Chapter 11 - Systems Approach to Designing

What relationship does Ohm's law describe?

It describes the relationship between voltage, current and resistance in an electrical circuit.

What is the primary function of a breadboard in electronics?

It is a device used to plug in electrical components to build and test temporary circuits without soldering.

What is meant by the 'polarity' of an electronic component?

It refers to the directional flow of electrons from one pole to another, meaning the component must be connected the correct way round.

How is 'resistance' defined in an electronic circuit?

Resistance is the opposition to the flow of electrical current.

In electronics, what is voltage?

Voltage is the electromotive force or potential difference that drives electric current, measured in Volts (V).

What is the term for the flow of electrons in a circuit?

The flow of electrons is known as current, measured in Amperes or amps (I).

What is the standard unit of measurement for electrical resistance?

The standard unit for electrical resistance is the Ohm, symbolised by Ω.

According to Ohm's law, what is the formula to calculate Voltage (V)?

Voltage (V) = Current (I) x Resistance (R).

Using Ohm's law, how do you calculate Current (I)?

Current (I) = Voltage (V) / Resistance (R).

State the Ohm's law formula for calculating Resistance (R).

Resistance (R) = Voltage (V) / Current (I).

In a simple circuit with an LED, what is a 'voltage drop'?

It is the amount of voltage used by a component, such as an LED, reducing the voltage available for other parts of the circuit.

A circuit has a 9V battery and a component causes a 2V voltage drop. What is the remaining voltage for the rest of the circuit?

The remaining voltage is 7V (9V - 2V).

Electronic systems can be broken down into three main stages. What are they?

The three stages are input, process, and output.

What is the function of an input component in an electronic system?

An input component produces a signal in response to an environmental change, such as light, sound, or temperature.

What is the role of a process component in an electronic system?

A process component responds to an input signal to control an output, often making a decision.

What do output components do in an electronic system?

Output components convert an electrical signal into a real-world outcome, such as light, sound, or movement.

A _ changes its resistance depending on light levels.

light dependent resistor (LDR)

What type of input component changes its resistance based on temperature?

A thermistor.

What is a reed switch?

A reed switch is an electromechanical switch controlled by a magnet.

Name two common types of process components.

Transistors and integrated circuits (ICs) are common process components.

How does a transistor function in a circuit?

A small current flowing to the base enables a much larger current to flow between the collector and the emitter.

Give an example of an output component with a visible outcome.

A light-emitting diode (LED).

Name an output component that produces an audible outcome.

A buzzer or a speaker.

What type of output component produces movement?

A motor.

Why is it important to connect polarised components like LEDs and batteries correctly?

They only allow current to flow in one direction, so they will not work if placed the wrong way round in a circuit.

Name a common electronic component that is non-polarised.

Resistors and LDRs are non-polarised and can be placed in a circuit either way.

What is the main benefit of using component symbols in schematic diagrams?

They are simplified pictures that are easy to replicate and interpret, making it quicker to draw and communicate circuit designs.

What are the benefits of modelling circuits using CAD software?

CAD allows circuits to be simulated and virtually tested without having to physically build them.

What material are Printed Circuit Boards (PCBs) typically made from?

PCBs are made from copper clad glass reinforced plastic (GRP).

On a PCB, what is the function of the copper tracks?

Copper tracks act like wires, allowing electrical current to flow between components.

What is the purpose of pads on a PCB?

Pads are where small holes are drilled for component legs to go through before being soldered into place.

What is soldering?

Soldering is a method of creating a permanent electrical joint by melting an alloy which then cools and solidifies.

What is an 'electromechanical' device?

It is an electrically operated mechanical device.

What is piezoelectric material?

It is a smart material that creates a small amount of electricity when pushed or squeezed, and flexes when electricity is passed through it.

How does an electromechanical bell or buzzer create sound?

It uses an electromagnet to attract a metal armature or clapper, causing it to repeatedly strike a bell or the magnet itself.

In an electromechanical buzzer, the noise is the sound of the _ hitting the magnet.

armature

Are electromechanical buzzers polarised or non-polarised?

They are polarised and must be positioned the correct way around in a circuit.

What is the function of piezoelectric material in a piezoelectric buzzer?

When current passes through the piezoelectric material, it flexes rapidly, creating sound vibrations.

Which type of buzzer typically operates at lower voltages and higher currents?

Electromagnetic (or electromechanical) buzzers.

Which type of buzzer is used when a compact and efficient sound is required, such as in smoke detectors and digital watches?

Piezoelectric buzzers.

In design, what is a 'context'?

The context is the situation within which something exists or happens, and it is the starting point in the design process.

What is a 'design brief'?

A design brief is a statement that explains what you are going to design and manufacture.

In a control system, what is a 'variable'?

A variable is something that can change, such as light, temperature, or moisture levels, which the system may need to monitor.

What is 'feedback' in a control system?

Feedback is a signal that is sent back in a loop, depending upon a condition, allowing the system to make adjustments.

A control system is where a computer or _ is used to respond to inputs and control outputs for a specific purpose.

microprocessor

What are the built-in input components on the back of a micro:bit v2?

The microphone, accelerometer, compass, and a temperature sensor located on the processor.

What is a key difference between an open loop system and a closed loop system?

A closed loop system uses feedback to make decisions and adjust its output, whereas an open loop system does not.

Give an example of an open loop system.

A toaster, which heats for a set time regardless of how toasted the bread is.

Give an example of a closed loop system.

A central heating system, which uses a thermostat (sensor) to turn the heating on or off to maintain a set temperature.

In a flowchart, what shape typically represents a decision?

A diamond shape.

What is the function of a switch in a circuit?

A switch controls the flow of current by making (connecting) or breaking (disconnecting) the circuit.

What is the difference between a momentary and a latching switch?

A momentary switch is only active while pressed (e.g., push switch), whereas a latching switch stays in position until pressed again (e.g., slide switch).

What does SPDT stand for in relation to switches?

Single Pole, Double Throw.

What is an actuator?

An actuator is a component that converts a control signal into physical movement or action.

What is the function of sensors in an electronic system?

Sensors are input components that convert physical properties of the environment into digital signals for processing.

What is a primary advantage of using on-board sensors on a microcontroller like a micro:bit?

They make the control system less expensive and more compact as no additional components need to be bought or connected.

What is pseudocode used for in system design?

Pseudocode is a way of writing out computer program instructions using plain English to plan the logic before coding.

What does 'incandescent' mean in the context of lighting?

Incandescent means emitting light as a result of being heated to a high temperature.

What is the unit used to measure the energy consumption of a light bulb?

Energy consumption is measured in Watts (W).

What is the fundamental property of a diode?

A diode is a component that allows current to flow in one direction but opposes the current flow in the opposite direction.

The positive terminal of a diode or LED is called the ______.

anode (+)

The negative terminal of a diode or LED is called the ________.

cathode (-)

What is electroluminescence?

It is the phenomenon where a material emits light when exposed to an electric field or current.

Why are LEDs considered more energy-efficient than incandescent bulbs?

LEDs transform electrical energy directly into light with very little energy wasted as heat.

Why must a resistor be used when connecting an off-board LED to a micro:bit?

A resistor is needed to limit the flow of current and protect the LED from being damaged by too much current.

What is an LED matrix?

An LED matrix is a group of LEDs arranged in a grid that can be controlled to display images or words.

What is the purpose of an input device in an electronic system?

An input device takes a signal from the physical world and converts it into an electronic signal that a process device can understand.

A _ allows current to flow when pressed, thereby 'making' the circuit.

push-to-make (PTM) switch

How does a light-dependent resistor (LDR) react to increasing light levels?

As the light gets brighter, the resistance of an LDR decreases.

What does NTC stand for in the context of a thermistor?

Negative Temperature Co-efficient, meaning its resistance decreases as temperature increases.

What is the purpose of an output device in an electronic system?

An output device takes a signal from the process device and converts it back into a physical, real-world signal like light or sound.

What component is typically found inside a buzzer to generate its sound?

A buzzer contains an oscillator, an electronic device used to generate a signal.

What type of component do speakers use to produce sound?

Speakers produce sound using an electromagnet.

What is often required to provide a signal that a speaker can use?

A driver circuit, such as an audio amplifier.

What is a subsystem in the context of a larger electronic system?

A subsystem is a smaller, distinct system that performs a specific task within a larger, more complex system.

What are the four key steps in the process of soldering a component to a PCB?

1. Clean the tip

2. Heat the joint (pad and leg)

3. Touch solder to the heated joint

4. Remove iron and let cool

What safety equipment is essential when soldering to protect your eyes and lungs?

Goggles should be worn to protect from solder 'spitting', and a fume extractor is needed to remove harmful fumes.

A 'cold joint' is a common soldering fault. What is its likely cause?

A cold joint is typically caused by the join or the soldering iron not being heated to a sufficient temperature.

On a micro:bit, how can the first row of LEDs also function as an input device?

The first row of LEDs can be used to sense ambient light levels.

What code block is used on a micro:bit to display text on its LED matrix?

The 'show string' code block is used.