Mastering Entropy

TL;DR: I’m using a relatively low powered cartridge heater to heat the water so that it can use the same power supply as the Arduino. For aesthetics it will be inserted into a sort of electric hob style spiral set up made from copper.

I said previously that some part of my brain had sketched a parts list for this project, however, now that I sit down to materialise that into an order form, it is becoming clear that it skimped on the details. It’s becoming increasingly apparent that a heater, a light and an Uno board does not constitute a parts list for this project. Finding a suitable heater is tricky, thankfully, as I mentioned in my last post, I’m interested in 3D printers.
There was a mild interest before with my uninspired Arduino build but this year at uni I had the pleasure of working to prototype some sensors and anytime something I needed didn’t exist I would just go home, design it and send it to the technician, the next day it would be sitting in a bag with my name on it. Completely bespoke, a perfect solution. Or at least perfect within the confines of my designing capabilities. I defy anyone to not be completely spellbound by 3D printers after having used them to do something genuinely useful. Imagine a world without compromise – if something is too big or too soft or too red, you can just tell this machine to make you a smaller, harder, bluer version. And it will . . . Madness. This obsession will no doubt lead me to buy one and Amazon is keen to be in on the action. I’ll go shopping for a first aid kit and the screen will contain the absolute minimum amount of medical supplies that it knows I’ll tolerate, the rest being a mosaic tile arrangement of: 3D printer parts at low low prices; stylish coffee makers crafted from exotic looking wood and shiny metal; and books that promise they’ll help me get my life together. Amazon really does know me, and now, so do you.
Thankfully one of these printer parts is the heater used to melt the printing material, which I think looks about perfect for heating a single cup of water.

Simply dipping it into the cup as an immersion heater would never suffice though, far too inelegant. Plus, as any Irish person will know, there is a horrible stigma around the use of an immersion heater – the cause of many’s a family argument:
“Who turned the immersion heater on/off?!!”
“The water from the central heating is plenty warm!”
“The shower ran Baltic after 5 minutes, I’ve near caught pneumonia!”
“Our electric bill is sky high because of that thing”
“Tell *insert family member* to quit using their xbox/laptop/electric heater all day if you’re worried about electric, I need a shower!”
Clearly an immersion approach won’t work. I think I could rig the heater up to a hot plate and use an enamel camping mug pretty easily though. I’ll use a copper wire to form a spiral that dips out at the centre to wrap around the heater. Copper also has the benefit of being very nice to look at.
I don’t think I explained it very well at all so here’s a photo:

The big question is will it work? The heater I want has to be small and take a 12V supply, this limits power to about a 50W, or, 3% of a typical kettle. I could have a heater similar to a kettle but it would require a separate power source as the Uno board (brains of the operation) can only accept a maximum of 12V. So, it’s either cap the heater at 12V too or provide it with power from somewhere else. If an immersion heater approach is inelegant, having two different power supplies wired into the clock is abhorrent.

I’ve done the maths around it a few times and it checks out that a 50W kettle would nearly boil a cup of water in about 20 minutes, which is fine as I’ll be asleep anyway. The problem is, this isn’t a kettle – it’s basically a hob and saucepan, which the internet slates as about 50% less efficient. I’m optimistic though, comparisons on efficiency are difficult to make, especially when I’m building this hob myself and can tweak it to make it more kettle-like. One solution I suppose is to put an insulating sleeve and lid on the cup to ensure it retains all the heat it is given, however, the inclusion of a plastic cup-cover is going to make designing this thing to look as good as it has a right to be (it is a bespoke, hand-built alarm clock after all), considerably more difficult.
For now I know I want a cartridge heater from a 3D printer, some copper tubing (the type used for refrigerant systems) and a 12V power adapter with enough juice to power the 50W heater and an Arduino Uno. I definitely don’t want the heater robbing the board of power.
This is where the mothers lifting cars to save children legend becomes germane, the brain has told the muscles to try and save the child, knowing if things get out of hand it can always take the reigns again and ensure its own preservation returns to being number one priority. It has forgotten, however, that it shares a blood supply with the same muscles it has commanded to perform a very bloodthirsty task. The muscles begin, politely, with their usual allowance of the body’s blood supply but that doesn’t cut it, so they start robbing blood from every other organ in the body, including the brain. The brain is now left with no blood to fuel it. It might very well want to slam the brakes and say hey, we’re in major trouble here, forget about the child, I need that blood to keep us safe. However, without the energy it’s being robbed of it can’t scream its message loud enough to overcome the bedlam besieging the muscles as blood floods into them from all directions. The whole process leaves the muscles torn apart and a brain that has known true anarchy for the first time, now unsure how willing the body will be to return to the dictatorial regime which up to now there had been no alternative to.
In a much less interesting way, if the Arduino turns on the heater which takes 50W from a 50W supply, that leaves nothing for the Arduino, so it can’t send the stop signal until the heater has reached temperatures where it melts its connection to the power supply, at which point there will most certainly be a smouldering puddle of plastic releasing every carcinogen under the rainbow on my bedside cabinet.
All of that isn’t completely true, the heater and Uno have a slightly more democratic way of splitting the power but there’s definitely the risk of a necessary stop command not being sent if the supply is overloaded.
A 60W supply should be fine.