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Using a thin wire instead of a resistor?

J

John Doe

Jan 1, 1970
0
Recently in a non-electronics group, I heard mention of using a thin
wire for resistance and a high current, low-voltage application
(roughly maybe a few amps at about six volts).

What about using a thin wire in place of a resistor?

I guess some resistors are made from a thin, coiled wire, but they
are insulated.

Thank-you.
 
J

JeffM

Jan 1, 1970
0
high current, low-voltage application...
What about using a thin wire in place of a resistor?
John Doe

It's possible--of course that's the same way they make fuses.
A longer, fatter wire might be better.
 
R

R.Lewis

Jan 1, 1970
0
John Doe said:
Recently in a non-electronics group, I heard mention of using a thin
wire for resistance and a high current, low-voltage application
(roughly maybe a few amps at about six volts).

What about using a thin wire in place of a resistor?

Using thin wire for resistance is common practice.
They are called wirewound resistors and are manufactured by all the leading
resistor manufacturers.
 
P

Paul Burridge

Jan 1, 1970
0
Using thin wire for resistance is common practice.
They are called wirewound resistors and are manufactured by all the leading
resistor manufacturers.

No they ain't.
 
K

Ken Smith

Jan 1, 1970
0
John Doe said:
What about using a thin wire in place of a resistor?

It is a great way to make a resistor with a huge surge rating but a bad
temp-co. I've used it a few times. Higher values need impractical
amounts of wire.

BTW: #40 wire is just about 1 Ohm per inch.
 
R

Roger Hamlett

Jan 1, 1970
0
Paul Burridge said:
No they ain't.
Actually, quite a few are, but I agree the 'wirewound resistor', does not
inherently meet the definition of using a 'short length' of wire....
Look instead at 'current sense shunts'. TT electronics do a range of
these, as do a couple of other manufacturers that I know of. Short lengths
of wire, with ends to either go through holes, or onto surface mount
tracks. Made of wires designed to give a relatively stable resistance with
changes in temperature, with the big advantage, of offering very low
inductance. Look at:
http://www.irctt.com/pdf_files/OAR.pdf
for a typical example.
Use of wire, is more common for 'zero ohm' links, where the resistance
presented is not the important factor, but getting the signal 'out' of the
board, may be. :)

Best Wishes
 
C

Clarence_A

Jan 1, 1970
0
Paul Burridge said:
No they ain't.
--


Are you saying that wire had no resistance, or that you don't know
of anyone making wirewound resistors?

Which leads me to ask:
Please list the resistor manufacturers who do not in some division
currently make a wirewound resistor.

Also, define "Leading resistor manufacturers" for the sake of
clarity!

The only problem is that most wirewound resistors are relatively
expensive, since most are considered to be precision, or power.
 
F

Fred Bloggs

Jan 1, 1970
0
John said:
Recently in a non-electronics group, I heard mention of using a thin
wire for resistance and a high current, low-voltage application
(roughly maybe a few amps at about six volts).

What about using a thin wire in place of a resistor?

I guess some resistors are made from a thin, coiled wire, but they
are insulated.

It depends on the application- your description makes it sound like you
are after a high current low resistance resistor. There are precision
milliohm high current resistors with 30ppm/oC stability and specially
designed to uniformly diffuse the heat out of the package. A copper wire
has 3900ppm/oC stability and undefined heat removal characteristics,
comparatively a piece of junk.
 
S

SCADA

Jan 1, 1970
0
John Doe said:
Recently in a non-electronics group, I heard mention of using a thin
wire for resistance and a high current, low-voltage application
(roughly maybe a few amps at about six volts).

What about using a thin wire in place of a resistor?

I guess some resistors are made from a thin, coiled wire, but they
are insulated.

Thank-you.

Ni-Chrome wire was very popular years ago. It has a high resistance, and can
withstand higher currents. I'm not sure where you can get it today. I
remember using "Picture hanging wire" many years ago from the five and dime,
that was probably aluminum wire!
 
S

Spehro Pefhany

Jan 1, 1970
0
On Sun, 30 Jan 2005 16:56:25 +0000 (UTC), the renowned
It is a great way to make a resistor with a huge surge rating but a bad
temp-co.

The tempco is pretty good if you use manganin wire, and not so bad
with Constantan wire. Brass is not as bad as copper either.

I've used it a few times. Higher values need impractical
amounts of wire.

BTW: #40 wire is just about 1 Ohm per inch.

--


Best regards,
Spehro Pefhany
 
J

John Larkin

Jan 1, 1970
0
Ni-Chrome wire was very popular years ago. It has a high resistance, and can
withstand higher currents. I'm not sure where you can get it today. I
remember using "Picture hanging wire" many years ago from the five and dime,
that was probably aluminum wire!

I recently bought a spool of # 16 Manganin wire to make some home-made
low-inductance precision resistors, wound on ceramic tubes. I posted a
pic in a.b.s.e. a while back. Manganin has a very low tc, below 10
ppm/k typically, and is solderable. One can make a pretty good current
shunt just by soldering a Manganin jumper between two plated-through
holes on a pcb. We also punch or photoetch funnily-shaped current
shunts out of sheet manganin.

Zeranin is even better, but is harder to get.

John
 
R

Rich Grise

Jan 1, 1970
0
Ni-Chrome wire was very popular years ago. It has a high resistance, and can
withstand higher currents. I'm not sure where you can get it today. I
remember using "Picture hanging wire" many years ago from the five and dime,
that was probably aluminum wire!

http://www.google.com/search?q=nichrome+wire :)

I picked up some on ebay once, surprisingly cheap. :)

Cheers!
Rich
 
B

Ben Bradley

Jan 1, 1970
0
Recently in a non-electronics group, I heard mention of using a thin
wire for resistance and a high current, low-voltage application
(roughly maybe a few amps at about six volts).

What about using a thin wire in place of a resistor?

One of Bob Pease's colums was about doing this (well, thicker wires
for a very low resistance). He made a round squirrelcage thing
(distributes the current to each wire equally) of wire with the wires
far enough apart so each wire doesn't heat up much, so the value
doesn't change much.
Here's the article:
http://www.elecdesign.com/Articles/ArticleID/2144/2144.html
 
T

Tony

Jan 1, 1970
0
The tempco is pretty good if you use manganin wire, and not so bad
with Constantan wire. Brass is not as bad as copper either.

I've been trying to find some decent data on the tempcos of Manganin,
Constantan and Nikrothal LX (or any other low TCR material) for a
while now - preferably a typical resistance vs temperature curve, but
the best I've been able to Google is that Manganin is either 10 or
15ppm/K, Constantan is either 20 or 74ppm/K (but over a wider range),
and Nikrothal LX may be 10 ppm/K - not quite enough consistency to
give me any confidence at all. Any chance you can point me to some
credible data (ideally over the range -40C to +60C)? Even better, a
trusted supplier? in Australia?

Tony (remove the "_" to reply by email)
 
P

Paul Burke

Jan 1, 1970
0
Tony said:
I've been trying to find some decent data on the tempcos of Manganin,
Constantan and Nikrothal LX

According to Tennent the Invaluable (1989 edition)

Constantan + or - 4 x 10e-5
Manganin + or - 1 x 10e-5

Paul Burke
 
S

Spehro Pefhany

Jan 1, 1970
0
[...]
What about using a thin wire in place of a resistor?

It is a great way to make a resistor with a huge surge rating but a bad
temp-co.

The tempco is pretty good if you use manganin wire, and not so bad
with Constantan wire. Brass is not as bad as copper either.

I've been trying to find some decent data on the tempcos of Manganin,
Constantan and Nikrothal LX (or any other low TCR material) for a
while now - preferably a typical resistance vs temperature curve, but
the best I've been able to Google is that Manganin is either 10 or
15ppm/K, Constantan is either 20 or 74ppm/K (but over a wider range),
and Nikrothal LX may be 10 ppm/K - not quite enough consistency to
give me any confidence at all. Any chance you can point me to some
credible data (ideally over the range -40C to +60C)? Even better, a
trusted supplier? in Australia?

Tony (remove the "_" to reply by email)

Careful- there's more than one alloy called Constantan and more than
one called Manganin-- I think I'd only trust data direct from the
alloy manufacturer. There are only a handful of companies world-wide
that make these alloys. Carpenter, Hoskins, Johnson-Matthey (precious
metal alloys), etc.

Carpenter shows Manganin 13 (9.5% Manganese, 86% Cu, 4.5% Ni) tempco
as +15ppm/K (average over some unspecifice range!), but the actual
tempco varies considerably over the normal operating range, peaking at
about 45°C, and actually goes negative below about 25°C and above
about 75°C.

Managanin 130 (12% Manganese, 84% Cu, 4% Ni) has a more negative
tempco that peaks at about 30°C.

To John Larkin: Interesting they recommend aging the material at
120-138°C for 25-48 hours to improve the stability. That's for
wirewound resistors, but I imagine it would apply to other forms that
have been formed, laser cut, or machined.


Best regards,
Spehro Pefhany
 
J

Jim Thompson

Jan 1, 1970
0
For limited temperature range, and low self-heating, I've found that
1/4" copper pipe worked just ducky for a 300Amp shunt.

(For a golf cart motor controller :)

...Jim Thompson
 
J

John Larkin

Jan 1, 1970
0
[...]
What about using a thin wire in place of a resistor?

It is a great way to make a resistor with a huge surge rating but a bad
temp-co.

The tempco is pretty good if you use manganin wire, and not so bad
with Constantan wire. Brass is not as bad as copper either.

I've been trying to find some decent data on the tempcos of Manganin,
Constantan and Nikrothal LX (or any other low TCR material) for a
while now - preferably a typical resistance vs temperature curve, but
the best I've been able to Google is that Manganin is either 10 or
15ppm/K, Constantan is either 20 or 74ppm/K (but over a wider range),
and Nikrothal LX may be 10 ppm/K - not quite enough consistency to
give me any confidence at all. Any chance you can point me to some
credible data (ideally over the range -40C to +60C)? Even better, a
trusted supplier? in Australia?

Tony (remove the "_" to reply by email)

Manganin has a parabolic curve of resistance vs temperature, peaking
at some temperature and falling off above or below. Within maybe 10
deg C of the peak, tc is only a few PPM. The peak temp depends on the
manganese composition and on the alloy's history - mechanical
stresses, like winding or fabrication, mess up the curve, and
annealing fixes it. You can buy "wire" manganin with zero tc (parabola
peak) near 25C, or "shunt" manganin with min tc around 80 c or
something, for big shunts that self-heat a lot. One alloy is "manganin
13" (13% manganese) and one is "manganin 12" but I can't remember
which is which.

I can post some data and curves to a.b.s.e. if anybody's interested. I
have that stuff at work.

John
 
J

John Larkin

Jan 1, 1970
0
To John Larkin: Interesting they recommend aging the material at
120-138°C for 25-48 hours to improve the stability. That's for
wirewound resistors, but I imagine it would apply to other forms that
have been formed, laser cut, or machined.

We punch and photoetch shunts from manganin sheet stock. I have some
curves of r-vs-t for as-punched and after annealing. This is *very*
tedious data to acquire! We anneal the stuff at 150C for 24 hours or
so, which seems to calm it down. It oxidizes them too, so we dunk them
in dilute HCl before we try to solder them. Manganin is solderable
with agressive flux, but not super-easily.

Harrison Alloys used to be the prime manganin supplier, and they had
lots of nice tc and annealing data. The company seems to keep changing
hands, became Harris-Driver I think, but I can't locate them on the
web. Last time I talked to them, some years ago, they didn't know much
about the stuff; it was sort of like a recipe they'd inherited. They
apparantly also made good batches and bad batches, sort of at random.

Manganin doesn't laser cut very well... too reflective or something.
Gums up milling cutters, too, like machining acrylic. Punching is
good, but the dies are expensive. Lately we photo-etch, cheap and
low-stress.

John
 
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