cross-posted from: https://lemmy.world/post/27589038
There is though. Iirc up to 15 digit subohm precision trimmed resistors are a thing just an uncommon and extremely expensive thing.
this post was submitted on 02 Jul 2025
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well there's certainly none in the chip aisle
They are, however, absolutely thrilled that the smallest resistor package is now ~ 1x the plank length on the narrow side.
This is EXACTLY how it went for me when I moved from a Physics to an Electronics Engineering degree at University.
Also, the trying to understand how the various circuits worked from the point of view of "electrons moving" was a hard to overcome early tendency (even simple things like LC circuits, for example, are only really understandable as ressonant stable states and for complex circuits you really have to go higher levels than "electrons" to be able to understand then in any reasonable amount of time).
On the upside when we got to things like how tunnel effect diodes worked, the whole thing was just obvious because of having had an introduction to Quantum Mechanics in the Physics degree. Also the general stuff about how semiconductor junctions work is a lot more easy to get if you come from Physics.
(In summary: Physics really helps in understanding HOW the various components in Electronics work, but doesn't at all help in understanding how to use them to assemble a complex structure to achieve a given objective. Curiously this also applies to Mathematics and Software Development)
Watching people repair old electronics on Youtube has opened my eyes to the realities of real-world electrical engineering. In short: it's all about tolerances.
A power supply may have a nominal voltage of 5V, but anything from 4.8 to 5.2 is a-okay. Why? Because your TTL components downstream of that can tolerate that. Components that do 5V logic can define logic zero as anything between 0 and 0.8 volts, and logic one as low as 2 volts. That's important since the whole voltage rail can fluctuate a lot when devices use more power, or draw power simultaneously. While you can slap capacitors all over the place to smooth that out, there's still peaks and dips over time.
Meanwhile, some assembly lines have figured out how to aggressively cost-reduce goods by removing whole components from some circuits. Just watch some Big Clive videos. Here, the tendency is to lean heavily into those tolerances and just run parts hot, under/over powered, or just completely outside the published spec because the real-deal can take it (for a while). After all, everything is a resistor if you give it enough voltage, an inductor if the wire's long enough, a capacitor if the board layout is a mess, and a heatsink if it's touching the case.
The way I got 100 in a lab once (electrical engineering) was by not using inductances in a frequency filter because their +/- is shit.
And your LEDs will last a lot longer if you remove one of those two resistors
You're getting a 10 ohm resistor and liking it.
More seriously, if you order it from an Electronics supplier, you can get a 6.2 Ohm resistor with a mere 1% tolerance (in some cases, even 0.5%).
That said an EE, except in very specific cases such as reference resistors, would generally use a 10 or 5 Ohm one with 10% tolerance for any circuit that was supposed to be mass produced since it's far cheaper and much more easy to source in the size you require.
Electronics engineering is a bit beyond my scope; as an electronics hobbyist or field repairman you're gonna get the closest I have in my kit at the time, I'll probably get within an order of magnitude of the spec unless it's somehow very damn critical or the schematic calls for one of the oddly common oddly specific values like 220 ohm.
Well, just think "How would I do this cheaply and get away with it" for a good enough "Engineering" approach for this case.
The really expert "Engineering" stuff related to things like maintenability, reliability, robustness and so on (which I myself am not qualified to talk about, as even though I have an EE degree, that's not actually the domain of Engineering I ended up working in so I haven't accumulated the professional experience that teaches one to take such higher level considerations into one's designs), isn't, IMHO, really necessary to understand to explain why those designing circuits commercially would chose the commonly available and cheaper components if they can.
Astrophysicists would be happy with a 1 ohm resistor.
You should see their simplified periodic table.
Use 2 E192 in parallel: a 6.19Ω resistor with a 4500Ω resistor. This gives 6.1846Ω which is close enough for rock and roll.
E192 resistors are expensive. E6 resistors 6.8Ω and 68Ω in parallel, available pretty much everywhere components are sold, result in 6.1818 Ω, which is within 0.05 % of the target, around the edge of what you can achieve without active temperature compensation.
I feel like this is one of those comments I want to hoard in the off chance that I ever get into this and start building shit but I know deep inside me that's never gonna happen.
For you and anybody else wondering, the GP is a joke and should not be taken seriously.
The reason there isn't a resistor with the value on the meme is because real resistors have error tolerances and are never the exact value on their marks. If you go assembling a card-castle of resistors with the wrong value so that the labels add up to the value you want, you will still have a resistor of the wrong value.
There's an old saying that engineers measure with a micrometer, mark with a grease pen, and cut with a hatchet. You do the math right first, check the tolerances and tools at hand, then you try whatever seems like it'll work keeping room for your second and third guesses. Never give the boss their company credit card back until you're pretty sure you won't need another hardware run of the day.
Still, it's useless to try to get a board of the right size by nailing together boards you've cut wrong. You throw it out and try to make a better cut on the next one.
The actual method for calibrating exact resistor values involves starting with a lower resistance and etching away parts of it with a laser to get to the exact value you want. You probably still couldn't get as many decimal places as OP tho
And then in a week it drifts into a different value and you have to calibrate it again.
And that's assuming your room temperature is controlled for all experiments.
And that's also assuming the current going through it is 0 so it is always exactly at room temperature.
Virgin theoretical physicist vs Chad experimental physicist goes brrr
For really sensitive applications like voltage references, they actually build a little enclosure around the part with a built in heater to keep it at a constant calibrated temperature. The boards also often have cutouts to reduce thermal transfer and things like the board flexing causing stress to the part.
The resistor itself won't really drift at a constant temperature, especially in a sealed environment where condensation, corrosion, and dust aren't a factor.
Though of course real programmers use vim
Emacs or die
Emacs means die. Vim4lyfe
I just raw dog it in Pico most of the time.
How?? Muscle memory fails me every time
I only ever used it in command lines. And use other simple IDEs (Textmate and a bunch of custom bundles on a Mac…) occasionally Atom based IDEs for some embedded electronics too, but only really as a hobby.
As a layperson, what happens if crumbs from my sandwich fall all over your chad experiment setup?
Just learn the math, it’s quite easy. IIRC you just add the reciprocals of the resistors then take the reciprocal of the answer.
1/Req = 1/R1 + 1/R2 + 1/R3 ….
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Welcome to the field of engineering! Your first lesson will be; "Tolerances and you"!
+/-15 %? Good enough!
pi == 3
As a calibration technician, this makes me hurt. Lol.
Cringes in Monte Carlo.
Pi is roughly 5.
Never, in any engineering field, have I EVER seen anyone simplify pi to 5. For that matter, I have never seen anyone simplify to 3. It is always 3.14. I feel like pi simplification is a weird meme that people think engineers do but is never practiced anywhere.
It's like if there was a meme about chefs saying they always replace eggs with grapefruit. No they don't, and it's nonsense to think they do.
For back-of-the-envelope or mental calculations, pi is often 3 or 10^(1/2).
The latter is better than 1% accurate, and has nice properties when doing order-of-magnitude/log space calculations in base 10.
There's less and less reason to do it (and it's never 5). On systems without floating point you might want to round it a bit, but only if the specific thing you're doing allows it, and even then you're more likely to do a fixed-point approach by using e.g. 314 and dividing by 100 later, or adjusting that value a bit so you can divide by 128 via bitshift if you're on a chip where division is expensive. However, in 2025 you almost certainly should have picked a chip with an FPU if you're doing trigonometry.
And while rounding pi to 3 or 4 is certainly just a meme, there are other approximations which are used, like small-angle approximations, where things like sin(x) can be simplified to just x for a sufficiently small x.
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I kinda wonder if there's a specific reason for that number other than just being an ass.
The humble potentiometer:
The least reliable resistor. Not to mention the trial-and-error getting it close enough to the target value.
linear potentiometer 100% pain, but Multi meter and rotary or digital potentiometer could be simple enough.
Nope, same problem as linear. Can you get angle correct to 4 decimal places and prevent the contact from oxidation?
"Digital potentiometers" are rotary encoders, which are switches, not resistive dividers. They are a useful input device for a microcontroller but not in an analog circuit.
Another option is a multi-pole rotary switch with selectable resistors in each position, but that only gives you the available values.
They are all larger and more expensive. Just use two E12 resistors in parallel or series, you can always get within 1 %. They cost a dime a dozen. The series was made for such combinations – did you know that 180 Ω and 220 Ω in parallel gives 99 Ω, a value useful for 1/100 dividers?
Good info. Cheers mate!
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