All items... Popular tags: Electronics (11), Linux (11), Hack (8), DIY (6), Other (6), Retrocomputing (6), Debian (5), Curiosities (4)

Curiosities: Inside a late-80s energy meter

2020-08-02 17:40:34, In: Electronics, Curiosities

And now something totally different, related more to electricity than electronics. These electricity meters were commonly installed since 1990s in many households and were used until early 2010s when they were replaced with digital meters. The principle of operation is quite simple: There are two coils: One energizes because there is mains voltage flowing through it all time. The second coil is put in series with energy receivers, so it energizes when current flows through it. If both are energized, it means that there is both voltage and current, and voltage times current equals power. Action of both coils induces eddy currents in a flat aluminum disc, it rotates and spins the counters, like in a peculiar low-power induction motor with 90-degree phase difference made by two coils.
The curent constantly present in voltage coil draws some energy, but it is not integrated to total power consumption.

A neutral wire is connected through a pass-through, while live is passed through coil. Additionally...

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Meanwhile in Linux kernel

2020-07-12 22:17:41, In: Linux, Rants

As the Kernel is constantly changing, the search is for 5.7.8 sources obtained 2020-07-10. In commit 49decddd39e5f6132ccd7d9fdc3d7c470b0061bb they introduced the following commit:

Merge tag 'inclusive-terminology' of git://git.kernel.org/pub/scm/linux/kernel/git/djbw/linux

Pull coding style terminology documentation from Dan Williams: "The discussion has tapered off 
as well as the incoming ack, review, and sign-off tags. I did not see a reason to wait for the 
next merge window"

So it means that the terminology will be phased out with successive commits. Do what you want, if I could suggest something, the master/slave terminology has been called active/passive in Polish since beginning of literal "computer engineering" instead of "building cybernetic machines" (read: early 70s) and went back to English only with...

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So, what's a real problem with 5G? The example with electricity.

2020-06-26 19:22:04, In: Other, Rants

I will start this post with a ?newspaper? cartoon from 1890s, criticizing the electrification of country in the early days of electricity, when it was known and more or less used, but most safety measures were non-existent. Unfortunatly, I'm not exactly sure about the source of the cartoon, some sources label it as "An unrestrained demon", and contrary to the source of this information it is probably earlier than 1900 looking from the shape of the pole, bulb and lantern. About the picture, unfortunately, it shows the true, sad state of electricity in the end of 19th century, when it was handled carelessly, without protections and only for maximizing profits. So don't take it entirely as false. Let's see how the electricity looked like in its early stages and why it was quite dangerous energy to use.
One more thing: I will try to write this in a simple words, sometimes neglecting engineering details, but I think that it should be understood by any people familiar with technology, not only these who like...

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Logitech N395 numeric keypad for Linux

2019-12-31 22:15:31, In: Hack, Linux

#Logitech N395 numeric keypad for Linux
# For =, ( and ) keys, version which does "Alt" combos.
#USAGE: Write this to a text file, run at start: 
#          xbindkeys -f /path/to/file
#
# WARNING: THIS WILL UNFORTUNATELY NOT WORK IN MANY TERMINALS.
#    due to Alt being used...
#
# Some definitions from: 
# http://users.skynet.be/linux-rixensart/3_peripheriques.html#keypad

#Keypad (
"sleep 0.04 && xdotool type "(""
m:0x18 + c:90

#Keypad )
"sleep 0.04 && xdotool type ")""
m:0x18 + c:87

#Keypad =
"sleep 0.1 && xdotool key BackSpace && sleep 0.04 && xdotool type "=""
m:0x18 + c:85

#Some other things in N305:
# - The "Excel" key runs Win+R then blindly types "excel" and presses 
#   Return. This seems not to be changeable in hardware. Symlink 
#   LibreOffice/OpenOffice/Gnumeric to "excel" and it may run in X.
# - The calculator launches XF86Calculator key.
# - The "Window" key fires single Alt-Tab.
#
# Good Luck as this is really poorly configurable. MCbx

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Mikrosha repair log

2019-11-22 12:35:44, In: Electronics, Retrocomputing

Mikrosha is a Soviet home/educational microcomputer made in LEMZ plant near Moscow. This looks like a quite consistent 8080 system with a CPU, a few 8255s, 8275 as display controller, DMA controller, timer and 32kB of RAM in 2118 clones (in case of failure I will be able to substitute with modified 4164, knowing that it's possible to put modified 4164 as 4116 and 2118s are like 4116s but single-voltage).
Review of the power supply unit shown that the -5V regulating transistor (total current: 50mA, no protection at all, dissipation: really poor) conducts C-E in both sides. That's why as I measured it initially, it gave -11.3V in -5V line. Replaced the transistor with the first 100mA PNP I had in my "desolder box", voltages returned to normal. The power supply unit has separation coil, transformer and linear regulators for...

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A TV Tennis game description

2019-08-24 21:17:37, In: Electronics, DIY

The device, a TV Tennis game, has been made using designs from different sources, especially a description in "Radioamator" and images of the prototype. The general rule is similar to "Odyssey" but the signal mixing is simplified while still giving TV-friendly signals. There are only NPN signal transistors and 74 chips, to be exact one 7474 dual flipflop, 7473 as divider and 7493 as additional divider. Other chips are 7400, in many possible configurations. All other things like delays or integrations are made using discrete components. If someone wants to build a similar unit, prepare for a long tuning and selection of components.
This is a general view of the device. It has a power switch, 1/2 player switch and speed setting. Two controllers consist of X/Y pots, serve and "Lift" buttons which changes deflection...

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Things to note: SyncThing under WinXP

2019-03-28 00:17:18, In: Other

PROBLEM: SyncThing 1.0.1 used to synchronize data on different machines updates itself to newer version, also under WinXP. Newer versions don't work under WinXP, so the program does not start again. Literally it's damaging itself.
SOLUTION: Turning automatic update off does NOT work in 1.0.1 it's specified like "Disabled by administrator" in options related to it. To disable updating manually, open your C:\Documents and Settings\[USERNAME]\Application data\Syncthing\config.xml ("Application Data" may be translated) and change autoUpgradeIntervalH parameter to zero (0). Now downgrade to 1.0.1 and start it. Currently it works, if it will stop there will be a problem with lots of XP machines connected to programmers and similar machinery.
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EU Copyright directive: Internet users like it.

2019-03-23 11:15:22, In: rants

Recently lots of media attention is focused on new European "Copyright directive", especially on laws allowing to implement upload filters and a so-called "link tax". So I decided to do something instead of this website darkening fashion and describe why it's too late for any protests. Let's go to the point: Both of these regulations: Upload filters and so-called "link tax", describe things which are already present since at least a decade, they have been already implemented and embraced by community - and quite everyone seems to be happy with it. Automatic upload filters are present in all platforms, as well as most hostings, services and rented private servers. There are a few forms of these filters:
- Legally censoring content using "terms of service" contract, which in practice is one-side, means you have to obey it and they may or may not. This is visible well in politically sensitive content, when the censorship noted in ToS does not exist when it's neded to divide people, and is exaggerated when...

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Things to note: PC LED display jumpers

2019-02-15 17:45:17, In: Retrocomputing

In PC casings a typical problem happens with LED display configuration. Configured to "HI/LO", it may be needed to change it, and jumpers are not always well laballed. There are many configurations. A simple one has two rows for two digits and one small row for hundreds. In this configuration, jumper settings are quite simple: You specify "turbo" configuration by placing jumpers across the row, and "normal" along the row. This way it is possible to set any value. Another type, with two digits, contains two rows of three and a logic chip. I found six revisions of these, all with different settings. What is important in this display it is needed to have Turbo connected some way to make it display at all. In some versions bottom row is for Turbo, while top for non-turbo, in other the middle row can be configured by horisontally aligning their jumpers, while Turbo required to put jumpers above and below. Some PCBs allow to be mounted inverted, so even if there's more than 199MHz, you can reverse it and have...

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Restoring the old PC-XT clone mainboard

2018-10-27 01:42:04, In: Electronics, Retrocomputing

A long time ago I got an XT mainboard. The history of it is known: previous owner got it from someone else, who told that it is damaged and cannot be easily repaired, so it became an interesting exhibit in a bookshelf. It was for last 2 years in my stuff and finally I decided to restore it to the working condition.

The mainboard is a really old one - it has an additional ISA edge connector on the side, all TTL chips from around 1984-85, socketed, but it was not an IBM. The logo, visible on a silkscreen under the processor, resembles a stylish written "S" letter with its center line shaped in an american resistor symbol.
It was a clone, but a clone made with some uncertainity. Not that there are circuit errors, it electrically still is a 5160, but the design itself is... like someone took schematics from the technical manual, looked at original PCB and said "OK, let's try to design it again", and this was the first try, made quickly to verify is everything OK. The mainboard has a piece of breadboard...

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