Wearable computers (by alaric)

One of my too many projects is to make a wearable computer.

Lots of people are interested in making wearables, but nobody's yet come up with one that hits a "sweet spot" of decent functionality along with it being unobtrusive enough to not be a pain.

Well, I'm a nerd, so I'm far happier to put up with obtrusiveness to get my pervasive cognitive-assistance fix... I've been fascinated by pervasive computers since I was a kid; I read about Steve Roberts' recumbent bicycle as a youngster, as well as plenty of fiction about brain implants and the like.

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Heating an old house (by alaric)

Sarah feels the cold keenly, while I can usually just put on some more warm clothes to deal with British winters. But even I was finding it hard to work in my home office when the temperature went below ten Celcius; fingerless gloves still let me type, but numb fingers increase my error rate, and the pain is distracting.

Part of the problem was that our house is draughty. There were a lot of gaps in the window and door frames, through which daylight could be seen; when it was windy and rainy at the same time, the wind blew rain in through the frame of the large window in my office.

So step one was to fix these. The large office window, it turns out, is somewhat curved, so when my brother in law was visiting, we screwed extra handles to it, pulled it properly closed with levers wedged in the handles, then did up the bolts at top and bottom to force it to stay in shape, which fixed a large source of draughts.

Then I want around a few other choice places, adding draught excluder strips where I could.

Next challenge was to increase the heat. We had only one real source of heat in the house, a wood/coal burning stove at one end of the house. Since it's a long thin house, this was little help for me in my office, right at the opposite end - but it didn't even make enough heat to keep Sarah happy sitting next to it, so she would often use the expensive electric fan heater to keep her temperature up, much to my concern (for if we can't pay the electricity bill, things will quickly become rather unpleasant).

Now, the grate in this fire was rather small compared to the size of the fire itself. The grate had only sides and a front, so had to be pushed back against the firebricks in order to not spill coal out. This meant that air coming in through the vents would tend to rise over the fire and up the chimney, taking heat away without imparting much oxygen to it. Even then, it would slowly wriggle forwards over time, spilling ash and coal down behind, until it came too far forwards for the ash shovel to be pushed underneath it, meaning the fire would choke itself. But as it moved forward, the effective volume fire increased, with a notable improvement in the heat output - even though the fire at the back would be starved of air from beneath, as it sat on a bed of ashes.

While rummaging through piles of random bits of metal lurking about the place from when we moved in, though, I found an iron grating that I suspected might be able to fit in behind the existing grate, enlarging it. Sure enough, it did - and it fitted so perfectly well that I suspect it was actually meant for it. Suddenly it was possible to have a large bed of coal in the fire, with air coming in through the vents from underneath it and being drawn up through; this led to an awesome increase in heat. However, it led back to the same old problem - we now didn't have room to get the ash shovel in underneath to take ash away. And so the fire would slowly choke itself with ash.

So I ordered two metres of 25mm square hot-rolled mild steel from Hindleys, my favourite home-engineering supply house. When it arrived I used my angle grinder to chop off two lengths of the stuff, then used them as spacers on either side of the grate to lift it up an extra inch.

And now the fire's awesome. I can easily get it so hot that it becomes mildly terrifying, an angry yellow glow emanating from the air vents as it roars away, the radiated heat unpleasant to be too near. A few days ago, it actually melted the plastic crates we store our newspaper and kindling in, purely by radiation.

But it's still rather cold in my office.

So we decided to spend some money on the problem, as it was in danger of harming my work. I went down to John Stayte Services, a local purveyor of awesome things. We buy our coal from them, but they also sell propane, butane, related accessories such as heaters and Sievert torches, workwear, and animal feed. To my delight, they had a deal on; a shipment of gas heaters had been damaged due to the shipping container being broken into by illegal immigrants who built a home on top of them for the duration of the voyage... so they were selling a slightly dented heater, along with a cylinder of butane, for £89 when normally a heater alone would cost more than that (and a gas cylinder £50 or so as an initial outlay).

I set it up in my office, lit it... and over the next few hours, the temperature rose from ten degrees to about twenty, with me correspondingly shedding layers of clothing. Since then I've been running the heater on low power, and the temperature's stayed around seventeen degrees; with the stones of the building having been warmed up, it's now not taking much heat to keep it nice and warm.

And so, I can proudly state, for the first time since we moved in, it's actually warm enough at home that we are turning down heat sources so as not to be too hot!

The workshop’s getting there (by alaric)

My good friend and colleague Andy came over to stay for a while, which meant I had 'entertaining a guest' as an excuse to do some of the fun stuff I've wanted to do for ages.

So we finished making the welding bench! I'd made the top and gotten part way through cutting the legs to length, so we finished cutting them and welded them in place, then welded extra flat strips around the bottom to make it reasonably rigid. It's all just tack welds, and it'll almost certainly need some diagonal struts added, but it stands upright and is surprisingly sturdy; I'm going to experiment with it a bit to see just how many more struts it needs. I'd also like to drill holes so I can mount my vice on it, too.

Then we cleared a space and moved my electronics workbench down into the workshop! This is great news, as it clears up space in the office (albeit revealing the piles of junk that were lurking beneath the bench), means all my tools are in one place (which is most convenient, as things were always in the wrong places), and creates more storage space in the little garage, meaning less stuff on the floor.

I've since reincarnated my power distribution rail, which I had when we lived in Ealing, but haven't used since; the idea being that it'd be good to do my electronics experiments on the end of a dedicated RCD so I don't trip the one in the house. It also splits the output into four circuits, each with a six amp circuit breaker (the smallest I could obtain easily).

I still need to get rid of a lot of waste cardboard that's sitting around, and we're still looking after Seth's motorbike, and there's still junk to be sorted - many things need to be elsewhere; the little garage isn't a place to store things we only use a few times a year, as we have the Big Yellow for that!

Although the lighting's not really good enough when I'm explaining the power rail, here's a quick video tour:

For my next trick, I'll stop procrastinating by building infrastructure, and get on with actually making myself a digital watch with an embedded ARM processor and colour dot-matrix LCD. Watch this space.

The van is fixed! (by alaric)

After the van's sad demise, it went off to Sarah's excellent uncle David to be fixed.

Anyway, he sorted it out, and I picked it up last weekend, but I've only had a moment to write about it now!

Basically, the front right wishbone had broken. It's a big triangular metal thing that attaches to the chassis on two hinges, and then attaches to the wheel at the other end, with the shock absorber coming down into the middle. As the van rides over bumps, it pivots on the hinges, regulated by the shock absorber. So it plays an important part in supporting the weight of the van.

However, knowing I'd be interested, after replacing it with a new one, David put the broken one in the van for me to take a look at!

I'd have expected something like this to be a solid casting - but no, it's two pressed sheet steel shapes welded together, making a hollow body. It looks like thick steel, 3mm or so, but near where it's cracked apart, it's more like 1mm. I presume that's due to corrosion over the years.

Here's the new one - in situ, under the van. It's the shinier, blacker, cleaner looking part, although it's already picked up quite a bit of mud.

The old one is now in the little garage, awaiting cutting apart to investigate its construction and exact reason for failure, then WELDING PRACTICE!

Learning basic manual metal arc (stick) welding and MIG welding (by alaric)

A long time ago now, when this blog was in its infancy, I wrote about how I had picked up a cheap manual metal arc welding set from B&Q since I needed to make some tools that would survive within the environment of the furnace. My existing metal-joining technology, silver soldering (aka brazing) would produce joints that would melt like butter at 600 degrees Celsius or so, which is a far cry from the thousand-degree environments I play with...

But as I mentioned slightly earlier, arc welding is easy to get wrong. I learnt from a book, so had only written descriptions to go by, and I was hard put to know what I was doing wrong that made my welds all messy.

Well, today I attended the Insight into Welding course at the Rural Skills Centre, which is near Cirencester, a short drive away from where I live. I had been looking for a welding course for a while - most of the courses I saw advertised at local colleges were formal affairs that took several days and ended up with you taking some kind of assessment, and ending up with an NVQ. All rather formal and constrained.

The Rural Skills Centre, however, does lovely little one-day or several-evening informal courses in all sorts of useful workshop skills. My welding course began with the instructor asking what the seven participant's past experience was, and what they hoped to learn - and then taught us just what we wanted to know, starting at the right level for us. Rather than having a fixed syllabus to be assessed against, we were basically paying to spend a day in a workshop with an experienced welding instructor. Which was perfect!

He quickly sorted out my arc welding problem - I held the electrode too far from the work, so it spattered all over the place and didn't heat the metal properly, thus creating a weld consisting of lots of little blogs sitting on top of the metal rather than bonding into it. Easy once you've seen how it's done properly 🙂

So having already got my money's worth before lunchtime, I practiced with the manual metal arc machine for a while, then moved up to try MIG welding - Metal Inert Gas. This is a much fancier setup than arc welding; the machine feeds a metal wire and shielding gas into the work for you when you pull a trigger, rather than you needing to manually control the distance between the end of an unweildy electrode and the work to within a few millimetres. As long as you have the voltage and wire feed speed controls on the machine set correctly for the wire you're using, the metal you're joining, and the kind of join you're doing, it's point and click - just hold the tip of the tool to the metal, pull the trigger, and keep the tip moving along smoothly, and you end up with lovely nice welds. Of course, knowing how to set the controls up right is the hard part, but we were taught foolproof techniques to home in on the correct settings.

So I spent much of the day practising with that, producing various kinds of joins in various thicknesses of mild steel. I'm quite taken by MIG welding - the equipment is a bit more expensive to buy and run than manual metal arc kit, but it produces vastly superior welds, and can be used on aluminium (manual arc can't do that).

But the best process for aluminium is TIG welding. A TIG welder doesn't put any metal out at all - it just produces intense head by driving an arc from a tungsten needle to the workpiece, while spraying the area with shielding gas like a MIG welder does. You have to feed your own extra metal in by hand to make the joint. But it's incredibly neat; the arc is tiny, and still - in the other processes the arc always seems to jump about a bit. The TIG arc was like a little flame a few millimetres long, and underneath it, the metal melted into a shiny puddle. Since it was so small you couldn't go very fast with it, but it produced incredibly neat welds! However, sadly, the TIG welding equipment is quite expensive, since the power supply needs to do some quite specialist regulation to create that easy-to-control neat arc!

So I'm going to keep practising my arc welding - but I'll be keeping my eye out for a MIG welder if I find one cheap or if I get rich... and I certainly wouldn't say not to a TIG if I somehow manage to find one I can afford!