot motors on how to move.
Examples of Sensors Used with Robots:
-
A factory robot uses a camera to find and pick up an object on a conveyor belt.
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A robotic milking machine uses a laser sensor to locate a teat under a cow for attachment.
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A robot vacuum cleaner uses a 360° camera to identify cleaned areas and find its docking station.
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A drinks dispenser uses sensors to detect coin types, cup position, water temperature, and if filters or overflow trays need emptying.
Programming Robots
Several methods can be used to teach a robot its movements:
-
Lead by the Nose: The robot motors are deactivated, and an operator manually moves the robot arm to the desired position, which is then recorded.
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Teach Pendant: An operator uses a handheld device to move the robot arm to the desired position, which is then recorded.
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Off-Line Programming: Robot movements are programmed and simulated entirely on a computer before the instructions are downloaded to the robot.
Robot Applications
Manufacturing:
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Forming: Punching, stamping, forging.
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Assembly: Welding (spot or seam), placing electronic components on printed circuit boards, applying adhesive, fitting and bolting assemblies.
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Spray painting and other surface finishing.
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Testing of parts and assemblies.
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Packaging: boxing, vacuum-packing.
Hazardous Environments:
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Handling nuclear materials or toxic chemicals.
-
Repairing flammable gas pipelines.
-
Military applications: bomb disposal, drones for surveillance or attack.
Space Exploration:
-
Planetary rovers gather data and transmit it back to Earth.
Healthcare:
-
Remote surgery using robots.
-
Artificial limbs.
Food Production:
-
Milking machines.
-
Planting and spraying of crops.
-
Sorting and cleaning of vegetables.
-
Cutting of meat and fish.
-
Making cakes.
-
Packaging of food.
Advantages and Disadvantages of Robots and Automation
Advantages:
-
Cheaper, faster, and higher quality than humans for repetitive tasks.
-
Enables mass production, leading to cheaper products.
-
Robots can work continuously around the clock.
-
Increases human safety by allowing robots to be used in hazardous environments instead of people.
-
Improves human health through artificial limbs and remote surgery.
-
Creates skilled jobs in design, programming, and maintenance.
Disadvantages:
-
Jobs are lost because robots can perform the work of many people.
-
Automation and robots consume large amounts of energy.
-
Expensive to buy and maintain.
Safety with Robot Installations
-
Ensure the robot's base is securely bolted to the floor or platform.
-
Ensure all people and objects are outside the robot's working envelope.
-
Ensure safety guards are in place around the robot.
-
For welding robots, ensure arc light shielding and fume extraction are in place.
-
Simulate robot movements on a computer before downloading the program to the robot.
Chapter 35: Design (HL)
1. Introduction to Design Principles
Design in engineering is a systematic discipline that provides a structured framework for solving problems and creating effective solutions. It plays a crucial role in managing complexity, ensuring product quality, and achieving predictable outcomes in product development.
2. The Eight-Step Design Process: A Systematic Approach to Innovation
2.1. Planning
Assign personnel and time to all design tasks. Without planning, key activities like testing may be overlooked.
2.2. Identify Requirements and Constraints
Document product attributes: function, aesthetics, safety, environment, materials, and cost, to ensure all aspects are considered.
2.3. Research Existing Solutions
Analyze existing products and technologies to avoid duplication and inspire innovation.
2.4. Develop Multiple Designs
Create a variety of design approaches to encourage creativity and find the best solution.
2.5. Select the Best Design
Evaluate each design against requirements and select the highest-rated option to avoid premature physical prototyping.
2.6. Build a Prototype
Construct a sample to test the design's viability and uncover flaws early.
2.7. Evaluate the Prototype
Test the prototype against all requirements to minimize errors before mass production.
2.8. Redesign
Refine underperforming areas through updated designs, re-prototyping, and re-testing.
This process helps control costs and manage risks as financial stakes increase closer to full-scale production.
3. Fundamental Design Factors for Product Development
-
Functionality: Intended purpose, users, dimensions, loads, and operating conditions.
-
Safety: Risk prevention (e.g., electric shock, sharp edges), lifespan, and features like Factor of Safety.
-
Environment: Energy use, end-of-life impact, corrosion, and working conditions.
-
Looks (Aesthetics): Style, surface finish, and visual appeal.
-
Manufacture-ability: Manufacturing methods, cost-effectiveness, and tolerance requirements.
-
Cost: Target price and cost of production at scale.
-
Materials: Select materials that satisfy all above requirements.
These factors are interconnected, requiring trade-offs and a holistic approach to decision-making.
4. Understanding the Factor of Safety (FoS)
FoS is the ratio of a product’s designed strength to its maximum expected load (e.g., FoS = 3 for 3000 kg capacity against 1000 kg load).
It ensures safety against unexpected stresses or flaws, especially in critical applications (e.g., bridges, aircraft).
A higher FoS is achieved through stronger materials, thicker designs, or design changes, reflecting lower accepted risk.
5. Leveraging Technology: Computer-Aided Design (CAD) and Manufacturing (CAM)
CAD software allows easy creation and modification of technical drawings, 3D modeling, and assembly testing.
CAM software uses CAD data to control machines (e.g., 3D printers, CNC tools).
This "digital thread" ensures precision, reduces errors, and accelerates production.
6. Prototyping: Types, Benefits, and the Role of 3D Printing
Types of Prototypes:
-
Visual Prototype: Non-working models for shape and style (e.g., car models, building concepts).
-
Material Prototype: Evaluates material choice and surface finish.
-
Functional Prototype: Working models to test functionality, even if materials or sizes differ.
Benefits:
-
Early detection of flaws
-
Time and cost savings
-
Effective communication of design
-
Physical testing of concepts
3D Printing: Builds prototypes layer-by-layer from digital files, usually using thermoplastics. This supports rapid iteration and cost-effective testing.
7. Testing and Evaluation in the Design Lifecycle
7.1. Purpose of Testing
Ensures the product meets:
-
Functional Requirements: Works as intended
-
Safety Requirements: Meets safety standards, including extended reliability
-
Environmental Requirements: Complies with regulations
-
Aesthetic Requirements: Meets design expectations, often via user feedback
-
Cost Requirements: Can be produced affordably
7.2. Broader Scope of Evaluation
Goes beyond testing and includes:
-
Design Quality
-
Effectiveness of Design Process
-
Testing Method Review
-
Market Viability
Evaluation ensures technical performance, efficient development, and market readiness.
8. Advanced Design Considerations and Material Selection
8.1. Functionality: Operational Stresses and Natural Forms
Designs must endure real-world stresses (e.g., wing flexing, corrosion).
Biomimicry—taking inspiration from nature—leads to sustainable and efficient designs (e.g., umbrella from insect wings).
8.2. Safety: Features, Materials, Electrics, and Medical Devices
Avoid sharp shapes; choose non-toxic, child-safe materials.
Electric components should be insulated and safe.
Medical devices require biocompatible materials that don’t irritate or corrode inside the body.
8.3. Environment: Minimizing Energy Use and Corrosion
Use energy-efficient systems (e.g., LEDs, renewables).
Prevent corrosion with non-corrosive materials, protective finishes, and smart design features (e.g., no water pooling).
8.4. Strategic Material Selection: Plastics and Metals
-
Plastics (Polymers):
-
Inexpensive, moldable, recyclable (thermoplastics)
-
Safe, non-toxic, and mass-producible
-
Reinforced variants (e.g., carbon fiber) offer high strength and low weight
-
-
Metals:
-
Selected for strength, toughness, corrosion-resistance, etc.
-
Lightweight metals and design reinforcements (e.g., triangulation) used in structures like arena roofs
-
Material choice is strategic, impacting performance, cost, and sustainability, and demands material science knowledge.
9. Conclusion
Creating a successful product requires a structured, iterative process, including:
-
Planning
-
Requirement analysis
-
Research
-
Concept development
-
Prototyping
-
Testing
-
Redesign
Design must balance functionality, safety, aesthetics, cost, manufacture-ability, and material choice, acknowledging their interdependencies.
Factor of Safety ensures reliability, especially in life-critical applications.
CAD/CAM technologies provide precision and speed, while prototyping, especially 3D printing, supports quick refinement.
Evaluation includes technical testing, design assessment, and market analysis.
Advanced considerations like operational stress, biomimicry, and strategic materials deepen the design process.
Ultimately, design is a collaborative, interdisciplinary pursuit, requiring coordination of engineering, user experience, manufacturing, environmental awareness, and commercial goals to deliver outstanding products.
Chapter 36: Engineering and Society
Energy in Modern Life
Modern life depends heavily on large amounts of energy to power homes, transport systems, businesses, and schools. Engineering provides the materials and machines needed to supply and transport energy in usable forms.
Sources of Energy
-
Renewable Energy Sources: Can be replaced and do not get used up. Examples include:
-
Solar power
-
Wind power
-
Wave power
-
Hydroelectric power
-
Bio-fuels / Biomass
-
-
Non-renewable Energy Sources: Cannot be replaced once used. Examples include:
-
Fossil fuels (coal, oil, and gas)
-
Nuclear power
-
Forms of Energy
Energy exists in various forms:
-
Electrical
-
Mechanical
-
Chemical
-
Heat
-
Light
-
Sound
-
Magnetic
Law of Conservation of Energy:
Energy cannot be created or destroyed, only converted from one form to another.
Converting Energy from One Form to Another
-
Battery: Converts chemical energy to electrical energy.
-
Bulb or LED: Converts electrical energy to light energy. (LEDs are more efficient and produce less heat.)
-
Solar Cell or Solar Panel: Converts light energy to electrical energy.
-
Motor: Converts electrical energy to mechanical energy (rotation).
-
Generator or Dynamo: Converts mechanical energy to electrical energy.
-
Power Plants: Convert source energy (chemical from fossil fuels, mechanical from wind, light from sun) into electrical energy, which is easy to transport via wires and can be converted into light, heat, or mechanical energy.
Engineering in Everyday Life
In the Home
Engineering provides man-made materials like concrete, steel, glass, and plastic.
Electrical lighting, modern heating, and insulation keep homes warm.
Utility services such as water, electricity, gas, phone, and internet are supplied.
Appliances like washing machines, dryers, ovens, and fridges simplify daily tasks.
Communications and Entertainment
Phones, Wi-Fi, and internet allow global communication.
Telecommunications networks use engineered materials like satellites, cabling, and masts.
Entertainment includes radio, TV, games, websites, social media, streaming films, podcasts, and music services.
Retail and Shopping
Large steel-framed buildings house supermarkets and shopping centres with various services.
Checkout, security, and payment systems support efficient shopping, money transfers, and purchase tracking.
Transport
Engineering powers vehicles like cars, ships, trucks, buses, planes, and trains using petrol, diesel, electric, or hybrid engines.
Materials include steel, aluminium, plastics, and composites.
Safety features: seat belts, airbags, crumple zones.
Energy-saving features: low weight, low emissions, hybrid systems.
Manufacturing
Engineering enables the creation of machines and tools for manufacturing.
Includes CAM software, CNC machines, automation, and robotics.
Computer systems track parts and orders through production lines.
Food Production
Farm machines are used for planting, spraying, watering, harvesting, and animal care.
Fertilizers and additives increase yield.
Food is processed and packaged using robots and machines, and preserved with chemicals, vacuum-packing, drying, pasteurizing, and freezing.
Global transport uses trucks, ships, and planes.
Materials
-
Metals and Alloys: Engineered for lightness, strength, toughness, and hardness.
-
Composites (e.g., Carbon Fiber): Offer high strength and low weight.
-
Smart Fabrics: Can have anti-allergy or antiseptic properties.
Negative Impacts of Engineering and Technology
Social Impacts
Overuse of computers and smartphones may cause:
-
Cyberbullying
-
Weakened personal relationships
-
Mental health and self-esteem issues
-
Fake news on social media
Pollution and Human Health
-
Fossil fuel burning causes air pollution and global warming
-
Carbon footprint: CO₂ released by people, communities, activities, or products
-
Consumer waste (e.g., plastics) pollutes land and sea
-
Water pollution from sewage, fertilizers, and chemicals
-
Environmental damage from mining and deforestation
-
Processed food may lack nutrients
-
Additives may pose health risks
Waste Recycling and Disposal
Recycling involves turning old products into new ones, reducing waste and often costing less than new materials.
Recyclable Materials:
-
Metals
-
Glass
-
Thermoplastics
-
Rubber
-
Paper
Organic waste can be composted.
Incineration of unrecyclable waste reduces landfill volume and can generate electricity, although toxic emissions remain a concern.
Inventors and Inventions
Transport
-
Dugald Clerk: Two-stroke engine
-
Frank Whittle: Turbojet engine
-
John P. Holland: Submarine
-
Charles Parsons: Steam turbine
-
Christopher Cockerell: Hovercraft
-
Igor Sikorsky: Helicopter (single rotor)
-
John Dunlop: Pneumatic tire
-
Nicolaus Otto: Internal combustion engine
Communications
-
John Logie Baird: Television
-
Trevor Bayliss: Wind-up radio
Computers and Office Equipment
-
Jack Kilby: Integrated circuit, handheld calculator, thermal printer
-
Steve Jobs: Co-founder of Apple – iMac, iPod, iTunes, iPhone
-
Chester Carlson: Photocopier
-
Bill Gates: Co-founder of Microsoft
-
Charles Hull: 3D printing
-
Charles Babbage: First mechanical computing device
-
George Boole: Developed mathematical logic used in digital design
Medicine
-
Marie Curie: Discovered radioactivity and two new elements
-
Theodor Maiman: Invented the laser
Other Fields
-
Viktor Kaplan: Water turbine with adjustable blades
-
George Devol: Industrial robots
-
James Dyson: Bag-less vacuum cleaner, Airblade hand dryer
-
Francis Beaufort: Beaufort scale for wind force
-
Eli Whitney: Cotton gin, muskets
-
Henry Maudslay: Lathe, standard screw threads
-
Michael Faraday: Electric motor, electromagnetic induction
-
Robert Boyle: Discovered the relationship between gas pressure and volume
-
Victor Popp: Air compressor and first pneumatic network