Notes, summaries, assignments, exams, and exercises for Technology for Secondary education

Construction and Engineering Terminology

Redesign (rediseño): Designing again in order to improve or change a design.

Regulations (Regulaciones): Laws and standards that a design must comply with, for example, safety regulations and quality standards.

Scale (Escala): The ratio between the size of items shown on a drawing and their actual size (in reality).

Schedule (horario): A list of planned activities or things to be done showing the times or dates when.

Set of (conjunto de): Collection/group.

Sketch (Boceto): A rough drawing of initial ideas, also used when production problems require engineers to amend design details and issue them to the workforce immediately.

Slab (Losa): The block of concrete that makes up a floor. It can be laid on the ground...

What are Gears?

Gears are mechanical elements designed to transmit turning movements.

Characteristics of Gears

Two main characteristics define a gear:

1. Number of Teeth (Z): This characteristic represents the number of teeth on a gear.
2. Rotational Speed (N): This characteristic represents how fast a gear rotates.

Gear Ratios and Speed Control

Different Number of Teeth

Using gears with different numbers of teeth allows us to modify a machine's rotational speed. If the output gear is larger than the motor gear, it will rotate slower. Conversely, if the output gear is smaller, it will rotate faster.

Same Number of Teeth

If two gears have the same number of teeth, they will rotate at the same speed.

Motor Gear vs. Output Gear

In a gear pair:

• The motor gear initiates

Seed Drill - Jethro Tull

He perfected a horse-drawn seed drill in 1700 that economically sowed the seeds in neat rows (1714). He later developed a horse-drawn hoe.

Four Crop Rotation - Lord Townshend

Flying Shuttle - John Kay

The flying shuttle was one of the key developments in the industrialization of weaving during the early Industrial Revolution. It allowed a single weaver to weave much wider fabrics, and it could be mechanized, allowing for automatic machine looms.

Spinning Jenny - James Hargreaves

The spinning jenny is a multi-spindle spinning frame and was one of the key developments in the industrialization of weaving during the early Industrial Revolution. It was invented in 1764 by James Hargreaves in Stanhill, Oswaldtwistle, Lancashire,...

What is the Internet?

The internet is a worldwide system of interconnected computer networks. When you connect your computer to the internet via your Internet Service Provider (ISP), you become part of the ISP's network.

The World Wide Web Explained

The World Wide Web (WWW or 'web' for short) is the part of the internet that you can access using a web browser, such as Google Chrome, Microsoft Edge, or Firefox. It consists of a large number of web servers that host websites. Each website normally consists of a number of web pages, which can contain:

• Text
• Images
• Video
• Animation
• Sound

Understanding Intranets

An intranet is a network that works like the internet but is only available within a particular organization, not to the public. An intranet may have...

Mechanisms: Transmitting Force and Motion

Mechanisms are devices used to transmit and convert forces and motion from a driving force or input to an output.

a) Levers

A lever is a rigid bar that is supported by a fulcrum. When a lever is balanced, it complies with the Law of the Lever:

F × d = R × r

Force (F) and Resistance (R) can be measured in Newton [N] or kilograms [Kg], but both must always be in the same unit.

There are 3 kinds of levers according to the position of the Force (F), Resistance (R or Load), and Fulcrum (P or pivot):

• Class 1: Force – Fulcrum – Resistance
• Class 2: Force – Resistance – Fulcrum
• Class 3: Fulcrum – Force - Resistance

b) Pulleys

We will study three kinds of pulleys:

Fixed Pulley

A fixed pulley is a wheel that has...

Fundamental Electrical Signal Parameters

• Cycle: A part of the signal that is repeated.
• Period (T): The time, measured in seconds, that one cycle lasts.
• Frequency (f): The number of cycles repeated per second (Hertz).
• Instantaneous Value: The value of the signal at any given moment.
• Maximum Value (V_max): The greatest signal value within a period (Peak Value).
• Minimum Value (V_min): The smallest signal value within a period (Trough Value).
• Effective Value (V_eff or RMS): The value of an equivalent continuous current that produces the same electrical work. V_eff = V_max / √2

Active and Passive Electronic Components

Active Components

These components are able to generate, modify, or amplify an electrical signal.

Passive Components

Acting as loads, these components...

Fundamentals of Electrical Circuits

An electrical circuit is a closed path in which electrons circulate. A basic circuit includes the following elements: a generator that provides power, a wire, a switch, and a receptor.

The continuous circulation of electrons through a circuit is called electric current.

Circuit Components

• Generators: Necessary to provide the energy required for electrons to move (e.g., batteries).
• Receptors: Devices that convert electrical energy into another type of energy (e.g., light bulbs, motors, resistors).
• Control Elements: Utilized for directing and interrupting the electric current (e.g., switches, pushbuttons).
• Protection Elements: If the current is too high in a circuit, cables and components can overheat and melt or

Dynamics of Suspension

Balance, Center of Gravity, and Roll Axis

The roll center is an imaginary point on an axle where lateral forces are transmitted to the wheels. The imaginary line connecting the front and rear roll centers is called the roll axis. The center of gravity is an imaginary point where the vehicle's entire mass is concentrated.

Charge Transfer and Axes of Rotation

A vehicle pivots around three axes of rotation:

• Longitudinal Axis (Roll): Rotation that occurs when cornering.
• Transverse Axis (Pitch): Rotation that occurs during acceleration or braking.
• Vertical Axis (Yaw): Rotation when the vehicle is subjected to various turning loads.

Sprung and Unsprung Mass

• Sprung Mass: The part of the vehicle that is supported by the suspension system

Pneumatic and Hydraulic Circuits: Design & Components

Pneumatic and hydraulic circuits consist of all components necessary to perform the movement or rotation of an actuator. Depending on the medium used, they are classified as pneumatic (using compressed air), hydraulic (using pressurized fluid like oil), or mixed systems.

The primary differences between pneumatic and hydraulic systems lie in their pressure source and the collection of oil in tanks for hydraulic systems; however, many of their components share similar symbolic representations.

Movement Diagrams

A movement diagram illustrates the position and speed of an actuator's stem. On the horizontal axis, time is measured in seconds. The vertical axis indicates position:

• 0: Retracted position
• 1:

LDR (Light Dependent Resistor): These are resistors whose resistance value changes when illuminated by light (visible or invisible, such as ultraviolet or infrared).

LDR Features:

1. Its resistance value depends on the amount of light that strikes it.
2. Ohm's Law does not apply directly.
3. Typically made from cadmium sulfide. This material, when kept in the dark, has very few free electrons, resulting in high resistance. However, when illuminated, it releases electrons, decreasing the resistance. This makes it a photoconductor.
4. Manufacturers provide values such as resistance in total darkness (R), resistance under illumination (e.g., 1000 lux), permissible maximum stress, and maximum power.
5. Can be used in lighting systems as detectors.

NTC (Negative Temperature