Introduction to Design Engineering
Welcome to the world of Design Engineering! This chapter is all about how we make products "smart" and "active." While other chapters in the Material Categories section focus on things like wood, metal, or plastic, this chapter looks at the electronic and mechanical components that give products functionality and movement.
Think of it this way: if a product's material is its body, then the mechanical parts are its muscles and the electronic parts are its brain and senses. Whether you are designing a robotic toy or an automated desk lamp, understanding these systems is key to making a successful prototype.
1. Electronic Systems: The "Brain and Senses"
Electronic systems follow a simple pattern: Input → Process → Output. We use these to help products respond to the world around them.
Inputs: Sensors and Switches
Inputs gather information from the environment or the user. In your GCSE, you need to know these specific types:
- Light Dependent Resistor (LDR): A sensor that detects light levels. Its resistance changes depending on how much light hits it. Example: A street light that turns on automatically when it gets dark.
- Infra-red (IR) Sensors: These can detect heat or distance. Example: A hands-free soap dispenser.
- Switches: These allow a user to manually control a circuit.
- Push-to-make: Completes the circuit only while pressed (like a doorbell).
- Tilt Switch: Detects if a product is being tipped over.
- Time-delay Switch: Keeps a circuit on for a set amount of time after being pressed.
Outputs: Light, Sound, and Motion
Outputs are the "results" of the system—the things the product actually does.
- Light-Emitting Diodes (LEDs): Provide efficient, low-power light.
- Speakers and Buzzers: Create sound alerts or music.
- Motors: Create physical movement (rotary motion).
The Process: Microcontrollers
A microcontroller is a small programmable component that acts as the "brain." It takes the signal from the Input (e.g., the sensor) and decides what the Output (e.g., the motor) should do based on the instructions you've programmed into it.
Quick Review: Remember that Input is the "trigger," Process is the "decision," and Output is the "action."
2. Mechanical Systems: The "Muscles"
Mechanics are used to introduce controlled movement to a product. To understand this, we first need to look at the different ways things can move.
Types of Motion
There are four main types of motion you must be able to identify:
- Rotary: Moving in a complete circle (like a wheel).
- Linear: Moving in a straight line in one direction (like a train on a track).
- Oscillating: Moving back and forth in an arc (like a playground swing).
- Reciprocating: Moving back and forth in a straight line (like a needle on a sewing machine).
Levers and Forces
Mechanical devices help us move Loads (the weight we want to move) using Effort (the force we apply). The Fulcrum is the pivot point. By changing the position of these three things, we can make it easier to lift heavy objects.
Mechanical Devices
These components change the magnitude (size) or direction of a force:
- Cams: These turn rotary motion into reciprocating motion. As the cam spins, a "follower" moves up and down.
- Gears: Toothed wheels that lock together. They can change the speed of rotation or the direction.
- Pulleys and Belts: Used to transfer rotary motion from one shaft to another, often over a distance.
- Linkages: Bars or rods connected together to change the direction of a force or create a specific path of motion.
Memory Tip: Think of Cams as the "up-and-down makers" and Gears as the "speed changers."
3. Material and Component Selection
When choosing electronic or mechanical components for your design, you must consider their properties and how they are sold.
Standard Components and Stock Forms
Most design engineering parts are standard components. This means they are made to a specific size and value so they are easy to replace and fit together.
- Electronic forms: Resistors, capacitors, diodes, transistors, and microcontrollers. These are often sold on reels or in packs.
- Mechanical forms: Gears, cams, pulleys, belts, levers, and linkages.
Factors to Consider
- Functionality: Will the component do the job? (e.g., Is the motor strong enough to lift the load?)
- Cost and Availability: How much does it cost? Can we get it in the stock forms we need (like rods or reels)?
- Environmental Impact: Think about the lifecycle. Can the electronic components be recycled? Are the materials used in the mechanical parts sustainable?
4. Math Skills in Design Engineering
Design and Technology involves a bit of math to make sure things fit and work! You should be comfortable with:
- Ratios: Used for gear speeds. For example, if a large gear has \(20\) teeth and a small gear has \(10\) teeth, the gear ratio is \(2:1\).
- Standard Units: We use metric units like millimeters (\(mm\)), meters (\(m\)), and grams (\(g\)). You might also see very small units like micro (\(\mu\)) or nano (\(n\)) in electronics.
- Area and Volume: Calculating the space a system takes up.
- \(Area = length \times width\)
- \(Volume = length \times width \times height\)
5. Structural Integrity
For electronic and mechanical systems to work, they need a solid frame. We use triangulation (forming triangles) to stiffen structures. In design engineering, we might also use reinforcing or webbing to make sure the casing of our device doesn't bend or break when the motor is running.
Note: For details on the materials used to build these frames (like woods or metals), please see the other chapters in the "Material Categories" section.
Summary Key Takeaways
- Electronics use a system of Input (Sensors/Switches), Process (Microcontrollers), and Output (LEDs/Motors).
- Mechanics involve four types of motion: Rotary, Linear, Oscillating, and Reciprocating.
- Devices like cams, gears, and pulleys change the way forces move.
- Selection of components depends on cost, functionality, and environmental impact.
- Math is essential for calculating ratios and ensuring components fit into the required space.