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nina_kali_nina

@nina_kali_nina@tech.lgbt

Managed by Terraform.

Or, as my "professional" email signature says, "IT expert and mixed media artificer".

Feel free to message me, I try to respond to everyone.

This profile is from a federated server and may be incomplete. For a complete list of posts, browse on the original instance.

nina_kali_nina , to random
@nina_kali_nina@tech.lgbt avatar

== Let's make a magnetophone / tape player / magnetic tape head at home! ==

Many people started following me after my DIY magnetic tape and DIY floppy disk experiments. A common request ever since was to make a DIY magnetic head, and, truth to be told, I was curious to experiment with it, too.

The task was daunting, and many people were convinced that it could not be done at all. In fact, I could not find a single mention of a successful experiment in the West, and scarce mentions of it in vintage Russian radio hobbyist magazines. But I know that it could be done; my father insists he made some magnetic heads over 40 years ago.

Just two weeks ago Hackaday.io made a post claiming that a (really cool btw) hobbyist made a tape player with a DIY tape head. I was excited at first, and then outraged - it was fake news! The DIY tape head was not (and could not be) used in the tape player on the video, and in fact could only erase tape.

Now, I present you The Real DIY Magnetic/Tape Head (and a DIY microphone)

🧵~

A partially disassembled reel to reel tape deck turning the reels really fast, and a hand is holding something to the tape

nina_kali_nina , to random
@nina_kali_nina@tech.lgbt avatar

~ Let's make RAM at home, thread #1 ~

In this thread: successful experiment with factory-made ferrite core memory (1 bit for now!), a brief explanation of the experiment, and failed attempts at making a core (so you wouldn't have to try it)

🧵 go~

nina_kali_nina OP ,
@nina_kali_nina@tech.lgbt avatar

If you didn't know, magnetic-core memory used to be the most commonly used previous generation of memory before SRAM and DRAM integrated circuits stole its market share, with a promise of cheap and dense memory.

The foundation of the core memory is a core. Simply put, it is a tiny ring of a ferromagnetic material, a mixture of iron oxide with other metal oxides, that can be magnetized and de-magnetized.

As you might remember from a physics textbook, an electric current generates a magnetic field, and the direction of the current changes the orientation of the magnetic field. If we let current through the core in one direction, it will magnetize the core one way; if we let the current in the opposite direction, it will magnetize the core in a different way.

Find a way to magnetize, read the magnetization of the core, and address thousands of the cores - and you get yourself RAM, or computer memory.

The most advanced ferrite core memory had millions of cores!

nina_kali_nina OP ,
@nina_kali_nina@tech.lgbt avatar

This specific type of core can be magnetized when a current of 0.3-0.5A passes through it. Ohm's law says that if the voltage we supply is 5V, we need our circuit to have the resistance of 10 Ohms to reach this current.

But we don't really need to supply this current all the time! The core changes magnetization really quick, so we need something that would generate a short pulse. Things that generate short pulses aren't great at dealing with high currents (0.5A is 20 times higher than what Arduino can handle), so we need a simple switch to control the current.

I am basically using a textbook circuit with a popular transistor 2N2222 that can handle currents up to 0.8A. It doesn't look super pretty on the bread board, and the reality is different from the model, so the current I see from the 5V supply is only 0.250A.

I pump the voltage up to 12V and smell the magic smoke coming out of the transistor. Of course it cannot handle this much emitter-base voltage, and dies.

The same circuit. The switch is off, the transistor's base is connected to the ground through a 20K resistor and therefore is 0V. Transistor is locked, so there is virtually no current flowing through the load (10.2 pA, which is basically nothing in this case)
The current source on a transistor switch assembled on a breadboard. Some jump wires connect small electronic components

nina_kali_nina OP ,
@nina_kali_nina@tech.lgbt avatar

@futurebird Best of luck! The hardest thing for me to do here was to set up the oscilloscope right to see the bit flipping without needing an opamp. I set the trigger on CH2 connected to the switch that opens the transistor, and had to set the timing to 500ns/div and voltage to 20mV/div to see anything. Adding some filters and capacitors around helped to remove a lot of the noise coming from EMF interference.

nina_kali_nina , to random
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I love semantic HTML. Each input field is so easy to describe in a sensible way. It can even be used by plugins and user-scripts.

nina_kali_nina , to random
@nina_kali_nina@tech.lgbt avatar

There is a concept that some of you might find helpful - "subjective units of distress".

Many years ago, I was struggling badly with my life, going through one mental breakdown after another. I asked my psychiatrist: "How can I live my life if my anxiety goes from 0 to 60 in the matter of seconds?". The psychiatrist said: "But Nina, no one, including you, goes from 0 to 60 instantly. It just feels this way."

So, he explained, human brain is silly and usually cannot tell the difference between not being distressed (SUDS 1) and quite distressed (SUDS 7). As long as we keep functioning, our internal brain state and suffering in it seems to be almost invisible for us.

If I am at SUDS 2, and accidentally spill morning coffee on my blouse, it will probably raise my distress to SUDS 4 or 5, but I will change to a new blouse and go to work.

If I am at SUDS 7 after a doctor's call, and spill coffee on myself, I'll go from being calm to a sobbing mess faster than you can say "therapy".

Keep track of your SUDS!

Subjective units of distress chart 10 - skills breakdown 9 - extreme distress, intolerable 8 - very distressed, trouble functioning 7 - quite distressed, starting to lose focus 6 - moderate to strong 5 - moderate, uncomfortable 4 - mild to moderate 3 - mild distress, able to focus 2 - slightly distressed, sad or anxious 1 - no distress 0 - at peace on the right there's Distress Tolerance skill chain: STOP TIPP - ACCEPTS - self-soothing - IMPROVE - Pros and Cons - Radical acceptance
ALT
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