CORE SKILLS AND KNOWLEDGE
SAFETY
Using equipment that is potentially hazardous is a requirement of this course. Learners will be instructed in the safe use of equipment, including:
- power tools, such as drills, saws, soldering irons, etc...
- chemical etching equipment
- appropriate storage and handling of chemicals including spill management
- toxic substances likely to be encountered including procedures to minimise risk of poisoning
- electrical safety including sources of dangerous voltage or current levels, and what to do in an emergency, e.g. when someone is receiving an electric shock
- workshop safety including safe practices for using equipment, basic first aid and what to do in an emergency
- safety equipment including Residual Current Devices (RCD’s, or safety switches), fuses, circuit breakers, Personal Protective Equipment (PPE).
SIMPLE CIRCUIT CONSTRUCTION SKILLS
Selecting, testing, measuring and calculating is to be incorporated into each module and, at the end of the course, learners will have encompassed:
- continuity testing
- breadboarding
- PCB manufacturing
- measurement and calculation of current, voltage, resistance, power, voltage gain
- uses of cathode ray oscilloscopes for displaying and measuring waveforms
- uses of signal generators, injectors and other waveform sources (e.g. microphones, antennas).
ESSENTIAL ELECTRONICS KNOWLEDGE
The following are relevant and basic to most aspects of the course. They must be encountered and applied frequently:
- safe working practices
- standard symbols, SI units and prefixes
- communication in a range of forms
- uses of block diagrams
- identification, and orientation of components
- measuring, recording, discussing, researching and reviewing
- electronic systems in homes and industries: what they are, who designs, uses, operates, services and sells them
- uses of computer applications for simulation and drawing circuits and design of printed circuit boards.
In addition, the following are to be revised, demonstrated or introduced within the modules where appropriate:
- AC and DC sources
- voltage or current control in power supplies
- series, parallel and series/parallel resistive networks
- power dissipation, effects of voltage or current changes, `P = IV`, `P = I^2R`, `P = V^2/R`, power ratings
- difference between analogue and digital signals
- uses of Integrated Circuits in circuit design
- magnets, magnetic materials, attraction, repulsion
- fields around loops and coils carrying a current
- uses of electromagnets in relevant technology.
CONTENT MODULES
Circuits that cover each dot point in each module must be built and tested.
Note: some individual circuits may apply to more than one dot point.
Module 1: Basic electricity and circuits (SUGGESTED 15% OF DELIVERY TIME)
This module introduces learners to the fundamentals of electricity and circuits, including the following:
- voltage, current, resistance and power
- Ohm’s law
- series and parallel circuits
- resistors, capacitors
- resistor colour code
- continuity
- switches
- semiconductors – LEDS, transistors.
Suggested Circuits and Activities:
- destructive testing of resistors (overheating)
- switch an LED on/off
- compare current to voltage in a resistor using graphs
- measure and compare how resistors in series and parallel affect voltage and current.
Module 2: Transistors as switches (SUGGESTED 15% OF DELIVERY TIME)
This module introduces learners to transistors as an active component capable of switching between conductive and non-conductive states. Concepts covered include the following:
- uses of transistors to switch current in a circuit
- voltage/potential dividers
- concept of transistor as a switch controlled by a voltage.
Suggested Circuits and Activities:
- compare collector current to base voltage and resistance
- switch an LED using light or heat sensors
- touch switch using a Darlington pair.
Module 3: Transistors for Timing and Control (SUGGESTED 15% OF DELIVERY TIME)
This module introduces learners to using a range of components to control a transistor, including the following concepts:
- capacitor voltage and current, leakage
- capacitor charging, time constant
- RC (Resistor Capacitor) delay circuits using transistors
- light or temperature sensing circuits using transistors.
Suggested Circuits and Activities:
- delay to turn an LED on/off
- give numerical indication of light level or temperature
- transistor astable circuit.
Module 4: Transistors as amplifiers (SUGGESTED 15% OF DELIVERY TIME)
This module introduces learners to simple amplifier circuits. The following concepts are covered:
- voltage gain, current gain, inverting of signals
- transistor linear region
- waves, amplitude, frequency
- bias voltage, coupling capacitors
- clipping, distortion of output signal
- multi-stage amplifiers.
Suggested Circuits and Activities:
- single transistor amplifier, measure voltage gain
- two-stage transistor amplifier
- use CRO to show clipping/distortion.
CONSTRUCTION PROJECT (SUGGESTED 15% OF DELIVERY TIME)
The learner is to complete at least one construction project. The project may be from an existing design, or one they have modified. A report detailing how the circuit was made, identifying hazards and listing injury prevention measures, and a basic description of how the circuit works is to be included for assessment. The project is to have a PCB manufactured and components soldered on by the learner, and it is to be housed and labelled appropriately.
Skills and knowledge applicable to projects:
- use of computer software for designing, testing and building circuits
- use of block diagrams to design, and describe operation of circuits
- use of PCB manufacturing technology to produce a circuit
- safe use of workshop equipment.
Suggested Projects:
- coin flipper (randomly selects between 2 LED’s)
- continuity tester
- audio amplifier
- crossover network for speakers
- tachometer for car
- alcohol breath tester.
OPTIONAL MODULES (SUGGESTED 25% OF DELIVERY TIME)
Upon completion of the compulsory modules outlined above, the learner must choose to undertake either an additional project, or study an appropriate circuit type of their choosing, or one of the following topics.
- Power supplies
Example practical projects: Set or variable voltage power supply, Overload protection circuit.
Derived from or related to these projects are topics including:
- AC and DC, rectifiers, transformers
- voltage ripple, smoothing
- voltage regulator IC’s
- circuit protection, Zener clamping, active overload protection, reverse bias protection
- alternative/renewable energy voltage sources, i.e. solar panel arrays, wind/water turbine generation.
- Digital logic circuits
Example practical projects: A logic probe, simple counter circuit with 7 segment display.
Derived from or related to these projects are topics including:
- difference between digital and analogue signals
- logic gates
- flip-flops: SR, D, JK type, and how to configure to a T type
- counters and shift registers
- 7-segment display, 5 x 9 display
- simple timing diagrams
- special function IC’s, such as BCD to 7 segment decoder.
- 555 timer circuits
Example practical projects: switch debouncer, egg timer, police/air raid siren.
Derived from or related to these projects are topics including:
- the three modes of operation (monostable, bistable and astable)
- frequency and duty cycle
- pulse width modulation (PWM)
- sourcing and sinking of current
- delays and debouncing.
- Communication systems
Example practical projects: simple transistor FM transmitter, AM receiver (crystal radio), TV remote control (PICAXE).
Derived from or related to these projects are topics including:
- resonance, tuneable resonant circuits
- frequency selective networks, passive filters
- modulation techniques, including amplitude modulation (AM) and frequency modulation (FM)
- waves, calculation of wavelength of radio frequencies.
- Microcontrollers
It is recommended that PICAXE microcontrollers be used:
- they are developed with electronics novices in mind
- they have comprehensive documentation, in language that learners can access
- the programming language is BASIC, and is accessible to learners.
Example practical projects: temperature controlled fan speed controller, LED flashing game, TV remote control.
Derived from or related to these projects are topics including:
o analogue and digital inputs and outputs, voltage and current limitations
o programming a basic microcontroller
o sensors, transducers, and other input/output components
o mechanical switch bouncing, and methods of debouncing
o types and range of sizes of microcontrollers. Manufacturers, performance of different microcontrollers.