Jekyll2020-05-20T01:27:29+00:00http://0.0.0.0:4000/feed.xmlBrettRDWrite an awesome description for your new site here. You can edit this line in _config.yml. It will appear in your document head meta (for Google search results) and in your feed.xml site description.Skateboard2020-05-13T00:00:00+00:002020-05-13T00:00:00+00:00http://0.0.0.0:4000/projects/portfolio/2020/05/13/skateboard<p><img src="/images/skate/first_ride.jpg" alt="first ride" class="image featured" /></p>
<p>When you’re building things, and you’re not sure about some of your design decisions, always get a sanity check from another engineer. I did that, and later discovered that this procedure yields interesting results if your engineering buddies are as batsh*t crazy as you are.</p>
<p>After hearing stories of range and power issues on other boards, I wanted about a Megajoule or more for range, and low resistance battery chemistry to avoid voltage sag. I wanted brakes, I wanted lots of braking power; With electronic brakes, your motors need to handle all of the power you move from source to sink, and the motor controllers need to be equivalently rated. Expecting to use this thing as a robotics platform, I wanted good low speed performance; that means motors with hall effect sensors and high torque. Being of impatient nature when it comes to machines, I wanted to reach cruise speed in a reasonable amount of time with a nearly empty battery; for BLDC motors, that means a very generous top speed.</p>
<p>Put the constraints together and you have a motor pack that, at any time of day, can dump 2kW over each wheel until you’re questioning the survivability of a dismount. This is where the sanity checks failed me.</p>
<p>I’d set out to make a capable commuter skateboard, and instead found myself commuting on an entry-level motorsport device. Fortunately, the VESC motor controller is very configurable, and you can dial in speed and power limits to suit the legislation of your regular stomping ground.</p>Robotic Chip Flashing Jig2013-04-08T00:00:00+00:002013-04-08T00:00:00+00:00http://0.0.0.0:4000/projects/2013/04/08/robot-chip-flashing<p><img src="/images/chip_flasher/tube-to-tube.jpg" alt="operational" class="image featured" /></p>
<p>I had a project where I needed a custom bootloader on a few hundred DIP AVRs. It takes a few tens of seconds to flash the bootloader, so I could reasonably expect to be done in less than an hour. Instead, I mounted a ZIF socket to a pan/tilt bracket and had myself a tube-to-tube chip programming robot. This took days to get it right.</p>
<p>To slip between the pins of one chip and the next, the zif socket needed some trimming.</p>
<p><img src="/images/chip_flasher/hacked_zif.jpg" alt="hacked zif socket" class="image inset" /></p>
<p>The AVR-ISP simply plugged into the back, so the script controlling it could handle pretty much any kind of automated testing, and bin the chips accordingly.</p>
<p>The wiring was extremely lazy and notionally reconfigurable. I’m still a fan of zip-ties in strip-board.</p>
<p><img src="/images/chip_flasher/lazy_wiring.jpg" alt="operational" class="image inset" /></p>Amplifrier2012-11-29T00:00:00+00:002012-11-29T00:00:00+00:00http://0.0.0.0:4000/projects/portfolio/2012/11/29/amplifrier<p><img src="/images/amplifrier/amplifrier_done.jpg" alt="completed system" class="image featured" /></p>
<p>The Amplifrier was part of hackerspace infrastructure.
The Artifactory was attached to a pretty enthusiastic music scene at the time, and had developed a stage and impressive sound system.
The problem with impressive sound systems is that they have impressively expensive failures when you turn the parts on in the wrong order.</p>
<p>Systems that are difficult to operate can be ok for skilled technicians, but the sound system was also serving tunes for the hackerspace on a daily basis; Some people were intimidated by it and didn’t use it, other people would refuse to ask for help and damage the equipment.</p>
<p><img src="/images/amplifrier/amplifrier_panel.jpg" alt="layout test" class="image inset" /></p>
<p>We put a Raspberry Pi V1 and a USB sound card in a rack case along with a bank of Solid State Relays.<br />
The Raspberry Pi served Music Player Daemon, pulling tunes from the network storage, and ran a bash script to monitor /proc/asound/ pcm output status.<br />
When audio data flowed through the sound card from any source, a bash script would sequence the relays to safely bring up the sound system, and sequence the system safely down again after audio data had stopped.</p>
<p>The hackerspace tunes acquired some taste and variety, and people stopped blowing up speakers.</p>Arcophone2011-03-07T00:00:00+00:002011-03-07T00:00:00+00:00http://0.0.0.0:4000/projects/portfolio/2011/03/07/arcohone<p>The Polyplasmic Archophone was a running joke in “why not” at the Artifactory from 2009 to somewhere in 2011.</p>
<p>It all started when SkoT decreed that the fledgling hackerspace needed a thing in the corner that went Zap! - For ambiance.
He bought a Jaycar Jacob’s ladder kit, and gave it to me to set up. About thirty seconds after we got it running, we had it apart again to break into it with an arduino playing a tune. SkoT saw immediately that it needed more voices.</p>
<p>A few months later, we had a custom IGBT and oscillator breakout board, a dozen Holden V6 ignition coils, a midi library and a lot of power. It went through several interstate tours and case rebuilds before it was retired.
<img src="/images/arcophone/arcophone_close.jpg" alt="zap" class="image inset" /></p>
<p>The noises it made could be described as “harsh”. It reeked of ozone and was the cause of at least one nose bleed from extended exposure.
An Arduino Mega running 12-voice midi synth could control pulse frequency and duty cycle on all twelve channels at once.
Key-Coil mappings were selected for thermal load leveling at run time.</p>The Polyplasmic Archophone was a running joke in “why not” at the Artifactory from 2009 to somewhere in 2011.