Assemble and test electronic and embedded systems DTG 7-10
Achievement standard 2.49 AS91376
The assembly and testing of electronic and embedded systems is focused on developing the skills needed to integrate technologies (hardware, software, mechanical) to produce a working prototype. These skills follow directly from those acquired during the development of an electronic environment as a functional model. It is also about the application of testing, debugging, and modification skills to ensure the prototype is operational, fit for purpose, and meets specifications.
Learning objective: DTG 7-10
Students will:
- demonstrate advanced assembly and testing techniques used in electronic and embedded systems.
Indicators
Students can:
- develop and produce a printed circuit board (PCB) using PCB CAD software
- construct and test reliable functional circuits on PCB, with improved track layout and soldering
- write and debug well-structured, clearly annotated, and readily understandable embedded software, which uses one extended feature or specialised command.
Progression
The step-up to level 7 requires two things of students: to construct an advanced system and to use advanced techniques. An advanced system is one where students work from functional specifications for a system and not with provided schematics or algorithms. Students must bring together in their own practice, various hardware interfaces – the examples in the standard would indicate that up to but no more than five or six interfaces would be required. Some of these must have analog data values (for example, light level, temperature, humidity, distance, force) so that students can meet the requirements for data-processing in the standard. Specifications for the system will require that students write software that stores sensor data in variables, and requires students to write programs that use data-manipulation techniques such as long term storage in EEPROM memory, mathematical calculations (for example, addition, subtraction, multiplication, division) and boolean logic (for, example and, or, not).
Examples of advanced techniques are listed in the standard; however, students must design a PCB for their system using a CAD package, and their PCB needs to include a multi-pin device. This could be a microcontroller, or if students are using a system such as Arduino or Raspberry Pi which already includes a microcontroller, then an interface board must be developed that includes multi-pin devices on it. These devices could be active temperature and humidity sensors or a motor driver with discrete transistors or an H-Bridge integrated circuit. Their PCB should require them to solder components to pads, which are close to other pads and tracks, and it should have a compact track layout. Students, where necessary, should be able to calculate some component values using common electronics formula using voltage, current, power and time constants. At this level, students should be capable of identifying for themselves and then fixing common faults with their boards such as incorrect component values, wrong component polarity, broken tracks, short circuits, poor soldering, and use voltage and continuity measurements to assist their fault finding as required.
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Teacher guidance
To support students to demonstrate advanced assembly and testing techniques used in electronic and embedded systems at level 7, teachers could:
- provide, or develop in negotiation with the student, specifications for an electronic environment that will require advanced techniques – the environment will include more than one subsystem and include at least one multi-pin device
- provide opportunity for students to select an extended range of components to match a schematic
- provide instruction for students in the design and production of a PCB using CAD techniques
- provide opportunity for students to develop advanced soldering techniques (for example, temperature controlled, desoldering) so that students can achieve consistently reliable results
- provide opportunity for students to use advanced multimeter functions to test an extended range of components (for example, capacitor values) to locate faulty components and other problems in a circuit, visual inspection, using an extended range of techniques in a logical manner (for example, voltage levels at the system and progressive subsystem levels)
- provide opportunity for students to perform systematic and logical testing, evaluation of data, and debugging in the electronic environment
- provide instruction in and examples for students that show how calculation and measurement can assist in the testing and debugging of the hardware and software in the system
- provide instruction in and examples of advanced techniques for the development, testing and debugging of clearly annotated embedded software that uses features such as variables and subroutines and simple data structures such as an array
- guide students to employ advanced techniques to evaluate, test and debug the assembled electronic and embedded system so that the overall system is functional.
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Contexts for teaching and learning
Provide an opportunity for students to analyse electronic projects that use a range of hardware interfacing techniques to overcome design issues. Provide an opportunity for students to undertake a project in developing a specified electronic environment (for example, prototype, product or system).
This outcome will require the student to integrate a range of techniques to develop a PCB for a microcontroller or major interface project (for example, to a smart phone, tablet, Arduino).
The outcome must also include student developed software to read and manage the data from and to multiple interfaces.
Students are required to use their workshop environment and equipment in a safe and correct manner at all times. Teachers should refer to the relevant sections in Safety in Technology Education: A Guidance Manual for New Zealand Schools.
Literacy considerations
Students will need support to identify sound design practices for direct current (DC) circuits with regard to voltage, current, and power specifications. Students should be developing awareness of aspects of construction such as: PCB track length and width with relation to component current requirements, switch debounce, component placement recommendations by manufacturers, separation of analogue and digital signal paths, and current carrying capacity for wire on and off their PCBs. Students will need to be introduced to power supply integrity requirements such as using large value electrolytic capacitors on power supplies and small value ceramic capacitors close to each integrated circuit to prevent DC voltage degradation issues. Guidance for these can be identified from manufacturer’s datasheets and design notes, otherwise by applying commonly recognised design practices.
Resources to support teaching and learning
Detailed case studies of electronics project development will be required, such as those found in specialised electronics and Amateur Radio magazines (Elektor, Silicon Chip, Everyday Practical Electronics, Circuit Cellar, Nuts and Volts, Break-In). Explanatory component and electronic theory can be found in a wide range of websites on the internet and from various textbooks. Many tutorials exist on the internet: sparkfun, EEVBlog, ladyada have a range of beginner and advanced tutorials. Manufacturer’s datasheets and application notes provide important details for student.
Assessment for qualifications
The following achievement standard(s) could assess learning outcomes from this learning objective:
- AS91376 Digital technologies 2.49: Implement advanced techniques in constructing a specified advanced electronic and embedded system
Key messages from the standard
Students will design and construct their own PCB for an embedded circuit or advanced interface to a high standard; this must be a PCB layout of high quality where signals degradation is not an issue (for example, short tracks, good decoupling techniques, correct track width and spacing).
Students will write, debug, and annotate their own software to manage the data from and to interfaces, and to prove the reliability of their design.
The step-up to merit requires skilful application of advanced techniques. Size and separation of solder pads should reflect the size of physical components. All wires on and off the board will have stress relief techniques applied to them and be restricted in placement to allow ease of manufacture. As well as having no faults with their workmanship, student’s soldering should be of a consistently high standard where solder joints are round in shape and shiny not dull, with no holes, no overheating of tracks or components has taken place, and there are no fractures in the joint.
The step-up to excellence requires students to efficiently implement advanced techniques. This requires a substantial improvement in their PCB track layout, one where the tracks are consistently sized and spaced, corners in tracks will be rounded or mitred to minimise etching issues and lifting problems, components will be placed so as to minimise track length. Wires to and from the board will be situated so as to provide for later maintenance. Soldering at this level will be consistent in size, and students will be proficient at applying the right amount of solder to joints so as to neither obscure/hide the joint nor make it weak with too little solder.
Resources to support student achievement
Last updated June 8, 2018
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