Precise Resistor Values

C

Cursitor Doom

Guest
Gentlemen,

During the course of recent internal probings, I've come across the usage
of an awful lot of resistors of unusually precise value: 1251 ohms @ 1%
and many of them are doing a job which clearly does not require such
precision (many used as current limiting for LEDs for example). I'm
guessing the manufacturer must have had millions of these things in stock
from some previous production run of a different instrument and just
wants to get rid of 'em? But then that begs the question: what (on earth)
kind of role would they have originally been specified for?? Come on you
high-end designers, throw me a mere hobbyist a bone here.



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On Sun, 01 Sep 2019 09:27:06 +0000, Jan Panteltje wrote:

Not a 'high end' designer here, but I guess (wild) somebody did
something like:

Volts 5 LED drop 1.65 Current required 10 mA

So resistor is (5 - 1.65) / 10e-3 = 335.000000 Ohm (Linux wcalc)
then put 335 .001% in the circuit diagram Spice freaks.

No sense of reality
Click to expand...

Nice theory, Jan, but it's not correct in this instance at any rate. The
actual physical component has markings backing up the precise value and
it's stated as such on the parts inventory too.


Take a hot air gun, heat up your circuit, so much for monte carlo and
put it in the fridge,.,,
Drop if from some height, <snipped worse tests>, high volts, low volts.
Click to expand...

LOL! I like your thinking! :-D



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On a sunny day (Sun, 1 Sep 2019 09:09:27 -0000 (UTC)) it happened Cursitor
Doom <curd@notformail.com> wrote in <qkg1s7$n65$1@dont-email.me>:

Gentlemen,

During the course of recent internal probings, I've come across the usage
of an awful lot of resistors of unusually precise value: 1251 ohms @ 1%
and many of them are doing a job which clearly does not require such
precision (many used as current limiting for LEDs for example). I'm
guessing the manufacturer must have had millions of these things in stock
from some previous production run of a different instrument and just
wants to get rid of 'em? But then that begs the question: what (on earth)
kind of role would they have originally been specified for?? Come on you
high-end designers, throw me a mere hobbyist a bone here.
Click to expand...

Not a 'high end' designer here, but I guess (wild) somebody did
something like:

Volts 5
LED drop 1.65
Current required 10 mA

So resistor is (5 - 1.65) / 10e-3 = 335.000000 Ohm (Linux wcalc)
then put 335 .001% in the circuit diagram
Spice freaks.

No sense of reality,
Where the world goes, F35 stealth, LOL, any passive RF radar can see it.

We, the neural nets, REALLY need to build and test circuits and get a feeling
for real values, else it all is lost.

AI will defeat us and robots will rule.. oops those will make the same mistakes.
one AI will invent math and an other one spice, and 1224.5 Ohm .001 % will be required.

Take a hot air gun, heat up your circuit, so much for monte carlo and put it in the fridge,.,,
Drop if from some height, <snipped worse tests>, high volts, low volts.
 
On Sunday, 1 September 2019 10:32:38 UTC+1, Cursitor Doom wrote:
On Sun, 01 Sep 2019 09:27:06 +0000, Jan Panteltje wrote:

Not a 'high end' designer here, but I guess (wild) somebody did
something like:

Volts 5 LED drop 1.65 Current required 10 mA

So resistor is (5 - 1.65) / 10e-3 = 335.000000 Ohm (Linux wcalc)
then put 335 .001% in the circuit diagram Spice freaks.

No sense of reality

Nice theory, Jan, but it's not correct in this instance at any rate. The
actual physical component has markings backing up the precise value and
it's stated as such on the parts inventory too.
Click to expand...

Another possibility is that somebody once designed a product that used
1250 ohms. The resistor itself was probably marked 1251. Somebody
else copied the design into another product and, looking at the
resistor markings decided that it was a 1251 ohm resistor.
Millions were ordered and this became a company standard part.
All future designs that needed about 1250 ohms then used this
part because there would be too much administrative hassle in
specifying a 1250 ohm resistor instead.

I have encountered a similar situation where I needed to design
a 600 ohm resistor into a product. The nearest value in the
company database with the right power rating was 601 ohms. Nobody
could explain why this value had been chosen. I think the tolerance
was +/-5%. The resistor marking was 601, so I am sure it was
a mistake.

Large companies will put each resistor value needed for a product
out to tender and the manufacturers will happily quote for any
value if the quantity is large enough. Once this has been done,
all future products that need a similar value will be forced to
use what is already there unless there is a compelling reason
to change. It can take weeks to get a new part into the "system"
and there is significant cost involved. The "large company" I
refer to is one that everyone here will have heard of.

John
 
On Sun, 01 Sep 2019 04:16:20 -0700, jrwalliker wrote:

The "large company" I refer to
is one that everyone here will have heard of.
Click to expand...

HP perchance?




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On Sun, 01 Sep 2019 04:36:03 -0700, jrwalliker wrote:

On Sunday, 1 September 2019 12:29:51 UTC+1, Cursitor Doom wrote:

HP perchance?

Think of blue bat wings.
Click to expand...

Motorola? Why not just say the name?



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
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Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> wrote in
news:qkg2tk$bud$1@dont-email.me:

Take a hot air gun, heat up your circuit, so much for monte carlo
and put it in the fridge,.,, Drop if from some height, <snipped
worse tests>, high volts, low volts.
Click to expand...

Then you can toss it off the back dock and if it still works you can
then get your CSA cert.
 
Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> wrote in
news:qkg2tk$bud$1@dont-email.me:

No sense of reality,
Where the world goes, F35 stealth, LOL, any passive RF radar can
see it.
Click to expand...

Not if it destroys the entire radar site 150 miles before it even
reaches the radar site's view horizon base.

Oh and that 'passive radar' 'picture' appears as if to be a small
bird. Usually ignored by the passive radar's operator or computer
analyzers. Way past "too late" time and also guess what... ignored
by radar guided air-to-air missiles.

The detection schema change requisite to track them would have
missiles flying off after non existent noise signatures. Way too
loose to call guided any more.
 
On Sunday, 1 September 2019 13:20:36 UTC+1, Cursitor Doom wrote:

> Why not just say the name?

You had no trouble working it out, but it is less obvious to
search engines.
 
On Sun, 1 Sep 2019 09:09:27 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

Gentlemen,

During the course of recent internal probings, I've come across the usage
of an awful lot of resistors of unusually precise value: 1251 ohms @ 1%
and many of them are doing a job which clearly does not require such
precision (many used as current limiting for LEDs for example). I'm
guessing the manufacturer must have had millions of these things in stock
from some previous production run of a different instrument and just
wants to get rid of 'em? But then that begs the question: what (on earth)
kind of role would they have originally been specified for?? Come on you
high-end designers, throw me a mere hobbyist a bone here.
Click to expand...

In these days of laser trimming, 1% is free. We buy all 1% resistors,
except when we need something better. I think the best we now buy is
0.05% 10PPM, which costs 20 cents in modest quantities.

1% surfmount resistors cost under a penny by the reel.

1251 ohms is an oddball value. "1251" could mean 1250 ohms, also
oddball.


--

John Larkin Highland Technology, Inc trk

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On Sun, 01 Sep 2019 07:37:29 -0700, John Larkin wrote:

In these days of laser trimming, 1% is free. We buy all 1% resistors,
except when we need something better. I think the best we now buy is
0.05% 10PPM, which costs 20 cents in modest quantities.

1% surfmount resistors cost under a penny by the reel.
Click to expand...

Yeah, but this is mid eighties we're talking here.

1251 ohms is an oddball value. "1251" could mean 1250 ohms, also
oddball.
Click to expand...

There are *plenty* of oddball values I've since discovered, having gone
to the trouble of seeking them out on the schematics:

316
19.6k
61.9
56.2
23.7
17.8k
3.83k

To name but a few of very many such examples!

In fact these weird values seem to outnumber the regular ones by some
measure. Weird!



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
 
On Sun, 1 Sep 2019 15:43:52 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Sun, 01 Sep 2019 07:37:29 -0700, John Larkin wrote:

In these days of laser trimming, 1% is free. We buy all 1% resistors,
except when we need something better. I think the best we now buy is
0.05% 10PPM, which costs 20 cents in modest quantities.

1% surfmount resistors cost under a penny by the reel.

Yeah, but this is mid eighties we're talking here.

1251 ohms is an oddball value. "1251" could mean 1250 ohms, also
oddball.

There are *plenty* of oddball values I've since discovered, having gone
to the trouble of seeking them out on the schematics:

316
19.6k
61.9
56.2
23.7
17.8k
3.83k

To name but a few of very many such examples!

In fact these weird values seem to outnumber the regular ones by some
measure. Weird!
Click to expand...

The Susumu thinfilms seem to come in oddball values.



--

John Larkin Highland Technology, Inc trk

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On Sunday, September 1, 2019 at 11:43:55 AM UTC-4, Cursitor Doom wrote:
On Sun, 01 Sep 2019 07:37:29 -0700, John Larkin wrote:

In these days of laser trimming, 1% is free. We buy all 1% resistors,
except when we need something better. I think the best we now buy is
0.05% 10PPM, which costs 20 cents in modest quantities.

1% surfmount resistors cost under a penny by the reel.

Yeah, but this is mid eighties we're talking here.

1251 ohms is an oddball value. "1251" could mean 1250 ohms, also
oddball.

There are *plenty* of oddball values I've since discovered, having gone
to the trouble of seeking them out on the schematics:

316
19.6k
61.9
56.2
23.7
17.8k
3.83k

To name but a few of very many such examples!

In fact these weird values seem to outnumber the regular ones by some
measure. Weird!



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the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
Click to expand...

Those are all standard E96 1% values.

https://en.wikipedia.org/wiki/E_series_of_preferred_numbers
 
On 2019/09/01 9:31 a.m., Michael Terrell wrote:
On Sunday, September 1, 2019 at 11:43:55 AM UTC-4, Cursitor Doom wrote:
On Sun, 01 Sep 2019 07:37:29 -0700, John Larkin wrote:

In these days of laser trimming, 1% is free. We buy all 1% resistors,
except when we need something better. I think the best we now buy is
0.05% 10PPM, which costs 20 cents in modest quantities.

1% surfmount resistors cost under a penny by the reel.

Yeah, but this is mid eighties we're talking here.

1251 ohms is an oddball value. "1251" could mean 1250 ohms, also
oddball.

There are *plenty* of oddball values I've since discovered, having gone
to the trouble of seeking them out on the schematics:

316
19.6k
61.9
56.2
23.7
17.8k
3.83k

To name but a few of very many such examples!

In fact these weird values seem to outnumber the regular ones by some
measure. Weird!



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

Those are all standard E96 1% values.

https://en.wikipedia.org/wiki/E_series_of_preferred_numbers
Click to expand...

Michael, thanks for the link! I had always wondered where those values
came from - that will help with our resistor and capacitor stock.

Wikipedia is most useful when it is accurate!

John :-#)#
 
Michael Terrell wrote...
On September 1, 2019, Cursitor Doom wrote:

There are *plenty* of oddball values I've since discovered, having
gone to the trouble of seeking them out on the schematics:

316
19.6k
61.9
56.2
23.7
17.8k
3.83k

Those are all standard E96 1% values.
https://en.wikipedia.org/wiki/E_series_of_preferred_numbers
Click to expand...

Right, very common, if they were E192, not quite as common.


--
Thanks,
- Win
 
On 1 Sep 2019 13:07:11 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

Michael Terrell wrote...

On September 1, 2019, Cursitor Doom wrote:

There are *plenty* of oddball values I've since discovered, having
gone to the trouble of seeking them out on the schematics:

316
19.6k
61.9
56.2
23.7
17.8k
3.83k

Those are all standard E96 1% values.
https://en.wikipedia.org/wiki/E_series_of_preferred_numbers

Right, very common, if they were E192, not quite as common.
Click to expand...

Win, I haven't looked particularly for this in your book but do you
have the equations for calculating 1% 5% and other standard resistor
values in there ?

I remember the old basic program to find the nearest value standard
resistor value from way back when.
 
boB wrote...
Win ... do you have the equations for calculating
1% 5% and other standard resistor values in there ?
Click to expand...

No, sorry, we don't, but it's readily available.


--
Thanks,
- Win
 
boB <boB@k7iq.com> wrote:
On 1 Sep 2019 13:07:11 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:

Michael Terrell wrote...

On September 1, 2019, Cursitor Doom wrote:

There are *plenty* of oddball values I've since discovered, having
gone to the trouble of seeking them out on the schematics:

316
19.6k
61.9
56.2
23.7
17.8k
3.83k

Those are all standard E96 1% values.
https://en.wikipedia.org/wiki/E_series_of_preferred_numbers

Right, very common, if they were E192, not quite as common.


Win, I haven't looked particularly for this in your book but do you
have the equations for calculating 1% 5% and other standard resistor
values in there ?

I remember the old basic program to find the nearest value standard
resistor value from way back when.
Click to expand...
Google for E192 "E series of preferred numbers"
--
Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 1623569 ------- Fax. 06151 1623305 ---------
 
On Sunday, September 1, 2019 at 5:18:05 PM UTC-7, boB wrote:
On 1 Sep 2019 13:07:11 -0700, Winfield Hill <winfieldhill@yahoo.com
wrote:

Michael Terrell wrote...

On September 1, 2019, Cursitor Doom wrote:

There are *plenty* of oddball values I've since discovered, having
gone to the trouble of seeking them out on the schematics:

316
19.6k
61.9
56.2
23.7
17.8k
3.83k

Those are all standard E96 1% values.
https://en.wikipedia.org/wiki/E_series_of_preferred_numbers

Right, very common, if they were E192, not quite as common.


Win, I haven't looked particularly for this in your book but do you
have the equations for calculating 1% 5% and other standard resistor
values in there ?

I remember the old basic program to find the nearest value standard
resistor value from way back when.
Click to expand...

It is nothing more than rounded log-spaced (geometrically spaced) numbers over a decade. For m-code, E96 is:

po = 96
n=0;
p = (round(10.^(2:(1/po):(3-1/po))))';
p = (10.^n).*p:),ones(size(n,2),1))

yielding:
p 100
102
105
107
110
113
:
:
887
909
931
953
976

for E192 (po=192) it yields:

p 100
101
102
104
105
:
:
931
942
953
965
976
988

The 5% class (E24) and 10% class (E12) are tricky because there are wrongly rounded values, and you have to fix them with special treatment. Here is the compare of "correct rounding" versus what we actually have:

10 10
11 11
12 12
13 13
15 15
16 16
18 18
20 20
22 22
24 24
26 27
29 30
32 33
35 36
38 39
42 43
46 47
51 51
56 56
62 62
68 68
75 75
83 82
91 91

It is interesting that the "bad rounding" of E12/24 works to our favor in certain resistor ratio problems. We can actually get some ratio combinations with the distorted E24 family that we can't with the E96 family. I mean there is less error in the ratio for some desired ratios. This is because the "always correct" rounding (to discrete values) tends to cluster the available ratios at "ratio-spectral lines" and leaves gaps elsewhere.
 
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