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0.1 ohm Resistors from Scratch Again

  • Thread starter Watson A.Name - \Watt Sun, the Dark Remover\
  • Start date
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
I'm up to my tricks of winding 0.1 ohm resistors from some fine copper
wire and a resistor to wind it on. But I'm having trouble with the
wire, in more ways than one.

I've got a bobbin of realllly fine wire, I think the bobbin was from an
old clock motor. I measured the wire with a dial calipers and got .0025
inch, which according to my reference manual is 42 AWG, if it was bare
copper. But it's enemaeled, so I'd guess that it's the next smaller
common size, 44 AWG.

But I don't know how thick the enamel is, so I decided to wind a foot of
it onto a 1/8W resistor. The winding was a bit tedious, and I left a
quarter inch on each end for soldering it to the leads. I used my HP
3478A in four wire mode to measure it, and get a fairly accurate
reading. I get between 1.495 and 1.515 ohms after a few attempts,
depending on how much I warmed it up while handling it.

So I looked that up in the ref manual and it showd that it should be
between 41 and 42 AWG, closer to 42. I'm thinking that the reason why
it's lower than 1.66, which is 42, is because it's wire from a foreign
country where they use metric wire sizes. So I go online and Google for
metric wire sizes.

Well, after more than an hour, I gave up. I found many tables, most of
them don't go smaller than 40 AWG. And I can find AWG to metric
conversion, but what I'm really looking for is a chart of metric wire
sizes as they would be found in some reference manual, metric of course.
But no such luck. I found a site that claims that Litz wire has
performance between stranded and foil wire.
http://ldsg.snippets.org/appdx-el.php3 So if you want high performance
crossovers, use foil conductors. And here's the gummint specs for
direct burial and gopher resistant telephone cable, in case you're
interested.
http://www.usda.gov/rus/telecom/publications/html/1753f206.htm

I found that the metric gauge is ten times the wire size in mm. So if I
go by the conversion table, it would be a wire somewhere between .65 and
..7 metric gauges, which are actually .065 and .07 mm respectively, if
they even make such sizes. If I work backwards and say that it's 1.51
ohms per foot or 4.95 ohms per meter or 4950 ohms per kilometer, where
is there a chart that will allow me to look up the ohms per kilometer to
find the wire size? I can do it with AWG, but I don't see one for
metric wire sizes.

Thanks for any guidance.

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D

Don Klipstein

Jan 1, 1970
0
Watson A.Name - \"Watt said:
I'm up to my tricks of winding 0.1 ohm resistors from some fine copper
wire and a resistor to wind it on. But I'm having trouble with the
wire, in more ways than one.

I've got a bobbin of realllly fine wire, I think the bobbin was from an
old clock motor. I measured the wire with a dial calipers and got .0025
inch, which according to my reference manual is 42 AWG, if it was bare
copper. But it's enemaeled, so I'd guess that it's the next smaller
common size, 44 AWG.

But I don't know how thick the enamel is, so I decided to wind a foot of
it onto a 1/8W resistor. The winding was a bit tedious, and I left a
quarter inch on each end for soldering it to the leads. I used my HP
3478A in four wire mode to measure it, and get a fairly accurate
reading. I get between 1.495 and 1.515 ohms after a few attempts,
depending on how much I warmed it up while handling it.

So I looked that up in the ref manual and it showd that it should be
between 41 and 42 AWG, closer to 42. I'm thinking that the reason why
it's lower than 1.66, which is 42, is because it's wire from a foreign
country where they use metric wire sizes. So I go online and Google for
metric wire sizes.

Well, after more than an hour, I gave up. I found many tables, most of
them don't go smaller than 40 AWG. And I can find AWG to metric
conversion, but what I'm really looking for is a chart of metric wire
sizes as they would be found in some reference manual, metric of course.
But no such luck. I found a site that claims that Litz wire has
performance between stranded and foil wire.
http://ldsg.snippets.org/appdx-el.php3 So if you want high performance
crossovers, use foil conductors. And here's the gummint specs for
direct burial and gopher resistant telephone cable, in case you're
interested.
http://www.usda.gov/rus/telecom/publications/html/1753f206.htm

I found that the metric gauge is ten times the wire size in mm. So if I
go by the conversion table, it would be a wire somewhere between .65 and
.7 metric gauges, which are actually .065 and .07 mm respectively, if
they even make such sizes. If I work backwards and say that it's 1.51
ohms per foot or 4.95 ohms per meter or 4950 ohms per kilometer, where
is there a chart that will allow me to look up the ohms per kilometer to
find the wire size? I can do it with AWG, but I don't see one for
metric wire sizes.

Thanks for any guidance.

With resistance below at 20-25 degrees C ONLY ROUGHLY, and close to
varying roportionately with absolute temperature (degrees K):

18 AWG is close enough to 1 mm , 1 ohm per 160 feet
19 AWG is close enough to .9 mm , 1 ohm per 125-128 feet
20 AWG is close enough to .8 mm , 1 ohm per 100 feet
21 AWG is close enough to .7-71 mm , 1 ohm per 80 feet
22 AWG is close enough to .625-.64 mm , 1 ohm per 62.5-64 feet
23 AWG is close enough to .56 mm , 1 ohm per 50 feet
24 AWG is close enough to .5 mm , 1 ohm per 40 feet
25 AWG is close enough to .44-.45 mm , 1 ohm per 31.4-32 feet
26 AWG is close enough to .4 mm , 1 ohm per 25-25.6 feet
27 AWG is close enough to .35-.36 mm , 1 ohm per 20 feet
28 AWG is close enough to .314-.32 mm , 1 ohm per 16 feet
29 AWG is close enough to .28 mm , 1 ohm per 12.5-12.8 feet
30 AWG is close enough to .25 mm , 1 ohm per 10 feet
31 AWG is close enough to .22-.23 mm , 1 ohm per 8 feet
32 AWG is close enough to .2 mm , 1 ohm per 6.25-6.4 feet
33 AWG is close enough to .175-.18 mm , 1 ohm per 5 feet
34 AWG is close enough to .16 mm , 1 ohm per 4 feet
35 AWG is close enough to .14-.142 mm , 1 ohm per 3.14-3.2 feet
36 AWG is close enough to .124-.128 mm , 1 ohm per 2.5-2.56 feet
37 AWG is close enough to .11-.111 mm , 1 ohm per 2 feet
38 AWG is close enough to .1 mm , 1 ohm per 1.6 feet
39 AWG is close enough to .09 mm , 1 ohm per 1.25-1.28 feet
40 AWG is close enough to .08 mm , 1 ohm per foot
41 AWG is close enough to .07-.072 mm , 1 ohm per .8 foot
42 AWG is close enough to .0625-.064 mm , 1 ohm per .625-.64 foot
43 mm is close enough to .055-.058 mm , 1 ohm per .5 foot
44 AWG is close enough to .05 mm , 1 ohm per .4 foot

Now, take these values as well as those from any wire table with half a
grain of salt. The reason: Tolerance, and some of the wire manufacturing
processes. The wire gets drawn through dies, and the dies experience wear
as they get used. The wire will get a little thicker as the last die
experiences more wear. Who knows when the die gets thrown into the trash
or maybe even the wire gets declared to be suitable for marketing by a
different wire gauge or (GASP!) the next larger size?

Also, consider that most metals, including copper, have resistance
varying roughly proportionately with temperature - as in having positive
temperature coefficient of around .33% of 25 degree c resistance per
degree C. (Nichrome has a significantly lower positive temperature
coefficient.)

Now for the above chart - I did not have a chart in front of me, but I
do remember that the AWG wire tables in the CRC handbook have figures
close enough to and I consider almost certainly within expectable
tolerances of what I call "1/3 octave numbers" - the powers of the 10th
root of 10. (Diameter of an odd gauge was a "1/6 octave number").
Resistance in ohms per foot at 20-25 C was close enough to a 1/3 octave
number, and resistance at 100 C was close enough to one "1/3 octave"
higher. I like to use the 100 C figures when designing magnetic
components.
As for how I got the term "1/3 octave"? Ever see what they call a 1/3
octave equalizer? This is a somewhat common tool used by touring bands
that drag along their own sound reinforcement ("PA") equipment and drag
along enough equipment to drag along an "amp rack" and an "effects rack".
1/3 octave equalizers tend to be in the "effects rack". If you see one,
look at the frequencies in Hz:
31.5-32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 315-320, 400, 500, 630,
800, 1K, 1.25K, 1.6K, 2K, 2.5K, 3.15-3.2K, 4K, 5K, 6.3K, 8K, 10K, 12.5K,
and 16K. Sometimes as high as 20K and as low as 25 and 20 Hz.

What's convenient about "1/3 octave numbers" is that any product or any
ratio of any two of these is another one of these. Any square of one of
these is another one of these. Half of these numbers have a square root
being another one of these, and the other half have square roots being
"1/6 octave numbers". Pi is one of the "1/3 octave numbers", and the
number of feet in a meter is not that far away - although cubic feet in a
cubic meter is close to a "1/6 octave number" that is not a 1/3 octave
one.
This enables easier rough engineering calculations in one's head. One
who has practiced multiplying in the head via usage of "1/3 octave
numbers" or "1/6 octave numbers" can get a final answer 5-20% off faster
than a more exact answer can be obtained with a calculator, and tolerance
in wire size (as affecting resistance per unit length) can get about that
bad.
It's a shame that most resistor and capacitor values come in 6, 12 or 24
per decade as opposed to 10 "1/3 octaves" per decade.

- Don Klipstein ([email protected])
 
J

John Woodgate

Jan 1, 1970
0
I read in alt.binaries.schematics.electronic that "Watson A.Name -
where is there a chart that will allow me to look up the ohms per
kilometer to find the wire size? I can do it with AWG, but I don't see
one for metric wire sizes.

Why do you need to know the 'wire size'? The wire you are using will
have been stretched slightly when it was wound on to the bobbin, so it
won't be an exact size anyway. It seems to me that if you are trying to
make a resistor, all you need to know is the resistance, and you can
measure that. If you are concerned about current-carrying capacity, any
figure you get from a table probably won't apply to wire wound on a
resistor. So what you do is to pass current through your resistor and
see how hot it gets. When you can't hold it for 10 s without pain, it's
carrying just a bit more current than is prudent.
 
C

Chuck Harris

Jan 1, 1970
0
John said:
Why do you need to know the 'wire size'? The wire you are using will
have been stretched slightly when it was wound on to the bobbin, so it
won't be an exact size anyway. It seems to me that if you are trying to
make a resistor, all you need to know is the resistance, and you can
measure that. If you are concerned about current-carrying capacity, any
figure you get from a table probably won't apply to wire wound on a
resistor. So what you do is to pass current through your resistor and
see how hot it gets. When you can't hold it for 10 s without pain, it's
carrying just a bit more current than is prudent.

It looks to me like Watsun doesn't trust his ohm meter, and is trying his
hand at making some standard resistors... unfortunately, copper wire manufacture
isn't all that standard... especially in the hair fine sizes.

Manufacturers only spend money on tightening up specifications that truly
matter to their customers. Cu wire size, though important, is only about 5%
important. Additional parameters that affect resistance are oxygen content,
copper purity, hardness, smoothness, imbedded stress and strain (if you don't
believe that stress and strain affect the characteristics of wire, lookup
"Wiegand effect" (for ferromagnetic wire).). When you buy spools of wire
that was meant for making precision WW resistors, you will notice that the spools
are hand stamped with ohms-per-foot values that have been precisely measured.

Large users of copper wire can order 'tween sizes that exactly match their
physical requirements. You will find motors, and transformers, wound with
odd sizes that you could never buy in an electronics store (17.5 AWG...).
Wire that you salvage is especially likely to be a 'tween size.

When NBS made their standard resistors, they used pure metal rods finely
machined, and polished, to standard diameters, and lengths. It was nothing
like the brutally inaccurate process used to draw wire through dies.
(put some drawn wire under a good microscope, and look at the grooves and
trenches in the surface.)

NBS's higher value resistors were made by using bridges to adjust the higher
value cut-and-try resistors against the low resistance physical "standards".

-Chuck
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
Don Klipstein said:
Sun said:
I'm up to my tricks of winding 0.1 ohm resistors from some fine copper
wire and a resistor to wind it on. But I'm having trouble with the
wire, in more ways than one.

I've got a bobbin of realllly fine wire, I think the bobbin was from an
old clock motor. I measured the wire with a dial calipers and got ..0025
inch, which according to my reference manual is 42 AWG, if it was bare
copper. But it's enemaeled, so I'd guess that it's the next smaller
common size, 44 AWG.

But I don't know how thick the enamel is, so I decided to wind a foot of
it onto a 1/8W resistor. The winding was a bit tedious, and I left a
quarter inch on each end for soldering it to the leads. I used my HP
3478A in four wire mode to measure it, and get a fairly accurate
reading. I get between 1.495 and 1.515 ohms after a few attempts,
depending on how much I warmed it up while handling it.

So I looked that up in the ref manual and it showd that it should be
between 41 and 42 AWG, closer to 42. I'm thinking that the reason why
it's lower than 1.66, which is 42, is because it's wire from a foreign
country where they use metric wire sizes. So I go online and Google for
metric wire sizes.

Well, after more than an hour, I gave up. I found many tables, most of
them don't go smaller than 40 AWG. And I can find AWG to metric
conversion, but what I'm really looking for is a chart of metric wire
sizes as they would be found in some reference manual, metric of course.
But no such luck. I found a site that claims that Litz wire has
performance between stranded and foil wire.
http://ldsg.snippets.org/appdx-el.php3 So if you want high performance
crossovers, use foil conductors. And here's the gummint specs for
direct burial and gopher resistant telephone cable, in case you're
interested.
http://www.usda.gov/rus/telecom/publications/html/1753f206.htm

I found that the metric gauge is ten times the wire size in mm. So if I
go by the conversion table, it would be a wire somewhere between .65 and
.7 metric gauges, which are actually .065 and .07 mm respectively, if
they even make such sizes. If I work backwards and say that it's 1.51
ohms per foot or 4.95 ohms per meter or 4950 ohms per kilometer, where
is there a chart that will allow me to look up the ohms per kilometer to
find the wire size? I can do it with AWG, but I don't see one for
metric wire sizes.

Thanks for any guidance.

With resistance below at 20-25 degrees C ONLY ROUGHLY, and close to
varying roportionately with absolute temperature (degrees K):

18 AWG is close enough to 1 mm , 1 ohm per 160 feet
19 AWG is close enough to .9 mm , 1 ohm per 125-128 feet
20 AWG is close enough to .8 mm , 1 ohm per 100 feet
21 AWG is close enough to .7-71 mm , 1 ohm per 80 feet
22 AWG is close enough to .625-.64 mm , 1 ohm per 62.5-64 feet
23 AWG is close enough to .56 mm , 1 ohm per 50 feet
24 AWG is close enough to .5 mm , 1 ohm per 40 feet
25 AWG is close enough to .44-.45 mm , 1 ohm per 31.4-32 feet
26 AWG is close enough to .4 mm , 1 ohm per 25-25.6 feet
27 AWG is close enough to .35-.36 mm , 1 ohm per 20 feet
28 AWG is close enough to .314-.32 mm , 1 ohm per 16 feet
29 AWG is close enough to .28 mm , 1 ohm per 12.5-12.8 feet
30 AWG is close enough to .25 mm , 1 ohm per 10 feet
31 AWG is close enough to .22-.23 mm , 1 ohm per 8 feet
32 AWG is close enough to .2 mm , 1 ohm per 6.25-6.4 feet
33 AWG is close enough to .175-.18 mm , 1 ohm per 5 feet
34 AWG is close enough to .16 mm , 1 ohm per 4 feet
35 AWG is close enough to .14-.142 mm , 1 ohm per 3.14-3.2 feet
36 AWG is close enough to .124-.128 mm , 1 ohm per 2.5-2.56 feet
37 AWG is close enough to .11-.111 mm , 1 ohm per 2 feet
38 AWG is close enough to .1 mm , 1 ohm per 1.6 feet
39 AWG is close enough to .09 mm , 1 ohm per 1.25-1.28 feet
40 AWG is close enough to .08 mm , 1 ohm per foot
41 AWG is close enough to .07-.072 mm , 1 ohm per .8 foot
42 AWG is close enough to .0625-.064 mm , 1 ohm per .625-.64 foot
43 mm is close enough to .055-.058 mm , 1 ohm per .5 foot
44 AWG is close enough to .05 mm , 1 ohm per .4 foot
[snip]
- Don Klipstein ([email protected])

Thanks, Don. But this is the exact chart I found online as I described
above. As I said above, what I'm looking for is a metric wire table,
not AWG.

Thank you.
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
John Woodgate said:
I read in alt.binaries.schematics.electronic that "Watson A.Name -


Why do you need to know the 'wire size'? The wire you are using will
have been stretched slightly when it was wound on to the bobbin, so it
won't be an exact size anyway. It seems to me that if you are trying to
make a resistor, all you need to know is the resistance, and you can
measure that. If you are concerned about current-carrying capacity, any
figure you get from a table probably won't apply to wire wound on a
resistor. So what you do is to pass current through your resistor and
see how hot it gets. When you can't hold it for 10 s without pain, it's
carrying just a bit more current than is prudent.

Am I 'chasing rainbows' by asking for a metric wire table? I was just
unpleasantly surprised that I couldn't find one online.

Thanks.
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
Genome said:
in message news:[email protected]...

Whoops...

http://genome.dna.tripod.com/docs/wires.htm

has a calculating thing at the bottom

DNA


Thanks. I'm a bit confused as to what the columns mean, especially the
IEC stuff. The calculator seems to give an answer, but if I plug my
predicted .07 mm value into it, does it give me an answer that is an
increment of the metric wire table? IOW, can I find a .07mm metric
wire?

I'm just kind of unwilling to believe that there isn't some kind of
metric wire table online.

Thanks.
 
J

John Woodgate

Jan 1, 1970
0
I read in alt.binaries.schematics.electronic that "Watson A.Name -
Am I 'chasing rainbows' by asking for a metric wire table? I was just
unpleasantly surprised that I couldn't find one online.

What did you Google for? "Giraffe"? "Metric copper wire sizes" produces
enough hits to appease anyone.
 
S

Spehro Pefhany

Jan 1, 1970
0
It looks to me like Watsun doesn't trust his ohm meter, and is trying his
hand at making some standard resistors... unfortunately, copper wire manufacture
isn't all that standard... especially in the hair fine sizes.

Manufacturers only spend money on tightening up specifications that truly
matter to their customers. Cu wire size, though important, is only about 5%
important. Additional parameters that affect resistance are oxygen content,
copper purity, hardness, smoothness, imbedded stress and strain (if you don't
believe that stress and strain affect the characteristics of wire, lookup
"Wiegand effect" (for ferromagnetic wire).). When you buy spools of wire
that was meant for making precision WW resistors, you will notice that the spools
are hand stamped with ohms-per-foot values that have been precisely measured.

Large users of copper wire can order 'tween sizes that exactly match their
physical requirements. You will find motors, and transformers, wound with
odd sizes that you could never buy in an electronics store (17.5 AWG...).
Wire that you salvage is especially likely to be a 'tween size.

When NBS made their standard resistors, they used pure metal rods finely
machined, and polished, to standard diameters, and lengths. It was nothing
like the brutally inaccurate process used to draw wire through dies.
(put some drawn wire under a good microscope, and look at the grooves and
trenches in the surface.)

NBS's higher value resistors were made by using bridges to adjust the higher
value cut-and-try resistors against the low resistance physical "standards".

-Chuck

It's trivial to measure resistance of a 0.1 ohm resistor fairly
accurately using a bench power supply, an ammeter, a voltmeter and
Ohm's law.

Wire taken from the same spool will have very similar diameter, since
it has all passed through the same drawing die.

A resistor as described also makes a reasonable* temperature sensor...
pure copper has a tempco in the +3800-3900ppm/K range, similar to that
of platinum or other more stable materials that are often used. As
such, you should consider the temperature when measuring the
resistance if you care much about the resistance value.

*not so reasonable if you use very fine wire

Best regards,
Spehro Pefhany
 
S

Spehro Pefhany

Jan 1, 1970
0
So trivial, that I didn't think it required mentioning.
Watsun, I believe, wants to be able to go to a wire table, and read out
that XX mm wire is YY ohms per 1000m, so he needs *exactly*

0.1 ohm x 1000m / YY ohms,

meters of wire to make his resistance. This will work, but not to within
the inherent accuracy of precision ohm meters, such as on a HP3478A DMM.

Then the best way to find the resistance per unit length of a given
spool is to take a known length, measure the resistance (using the
ammeter/voltmeter/bench supply if you don't have a Kelvin connection
milliohmmeter), and divide by the known length. ;-)
I am just guessing as to why he really wants to make a precision 0.1 ohm
resistor from scratch. My guesses are based on some of the themes of past
postings by Watsun on the subject. I am probably totally off base.

He'll *never* make what I would call a 'precision resistor' from
copper wire. A few degrees C temperature change and the resistance
will have changed by a whopping 1%.

If you're happy with the 10% tolerance range + tempco, maybe you have
a hope. I was able to get away with it in that general region,
although I hedged by having more like 20% adjustment range.
True, but the die will increase in size somewhat by the time it reaches
the end of a large spool. Copper is a very abrasive material, and eats
dies for lunch. When the #38 die becomes too big, it becomes a #37 die.

-Chuck

Thus you should avoid making one resistor from the beginning of the
spool and the next from, say, the other end of the spool. ;-)

Magnet wire is drawn through diamond dies which don't wear very
rapidly. I suspect that surface issues have a lot more to do with
variations at smaller diameters. Personally, I wouldn't go much below
AWG30 for this sort of thing. Another issue is that the finer wire
stretches pretty easily. If you stay below the elastic limit that
might even be a useful feature.


Best regards,
Spehro Pefhany
 
R

Rich Grise

Jan 1, 1970
0
Now, take these values as well as those from any wire table with half
a
grain of salt. The reason: Tolerance, and some of the wire
manufacturing processes. The wire gets drawn through dies, and the dies
experience wear as they get used. The wire will get a little thicker as
the last die experiences more wear. Who knows when the die gets thrown
into the trash or maybe even the wire gets declared to be suitable for
marketing by a different wire gauge or (GASP!) the next larger size?

Considering that the dies are made of diamond, I'd guess that you can
draw an awful lot of copper before the hole wears away perceptibly.

This was just the first google hit on "wire drawing die":
http://www.e6.com/e6/page.jsp?pageid=600406070

Cheers!
Rich
 
Q

qrk

Jan 1, 1970
0
On Sun, 18 Sep 2005 15:57:42 -0700, "Watson A.Name - \"Watt Sun, the

[snipped lots of words asking about where to find standard metric wire
size data]

Use the IEC60317 chart. The following chart covers the equivalent of
24 to 50+ AWG. Bold values are common sizes.
http://www.elektrisola.com/english/iec60317-1.pdf
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
It seems that you have reasonably characterized the wire; so many
ohms i so many feet; isn't that good enough?

I suppose I could mark the bobbin "1510 milliOhms/Ft" or something like
that. But then when I come back in six months and want to use the wire
for something, and I really have to know the wire gauge, then I'm still
nowhere. Why? Because I still haven't directly correlated the one
single measurement with the wire gauge. I suppose I could make a half
dozen or so resistors each with a foot of wire as close as I can get,
and then measure them and take an averagee so that I can be reasonably
certain that the one and only measurement I'm now relying on wasn't
distorted by stretched wire or shorted turns or a bad solder job, etc.
Does it really matter if it is #42, #43 or #44?

Yes. "Size Does Matter!"
Call the result a WWW resistor, for "Win's Wire Wound" resistor and
do not ask What, Where, or When.

BTW, it has a couple microhenrys inductance. :eek:)
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
[snip]
Large users of copper wire can order 'tween sizes that exactly match their
physical requirements. You will find motors, and transformers, wound with
odd sizes that you could never buy in an electronics store (17.5 AWG...).
Wire that you salvage is especially likely to be a 'tween size.

This is exactly wnat I'm noticing. The wire seems to be something like
41.5 gauge.

Or as someone else mentioned, the dies were so worn that the wire is
considerably larger diameter than it's supposed to be.

[snip]

ONe thing I found out is a pound of copper makes enough 42 AWG wire to
stretch across the city! More than ten miles.

Thanks for the info.
 
C

Chuck Harris

Jan 1, 1970
0
Watson said:
BTW, it has a couple microhenrys inductance. :eek:)

It doesn't have to have all that much, bend the wire into a hairpin
loop before you wind, and most of the inductance will cancel out.

-Chuck
 
J

John Woodgate

Jan 1, 1970
0
I read in alt.binaries.schematics.electronic that Rich Grise
Considering that the dies are made of diamond, I'd guess that you can
draw an awful lot of copper before the hole wears away perceptibly.

Well, in one way, but consider how many miles (and even more km) there
are in a big reel of 40 gauge. 'An awful lot' can pass through in just a
few hours.
 
J

John Woodgate

Jan 1, 1970
0
I read in alt.binaries.schematics.electronic that "Watson A.Name -
BTW, it has a couple microhenrys inductance. :eek:)

I'd tell you how to do an Ayrton-Perry winding, but it would upset the
Moebius Coil people. (;-)
 
F

Fred Bartoli

Jan 1, 1970
0
John Woodgate said:
I read in alt.binaries.schematics.electronic that "Watson A.Name -


I'd tell you how to do an Ayrton-Perry winding, but it would upset the
Moebius Coil people. (;-)

Oh, you're too fast for me.
 
J

John Woodgate

Jan 1, 1970
0
I read in alt.binaries.schematics.electronic that Robert Baer
An rule of thumb that i have used for ages is: run no more than X
milliamps of current thru a wire of X circular mils of area; this gives
negligible IR losses.

The conductor size based on voltage drop is very much larger than the
conductor size based on temperature rise. A wire whose 'area' is X
circular mils has a real area of 0.7854X x 10^-6 square inches. X mA
through that area is a current density of 1273 A/in^2.

Modern transformers (in which it's quite difficult to dispose of the
heat from the conductors) are commonly designed with a current density
of 3000 A/in^2 or even more.
 
W

Watson A.Name - \Watt Sun, the Dark Remover\

Jan 1, 1970
0
John Woodgate said:
I read in alt.binaries.schematics.electronic that "Watson A.Name -


What did you Google for? "Giraffe"? "Metric copper wire sizes" produces
enough hits to appease anyone.

I Googled for metric copper wire table and got over 300 000 "hits".
What I found were tables of AWG with a column with the metric equivalent
sizes, or IOW, just multiplying the diameter by 25.4. Few of the tables
go below 40 AWG, which is what I need (some don't go below 30 or even 20
AWG).

I tried your suggestion, metric copper wire sizes. Many of the URLs are
the same, judging by their purple color which means I've viewed them
recently. I've spent a substantial amount of time searching thru them.
A lightning storm passed thru, causing a momentary power failure which
caused the PC to reboot, oh, well. I decided to watch TV for awhile,
which doesn't have to spend time rebooting. ;-)
If anyone wants to offer a URL, I'm willing to check it out. Meantime,
I'm still searching.
 
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