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Check if your IKEA chair is compatible with your screen

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Re: Check if your IKEA chair is compatible with your screen

#161

I once had the problem that running make with too many parallel jobs (-j) would change my keyboard layout. The machine was some laptop mainboard glued to the backside of my monitor, and the USB socket came out at the top of the mainboard. On its way down, the USB cable for the keyboard passed across the whole mainboard. On high load, the mainboard created enough interference to cause the connection to reset, re-hotpl…

These kind of weird software/hardware bugs remind me of this: https://www.gamedeveloper.com/programming/my-hardest-bug-eve...

Re: Check if your IKEA chair is compatible with your screen

#162
Back in CRT days I was given a tiny desktop fishtank with plastic fish that swam in it.

I turned it on and my screen image started gently moving around.

The fish swam with magnets and having the little tank next to the screen was causing the screen image to move around.

Re: Check if your IKEA chair is compatible with your screen

#163

Earlier quoted context omitted.

I currently have an RPi4 mounted to the back of my TV for easy Kodi streaming, but I never considered using the business end of a laptop. I'm sure I have a decade old laptop with a broken screen sitting at the bottom of a shelf somewhere...

Its the stuff what happens when you think 'what can i do with the hardware that i have' instead of 'which hardware to buy'.

I used to think this way, but then HN scared me into thinking that all this 5+ year hardware is much less power-efficient, so now I just... avoid the issue entirely, and don't do anything requiring hardware, old or new.

Re: Check if your IKEA chair is compatible with your screen

#164

Earlier quoted context omitted.

One stupid little thing I realized after having sometimes been consistently zapped by mybcar door and other times not getting zapped in the same weather and humidity: If I open the door and grasp for the (metal) edge of it before I start sliding out of my seat I will be grounded and consequently not build up charge as I leave the seat.

We had some carpet at my old workplace that would always charge you up and get you zapped. Whenever you touched anything metal. So the old and wise folks there immediately told you to grab your key when you get up and then use it to touch something metal, so the spark is between your key and the metal object and you don't feel anything.

I am a static electricity "magnet". I keep getting shocked a lot, painfully, in environments where no one else is, which is kind of bad for my mental health if I focus too much on it. I've learned all kinds of methods to cope.

For example, we have a few bar stools at home; sitting on one always primes me for getting shocked after getting off it. I figured a few rules, such as never wearing anything isolating on my feet, so I can dissipate charges by keeping one foot on the metal part of the chair; or, failing that, I make sure there's always a metal object in grasping range, which I can use to later discharge in a less painful way.

(Pro tip: don't do the metal discharge thing with the hand you wear rings on, and hold the metal item so it doesn't touch the underside of your fingers - getting a shock through a nerve isn't pleasant at all.)

Another thing: I always keep a metal coat hanger around the bedroom, so that whenever I have to deal with blankets, I can keep "swiping" them to collect charge and then transfer them away by touching something grounded with the coat hanger.

Also: I always have my keys on me when away, in an easily-accessible place, specifically so I always have a metal object I can use to offload static charge in a pain-free way.

Also: over the years I kind of habituated all kinds of subtle behaviors designed to keep me safe from getting shocked by my wife or kids. Basically, if I feel one of them just got charged (e.g. via the blankets or the bar stool mentioned before), or I haven't kept track of their recent movements in a static-rich environment, if there's a need or chance of any kind of physical contact, I instinctively first touch using my elbow or some other pain-minimizing way, just to equalize charges with them. My wife sometimes notices when I do it to her, but fortunately, she is quite understanding.

Re: Check if your IKEA chair is compatible with your screen

#166
post #23

One of my first jobs 30+ years ago was ESD testing automotive and consumer electronics. I would spend a week with a discharge gun methodically running different discharge energies and waveforms both directly onto the devices as well as onto radiators at various distances from the device under test, as well as any cabling/harnessing that attached to the device. Then the design team would figure out the reason for any…

This reminds me of the 1st electronics company I worked at. We didn't have any ESD equipment, so I built a circuit which took power from a wall socket and pumped the voltage up to 2kV using diodes and caps, and sent that through a simple human body mode resistor/cap (https://en.wikipedia.org/wiki/Human-body_model) to do ESD testing. It worked well enough for the simple testing that we did, and was successful at finding weaknesses of our PCB layout for static protection.

Re: Check if your IKEA chair is compatible with your screen

#167
post #29

Earlier quoted context omitted.

Perhaps a silly question, but does turning it off and back on again also resolve the problem? I can occasionally hear such noises from monitors, and have always thought it was some kind of interaction with the phase of the AC power and some kind of internal physics of the monitor. Generally, turning it off and back on again fixes it for me.

In the old CRT days that could be plausible, but in these days of lcds and switching power supplies it seems less likely. But as this article describes, you never know!

> But as this article describes, you never know!

When we were teenagers, my friend used to call it "waving a dead chicken". He coined this term to describe the way he would resurrect dead inkjet printers that even I gave up on - by disassembling and reassembling them until they started to work again, while being perfectly open that he has no idea how it could fix the problem, just that in practice it often did.

While this was just a funny term and pretty absurd approach for fixing things (even though it worked!), I took away from it an important realization: the scope of possible causes of a weird, randomly-occuring problem is much larger than I'd normally assume. Over the years, I learned to identify some "outside context" things for computers - ESD, thermals, UV exposure, RF interference, voltage spikes in power lines, devices being almost but not quite connected. Because of that, when in a bind, "waving a dead chicken" may just be called for - in forms of e.g. percussive maintenance (hitting the thing with a wrench), moving things around, switching cables, disassembling, etc.

Re: Check if your IKEA chair is compatible with your screen

#168
post #3

Remotely related, my screen makes a noise, somewhere between static and a whine, while displaying certain text files. Minimizing or closing the editor stops the noise, getting the text back on display restores the noise. I suppose it's some sort of resonance phenomenon.

sometimes when manipulating 3D CAD models, I can get a similar noise from my graphics card / monitor at certain orientations of the model sweeping back and forth as I rotate it I have a feeling that grey #A5A5A5 is row-hammering something

Same here; my PC GPU would make a high-pitched whine in certain conditions, most often encountered in a CAD program when I was rotating things around. I assumed it's the dark-grey coordinate system / grid on lighter-grey background making some kind of digital equivalent of Moiré patterns on the traces in the GPU card, that happen to generate an audible frequency.

Re: Check if your IKEA chair is compatible with your screen

#169

I've probably mentioned this story here, but my first job out of school was working for a nationally known cash register manufacturer, writing front-end software for the cashiers to use. This didn't happen to me but was told to me by an old-timer my first week there (mid-90s). A group had done an install at a grocery store. They did in-house testing of the new system, then rolled it out to 1 or 2 lanes to try it out…

A few times in my life I've been in some store where the barcode reader would not make an audible *BEEP* when scanning something. I wonder how long would it take to discover the cause of the issue you described in one of such stores.

Re: Check if your IKEA chair is compatible with your screen

#170
post #137
post #97

you should NOT ground your chair directly, only ground it through a large resistor, 100K or so. (you might want to check that value, it's from memory, I think you want any potential electric "shock" to be down below the 1 milliAmp range) I'd use a ground strap designed for wearing while you handle MOSFET ICs. if you ground your chair directly, it is likely to make YOU be the best circuit to ground when you handle you…

Also prevents unexpected shocks to the buttocks upon sitting. Directly grounding shouldn't be particularly risky though. It's not uncommon to have a metal desk touching a grounded but not double-insulated chassis or dangling USB cable. And I get the impression that electrical systems are engineered so that users aren't touching live contacts when plugging things in - maybe less so in the case of US plugs. That said,…

a grounded desk is safe-ish because your desk would be the path to ground, and if not, current entering your hand would likely exit your elbow.

if your chair is the path to ground, you, via your heart, are the path to ground

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