Knowledge of electronic environments DTG 7-8
Achievement standard 2.47 AS91374
Knowledge of electronic environments focuses on the concepts and operational function of components that underpin the understanding of how electronic environments (functional combinations of hardware and embedded software in the real world, such as circuits, prototypes, or products) are developed, assembled and tested.
Learning objective: DTG 7-8
Students will:
- demonstrate understanding of advanced concepts and components in electronic environments.
Indicators
Students can:
- use advanced concepts of electronics to discuss the implications of multiple variables on the performance of electronic environments
- discuss the advantages and disadvantages of different electronic components to achieve desired advanced operational functions.
Progression
Students will need sound basic understandings from level 6 to progress to level 7, as advanced concepts build increasing depth to those already obtained. The power handling characteristics of components is one crucial understanding to develop. Power ratings and heat dissipation relates to power calculations, which lead from conceptual understandings of voltage drop across a component and current through it. This means being able to calculate the power ratings needed for BJT or MOSFET transistors, which are used to switch various high power loads (for example, motors, solenoids, relays ), and how diodes function to protect circuits from these devices. Also the power ratings of active devices such as microcontrollers need to be understood in terms of the maximum load that can be connected to an individual output pin versus the overall maximum ratings of the microcontroller itself. Voltage regulator circuits are common in electronics and students should understand the power dissipation requirement of voltage regulator IC and relate heatsink size to this.
Students’ software understandings must also progress and they should understand analogue to digital conversion (ADC), the digitisation of continuously variable analogue signals (using light, sound, humidity, temperature or gas sensors) into digital values so that they can be processed in a micro-controller based system. Students’ understandings about software should include the benefits of reusing program code via subroutines or functions and how variables are used to store data as well as how they are then used in comparisons and calculations within programs. Students should be able to express the benefits of program structure, commenting and logical layout to improve readability and maintainability. Having students undertake a practical task in a real context, provides an authentic opportunity for assessment of their understanding.
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Teacher guidance
To support students to develop understandings about advanced concepts and components in electronic environments at level 7, teachers could:
- provide an opportunity for students to learn about advanced concepts, including power and heat dissipation, analogue and digital signals, amplification, logical AND/OR and truth tables, parallel and series, how a single component type may have varied roles through hands-on practical work and research
- provide opportunities for students to discuss and investigate, practically, software programme development using advanced concepts, such as variables, binary notation (bits, bytes and words), logical structuring of software programmes (for example, flowcharting) and the use of subroutines and variables
- provide opportunity for students to experiment with an extended range of components in circuits, such as a diode (pn and zener), capacitor (various types), npn transistor or FET – and an extended range of common sensors and actuators, such as Hall sensor, servo
- guide students to explore the properties of integrated devices, for example, H-bridge, voltage regulators
- guide students to research information (books, online) about the properties and operation of components, and guide them in selecting relevant material from these sources
- support students to perform calculations, including power rating, parallel and series, based on parameters important in the behaviour of real circuits
- provide the opportunity for students to explore an extended set of subsystems, including temperature sensors, LCDs, amplifier stages, and enable students to recognise these in advanced circuit schematics.
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Contexts for teaching and learning
Practical project based contexts, supported by theory and investigative research, provide students with more motivation to learn and more opportunity to express their understanding than a research based task. However, this learning objective is a knowledge objective as opposed to a skills objective so it is the theory that is being focused on under this learning objective.
As the concepts at level 7 require significant depth, a medium sized electronic environment will provide students the opportunity to increase their depth of understanding rather than breadth of knowledge. Electronic environments must be microcontroller based (or other programmable device such as Raspberry Pi, Beaglebone, Android phone or tablet with appropriate hardware interface). They should include multiple analogue and binary (switch/two-state) inputs as well as several outputs, some of which could include transistor or IC amplifiers for motor, solenoid or relay control of other higher power DC actuators. These projects could include environmental controllers, small robots for simple purposes, a simple model railway controller, automated pet feeder or a special purpose timer.
Note: that it is not advised to have students working with the control of mains powered equipment. Teachers should refer to the relevant sections in Safety in Technology Education: A Guidance Manual for New Zealand Schools.
Literacy considerations
Students’ literacy in electronics can be measured by their correct use of the language of electronics. Power and heat dissipation should be accurately related to voltage drop and current. Digital and analogue concepts should be correctly expressed and students should understand the limits of different number representations in programming, for example byte, word and integer. The understandings of truth tables for Boolean logic (And, Or and Not) should be expressed accurately and these understandings used within program code. Software loop commands (such as - do, while, for) should be correctly used and should not be confused with each other or other common programming commands.
It is important that students have the ability to move fluently between circuit diagrams and layout diagrams at level 7 and use these as references when testing and fault finding. They should see the schematic symbol, the layout representation, and the physical component as the same thing. Systems concepts can be reinforced with the use of block diagrams, and subsystems should be related to sections of schematics and layout diagrams. Students should have a growing familiarity with electrical specifications found in component datasheets and that reliable use of components comes from over specifying components (de-rating or over engineering) when used in practical circuits.
Resources to support teaching and learning
Other resources
Many hobbyist electronics magazines (Elektor, Silicon Chip, Everyday Practical Electronics, Circuit Cellar, Nuts and Volts, Break-In) have exemplar projects. Explanatory component and electronic theory can be found in a wide range of websites on the internet and from various textbooks.
Assessment for qualifications
The following achievement standard(s) could assess learning outcomes from this learning objective:
- AS91374 Digital technologies 2.47: Demonstrate understanding of advanced concepts used in the construction of electronic environments
Key messages from the standard
Students will need to demonstrate understanding in a selected range of advanced concepts to meet the assessment criteria. The concepts demonstrated must be within the context of a particular electronic environment and be demonstrated during the students own practice not for instance as isolated component research tasks.
Students need to show understanding of a selection of concepts from the standard and not all those listed; depth of understanding is preferred to breadth of coverage in their work. Understanding at this level would be exhibited by a student when they are able to describe/explain/discuss some areas from explanatory note 4, as well as microcontroller concepts and some areas from explanatory note 5 as listed in the standard. Teachers should be clear that quantity is not the focus for assessment but depth of student understanding. If students' work was to cover no more than three or four areas from each explanatory note, they would have the opportunity to fully address the requirements of the standard without lessening their opportunity to meet the depth and comprehension required for higher grades. A student who demonstrates understanding in some concepts should not be penalised because they do not understand others as well.
The step-up to merit for this standard requires that students can explain their understandings. This requires that students use specific references to data from manufacturers’ datasheets, calculations, and their own experimentation.
The step-up to excellence requires students to consider their choice via detailed analysis and exploration of specifications and alternatives. This would include annotated research and/or a sequence of systematic trials prior to final implementation in their outcome.
Resources to support student achievement
Last updated June 8, 2018
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