How fun! Once, after climbing around in a dusty old church attic like this, I had to head straight to the airport for a flight. Barely made it on because something in the dust kept flagging as dangerous. They were using a test strip on my backpack and clothing and analyzing it in some kind of machine. Stressful as I was already pressed for time! Finally got a clean test and they let me through.
Ion mobility spectrometry is the tech that powers these, and they're VERY sensitive and VERY prone to false positives because it's just looking for ion signatures ("I smell a nitrate/glycerin/etc."). I'm not sure if they're changing modes on the machines between swabs or something, but the machine is a cue for more in-depth inspection, not "zomg I found a bomb". So, some repeated scanning to rule out a false positive or burn off gunk that's accumulated in the machine i.e. we just got a speck of something on the wand or something is gunking up the scanner as opposed to "someone covered in residue that is scary".
If this was in the US, it's all security theater. Basically if you get flagged, they swab everything in your bag to find what's getting flagged, and if it's legitimate they pass you through, or they keep swabbing you if its just your hands/arms because they also inspect your bag. It's kind of dumb, but also kind of makes sense.
For extra fun times, baby wipes / wet wipes get flagged as explosives in the US when they use the sniffer devices.
I will be the first to join you on "most of TSA is security theater"; the baby wipes are glycerine getting flagged by ion mobility spectrometry. The machines are fast because they just look for basic chemical building blocks, not doing full spectrometry to figure out the whole compound. So glycerin, nitrates, etc. set it off (and someone else's sticky glycerin e.g. sunscreen can gunk up the machine for multiple subsequent people).
Fred Dibnah was a treasure. If you enjoyed 5 minutes of Big Ben, here's an hour of his day job in heavy industrial steeplejacking - "The Ups and Downs of Chimneys" https://www.youtube.com/watch?v=KK2wF_-yoEg
> The "Status" LED flashes some kind of code - long long, short short short. I assumed the number of flashes would correspond to the time but apparently not. We didn't have time to figure this out before we had to leave.
long-long-short-short-short is 7 in morse code. They don't say what time they tried this or if it ever changed, though, so that's just a hypothesis.
It's almost certainly this. I suspect the advance button can be used to advance the time via morse code LED flashes and only then committed when you get to the right hour.
Perhaps the long-press commits the hour, which is why it rang once initially.
What a lovely blog in general: some really fun retro-computing projects, written up in a very thoughtful, human way. Feels like a throwback to the earlier hacking spirit of the internet. Thank you, Colin: your "experiment with writing" is a success as far as I'm concerned!
The battery on that circuit looks very much like a backup battery we have connected to our house alarm.
We moved in to the house in 2003 and that battery died this year, so I would imagine that it is already or will very soon die. That said, if it's a backup battery and the electricity supply is stable then it may not make any difference.
Design spec is up to 5 years. The one in the photo looks like it may have a date written in Sharpie on the side. I don't think it's 25 years old though. The "090323" on top could be DDMMYY indicating a battery from 2023.
Seeing the number of holes in that ceiling I really am concerned that the floor the clock is on is the same as the one with the holes, and I would advise that you secure the floor if you return to the attic.
Yeah I repair old cameras these days. The amount of cameras I've fixed by just poking at random stuff until it unjams is surprisingly high. Even more so the number I've "fixed" by just replacing the batteries.
How fun! Once, after climbing around in a dusty old church attic like this, I had to head straight to the airport for a flight. Barely made it on because something in the dust kept flagging as dangerous. They were using a test strip on my backpack and clothing and analyzing it in some kind of machine. Stressful as I was already pressed for time! Finally got a clean test and they let me through.
Is the solution to a positive swab really to keep swabbing until negative?
Ion mobility spectrometry is the tech that powers these, and they're VERY sensitive and VERY prone to false positives because it's just looking for ion signatures ("I smell a nitrate/glycerin/etc."). I'm not sure if they're changing modes on the machines between swabs or something, but the machine is a cue for more in-depth inspection, not "zomg I found a bomb". So, some repeated scanning to rule out a false positive or burn off gunk that's accumulated in the machine i.e. we just got a speck of something on the wand or something is gunking up the scanner as opposed to "someone covered in residue that is scary".
Apparently! That or I just have a trustworthy face haha
If this was in the US, it's all security theater. Basically if you get flagged, they swab everything in your bag to find what's getting flagged, and if it's legitimate they pass you through, or they keep swabbing you if its just your hands/arms because they also inspect your bag. It's kind of dumb, but also kind of makes sense.
For extra fun times, baby wipes / wet wipes get flagged as explosives in the US when they use the sniffer devices.
I will be the first to join you on "most of TSA is security theater"; the baby wipes are glycerine getting flagged by ion mobility spectrometry. The machines are fast because they just look for basic chemical building blocks, not doing full spectrometry to figure out the whole compound. So glycerin, nitrates, etc. set it off (and someone else's sticky glycerin e.g. sunscreen can gunk up the machine for multiple subsequent people).
If you enjoyed this, here's Fred Dibnah exploring Big Ben and discussing some of the engineering details. https://www.youtube.com/watch?v=Vi1cqR1bJC4
Fred Dibnah was a treasure. If you enjoyed 5 minutes of Big Ben, here's an hour of his day job in heavy industrial steeplejacking - "The Ups and Downs of Chimneys" https://www.youtube.com/watch?v=KK2wF_-yoEg
One of many old clocks in Edinburgh that needs fixing. The one on the Balmoral Hotel had to get a lot of work done.
There were three identical street clocks in Edinburgh that the council there have tried to remove. They succeeded with the one at Tollcross.
> The "Status" LED flashes some kind of code - long long, short short short. I assumed the number of flashes would correspond to the time but apparently not. We didn't have time to figure this out before we had to leave.
long-long-short-short-short is 7 in morse code. They don't say what time they tried this or if it ever changed, though, so that's just a hypothesis.
It's almost certainly this. I suspect the advance button can be used to advance the time via morse code LED flashes and only then committed when you get to the right hour.
Perhaps the long-press commits the hour, which is why it rang once initially.
This is what I want the internet to be. Great read.
I'm confused… You don't want to read about the newest LLM models on the HN front page all day long, every day of the week? SAD!!
i wish i could fix The Sun clock on Broadway and Chambers
it's literally kittycorner from City Hall, and hasn't been running for a while...
i'd do it for free if i knew who to even bother about getting up into it
There's a Reddit user who posts in a car repair subreddit about his work repairing bell-tower equipment. Very cool.
https://www.reddit.com/user/dingdongbellguy/
Such a pleasant surprise to wake up and see my hometown at the top of hackernews!
Send it to Big Clive with a felt pen enclosed.
Genuinely underrated way to understand circuits. When I was younger and dumber I thought his practice was a bit silly, but man, it really is king.
What a lovely blog in general: some really fun retro-computing projects, written up in a very thoughtful, human way. Feels like a throwback to the earlier hacking spirit of the internet. Thank you, Colin: your "experiment with writing" is a success as far as I'm concerned!
The battery on that circuit looks very much like a backup battery we have connected to our house alarm.
We moved in to the house in 2003 and that battery died this year, so I would imagine that it is already or will very soon die. That said, if it's a backup battery and the electricity supply is stable then it may not make any difference.
It's a standard sealed lead acid battery:
https://www.rapidonline.com/yuasa-yuvolt-yucel-y1-2-6-valve-...
https://static.rapidonline.com/pdf/18-5207_v2.pdf
Design spec is up to 5 years. The one in the photo looks like it may have a date written in Sharpie on the side. I don't think it's 25 years old though. The "090323" on top could be DDMMYY indicating a battery from 2023.
This sounds like such a fun project, especially to share with like minded friends.
If you like old buildings, clock and bell mechanisms, or rigging, there's a fascinating series of bell tower repair videos on youtube:
https://www.youtube.com/@DingDongitsthebellguy
He also posts on reddit under dingdongbellguy
Seeing the number of holes in that ceiling I really am concerned that the floor the clock is on is the same as the one with the holes, and I would advise that you secure the floor if you return to the attic.
I want friends like that!
I dunno if setting the time counts as fixing...
sure it does. the mechanism was no longer functioning properly. and its a repair even moreso considering the unknown nature of the system.
sometimes you get paid because you know things, sometimes you get paid because you know how to figure things out.
Yeah I repair old cameras these days. The amount of cameras I've fixed by just poking at random stuff until it unjams is surprisingly high. Even more so the number I've "fixed" by just replacing the batteries.
They don’t seem to be in contact with the people who actually fixed it.