EE3300/EE5300 Electronics Applications

Design Project

Overview of design project

This is a design project in which you will gain experience in developing electronic circuits. You will be expected to:

1. Select a specific problem or task that requires an electronic circuit solution.
2. Brainstorm and read the literature to find possible circuit mechanisms or ideas that might be relevant to your task.
3. Perform the detailed design using some mix of hand calculations and computer simulations.
4. Experimentally validate (at least some aspects of) your design.
5. Iterate this procedure using a systematic engineering design approach to create improvements and fine-tune the circuit performance.

You may select your own problem or choose from the list of suggested projects, given below.

At the end of the block mode, you will be required to present your work to the class, explaining your project and your results.

This is an individual project. Your work must be your own. You are encouraged to discuss ideas with classmates and seek information from a variety of sources. You’re allowed to use generative AI tools.

At the end of the project, your evaluation will be primarily based on the systematic engineering design process you followed, your ability to critically analyse the resulting system, and your ability to communicate your work.

Projects

Project idea 1: Signal amplifier circuit with large dynamic range

A common requirement for sensor electronics is to amplify a signal from a sensor and present it to an analog-to-digital converter (ADC) for subsequent analysis in software. An interesting challenge arises when the sensor needs to be able to handle inputs that vary over many orders of magnitude, for example:

1. A power measurement device might need to measure currents ranging from microamps to amps.
2. A light meter might need to operate across the range from a moonless night to a bright sunny day

Even a high-quality ADC will have a limited resolution. An amplifier gain suitable for the highest input signal would be insufficient for the small input signal. Consider the light sensor scenario where we wish to build a device capable of accurate measurements across the full range of light intensities. For example, suppose you build a simple amplifier with a gain chosen such that lux corresponds to a full-scale ADC input voltage of 3.3 V. Then lux would be a mere 33 nanovolts. Such a tiny signal could not be accurately measured by the ADC.

If you select this project, your task is to develop an amplifier circuit for a sensor that can handle a wide range of input signals. Your goal is to appropriately interface with the chosen type of sensor (e.g. a photodiode, a current measuring shunt resistor, or another sensor of your choice). Your system must maintain high accuracy across the full range of input signals.

There are a variety of design strategies and you’re encouraged to search for inspiration in the literature. One interesting idea is to provide multiple voltage outputs, each with a different gain setting. The example in Figure 1 shows a transimpedance amplifier where each voltage output is useful for a different range of sinking input currents. The p-channel JFETs and act to shunt one of the feedback resistors once their source voltage exceeds a certain threshold, to avoid the op-amp saturating to the positive rail. The voltage taps would be buffered and voltage clamped (using Zener diodes, for example) before being presented to separate channels of the ADC.

Suggested technical criteria to assess your design:

• Optimise your design for a wide dynamic range, as appropriate for your chosen sensor.
• Measure the achievable bandwidth (i.e. how quickly can it respond to changes in the input signal).
• Measure the noise at the output of the amplifier.
• Check the linearity of the amplifier across a wide range of input signals.

Project idea 2: Function generator

This project asks you to develop a function generator capable of producing a sine wave and square wave. You can select a fixed frequency (e.g. 5 MHz) but should provide an adjustable output amplitude.

A starting point is the Colpitts oscillator circuit shown in Figure 2. This circuit produces a sine wave whose frequency depends on the inductor and capacitor values. (Do some research to find the oscillation frequency for the Colpitts oscillator circuit.)

This design uses dual power supplies and . The transistor (and hence the amplifier gain) can be adjusted by varying the voltage of . This biasing scheme is convenient for laboratory experiments, but for your final product, you should consider converting to a single power supply.

If you select this project, you have the option to wind your own inductor using the supplies provided by the electrical workshop technicians. This will allow you to precisely tune the oscillation frequency instead of being at the mercy of component tolerances. Make sure that you use an LCR meter to test the inductor(s) that you make.

You may wish to add analog filters to your circuit to improve the quality of the sinusoid.

Suggested technical criteria to assess your design:

• Frequency of oscillation, measured using an oscilloscope or spectrum analyser. This should be as close to your target frequency (e.g. 5 MHz) as possible.
• Harmonic distortion, defined as the amplitude of each harmonic relative to the target sinusoid. For example, given a 5 MHz fundamental frequency, the first harmonic is at 10 MHz, and the we are interested in the amplitude of this signal relative to the fundamental. In the electrical workshops, you have access to a Rohde & Schwarz FSC6 or FSC3 spectrum analyser. On the spectrum analyser, select the Harmonic Distortion measurement. For the number of harmonics that you specify, it will show the frequency and amplitude on the screen. You are trying to minimise the amplitude of the harmonics relative to the amplitude of the fundamental.
• The range of output amplitudes that can be set.
• The rise time, fall time, and settling time of the square wave output, measured using an oscilloscope.

Project idea 3: Power amplifier or high speed switching circuit with protection

Build and characterise a power amplifier or switching circuit. A power amplifier can deliver a varying voltage or current signal to a load, while a switching circuit allows some digital electronics to control the power to a high voltage or high current load. You may choose a specific application or design a general-purpose circuit that can handle any voltage or current that can be supplied by our standard bench supplies in our laboratory (you should check their voltage and current ratings).

You must include protection circuitry so that your driver is not damaged if the outputs are shorted together.

Some inspiration can be found in AoE Section 2.5.5 (p. 121) for a BJT-based power amplifier or section 3.5.6 (p. 202) for MOSFET-based switching circuits.

Suggested technical criteria to assess your design:

• Power handling capability (i.e. maximum voltage and current that can be switched).
• Speed of switching when driving resistive or inductive loads.
• Fault handling (e.g. robustness under different types of fault conditions, isolation to prevent damage to the low-voltage side).
• Efficiency of the switching circuit (i.e. power dissipated in the driver circuitry).
• Additional features (e.g. adjustable duty cycle, ability to handle high speed pulses, ability to drive a floating load that is not referenced to the same ground as the switch, etc).

If you implement a switching circuit, then you would be expected to simulate and measure the characteristics of several different designs. Don’t just put a single logic-level MOSFET on a breadboard and call it a day! For instance, you might analyse the static and dynamic performance of several different switching circuit designs that each use different semiconductor devices (e.g. BJTs, MOSFETs, IGBTs, …).

Project idea 4: Regulated DC power supply with current limiting

Design a power supply to convert AC to regulated DC. There are transformers available in the workshop that you can use to step down mains voltages. You’ll need a rectifier circuit and then a regulator circuit that uses feedback to maintain a constant output voltage.

A simple version (without protection) is shown in Figure 3.

You must include protection circuitry, e.g. current limiting so that your circuit is not damaged if the output is shorted to ground.

There are also other ways to obtain the reference voltage. Voltage ripple affecting will be a key issue in the performance of this type of regulator. Consider introducing filtering, but remember to consider the dynamic resistance of the Zener diode.

Suggested technical criteria to assess your design:

• The stability of the output voltage under varying load conditions.
• The magnitude of the ripple in the output voltage. It should be suitably attenuated (i.e., measure the ripple and introduce design improvements to reduce it).
• The protection circuits (e.g. current limiting) should be effective.

Proposing your own project

You also have the option to propose your own project. Your project must be related to the course material but is otherwise open-ended. It must be complex enough to enable you to tell an interesting design story at the end of the study period, but also must be achievable within the available time and with equipment that we have in stock or can obtain quickly. To propose a project, send an email to the course coordinator with:

• A brief description of the project,
• Some initial design concepts (e.g. relevant circuits that you’ve seen in literature that you will use as a starting point), and
• The technical criteria that you’ll use to evaluate success.

Literature review for EE5300

If you are enrolled in the Masters-level version of this subject, then you are additionally required to engage more critically with the literature. Here “literature” is interpreted broadly to mean all reputable sources of information including peer-reviewed academic research, textbooks, device manufacturer’s application notes, websites (trust but verify!), and so on.

Choose one of the following options:

1. Review of circuit designs: Briefly review a selection of alternative circuit designs drawn from academic literature and/or textbooks. Select some alternative circuit designs (that you didn’t build), explain their operational principles, and critically analyse the strengths and weaknesses of each approach. Your goal should be to teach the audience about some interesting and creative circuit design ideas.
2. Review of applications: Briefly review the academic research on applications where your chosen type of circuit is used. For instance, if you’re building a circuit to interface with a certain type of sensor, then you might review literature where that sensor is used in biomedical devices, manufacturing, environmental monitoring, agriculture, smart cities, etc. As another example, if you’re building a switching circuit, then you might review papers on applications in power electronics, battery management, or renewable energy integration. Select 2 - 5 high quality papers in which a similar type of circuit is used, explain the contributions of the papers and give a critical analysis of the strengths and weaknesses of the approaches taken.

Your review will form part of your presentation. You’ll be given extra time.

Presentation

You are required to give a presentation including:

• The project you selected and the problem you were trying to solve;
• For EE5300 students, your review of the literature;
• A description of the engineering design process (i.e. “tell a story” about the process you followed, what went wrong, what you learned, how your design changed);
• The measurement results from initial prototypes and the final version, ideally showing an improvement in performance; and
• The lessons learned, critical reflections, and insights that you have gained.

When presenting your measurement results, please obtain high-quality figures (e.g. save them directly from the instruments) instead of just taking a photo on your phone. Make your work look professional.

EE3300 students have 5 minutes total (comprising 4 minutes of presentation followed by 1 minute of questions), while EE5300 students have 10 minutes total (with 8-9 minutes for the presentation followed by 1-2 minutes of questions).

The time limit will be strictly enforced. You are encouraged to use the time to discuss the unique aspects of what you did. Consider that your audience have already built their own design projects so don’t waste time on generic matters that everyone will be familiar with. Be interesting and tell us the specific directions that you took, what worked, what didn’t work, what you learned, and so on.

Peer feedback during presentations

During the presentations, you will be asked to provide feedback to your peers. This will be implemented using an online web form. You will be asked to write constructive feedback on the technical content and communication skills of each presenter.

An AI tool will be used to summarise and anonymise the feedback collected during the presentations. This will be checked by teaching staff before being sent to the presenters. This will help you reflect on your presentation.

Deliverables

There is no report. Your only deliverable is the presentation.

Since different people may have presentations scheduled on different days, the available time will be equalised by requiring everyone to submit their slides to LearnJCU by Friday of Week 6. The file you submit to LearnJCU will be downloaded onto the presenter PC for you to use during your presentation time. This ensures that all students have the same amount of time to work on the project regardless of the date of their presentation.

Your presentation slides must include all the necessary information to convey your technical achievement. Due to the time limit, you may not be able to include all details in the regular presentation. Therefore, if you have extra evidence that you want to show, then you can include it in extra slides after the end of your presentation. Please do this only if you intend to refer to that extra material in your self-reflection for your portfolio.

Make sure that your presentation slides include:

• Schematics and photographs of initial prototypes;
• The schematic and photograph of the final circuit design; and
• Measurement results at each stage of development, showing how the circuit performance changed with each iteration.

Project timeline

Assessment criteria

In your portfolio submission, you will reflect on your achievements in the design project. You are required to reflect on the following aspects:

• Product: How effective is the design and the final manufactured product? How well does it address the problem that you set out to solve? What functionality did you implement? Is there evidence of clear progress towards a design that is likely to be successful?
• Process: Is there evidence of a systematic engineering design process (e.g. ideation, analysis, testing, refinement)? Is there justification for the choices made at each stage of the design? Was the process justified by appropriate engineering criteria?
• Criticality: Are you able to assess the relative strengths and weaknesses of the system? Can you analyse the system in a broader context? Did your critical reflection lead to insights into next steps or future work?
• Communication: How well do you communicate your design process and results? Do you present technical information clearly and professionally? Was your presentation engaging and informative to the audience?
• Literature review: (EE5300 only) How well did you engage with the literature? Did you identify important challenges and summarise progress to address them? Was information from a variety of sources effectively synthesised? Did you critically analyse important papers in an insightful way?