Free Software collaboration at the National Library of Ireland

RTE recently carried a news piece announcing the release of a large volume of historical digital images by the National Library of Ireland. One detail in the piece caught my eye: it quoted the library’s Digitisation Programme Manager Sara Smyth as saying Since 2010, we have overhauled our digitisation workflows and put in place key technical infrastructures. We achieved this with limited full time technical resources and a very restricted budget by collaborating on international open source projects. (emphasis added). This sounded like a great thing. I wondered what projects these were, so emailed Ms Smyth. She and a colleague wrote back, kindly supplying plenty of detail, which this post reports. Engagement with open source projects generally Perhaps unsurprisingly, Systems

Continue reading

An original escapement design?

© Trustees of the British Museum[source page] On a recent visit to the British Museum in London, I was interested to see a very curious escapement mechanism in one of the clocks, a creation of Thomas Tompion in the 1670s. I am certainly no expert on clocks, but I had never seen an escapement where the pendulum swings across the plane of the gear wheels. Frustratingly, the actual mechanism was very small, and in the middle of quite a large glass case, so I could not see it well enough to work out what it was doing. I spent a bit of time thinking about it, and came up with an idea for what might be happening, but now the

Continue reading

An oscillator from a jam-jar lid

Fiddling with a jam-jar lid suggested its tamper-evident pop-up button exhibited hysteresis, and so I did some experiments on a blackcurrant jam lid to test this. Adding weight 50g at a time, the lid flexes very slightly, but stays popped up with 800g on top. It pops down when you add 50g to make 850g. Removing weight 50g at a time, the lid does not pop back up straight away. It stays down as you decrease the weight to 650g, but when you remove 50g to leave 600g, it pops back up. This confirms the suspected hysteresis. I read a long time ago that if you take a system with hysteresis, and introduce negative feedback from the response to the

Continue reading

Debugging a Hot Wires circuit

Jude was given an electronics set for her birthday, called Hot Wires. You connect components together with poppers to make circuits, and it’s generally very good. One of the experiments is called ‘traffic lights’, and is supposed to be a circuit where you choose whether a green light or a red light shines, by pressing a button. Simplifying slightly, its circuit is The LED modules actually have series resistors inside them, so it’s safe to connect them across the battery voltage like that. With the button switch (bottom left) not pressed, only the red LED is supposed to light. If you press the button switch, the red LED is supposed to go out and the green LED light instead. But

Continue reading

A fruitful exchange with the State Examination Commission

While looking through some past and sample papers to help with some volunteer maths tutoring I do, I came across what I was fairly convinced were errors in a question in a sample paper written by the State Examination Commission. What followed was a very positive exchange of correspondence with the examiner, and the end result is that they are going to review the question. It was refreshing to have such an exchange with a public body, in particular with somebody who directly and properly engaged with my query. If only all interactions with public bodies were as satisfactory. The question The question at issue is Question 1 on paper 2 of their 2012 sample. It reads, in relevant part, The

Continue reading

A Lego escapement (and failed slow-motion)

I recently came across a post on the Makezine blog showing a video of a very pleasing mechanism, the MacDowall single-pin escapement. Zach and I recreated it as best we could, although we didn’t go as good a job as the original when it came to a rigid support structure. Nevertheless, our copy worked: My other aim with this was to experiment with temporal aliasing, to create a slow-motion version of the mechanism. For this to work, I would make a video by taking, say, every 61st frame of the original video. Since the pendulum’s period is very unlikely to be an exact multiple of the frame time, I would get a strobe effect and see the mechanism in slow

Continue reading

Cobra: a Dragon 32 game from my past

About thirty years ago, my dad and I wrote a game for our Dragon 32 home computer. It was originally a pen and paper game for two players; in our version you played against the computer. I have tried to recreate the experience on the web. It needed a bit more room than this blog format allows, so it has its own page: Cobra: a Dragon 32 game from my past Looking back now, I realise how much time Dad put in to this project, and how much effort my parents put into encouraging my interests in general. I’m very grateful to them. Epilogue Thanks to Nick Gray, I now know that this game is a variant of the Black

Continue reading

Snakes and ladders: end-game rules

My 5-year-old son is mysteriously keen on a Snakes And Ladders game we have, but there is often some discussion about what the ending rule should be. The winner is definitely the person who lands on square 100 first, but what to do if you roll a number which would take you past square 100? There are two rules we play: You win. You bounce back off the end of the board. E.g., from square 98, a roll of 6 would take you: 99, 100, 99, 98, 97, 96. Photo © Nick Fedele. CC-BY-SA-2.0 Empirically, the game takes way longer if you play the ‘bounce’ rule than if you play the ‘win’ rule. But how much longer, on average? It turns out that

Continue reading