Graph of the Day #36 – Only two seasons, it’s just a question of ratios

If you like this graph and associated commentary, remember to check out the rest of my graphs on this blog, here: Graphs of the Day

So why graph number 36 without graphs 32-35? Have I forgoten how to count? Am I having a brain fumble right now? … Well, I can’t rule any of those out, but no; I just thought that this one needed to be published while we are still in the grip of that most merciless of seasons: Spring.

GOTD #36 - Only two seasons, it's just a question of ratios.jpg

I have friends from different walks of life, but there’s something very comforting about discussing the weather with engineer friends at work, and being able to say things like “yeah, you intuitively expect it to be a nice analogue S-curve, but in reality it’s more like a bulls**t PWM output, that makes it impossible to give the kids the right amount of bedding”… and they just nod in agreement and I don’t have to spend the next 5 minutes at a whiteboard explaining myself.

Also, climate change is real.

You should listen to the experts who study the climate, as they are actually the only experts on the topic, and peer reviewed publications are the most reliable methods for sharing their knowledge, as it lets other experts in the field disagree and\or comment. Also, there isn’t really any money in climate change, so most of the vested interest is on the side of burning fossil fuels… no-one ever got rich by studying in academia.

Also, even companies that DO have a vested interest in denying climate change are acknowledging the issue (Shell, South32, etc)… I mean, mostly their reponse is a bit soft, because they have a vested interest, but they acknowledge that it’s a disasterous issue… Look, we all need to do better, okay? Just acknowledge the problem and work harder, everyone.

Graph Number: 36

Graph title: Spring in Brisbane
X Axis: Season

Y Axis: Temperature

General shape of graph: S-curve + PWM digital equivalent

How it works: This spring in particular seems to have had a lot of up-and-down weather. Rather than the days gently increasing from cold winter, through warm winder to hot summer, it seems to have been jumping from winter to summer, then back. the duration of these excursions from cold to hot seems to have been increasing in duration, to the point that now hot is the norm and then we’ve had the occasional brief cold snap… this is called Pulse Width Modulation. The signal is either on or off, and it pulses on for a certain portion of each cycle (the cycle period remaining constant). As the width of the pulse increases, the average value increases in the same proportion. If the cycle duration is short enough, compared to the response of the system, this is a really great way of using a digital control system to control an output. The inertia of the system means that the output is smoothed out, so you see it as a linear change in value. Good applications are:

  • Controlling the torque\speed of a DC motor.
  • Controlling the heat of an oven, sous vide, 3D printer nozzle or other heater that needs to achieve a temperature set point.

It’s not a good method for controlling the weather, because I like to be able to wear the same jacket each day, and use the same type of blanket on the kids bed for an extended duration without worrying if it’s now too cold for them.


Graph of the Day #31- Keeping it in Proportion

If you like this graph and associated commentary, remember to check out the rest of my graphs on this blog, here: Graphs of the Day

GOTD #31 - To Nuke, or not to Nuke.jpg

It’s been a while since I posted any graphs. Sorry about that (I assume, of course, that a great many people have been disconsolate without my intermittent insanity). What can I say? Life happens.

This one was drawn a long time ago, inspired by work lunches and the many, many minutes spent staring at my lunchbox, trying to figure out if I should microwave my lunch, eat it cold, or separate a portion to microwave it separately before reassembling the meal (Hah! not going to happen).

Seriously, I have spent far longer than you’d expect (but still a totally acceptable and not at all weird) amount of time staring vacantly at my lunch box.

A coworker once tried to restart me, thinking that my OS had frozen.

Bon appétit.

If people just designed things right to begin with… #4 – MORE POWER!!!

So the other day my wife said that she needs some portable lights, for some twilight markets that she’s going to. I had a nagging feeling that we had a solution somewhere in our home, but I couldn’t think of exactly what it was, so we went to look at Bunnings. And let me tell you, they had a HUGE range of unsuitable options that were all various combinations of:

  • Too expensive
  • Too weak
  • Too focused
  • Requiring AA or AAA batteries
  • Having built in batteries that won’t last the whole evening.

What I needed what something that would:

  • Use high capacity, rechargeable batteries
  • Ideally use replaceable batteries, so that I could have multiple batteries ready to go (giving extended run time)
  • Produce plenty of light (ideally 2000+ lumens)
  • Spread the light well over one or two tables (not so diffuse that you can’t see well, but not so focused that it’s like a spotlight)
  • Cost little or no money
  • Reuse existing materials, to reduce waste (because the environment is important)

So in my head I crammed together all of the spare parts and bits and pieces that I have laying around the house and garage, and here’s what I came up with:

  • We have plenty of standard LED lightbulbs of various power ratings and good brightness (shout out to the Lightbulb Audit), 240V AC.
  • We have plenty of bedside lamps
  • I have a 12V DC to 240V AC inverter in the car.
  • I have a 16-24V to 12V power supply on a wheelchair robot, that’s gathering dust in the garage.
  • I have multiple 20V cordless tool batteries (for the electric lawn mower), with enough capacity to power a light source for hours and hour. These are Xfinity (i.e. Aldi cordless tools) batteries. We have 2x4Ah and 2x4Ah batteries.

When I put them together in that order, I had a system that will achieve all of my requirements. All that it needed was some 3D printing to connect it all together and make it look flash. I also needed to buy a lighter socket from Jaycar, so that I didn’t have to dodgy up the connection between the DC converter and the inverter.

Check out the 3D models on Thingiverse if you want to print a copy for yourself:




In the end, it all connected up neatly together, and actually looks really good! I think I’ll upgrade it in the near future to include a USB output (I have a 12V to 5V USB charger adapter laying around) and maybe include a set of 20V and 12V output screw terminals, just for the heck of it. And maybe I’ll make some other random DC tool attachments!

You can see in the photos some red “speed stripes” on the battery connector… I may have trial fit the connector before I’d finished removing all of the support material post-printing, which caused a delamination crack, so I had to use my 3D pen to weld it back together along the crack.

After some testing, I confirmed that I can get about 1.5 h of run time, using a 2 Ah with 3 lamps totaling 19.5 W rated power.

For the parts I used:

Crimped spades:

12VDC socket:

Batteries: Xfinity cordless tool batteries (Available intermittently from Aldi)

DC-DC converter: Unsure. Just needs to be rated for 20V input and 12V output, as high a current rating as you can get. I’d say aim for 2A minimum to run a couple of lights. Ideally much higher.

DC-AC inverter: 150W 12V DC to 240V AC inverter. Available from Jaycar.

Graph of the Day #30 – Hierarchy of Controls

If you like this graph and associated commentary, remember to check out the rest of my graphs on this blog, here: Graphs of the Day

GOTD #30 hierarchy of controls

Anyone in design, engineering, construction, or related fields would probably know about the hierarchy of controls. And anyone in an engineering or drafting environment would understand exactly what I’m talking about here.

Everyone else… well, you can’t please all of the people all of the time.

Graph of the Day #29 – Happiness is Finite

If you like this graph and associated commentary, remember to check out the rest of my graphs on this blog, here: Graphs of the Day

GOTD #29 - Happiness is Finite.jpg

We all have that coworker who is just too damn cheery. Let’s call them “Jesse” (because that’s what my one is called). Walking around, smiling, with their “pro-happiness” agenda…

Most of us, when someone says “howzitgoin’?”, understand that this is just a general greeting of sorts, and reply with a polite obfuscation. We do this because we realise that, while the other person may (in theory) care about it going well, they don’t actually want to know how it is going. The “it” in this scenario, is you keeping your shit together enough to make it through the next 8 or so work hours without making it their problem. If you actually tell them how it is going, and expose to them the turbulent mess of mild (or serious) psychological issues, goopy organic systems on the verge of complete breakdown, and general disorder which is lurking beneath what is really quite a thin water resistant membrane covered in probably the wrong amount of hair (i.e. your skin)… well, they would probably think you’re a complete loony.

And rightly so.

But not this guy. This guy? He tells you how he’s going. He tells you that he’s doing great. And the worst thing? The worst thing is that he actually means it!

Like a bastard.

Anyway. If you see them walking around the office, soaking up all the happiness like a sponge… just remember this graph, and… Okay, I won’t advocate actually causing anyone real harm or inconvenience, but… I dunno… drop an onion on his head?


Serious note: While I make light of psychological problems in this post, I am a big supporter of anyone and everyone taking measures to look after their mental health. I believe that mental health actually IS part of your health, and I think that we need to get rid of the remaining stigma and tendancy of some people (idiots) to belittle the persuit of mental health. Please people look after your mental health, and the mental health of those around you.


  • Talking to your GP about your mental health, the next time you are seeing them about your physical health. you can squeeze this kind of discussion into a doctor’s visit without paying for it. Win!
  • IF you have anything that’s stressing you out, consider talking to a psychologist; It’s not just for crazy people any more.
  • Exercise
  • Sleep
  • Have a close friend that you can talk to
  • Have a hobby

Graph of the Day #28 – Problem belong someone else

If you like this graph and associated commentary, remember to check out the rest of my graphs on this blog, here: Graphs of the Day

GOTD #28 - So chunky you could carve it

So, just to be clear: This post does not constitute engineering advice. I’m not trying to tell you when to start treating your slurry as non-Newtonian; that’s obviously a complex question that depends on the liquid, the solid, particle size and shape, etc… but what I will tell you is this: If you want to talk about handling something that’s MOSTLY ore, but has more than 20% liquid (w/w) in it? That problem belong someone else. I mean, I’ll have a crack at most things, but really, I’m a bulk materials handling engineer.

This graph was prompted by someone asking about conveying material with 30% moisture, and I’m like “go talk to the pumping guys!” and when I spoke to one of the pumping guys later and mentioned it off-hand, the response was “*sigh*…really? just add a bit more water… what a pain”.

I dunno… there isn’t really much humour to be had here, but if you have a hobby or profession that has anything to do with water or rocks, why don’t you try to have some fun and see where you would sit on this graph. in fact, why don’t you print a copy, mark yourself on the graph, then upload it and let us know in the comments! for instance:

  • Do you study asteroids? —– > 0% solids and >100m particle size (okay, I’m using 0% solids as short-hand for 100% water, or ice)
  • Do you study planets? —- > 90% solids and >10,000km particle size
  • Where would fishing sit on the graph?
  • etc

Maybe you can come up with some humourous additions… I’m all about the user-generated content!

Graph of the Day #27 – Triforce of Obscurity

If you like this graph and associated commentary, remember to check out the rest of my graphs on this blog, here: Graphs of the Day

GOTD #27 - Triforce of Obscurity.jpg

When you feel like no-one cares, just remember that someone, somewhere, actually cares, and they are on the line just as much as you are, and they have the power to help you achieve your goals…

You will never meet this person.