Month: October 2022

MariaDB/SQL query gotcha and optimized solution (#E18)

Haven’t had a general advice post for a while, have we.

My small fleet of ESP32 boards across the apartment is still gathering information for the AVM Fritz DECT 301 radiator control units that just started the heating season. While their queries are really simple, quick and fully automated, I also have an HighCharts overview plot of all data with user-defined query depth, usually 300 minutes / 5 hours, but I think there’s no arbitrary limit to it. One could plot all 2 million rows of data…but I’m not gonna try.

Anyway, I recently noticed query times went up significantly, and the whole thing never was blazing fast in the first place. […]

o2 DSL Router Premium disassembly/yellowing surprise (WHL #80)

I don’t often visit family, but when I do, my car is usually filled to the roof with old tech crap when I come back…and so is the apartment over the next couple of weeks, until everything is checked, repaired (if needed/viable) and subsequently stored, gifted, sold or binned.

Well, there’s this old o2 router (different labelling, I know…) back from the era where

a) internet providers were able to force you using their crappy loaner hardware (I did hack a similar unit back in the days, te-he-he),
b) those devices sometimes contained a WiFi module that was disabled by default but could be unlocked for a couple bucks per month (I never got why people do this over 24+ months instead of just buying a standalone AP), and
c) not sending back those miracles of NATted IPv4 tech at the end of your contract could easily cost you north of 100€, a ridiculous money-making scheme that was only stopped years later by court decisions that got delayed and appealed forever. […]

Leoch DJW12-5.0(F2 12V5.0Ah) Maintenance-free Sealed Lead-acid Battery cohort testing and refilling (WHL #79)

Batteries. Plain old lead-acid batteries for today.

Before I left to Scotland, IT dropped a bunch of UPS batteries in my office. And since I wasn’t present, they asked my colleague to get them tested, you know, just sort out the bad ones. Sure thing.

It’s 119 of them, plus two dozen more of a larger size (9Ah) that are more common in those desktop APC units that I also use at home. All in all over 200kg of lead. Well, thanks a lot…

Thing is: I don’t have time for that. And it’s not my job. And with the limited equipment I have at hand (at work…), it took me well over a month to get them all tested alongside regular work. […]