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Why do electronic components have such odd values? (2021)

digilent.com

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Re: Why do electronic components have such odd values? (2021)

#81

Post by xg15 »

Denvercoder9 wrote: post #63
throw0101d wrote: post #34

This part is the thing that made me understand the numbering series: > […] Continuing this trend, rounding as needed, and we end up with the series 10, 15, 22, 33, 47, and 68. Components built to the E6 standard have a 20% relative error tolerance, and if we look at the values again we’ll see a trend. Starting with 10 again and adding 20% error we end up with 12. Moving to 15 and subtracting 20% we get… wait for it……

I feel like the author conflates tolerance in component value choice and fabrication tolerance. The E-series were chosen so that if you have perfect resistors (no fabrication tolerance) of only their values available, you can replace any resistor value you need with one from the series, and you'll never be more off than a fixed error (e.g. 20% for the E6 series). This only works with perfect resistors, though. If you…

I didn't understand the Renard Numbers tangent until realizing it's the same principle of exploiting "usage tolerance": He replaced the 400 different cable lengths with 17 "standard" cables that can be stretched to any of the desired actual lengths. The choice of numbers ensures that the "stretch", i.e. error never exceeds a certain factor.

Re: Why do electronic components have such odd values? (2021)

#82

Post by gmueckl »

xw390112 wrote: post #66
Denvercoder9 wrote: post #63

Earlier quoted context omitted.

I feel like the author conflates tolerance in component value choice and fabrication tolerance. The E-series were chosen so that if you have perfect resistors (no fabrication tolerance) of only their values available, you can replace any resistor value you need with one from the series, and you'll never be more off than a fixed error (e.g. 20% for the E6 series). This only works with perfect resistors, though. If you…

In 2024, if your resistor vendor has even 5% tolerance, you need to find another vendor.

AFAIK, it used to be that parts binning was used to sort parts by tolerance. So the 5% bin wouldn't include <1% parts because those were already selected into the 1% bin in the factory and so on. Is it still like this?

Re: Why do electronic components have such odd values? (2021)

#83

Post by Dylan16807 »

nomel wrote: post #76
Dylan16807 wrote: post #54

Earlier quoted context omitted.

If you're going to say "Complete nonsense." you shouldn't get the calculation wrong in your next sentence.

Very true, I was writing as absolute value, not % (magnitude is where my day job is). My point still stands: it is complete nonsense that tolerance goes down.

They said it "should" go down, but that another comment saying the worst case is the same is "also correct".

I do not see any "complete nonsense" here. I suppose they should have used a different word from "tolerance" for the expected value, but that's pretty nitpicky!

Re: Why do electronic components have such odd values? (2021)

#84

Post by londons_explore »

klodolph wrote: post #44
Workaccount2 wrote: post #22

Wikipedia has a nice table of these values that I actually have printed out and hanging above my bench. https://en.wikipedia.org/wiki/E_series_of_preferred_numbers#... The fact of the matter is that nowadays, E96 series resistors are readily available and dirt cheap. And if you need more precision than that, you either don't know much about electronics or you know a whole lot about electronics, heh.

Yes—although E96 is cheap, I’m still very fond of E12. You get to keep less stock. I’ll even use two resistors rather than use something outside E12, most of the time. Maybe it’s habit? Hell, I don’t even think all of E12 is necessary. I’ll stick to E6 most of the time.

Being a mostly-digital electronics guy, I think 0.1, 1, 10, 100, 1k, 10k, 100k, 1M and 10M is a perfectly fine series for pretty much any usecase.

Sense resistor? 0.1 ohm.

Resistor for an LED: 100 ohm

Pull up resistor: 10k

Bias resistor for some mosfet gate: 10M

Voltage divider to measure the battery voltage with an ADC: two 100k resistors.

It's super rare I need anything else. I hate fiddling about with switching the reels on the pick'n'place anyway.

Re: Why do electronic components have such odd values? (2021)

#85

Post by rchowe »

gmueckl wrote: post #82
xw390112 wrote: post #66

Earlier quoted context omitted.

In 2024, if your resistor vendor has even 5% tolerance, you need to find another vendor.

AFAIK, it used to be that parts binning was used to sort parts by tolerance. So the 5% bin wouldn't include <1% parts because those were already selected into the 1% bin in the factory and so on. Is it still like this?

It depends on the component and the company/process. Laser trim time for thin film is a significant cost-driver, so if possible you want to aim for a specific value and reject or bin-sort the rest out. My company only makes 1% tolerance resistors by laser trimming.

Re: Why do electronic components have such odd values? (2021)

#86

Post by [deleted] »

xw390112 wrote: post #64
throw0101d wrote: post #34

This part is the thing that made me understand the numbering series: > […] Continuing this trend, rounding as needed, and we end up with the series 10, 15, 22, 33, 47, and 68. Components built to the E6 standard have a 20% relative error tolerance, and if we look at the values again we’ll see a trend. Starting with 10 again and adding 20% error we end up with 12. Moving to 15 and subtracting 20% we get… wait for it……

[dead]

[deleted]

Re: Why do electronic components have such odd values? (2021)

#87

Post by picture »

londons_explore wrote: post #84
klodolph wrote: post #44

Earlier quoted context omitted.

Yes—although E96 is cheap, I’m still very fond of E12. You get to keep less stock. I’ll even use two resistors rather than use something outside E12, most of the time. Maybe it’s habit? Hell, I don’t even think all of E12 is necessary. I’ll stick to E6 most of the time.

Being a mostly-digital electronics guy, I think 0.1, 1, 10, 100, 1k, 10k, 100k, 1M and 10M is a perfectly fine series for pretty much any usecase. Sense resistor? 0.1 ohm. Resistor for an LED: 100 ohm Pull up resistor: 10k Bias resistor for some mosfet gate: 10M Voltage divider to measure the battery voltage with an ADC: two 100k resistors. It's super rare I need anything else. I hate fiddling about with switching th…

Have you tried 10 kΩ for LED and FET pull down?

100 Ω sounds like way too much current for modern LEDs. I often end up using 100 kΩ especially for green LEDs. They are very visible under indoor lighting even with 1 MΩ and 3.3 V supply.

For pulling down FETs, you want something in the range of 10 kΩ. 10 MΩ sounds way too high, which makes your circuit sensitive to being touched or affected by moisture, especially if there are near by components connected to the power rail.

My digital electronics grab bag consist of 22 mΩ for sensing, 100 kΩ for battery voltage divider, 22 kΩ for one of the 3.3 V buck converter feedback dividers, 10 kΩ for everything else like I2C pulling.

Re: Why do electronic components have such odd values? (2021)

#88

Post by bsder »

gmueckl wrote: post #82
xw390112 wrote: post #66

Earlier quoted context omitted.

In 2024, if your resistor vendor has even 5% tolerance, you need to find another vendor.

AFAIK, it used to be that parts binning was used to sort parts by tolerance. So the 5% bin wouldn't include <1% parts because those were already selected into the 1% bin in the factory and so on. Is it still like this?

Mostly, no. Nobody except for expensive precision resistor companies are actually measuring resistors more than statistically.

The resistors are manufactured so that they are "guaranteed by manufacturing" such that the outliers are 1%, 5%, 10%, etc. And they do statistical checks on batches, but not really looking for the 10% outlier (which is stupendously rare and very difficult to catch) but looking for slight drifts off nominal (which are much easier to spot) which would result in more outliers than expected.

As such, if you measure resistors, you tend to find that you get really close to nominal--much closer than you would expect for 10%, say. Resistors are so cheap that binning simply doesn't make economic sense.

Re: Why do electronic components have such odd values? (2021)

#89

Post by mb_72 »

xw390112 wrote: post #64
throw0101d wrote: post #34

This part is the thing that made me understand the numbering series: > […] Continuing this trend, rounding as needed, and we end up with the series 10, 15, 22, 33, 47, and 68. Components built to the E6 standard have a 20% relative error tolerance, and if we look at the values again we’ll see a trend. Starting with 10 again and adding 20% error we end up with 12. Moving to 15 and subtracting 20% we get… wait for it……

[dead]

'Laser-trimmed resistors' will be the next selling point on a boutique guitar FX company's 57th clone of a Tubescreamer.

Re: Why do electronic components have such odd values? (2021)

#90

Post by LeifCarrotson »

bsder wrote: post #88
gmueckl wrote: post #82

Earlier quoted context omitted.

AFAIK, it used to be that parts binning was used to sort parts by tolerance. So the 5% bin wouldn't include <1% parts because those were already selected into the 1% bin in the factory and so on. Is it still like this?

Mostly, no. Nobody except for expensive precision resistor companies are actually measuring resistors more than statistically. The resistors are manufactured so that they are "guaranteed by manufacturing" such that the outliers are 1%, 5%, 10%, etc. And they do statistical checks on batches, but not really looking for the 10% outlier (which is stupendously rare and very difficult to catch) but looking for slight drif…

Is this how LEDs are binned as well, or are they powering each node on the wafer before packaging? They're orders of magnitude more expensive than resistors, so I figure they might...

There are all kinds of crazy parameter variations in optoelectronics. I understand that resistors are really close to nominal because the manufacturer's ability to tune the process controls are so much better than the standard 5% and 10% bins, but it seems that LED manufacturing is way more difficult and they can't always tune the process to get exactly what they want.

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