This website is not masterful. It is devoted to things
I do either because they need doing, or because I enjoy doing them,
and which someone else might possibly want to do. Perhaps if my
mistakes are included here in enough detail someone else might not
make them…
I am not an engineer, or a software developer, or a mechanic, or a
carpenter, or a bookbinder, or anything else I might pretend to be on
these pages. I am just an Amateur, but in real life I’m a PhD student
in Theology. Except insofar as the aformentioned things I am not come
in to it, this is unlikely to be apparent here.
This website is purely static, and is the successor to a wordpress
blog.
Napkin Rings
Posted on October 26, 2018
(Last modified on October 6, 2020)
| John Morris
One expects a student’s life to have a certain ascesis to it. One, for instance, does not buy rings for one’s napkin, one makes them. And so I procured some cord (the seller considered me carefully and then said that I had a face which permitted me to indulge in sailing, which in turn justified buying cord to tie knots—‘Sailors fiddle’, she said approvingly; though I cannot play the violin). And I procured a helpful video on the tying of 3-lead 8-bight Turks Heads, because I can never remember any of these fancy knots.
[Read More]Clap-clap switch
Posted on September 19, 2018
(Last modified on October 5, 2020)
| John Morris
I’ve always thought of those clap-activated switches as a bit of a gimmick—after all, you can always just move the lightswitch if it’s that hard to get at. But currently my mother is hobbling around on crutches, and it suddenly struck me that turning the uplighter on from the doorway would be handy. A rummage through the junkbox found a board—I think from an old washing machine—full of relays, and 5v relays at that, so no need for a voltage multiplier to turn the relay on.
[Read More]ChuffChuff (cheaply)
Posted on August 29, 2018
(Last modified on October 3, 2020)
| John Morris
On a rainy day here I wondered exactly when I should book a ticket up to Durham for another term. Most of the booking websites will help you, but not much: it’s tiresome to check a few days to see what the price variation is—and it can be fairly enormous. I was also curious as to what the long term trends might be: they don’t just seem to go down. All of which suggested some code to screenscrape all the tickets from somewhere and analyse them.
[Read More]Compiling KiCAD/WxWidgets
Posted on August 13, 2018
(Last modified on October 3, 2020)
| John Morris
Since this has, alongside other things, occupied a whole day, I thought I’d put it up here in case anyone else tries. Back in the day KiCAD had a python scripting console. Currently that would be very useful: but it’s implemented with gtk2, and everything ships with wxwidgets compiled against gtk3. So we have to compile wxwidgets, which is fairly straightforward: get the sources compile—except it’s not a ./configure, make, make install job: rather a python script calls other python scripts, and so on.
[Read More]Basic Counter
Posted on August 2, 2018
(Last modified on August 13, 2021)
| John Morris
Now that we have a working counter and display the next thing to look at is the timebase. The timebase I built when first working on this counter is odd. It uses, for some reason, a 3.2768MHz crystal divided by (2^16 * 10n) to get a gate pulse which is a multiple of 1s, then further divided and decoded by a 3-to-8 decoder to generate pulses which latch the counter onto the display, and reset the counters.
[Read More]'Off and on again' remotely
Posted on August 2, 2018
(Last modified on August 13, 2021)
| John Morris
The internet in Durham, which was allowing me to use the workstation there remotely, has gone down; support tell me to ’turn it off and on again’. But obviously I can’t do that remotely. Ah well, it wasn’t really needed. But what if it were? I’ve run servers over unreliable wifi links with good uptime before, with a failsafe script which rebooted everything if it couldn’t ping the gateway for too long—and looking at the logs, sometimes it was needed.
[Read More]Display Board
Posted on July 31, 2018
(Last modified on August 13, 2021)
| John Morris
I started this peice of test equipment when I was about 15, I think, built the timebase with enthusiasm, the counting chain with a bit less, and then wondered how on earth I was to attach the 7-segment displays. Surely not one wire each?! So the project languished, and eventually got relegated to the shelf without ever being finished. All I had was the breadboard and two schematics which nearly corresponded with what was in front of me:
[Read More]CD Player Line-In
Posted on July 31, 2018
(Last modified on October 5, 2020)
| John Morris
This is a very simple project indeed: add a line-in input feeding the amplifier in my sister’s CD/Tape/Radio, which has much better sound than the ‘device’ she mainly plays music from. How hard can it be to find the amplifier IC and feed in directly?
Taking the thing apart was none too hard, and it’s cheap ’90s hardware so all through-hole and single-sided PCB. I found the mode switch, traced it back to the amplifier, paid careful attention to the pinouts and soldered a small cable onto one input, the other end going to a 555 ‘signal generator’ kit I had lying around.
[Read More]More bookbinding tools
Posted on July 26, 2018
(Last modified on August 13, 2021)
| John Morris
A while ago I made one of those vices used for bookbinding which is called a ’lying press’, not because it is used to print articles for the Lügendpresse, whoever that might be, but because it is a press and lies down, in a bench called a tub. There are many drawings, etc, all over the internet. My press is a little different: I used old windowsill ‘mahogany’, and took advantage of the profile to make one side a ‘backing press’ with protruding jaws planed away after a picture I found in an old book somewhere.
[Read More]Proof of Concept
Posted on July 20, 2018
(Last modified on October 6, 2020)
| John Morris
By this point we have all we need for a basic charge, and I do actually need to charge some batteries. I can build a simple current regulator with an LM317 and a resistor, which will be good enough for now.
No Termination The simplest thing would be just to charge some batteries and log to the computer. There’s a marvellous thing out there called FeedGnuPlot which makes graphing realtime or static data so easy one has to resist the temptation to graph everything.
[Read More]