ramblings of an electronic engineer.

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Im currently enjoying my one week of holidays at the moment so I thought I’d take this time to let you know what I’ve been doing and some things I am currently planning. Lets start with projects I’m working on.

Last week I finished building a heart rate monitor which I now have to write a report. The heart rate monitor works by shining a light into you finger and recording the light coming back. We do some filtering and amplification of the returning signal to retrieve the heart rate of a person. So one project this holidays is to make a few more heart rate monitors to give to friends etc that are interested oh and write a report and blog post about how it operates.

The second electronic project I have started on is making a neurophone which is a device to supposively transmits sound to your ears using the central nervous system. I’m a little skeptical that it will work however once I get in a piezo transducer ill soon find out so at the moment I’ve done as much as I can to finish the project and need an electronic parts order to come in. *sigh*

The last project I’ll be working on is creating a air quality tester. I had the idea to make this for about a month now and the idea has been shaped, researched and refined during that time. The general idea is to create a circuit that will log a GPS coordinate and the corresponding air quality characteristics onto a sd card that can then be look at later. I can then attach this unit to my bike and ride around and find is the air quality of the gold coast changes much as I go to more populated areas. Again I’m waiting for some parts to come in but i will get a head start designing the circuit diagram.

Apart from these projects I have a ton of uni work to complete, a couple of books that I want to read and of course blogging. I’ll keep you posted with how I’m going.

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Pizza Vending Machine

Came across this yesterday on reddit, a vending machine that make pizzas in 3 minutes.

For about $5 a pizza the ‘Lets Pizza’ vending machine you see each process of you pizza been made (forming dough, toppings, cooking) until three minutes later you can retrieve your freshly made pizza. Have a look at the promo video.

Also if you (like me) are more interested in the internals of how the machine works check out this video of the machine been put together. (Skip to around 5:35)

[Product Page]

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‘Popinator’ – the world’s first fully automated, voice activated popcorn launcher.

Some things are completely lazy, yet incredibly awesome. This is one of those things, a popcorn launcher that fires a piece of popcorn at your mouth whenever you say ‘pop’. The launcher detects your voice from two microphones, from the small time delay between the sound of your voice been detected by each microphone it can adjust the pan and tilt of the launcher to shoot the popcorn in the direction of your mouth for consumption. Check out the video for a demo of how it operates.

[Product Page] via [Oh Gizmo]


Benfords Law

Benfords Law is one of the most fascinating things that I have ever come across, however to explain what it is lets play a game (actually the game I learnt about Benford law). Lets firstly list the numbers from 1-9

1 2 3 4 5 6 7 8 9

Now we are going to group these into two groups, one from 1-3 (Group A) and the other from 5-9 (Group B). For the purposes of our game the number 4 will be a dead zone that us no points will be gained on it (keep reading it will make sense).

(1 2 3) 4 (5 6 7 8 9)

Now the way the game will work is we will pick each pick a different group of numbers group A or group B. Each round we will then times two unknown values together in wolfram alpha and look at the first digit of the number, if it falls in your set of numbers you get a point, first to ten points wins.

So for example it first round might be the mass of the sun * the number of people living in america = 6.14×10^38 person kilograms (mixed units can be strange). The first digit is a 6 therefore group B would get a point.

Again if you searched for US debt * planks number = 15.86 trillion planck US dollars, group A would get a point.

So we start our game and you been a logical rational human begin choose group B because there are more numbers in that particular group and you have more changes of the first digit been one of your numbers. I however foolishly choose group A.

Now let me tell you why I will win almost every time. (hint its due to benfords law)

So we expect the probability of the first digit been any given number to be something like this:

In actual fact the probability distribution looks something like this:

So yeah, Benfords Law essentially states that there is a logarithmic probability distribution of the first digit of most lists of real-world data. This means looking back to our game the actual probability of each group winning per round is:

Group A: 60.2%

Group B: 30.1%

‘Dead Zone’: 9.7%

I’m not going to get into why the probability is distributed this way, however if your interested check out Wikipedia or Wolfram MathWorld. (My way of saying I can’t explain why it is that way)

Benfords Law works for a large range of real life data, testingbenfordslaw.com has many various examples of real life data sets that follow Benfords Law for example twitter users by followers count.

There are however some data sets that do not follow Benfords Law these include

  • Data sets where numbers are influenced by human thought (eg. shopping centre prices which are set through psychological thresholds)
  • Data sets where numbers are assigned (bank account numbers, telephone numbers…)
  • Data sets of bank accounts with a built-in minimum or maximum

In the real world Benfords Law is actually used as part of a set of analytical tools to detect fraud. If data sets in accounting don’t follow the logarithmic probability, accounting fraud has likely taken place. Here is an example of Benfords Law used to detect accounting fraud.

So there you have it. Benfords Law. One of my favourite counterintuitive curiosities.

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Timelapse: Santos GLNG City of Lights | Brisbane Festival

Last Friday my friend Matthew and myself decided to do some photography around the Brisbane CBD toped off with a timelapse of Santos GLNG City of Lights. The Light show runs for 10 minutes or so three times a night (7pm, 8pm and 9pm). We originally decided to shoot at one location for the first show of the tonight, however after we shot the first timelapse which each frame was a little overexposed we decided to stay and try again with more appropriate setting. For those who are thinking of going and want to shoot some pictures here are the setting we used:

For the timelapse we shot on a Canon 60D with a Tokina 11-16mm lens. Each frame was exposed at 2.8f for 1/25th of a second at 800 ISO. A frame was taken every 2 seconds for the duration of the show. For stills we used a  Canon 60D with a 18-135mm IS lens. Each frame was exposed at 5.0f for 1/10th of a second at 800 ISO.

I’ll post up photos of the day soon. Let me know if you have any questions.

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Review: MAKE Magazine – Volume 31

To summarise MAKE volume 31 is a few words is not quite a fair task mainly because of the copious amounts of stories, projects and interesting subjects that lie within. Wether your interested in remote controlled cockroaches, binaural beats, DIY scanning electron microscope or creating high voltage (22kV) sparks from running water MAKE volume 31 seems to have something for everyone who is interested in hacking, making and crafting.
The theme of this issue of MAKE is punk science, the concept of running with your ideas and projects first, then questioning yourself afterwards. The most prominent feature article on this for me would have to be a hackerspace in Japan during the aftermath of  the Fukushima Daiichi nuclear disaster. Instead of waiting around for information on radiation contamination they put together a system to record radiation levels (with corresponding GPS co-ordinate) while driving around. Although crude at first (geotagged pictures of a geiger counter display readout) the system kept on been revised and developed into a complete system. This example reflects well the ideology of this issue of MAKE: Doing first, questioning yourself later.

This issue of MAKE also comes with loads of projects people have done to draw inspiration from as well as a good selection of projects you can do at home with full instructions, bill of materials etc. Some of the more notable (at least for me) projects this issue were Lord Kelvin’s Thunderstorm, a system to generate HV sparks and PVC pipe speakers which use PVC pipe to create a resonation chamber. I can’t wait to have a crack at trying some of these projects (in particular creating HV sparks from flowing water), In addition to this the projects mentioned have also given be some ideas for future personal projects.

All in all I’ve really pleased with this issue of make. I do wonder if some of the projects and stories I could have found out about elsewhere on the internet, however I’m not overly worried because what I see MAKE doing here is sharing and showcasing peoples projects, ideas and storied so that a wider community of hackers and makers can benefit from them.

Disclaimer: I received a free copy of MAKE Magazine Volume 31 to review through O’Reilly Blogger Review Program. All comments represent my thoughts and opinions.

I review for the O'Reilly Blogger Review Program

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Counterfeit Gods | Spoken Word

7 months ago you may remember Jefferson Bethke’s viral video Why I Hate Religion, But Love Jesus that received over 22 million views. Today Jefferson is back again with a new spoken word video inspired by Timothy Keller’s book Counterfeit Gods.

Jefferson takes on the reality that whoever you are, wether you believer in God or not there is something in your life that you look to to give you the satisfaction and security that only God can fulfil. For some this may be their career, how well they are doing compared to the ones around them, for others their family/significant other.

Some worship in stadiums, some worship in bars.
We worship our posessions, we worship our cars,
We worship science, or we worship the arts,
But see it don’t matter what clothes your idol’s wearing, the disease is our hearts

Romans 1:25 describes this as worshiping creating things not the creator

They exchanged the truth about God for a lie, and worshiped and served created things rather than the Creator (NIV)

How do we identify these functional saviours? Jefferson points out

If you can’t give it up, you don’t own it. It owns you.

The problem with these things is that in the end they never give ultimate satisfaction. So what has God done about this? God in his rich mercy sent his son Jesus to pay the price of our sin by dying on the cross and conquering death coming back to life. What to we have to do to be saved? Romans 10:9

If you declare with your mouth, “Jesus is Lord,”and believe in your heart that God raised him from the dead, you will be saved.

As Jefferson concludes

But like a Father, he couldn’t bare his children to not be free
So he thought up that tree, paid our fee, for specs of dirt like you and me
So my plea is let Him restore His proper place,
I promise you He loves you right now. Just trust in His grace.


7 Eleven BYO Cup Day 2012

Each year 7 Eleven has a special day where you can fill up a cup with slurpee mixture for $2.90 and this year that date is today. But before you go searching for the biggest vessel you can find here are some thing to note.

  • The cup must me water tight
  • The cup must be clean and safe to consume from.
  • The cup must be no larger then 23cm (width) x 26cm (height)

So currently I have three candidates for cup from myself, a 4 litre ice cream can, a celebrations (chocolate) box and a glass jar (complete with cork). By far the glass jar is my favourite choice (and it fits within the size restrictions, just) however measuring all sort of things around the house got be thinking. What is the maximum amount of slurpee you can get?

The Maths

Ok so first we need to calculate the amount of volume the ideal vessel can hold. The size dimensions are 23cm wide and 26cm high however we aren’t told if the width is the diameter of a circular base, width of a square base or the hypotenuse of a square base. From the promo video (above) we see that the hole each cup has to pass through is round so we will run with that.

max volume = pi*r^2*h

max volume = pi*0.115^2*0.26

max volume = 0.0108 cubic meters

Now we know that there are 1000 litres of water in a cubic meter so…

max litres = 1000*0.0108

max litres = 10.8 litres


So there you go, the maximum amount you can hope to get 10.8 litres of slurpee mixture which works out to be about 27c per litre. If you can get an optimum square container passed it work out to be about an extra 3 litres you can fit in but it’s up to each 7 Eleven employee to allow your container. So in light of that here are my three tips for BYO cup day.

Find the biggest cup you can, that fulfils the previous conditions.

It just makes sense, the lager the cup the more value for money you get. For my cups I’ve found, each only hold about 4 litres but that’s still not that bad. If you can’t find a cup I have a couple of friends that are going to try to use a family sized KFC bucket so you can give that a try.

Think about how your going to store it

Depending on how thirsty you are (and how many friends claim a share to your spoils) you should probably think about how you are going to store the remains of what you cannot finish. Here I’d recommend freezing it and cutting off pieces to either enjoy as an ice block or crush up with an smoothie maker or similar to try to make a slurpee consistency. What ever you do it’s doubtful you’ll get it to the same texture as you bought it for reason i’ve mentioned before.

Don’t worry if you miss out.

There will be plenty of other opportunities in the following years to get free slurpees and other promotions on 7/11 day, 7/11 $1 Day etc… Not convinced? I find it can be helpful to realise how fortunate we are in Australia. Many (>90%) of the word will never see/know what a slurpee is, so if you miss out on the opportunity to get one for better than normal value  no it’s not the end of the world.