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0.1 ohm Resistors from Scratch Again

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

Rich the Newsgroup Wacko

Jan 1, 1970
0
I read in alt.binaries.schematics.electronic that Don Klipstein


Well, they MAY be, but there are many alloys with much lower TCRs.
Constantan is one,

Is that mined in Constantanople?
 
J

John Woodgate

Jan 1, 1970
0
I read in alt.binaries.schematics.electronic that Rich the Newsgroup
Is that mined in Constantanople?
No, but it's used for making istanbullets.
 
S

Spehro Pefhany

Jan 1, 1970
0
I read in alt.binaries.schematics.electronic that Rich the Newsgroup

No, but it's used for making istanbullets.

"Constant resistance since 1453".


Best regards,
Spehro Pefhany
 
J

John Woodgate

Jan 1, 1970
0
I read in alt.binaries.schematics.electronic that Spehro Pefhany
"Constant resistance since 1453".

Well, it's 2032 here now, so that's less than 6 hours. What's the
LONG-term stability like?
 
B

buck rojerz

Jan 1, 1970
0
I read in alt.binaries.schematics.electronic that Rich the Newsgroup

No, but it's used for making istanbullets.

OOOhhhh! That WAS a good one. :))
 
W

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

Jan 1, 1970
0
Don Klipstein said:
A coil on a resistor body will heat up more than a few inches of wire in
open air.
Air cooling is less when the wire is on a surface. In addition,
probably more significant, is wire turns on a resistor body being heated
by heat from adjacent turns of the coiled winding.

Sounds to me, Don, a lot like the tungsten wire in a light bulb. ;-)
 
W

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

Jan 1, 1970
0
Don Klipstein said:
That's a more difficult part, given temperature coefficient of
resistance of copper! How to measure cold and when in use? Maybe
make a resistor measuring only a little low ehen cold, and see what it
does when in use, and improve from that!

- Don ([email protected])

I've since gone to the larger 36 AWG, which is a bit under 3 inches for
a tenth of an ohm. So no problem.
 
W

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

Jan 1, 1970
0
Don Klipstein said:
One thing to keep in mind:

Wirewound power resistors are typically made with nichrome wire, which
has an unusually low temperature coefficient of resistance about half that
of copper and most other metals.

And, IIRC, it's also a lot more difficult to solder.
 
W

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

Jan 1, 1970
0
Don Klipstein said:
This is opposite of what should be the truth. Copper wire has
resistance increasing with temperature, roughly proportionately with
degrees K.

Looks like you have some measurement error.

I think what's happening is when I pinch it with my fingers, I'm cooling
it, not warming it.
 
W

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

Jan 1, 1970
0
John Woodgate said:
I read in alt.binaries.schematics.electronic that Don Klipstein


Well, they MAY be, but there are many alloys with much lower TCRs.
Constantan is one, and Eureka is similar. Manganin has very nearly zero
TCR and is used for high-precision resistors.

Recently I had to do some work in the physics lab at our other campus
(they have some HP 6205 power supplies for doing some experiements).
They have several of these "slidewire" resistance wire gizmos. The
description says it uses nickel-chromium, I presume is the same thing as
nichrome.
http://sargentwelch.com/product.asp_Q_pn_E_CP83191-00_EA_A_Wheatstone+Br
idge%2C+Slidewire%2C+CENCO_E_

When you think about it, this is how Sir Thomas and Luigi and the others
started out, except they used batteries. Some interesting experiments
here.
http://www.lhup.edu/~dsimanek/scenario/labman4/wheats.htm
 
W

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

Jan 1, 1970
0
Ban said:
Really, I don't know what this is all about, every bit of the "experiment"
can be predicted by anybody, so WTF is the OP doing?

I'm making my own 0.1 ohm resistors. I can't buy (locally, anyway) a
small 0.1 ohm resistor, and I don't need even a tenth of a watt
dissipation when I use it for current sensing. And I can't buy special
wire other than copper in small quantities locally. I could buy a
wirewound resistor and break off the ceramic and cement hopefully
without damaging the wire, and then use the wire to wind some other
resistors. But I'm doing just fine with 2.9" (73.4mm) of 36 AWG copper
wire wound on a 1/4W resistor. It's reasonably accurate, maybe within
5% or less. And it works okay at room temp.
 
W

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

Jan 1, 1970
0
Thanks, J.F. You're beginning to sound like Toak/Nunya whatever. I'm
just trying to share my experiences with others. If you don't have
anything constructive to say, then I invite you to make no comments.
But then we all know that you wouldn't take my invitation seriously.
Have a nice day.
 
W

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

Jan 1, 1970
0
Rich the Newsgroup Wacko said:
Is that mined in Constantanople?

Of courese not, silly! Everyone knows it was made from the throne of
the great Roman ewmperor Constantine (until they ran out, and had to use
his chamberpots)! ;-)
 
W

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

Jan 1, 1970
0
John Woodgate said:
I read in alt.binaries.schematics.electronic that Rich the Newsgroup

No, but it's used for making istanbullets.

Anyone (in the U.S. at least) watch Guns, Germs and Steel on PBS the
other night? http://www.pbs.org/previews/gunsgermssteel/

They showed how a couple hundred conquistadors decimated tens of
thousands of Aztecs with this silly blunderbuss or trabuco, which could
barely hit the side of a barn. And their horses, of courses, had a lot
to do with it. Interesting.
 
N

NunYa Bidness

Jan 1, 1970
0
Thanks, J.F. You're beginning to sound like Toak/Nunya whatever. I'm
just trying to share my experiences with others. If you don't have
anything constructive to say, then I invite you to make no comments.
But then we all know that you wouldn't take my invitation seriously.
Have a nice day.
<buzzards circling overhead..>

Were you to review the facts, you'd find that I started out by
jumping on Johnny boy for something just as stupid.

Then, all you assholes chimed in on his side. THEN I called you all
assholes, if not worse.

Were it not for you jumping on Johnny's side, I would never have
made a single derogatory remark to you.

Put that in your invitation log.
 
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