Backup Generator / UPS

Why did I make it? My engineering curiosity was piqued when the replacement of the family lawn mower coincided with a brutal 5-day electricity outage.

What can it do? This hybrid system is capable of a sustained 1kVA output (500VA alternator output + 500VA battery supplement) and can handle 2kVA surges which result from the inrush current of highly inductive loads, such as fixed-speed fridge compressors. The onboard pure sine-wave inverter has a built-in automatic changeover switch which can provide uninterruptible power to sensitive electronics. For smaller loads, the system can be silently operated in battery-only mode for a few hours before the engine must be started to recharge the battery. It was cheaper to build than a commercial generator and allows me to have off-grid power in case of emergency.

What skills did I learn? Automotive electrical basics, arc-welding, basic CAD design, how to rebuild a carburetor and tune a small engine, use of different power tools, wiring considerations, and more.

Specs:

Power output: 1kVA (1 hour), 500VA continuous, 2kVA surge

Features: Power and energy monitoring, delayed field excitation for easy engine start, fault detection

Construction: Steel tube frame

Engine: 4-stroke gasoline lawn mower engine

Dynamo: 12V alternator from scrapped Mitsubishi

Drivetrain: Belt-driven gear reduction

Dual-tube Geiger Counter

Why did I make it? I wanted to compare background radiation levels which required a sufficiently sensitive device, as well as test Uranium glass sculptures.

What can it do? This Geiger counter is based on Soviet technology and is capable of measuring low and high-range ionising beta and gamma radiation in terms of counts-per-minute. A physical meter, LED, buzzer, and OLED display provide a blend of retro and modern interactive elements.

What skills did I learn? Operation and calibration of different Geiger-Müller tubes, I2C OLED programming, perfboard building, enclosure building, Arduino programming

Specs:

Tube selection: SI-21G/СИ-21Г (low range, high sensitivity), SI-3BG/СИ-3БГ (high range, low sensitivity)

Features: dual-sensitivity, counts-per-minute readout, logarithmic moving-average readout, battery-power, stealth mode, radiation alarm

Motor Controller w/ Feedback

Why did I make it? An old washing machine suffered a catastrophic failure of its control board. Rather than scrapping the perfectly healthy drivetrain, I opted to build my own motor controller to serve as a multidisciplinary learning experience.

What can it do? The controller is capable of driving a 500W DC motor bidirectionally. It can operate in closed-loop mode using a tachometer as feedback. The controller automatically switches stator winding configurations on the fly, depending on the target speed and loading of the motor. This results in a higher maximum speed whilst ensuring low-end torque.

What knowledge was gained? Intuition for PID controller tuning, computer control system considerations (e.g. computational speed, noise, robustness), motor principles, EMI considerations, observed switching losses, flyback diode selection, and more.

Application: My experimentation with this setup led to the development of a crude “Leslie” speaker prototype, which produced the desired vibrato+tremolo effect, but was ultimately compromised due to the excessive noise produced by the worn washing machine bearings.

Assorted University Projects

Robust microelectronic level-shifter: Designed in Cadence within a 45-nanometer architecture, this level-shifter is able to shift and scale an input signal with minimal distortion and error across its different gain modes. The design was demonstrably robust when accounting for process variations in Monte Carlo simulations.

Rain-sensing washing line cover: A viable product prototype and business plan was developed for a design course.

Software aspects: WiFi web interface, Bluetooth, and messaging alert functionality – ESP32 microcontroller. Robust state machine for motor operations.
Hardware aspects: PCB design, TH and SMD soldering, motorised articulating rain cover with self-calibration, waterproof enclosure.

Embedded home automation system: A system which controls a hypothetical smart home in the Snowy Mountains. A touchscreen interface manages user input and provides the real-time status of smart systems. An automation algorithm controls certain functions based on ambient conditions, e.g. lighting systems activate at night to deter burglary, heating system activates in sub-zero temperatures to prevent freezing of pipes. Coded in a mixture of C and Assembly. Nominated as a finalist within an embedded design course.

Solar-powered gondola: The only design in the cohort which fully achieved the design objective. This was primarily due to the designed compliance of the traction drum mounting arm, which created a highly desirable dampening effect. This counteracted resonance in the tether rope due to strong wind. Another advantage was the incorporation of a supercapacitor bank, which discharged excess electrical energy when passing clouds decreased solar panel throughput. Working around the low-power constraints of the mandated solar panels was a challenge. This was met by designing a mechanical automatic reversal mechanism which allowed for higher overall efficiency in comparison to a microcontroller-based solution.