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David Scholten

Power Electronics & RC Models

location
Adelaide - Australia
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Things I've Built

150g Combat Robot for Adelaide Robot Combat (ARC)

A weapon-less pusher type, this 150g 3D printed robot is defined by its interchangeable armour, absurdly fast/powerful 15W motors, wide tyres and gyro stabilisation. However, straight paths without the gyro are impossible during acceleration!

PV Peltier Water Collector

Using 45 Watts of PV power (~18V MPP), two 30W Peltiers (0-9V), an MPPT buck converter (IV-matching) and a temperature switch (anti-frost), water is slowly collected at the cold-side heat sink where it falls through a funnel and into a bottle.

Breadboarded 80-LED Analogue Oscilloscope

A very old project. By using a single VU meter IC (LM3915?) and a another IC that sequentially connects the columns of LEDs to ground (i.e. the time scale), the VU meter effectively "sweeps" across the waveform in a quick succession.

Pulsed 800A Thyristor Solid State Switch

To control the discharge of my 50V/0.3F capacitor bank in a modular fashion I took an 800A peak thyristor, a piezo buzzer, a 9V battery and a momentary switch and then stuffed them all into an off the shelf project box with power I/O terminals.

Class-D Custom Bluetooth Speaker Unit (36W Max)

A 60W 12V plug pack power supply is boosted to 24V, which is then fed to a 50W class-D amplifier with bluetooth audio receiving capability. The output is then split at 3.8kHz with a 2nd order high & low pass filter for the 8Ω tweeter & woofer.

Peltier Freezer Ice Crystal Time Lapse

Two cascade Peltier units (top: adjusted to ~36W, bottom: ~72W) This draws about 9-10 amps total at 12V. Heat pump transfer is 15W optimally and the minimum cold side temp reaches -30°C. See: https://www.youtube.com/watch?v=s0KKzHtkc5o

128W Full-Bridge Class-D Audio Amplifier

32V & 4A input, 600kHz switching frequency and a soft start relay. These amplifiers are very hard to design but are very rewarding when they are done right. I would highly recommend them for anyone that wants to learn about power electronics.

Talking Animatronic Gundam Robot

Contains 6 servos, a text-to-speech unit, glowing eyes, audio reactive LEDs throughout, a spinning gun, power supply, audio amplifier, music, transformer, a brain and manual controls!
See it here: www.youtube.com/watch?v=E8185o7we04

180W Variable Linear Power Supply

A 1-30V, 6A linear power supply housing a T0-3 regulator, circuit and a serious heat sink. Features include: A soft start relay, a temperature-based two speed fan, under/over voltage alarms and disconnects, various displays & indicators + more!

MATLAB Code for 3D Printing Math Functions

I thought it would be a fun idea to visualise some math functions as 3D prints. The MATLAB script that I created took an equation, converted it to a surface plot, added a solid base underneath and generated an STL file for 3D printing.

Class A 32-Ohm Headphone Amplifier

My 32-ohm headphones were proving troublesome to use so I designed an impressive sounding class-A amplifier to help. There is no voltage gain as this "amp" only acts as a current buffer, increasing the impedance of the headphones to infinite.

PhD 4/4: Inverter H-Bridge Decentralised Cascaded System

I put together 4 control boards and 4 H-Bridge power stages to make a decentralised multilevel cascaded grid-tied inverter. The input is DC power which is converted and sent back to the grid. Effectively, this system educates and heats the room.

PhD 3/4: Bi-Directional Analogue/Digital 3.3V to 5V Converter

Now you think I would have realised that a serious H-bridge should be operable from 3.3V. Well I stuffed that up and as a result I needed a way to allow my 3.3V microcontrollers (Arduino Due) to interact with my 5V H-bridges and their sensors.

PhD 2/4: Inverter H-Bridge Power Stage V2.0

The final version of the H-bridge for the cascaded inverter of my PhD. This final version was much more robust, had a LOT of protection and other features that made controlling it so much simpler. To date, non of these boards have failed in use.

PhD 1/4: Inverter H-Bridge Power Stage V1.0

During the earlier stages of my PhD I realised I would need H-bridges for my cascaded inverter at a later point. I went about designing and constructing a very early version of the H-bridge to test. This was the first time I had used Altium.

Align Trex 550 Helicopter Assembly

The Align Trex 550 is a 1400W model helicopter with a body length of 1 metre and a battery life of 10 minutes. Assembling this allowed for a deep understanding of the mechanics of helicopter flight and maintenance. Very educational!

Prusa i3 3D Printer Assembly

To enter the world of 3D printing I purchased a Prusa i3 1.75mm from the official website and put it together. This was an exercise in mechanical assembly and greatly deepened my understanding of how 3D printers work.

Class AB Amplifier (Stereo 15W)

My first "serious" amplifier project! A dual 15W class AB amplifier with a bias current of about 1A per channel (that's a total standing heat dissipation heat of near 60W)! Summary: Dual Transformer-->Rectifiers -->Caps-->+/-15V-->Amp ALSO FAN!

FPV RC Car

A 200W remote control car with video/audio transmission. Features include a front/rear camera (with pan/tilt), front(10W)/rear(1W) headlights, rear microphone, 900MHz video with OSD, 2.4GHz control, and a fluffy doll for attracting children.

Room Automation Board

Using a micro-controller and the insides of a remote from a network of wireless mains relays, I automated the devices in my room. There is a motion sensor, a wireless "bedtime" switch and a set of pre-programmed configurations.

50V Capacitor Bank

A 50V capacitor bank made up of 10mF caps (31 of them). The total maximum energy is 387.5 joules. There is a controllable bleed resistor and voltage/current multimeters powered by a single 9V battery. The ultimate DC-link capacitor!

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