Moving house (by alaric)

I hate moving house. It's a lot of work, for a start. It's a period during which all your stuff is packed away so you have to make do continually. And you have to tear apart the home you spent years building, while remembering all the fun times you had in the cold, empty, rooms you are carrying boxes out of. It feels a bit like burning your own wedding photos...

...but soon, it will be over, leaving just the mild frustration of living in a home where many of your possessions are still "in a box somewhere", but at least then you're on the upward path of things continually getting better as you unpack things and find them new homes, slowly customising your new space.

I'm looking forward to sorting out my workshop. It's currently just full of things all over the floor. I'm taking a week off of work to recuperate from the moving, and to sort it out. I'm going to pile everything at one end so I can paint the floor and finish painting the wall, then move everything to the nice end so I can finish the floor and walls in the other end. I'm going to set up my desk, my electronics workbench, and my welding bench. I'm going to run Ethernet into the house so I can get network connectivity. I'm going to set up a 12v power distribution system for fun stuff, such as a Raspberry Pi in a box driving an LED matrix display and a USB hard disk (as a Ugarit distributed storage node) and crazy future home automation experiments and LED lighting in the nearby shed (it's hard finding stuff in there in the dark). I'm going to fix the leaky roof and the draughty eaves so it's warmer and dryer in there. I'm going to rebuild my furnace and experiment with casting aluminium bronze. I'm going to build my wife a radio telescope. I'm going to build my wearable computer and continue my project to bring about my own technological singularity. I'm going to make time for myself to turn some of my unrealised ideas into beautiful things.

Alaric’s projects for this year (by alaric)

This year's going to be pretty busy with settling into the new home, but I have a few projects.

1. Finish the ring casting I nearly finished before the move. That's a priority.
2. Resurrect my aluminium foundry. In particular, it's our bronze wedding anniversary, so Sarah's going to design a pattern for a sundial, which I will cast in Aluminium bronze, a nice alloy that I can make myself from my scrap aluminium and bits of old plumbing...
3. Continue with minor stuff on Ugarit, but as a milestone, build the distributed storage backend, which will rock.
4. Work on my wearable computer project. No specific milestone for this, as it's currently a long drawn out research/prototyping phase as I sort out many details.

Wish me luck... I usually suffer from "all my weekends getting eaten up", but as my New Year's Resolution has been to spend at least one day every two weeks doing something fun with my children, I'm going to be booking weekend days in my calendar in advance through the year for that and my own projects. Before they get filled up!

Ring casting (by alaric)

A friend has asked me to cast her some silver wedding rings. So I am adapting my aluminium casting experience to silver...

The thing to use for silver moulds is cuttlefish bone, which is soft enough to easily carve into shapes, but can withstand the heat of molten silver. For a single pour, at any rate.

In order to get a repeatably round shape of the correct diameters for the two rings, and so I can quickly carve new moulds if my pouring fails so I can try again, I decided to make boring tools that carve ring shapes of the correct diameters.

As you can see, they're made from nails, hard soldered together, and ground to a cutting tooth at the end. The central spike goes down a guide hole I drill in the cuttlefish in advance.

The tool needs to come down exactly perpendicular to the flat surface of the cuttlefish (made by sawing one side off and then sanding it flat), so I made a special jig to hold them:

Then it's just a matter of fitting the tool in a chuck and bringing it down. I first tried rotating the tool by hand, but the result was a bit rubbish, so I bit the bullet and just turned the Dremel motor on, which produce a quite perfect circle.

I made a couple of moulds, each with a matched flat cuttlefish to go on the other side. I had to carve channels for the silver to flow in by hand, using a screwdriver for rough gouging and a craft knife for the finer parts.

The silver was heated by blowtorch, in a refactory cup called a scorifier:

But first I had to prepare the silver I was given - in the form of a coin, which I felt a bit bad about sawing in half:

I melted half of the silver and poured it into the first (roughest!) mould:

When I cracked it open, it seemed I'd not used enough silver, but everything had otherwise gone well:

So I pulled the incomplete casting out, crushed it up, and added the other half of the silver, and gave the second mould a go. Here's a picture of it with the channels cut, before I clamped it:

I put it all together and got ready for some melting:

But this time, as soon as I started pouring, the silver suddenly froze on me, so hardly anything went into the mould:

It seems that the larger mass of silver wasn't heated up quite as far as the first pour had. I need to rearrange my firebricks to make a better forge to heat the silver in, so heat loss is slower, I suspect...

Hall effect sensors (by alaric)

At the Bristol Hackspace this evening, I powered up a Hall sensor.

The Allegro A1321 takes a 5v supply and outputs 2.5v - plus or minus 5mV per gauss of magnetic field in the sensor.

It turned out that small magnets don't produce many gauss, so I added a 741 op-amp with a gain of about 100 to get more useful output voltage deflection!

Here's the experimental setup:

WIth no nearby magnets, we read about 3v:

But with a very nearby magnet, we get a large deflection, which drops as we get the magnet many cm away, but is still significant:

Clearly we still get significant readings a good distance away, and the nonlinearity isn't too bad; it doesn't max out with the magnet very close but still varies many cm away.

For my next trick I'll make a few of this circuit on some veroboard and hook the outputs up to an AVR with several ADCs that I have lying around, and try comparing the results to measure position (and maybe orientation?) of a magnetic probe...

Motivation (by alaric)