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
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.
The standard resistor values are a bit weird at first but when you’re in the zone and you start getting used to what they usually are you start becoming relatively decent at making an educated guess for what the values should be. The actual IRL values are predictably defined and you start remembering the possible options over time.
Someone’s probably made a program that can do it for you though. My own shitty circuits are all built from standard example circuits so I haven’t had to think about this stuff often. Or like I’ll mix and match them illogically in a pinch (on the breadboard) and figure it out later (I don’t build the final circuit lol). Or of course, the venerable using-a-potentiometer-exactly-where-you-shouldn’t technique, which is one of the pillars of modern engineering.
you start becoming relatively decent at making an educated guess
Oh, this reminds me of a guy who could guess hexadecimal colors by eye after doing it for a while, and also another guy who could guess some concentrations in a test tube without using the spectrometer. Kinda wild but it makes sense.
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
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 ….
Note that if it’s a series circuit you simply add resistance.
I’m just an electrician though, we don’t actually use the math or the theoretical stuff terribly often
Ohh, I remember this from uni physics class. I guess I just don’t know how to apply it in any practical sense though. Lol Thanks for reminding me!
The standard resistor values are a bit weird at first but when you’re in the zone and you start getting used to what they usually are you start becoming relatively decent at making an educated guess for what the values should be. The actual IRL values are predictably defined and you start remembering the possible options over time.
Someone’s probably made a program that can do it for you though. My own shitty circuits are all built from standard example circuits so I haven’t had to think about this stuff often. Or like I’ll mix and match them illogically in a pinch (on the breadboard) and figure it out later (I don’t build the final circuit lol). Or of course, the venerable using-a-potentiometer-exactly-where-you-shouldn’t technique, which is one of the pillars of modern engineering.
Oh, this reminds me of a guy who could guess hexadecimal colors by eye after doing it for a while, and also another guy who could guess some concentrations in a test tube without using the spectrometer. Kinda wild but it makes sense.
He probably played a lot of hexcodle.
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This guy electrons!!! <3