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Mat Bettinson
Works at University of Melbourne
Attends University of Melbourne
Lives in Melbourne
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Just what America needs, a full on batshit crazy anti-science climate change denialist for a prez.
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Mat Bettinson

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Hard waste comedians.
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Bohemian Mattressy
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No... Tones, stay to the election! #auspolitics  
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John Hardy didn't vote for Abbott's profile photoMat Bettinson's profile photo
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Tones for PM, err...
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Why does news radio always report on stockmarket indexes, e.g. NASDAQ, FTSE etc? Who actually cares? Anyone that does actually care is surely plugged in with more detail. Particularly amusing is when the markets trend down and suddenly it's being widely reported despite having pretty much zero to do with 99% of people's lives.
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40 years ago today

Cyclone Tracy wiped out the town of Darwin. I was there. I was three years-old. What I remember is an animal-like howl of wind while I clutched to my mother in a cupboard in the concrete storeroom underneath the house. I have to say, it's not clear to me how much of that is a genuine memory or something passed down through multiple tellings. Anyway, Tracy destroyed the town and my mother and I were evacuated by a RAAF transport plane along with the rest of the women and children. My father stayed to help rebuild. 

The town was transformed by the destruction and rebuild. Previously it was a colonial outpost with tropical two-story housing where living in the louver-walled upper floor negated the need for air conditioning. In the rebuild, everyone lived in concrete bunkers built to the 'cyclone code'. Paranoia about cyclones continued for decades. Twisted girders embedded in concrete served as an artful reminder for the transient population. For those that were there, Tracy isn't something you forget.
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I now live in one of those concrete bunkers. It's hot but great in a cyclone. 
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Reducing power of the thing to reduce power

So, a few days ago I knocked up this quick 'n dirty micro controller to broadcast timing from the watt-hour LED on my power meter. Ironically, there's no power available in the power box so I just deployed a box of four AAs and a DC-to-DC converter driving the 3.3V power on the controller directly. It should last aggggeeeess. It lasted less than three days. So I measured the draw and it was 25mA. Quite a lot.

The problem is that I was basically running a busy loop, timing the LED flashes precisely. I was also collecting about 20 of them and sending the timing to the server. Later I realised that the timing of the LED is irrelevant. I just need to count the flashes and then record how many occur within a given period and write that to a DB with a timestamp. I basically just need to send a single number and I can put the mcu and it's built-in RF module to sleep for long periods. As in tens of milliseconds before it wakes up to take an ADC reading of the LDR, and minutes before a short packet is sent with the count.

Quite a lot more code, low power states are tricky. Much of the timers switch off too. None of it matters. The logic on the mcu basically just counts pulses and then sends a packet to the server with an ACK request. If it gets no ACK after a few retries then it gives up and will try again later, but doesn't reset the pulse counter. So essentially as long as this thing runs, the cumulative power consumption written to the DB should be 100% accurate, despite me fucking about with the server code.

Anyway, the result was... 25mA to 2.5mA with the blue LED on (pictured) and 1.5mA with it off. I made the LED reflect the sensor for testing purposes so it's 50% duty cycle, so total power consumption is around 2mA. The radio transmission occurs so quickly and infrequently it's negligible. Let's call the DC2DC converter 75% efficient. Should be less than 1.4mA from the battery pack. With 2000mA batteries, it should run for two months. Bit better than two days eh?
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Jay Van Der Zant's profile photoOliver Wagner's profile photoMat Bettinson's profile photojeckziel cortes's profile photo
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Possibly, it'd have to be a low drop-out reg though as it's only 300mV of headroom. I actually ditched the DC converter anyway since the quiescent current is larger than the draw of the mcu with the low power code.
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Mat Bettinson

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Shook my head in amazement at the new Macbook. Apple disappearing up it's design arsehole, vanquishing all ports, slapping in a crap mobile processor. It thought it was just me that thought this was depressing but no, look at this testimony from Apple's chief engineer!
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Stephen Dickson's profile photoRyan Eastman's profile photoMr. Señor's profile photoMat Bettinson's profile photo
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+Ryan Eastman Congrats for adopting the Apple apologist position. The problem is, dear chap, they've called this thing a Macbook. The last Macbooks were bristling with ports. They had USB, firewire, mini DVI, optical audio and more. Then we had the Macbook Air, which is supposed to be Apple's sub-brand of ultra portable. The Air is a current model and has USB 3 and Lightning ports. 

This new Macbook is actually a tablet-like device. The PCB is about the size of a playing card. It's got a netbook/tablet CPU. No ports at all. It costs 50% more than the Air.

I have no doubt it has a market but essentially this is a netbook, or a Chromebook, for about four times more money. It's stupid. 

Which isn't to say that the Air and the Macbook Pro aren't great, they are. I just don't see why one has to worship at the altar of Apple when they do retarded moneygrabbing stuff like this. I apologise if that doesn't fit with your world view.
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By golly there's a lot of adverts on American TV. Also, people seem to be quite happy to conduct their lives without loud advertisements playing in the background. 
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Macbook today. University loan job. Student has made their video presentation in iMovie on it. Then on the day it is to be shown, the thing wont boot. Or rather, after about three hours it had a progress bar that moved half way, while heating up the laptop.

Someone who knows about Macs says, what about recovery mode? Oh aye, they have that do they? Of course it's some secret vulcan death grip combination of keys. Whereupon one is asked to enter a password no one knows. Okay.

So if we get into this, we'd have a recovery console, I ask. Oh no. You'd get some icons allowing you to restore a backup or something.

It's pretty infuriating actually. All this computer stuff around which I'm singularly unable to figure out how to diagnose much less fix. That's to say nothing of the UI abomination that MacOS is. I feel pretty confident on that point, having had to teach Macs to a whole heap of international students that have been lucky enough to never have seen them before.
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Peter Strempel's profile photoPeter da Silva's profile photoEmlyn O'Regan's profile photoMat Bettinson's profile photo
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That right +Peter da Silva ? I think I'll borrow one and check it out, also scope out the shell and FS in a bit more detail.
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Undergrad (local) student paper topic: Avoidance strategies for game of thrones spoilers in the tertiary education classroom
Australia Awards international student paper topic: Fundamentals of water treatment to minimise childhood mortality

I'm not making this shit up.

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I'm handy like that. Dots joining.
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George Monbiot is right. Even our supposedly liberal national broadcasters are complicit in the elitist echo chamber of our media.
George Monbiot: If you think the news is balanced, think again. Journalists who should challenge power are doing its dirty work
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Yes. As the Scots in my circles did apprise me of during the referendum.
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Power meter redux

So, as I previously explained, I knocked up this Arduino to measure house power consumption by counting LED flashes with a light-dependent resistor. The quick 'n dirty attempt worked but drained a pack of four AA batteries in less than three days. Largely because it was sat there regularly using the ADC to measure the resistance. I was also naively timing the pulses which I later realised I don't care about. I went on to explore low power ways of doing things, basically putting the controller into sleep mode. Measuring light with an LDR is a little sub optimal.

So what I tried instead was using an LED to sense light (yes they do!) with a simple op-amp and comparator circuit which then drives the interrupt pin on the Arduino. The MCU sits in deep sleep almost constantly, only waking briefly when this circuit fires, to increment a watt-hour counter. Proper timers just don't work when you do this. So instead I use another interrupt, the watch dog timer, (Jeelib's Sleepy class), to go to sleep for 64ms intervals and just count those. 

Sleepy::loseSomeTime(64); 

This will exit when either the watchdog timer has fired or if some other interrupt has fired (like our flash detector). That's why I'm not calling this for say 6000ms. The pulses don't happen often, when I lose some fraction of 64ms, that's much less of an impact on overall timing. So now the device broadcasts watthour readings every two minutes given or take a couple of seconds. Total power consumption is so low it's hard for me to measure being as it's less than half a milliamp, certainly many months on batteries.

When it wakes up to broadcast it's around 10ma for a few seconds as it waits for server acknowledgement etc. Anyhow, getting mcus to do things via interrupts is cool, I must do more of it.  
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Work
Occupation
Linguistic grad student, researcher and sinologist.
Employment
  • University of Melbourne
    Researcher, 2013 - present
  • Tantalus
  • Alienware
  • Intent Media
  • Codeplay
  • Eurogamer
  • Ziff-Davis
  • EMAP
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Currently
Melbourne
Previously
Darwin - UK - Australia - Israel
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Geeky linguaphile
Introduction
Ex-journalist and ex-videogame industry guy with an electronics engineering background. Obviously that wasn't odd enough so I several years ago I abandoned my career to go back to university to study Chinese and linguistics. I'm now a PhD candidate in theoretical linguistics and my research aims to combine technology and new methods to scale up endangered language documentation.

I'm also broadly interested in China, I  brew my own beer, build weird robotic contraptions, play psychedelic synthesizer and grow chillis. Things I post about: Various computing and technical subjects, linguistics, Australia and Melbourne, China and the Chinese language and all sorts of political commentary, somewhat left of centre.

Bragging rights
Bragging rights? Oh how very American of you.
Education
  • University of Melbourne
    PhD linguistics, 2014 - present
  • University of Melbourne
    BA (Hons) Linguistics + Chinese, 2010 - 2013
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Male
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Lurks, Chinamat
30 years old apparently, and looking it. There's not many good venues on the south coast and sadly this isn't one of them. The decor is shabby worn 1970s with the owners feeling no need to update the venue in the last 30 years. Strangely despite ample room available in the lobby the operators like to have everyone queue up outside in the cold for a random abitrary length of time. Maybe to make it look busy, like nightclubs do. Inside the toilets are under a puzzling state of construction without you precisely knowing which are and aren't. Likewise internal signage is very poor and at any gig there's crowds of people walking around asking where anything is. If it's a seated event you can look forward to hard plastic seats big enough for a child at best. It's a horrible venue and the only reason anyone uses it at all is that there isn't anything better of this size.
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Public - 6 years ago
reviewed 6 years ago
It's somewhat tricky to find a genuine australian burger in Melbourne but this place is the real deal. One guy working in the shop with a large grill often gets a bit overloaded so you need to wait to put an order in but the results are spectacular. A proper 'the lot' burger with bacon, egg, beetroot and pinapple is pretty tricky to cram into a box but cram they do. One thing though, they don't serve real chips - just those american style string fries. They're also not very good so skip the fries and up your burger to 'the lot' and bob's your uncle!
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Public - 6 years ago
reviewed 6 years ago
2 reviews
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