Author Topic: DIY Resistance wire  (Read 2639 times)

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Offline Labrat101Topic starter

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DIY Resistance wire
« on: January 14, 2022, 09:20:06 am »
Though sheer boredom I was was looking for a Shunt resistor .
So going though years of stock piled parts etc . I needed a 0.05  \$\Omega\$ @ 50 amp .
So not finding anything that was suitable . I went into.. How hard can it be to make it  :palm:
 Copper wire ... No
 Steel wire .. Hum has a high resistance but very unstable with temperature   another No.
Putting my soldering Iron on the cleaning wire .. Brain wave . low frequency .
Those stainless steel pads we use to clean our soldering iron tips . are 410 Stainless steel  11.5% nickel chrome    :-+
 Yes . looking Good . measured it 18mm is showing 1.1030  \$\Omega\$ .
 Also taking a piece about 15cm long powering it from my lab power with 5v @ 1amp it become a very handy foam cutter .
 These steel cleaning pads Have many uses . Maybe not the best .
So just rapping this wire round a couple of copper posts , A few times I was able to get my  0.05 \$\Omega\$  for testing an quick repair of my
electronic load .  :-+ 

 These wire cleaning pads have a melting point of about 1500 C  Resistance aprox 0.5  \$\Omega\$ per cm 
  I guess they aint Quality controlled so there will be different specs .

  I'm sure there are many other DIY thing that can be made from reusing this stuff
 
  Have Fun and don't burn your fingers  .

  More Ideas welcome

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Offline jonpaul

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Re: DIY Resistance wire
« Reply #1 on: January 14, 2022, 11:58:10 am »
Use only Nichrome wire, for heaters and high temp. Crimp do not solder.

Shunts need a low TC, various resistance wire are available.

Steel wool will burn.

Jon

An Internet Dinosaur...
 

Online Kleinstein

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Re: DIY Resistance wire
« Reply #2 on: January 14, 2022, 12:22:42 pm »
The stainless steel pad is a bid thin for a high current shunt. Otherwise the usual stainless steel is reasonable low TC for a material not specially made for that.
The problem is only the soldering, which is hard and needs special flux.
 

Online Zero999

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Re: DIY Resistance wire
« Reply #3 on: January 14, 2022, 01:12:00 pm »
Does it copper plate easily? If so, perhaps that'll make soldering easier.

50A through 50mΩ is 125W. How did you stop it vaporizing?
 

Offline Labrat101Topic starter

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Re: DIY Resistance wire
« Reply #4 on: January 14, 2022, 01:41:31 pm »
Use only Nichrome wire, for heaters and high temp. Crimp do not solder.

Shunts need a low TC, various resistance wire are available.

Steel wool will burn.

Jon
I know steel wool burn .
This is Not the steel wool stuff .  its 1mm x 0.05 mm spring wire it seem to handle about 6 amps without a problem .
 the one I have is very tight spring wound . and cheep . as far a I can tell from running a few tests it has a high content of chrome .
 It was more of a Fun thing .

I did also find some 3kw Nichrome wire afterwards and Yes its better .
 
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Offline Labrat101Topic starter

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Re: DIY Resistance wire
« Reply #5 on: January 14, 2022, 01:56:02 pm »
Does it copper plate easily? If so, perhaps that'll make soldering easier.

50A through 50mΩ is 125W. How did you stop it vaporizing?
I don't think it can be copper plated .. I wound it round 2.5 mm copper wire and bent the end over and crimped it with a crimper .
 Not sure how you got to this .
  50A through 50mΩ is 125W.  :-//  No.  ( its OK a Common mistake that a lot of people fall for)
 Its the voltage drop across the shunt which is 75mv per Amp   . 75mv * 50A = 3.75 W

 
« Last Edit: January 14, 2022, 01:59:29 pm by Labrat101 »
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Online Zero999

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Re: DIY Resistance wire
« Reply #6 on: January 14, 2022, 02:38:23 pm »
Does it copper plate easily? If so, perhaps that'll make soldering easier.

50A through 50mΩ is 125W. How did you stop it vaporizing?
I don't think it can be copper plated .. I wound it round 2.5 mm copper wire and bent the end over and crimped it with a crimper .
 Not sure how you got to this .
  50A through 50mΩ is 125W.  :-//  No.  ( its OK a Common mistake that a lot of people fall for)
 Its the voltage drop across the shunt which is 75mv per Amp   . 75mv * 50A = 3.75 W
You seem to be confusing the numbers.

If it's 75mV per amp, then it has a resistance of 75mΩ, not 50mΩ
R = V/I = 1/0.075 = 0.075Ω = 75mΩ

If it has a voltage drop of 0.75mV, at 50A, then the resistance is 0.75/50 = 0.015Ω = 15mΩ

But 50A through 50mΩ is 125W.
P = I2R = 502*0.05 = 50*50*0.05 = 2500*0.05 = 125W

Or if that's not easy to understand.

Calculate the volt drop:
V = IR = 50*0.05 = 2.5V
Calculate the power:
P = VI = 2.5*50 = 125W
 

Offline Labrat101Topic starter

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Re: DIY Resistance wire
« Reply #7 on: January 14, 2022, 03:22:13 pm »
Does it copper plate easily? If so, perhaps that'll make soldering easier.

50A through 50mΩ is 125W. How did you stop it vaporizing?
I don't think it can be copper plated .. I wound it round 2.5 mm copper wire and bent the end over and crimped it with a crimper .
 Not sure how you got to this .
  50A through 50mΩ is 125W.  :-//  No.  ( its OK a Common mistake that a lot of people fall for)
 Its the voltage drop across the shunt which is 75mv per Amp   . 75mv * 50A = 3.75 W
You seem to be confusing the numbers.

If it's 75mV per amp, then it has a resistance of 75mΩ, not 50mΩ
R = V/I = 1/0.075 = 0.075Ω = 75mΩ

If it has a voltage drop of 0.75mV, at 50A, then the resistance is 0.75/50 = 0.015Ω = 15mΩ

But 50A through 50mΩ is 125W.
P = I2R = 502*0.05 = 50*50*0.05 = 2500*0.05 = 125W

Or if that's not easy to understand.

Calculate the volt drop:
V = IR = 50*0.05 = 2.5V
Calculate the power:
P = VI = 2.5*50 = 125W
Yes sorry it was a typo ..
I am using a 0.05  \$\Omega\$
But they  barely get warm and 125watt is hot to touch  .
 The mosfets are rated @ 520 w each and there are 2 in parallel  They are cooled on a large Copper heat sink . dual fan in & out
 They pump out a lot of heat
the shunts are only going about 15 to 20 degrees above ambient . no forced cooling .



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Offline Benta

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Re: DIY Resistance wire
« Reply #8 on: January 14, 2022, 08:09:08 pm »
AFAIK, 0.05 ohm is the same as 50 milliohms.
I also get 125 W (P = I2R)

I don't understand your specifications/calculations here.
Perhaps this would more be something for allaboutelectronics or electronics-tutorials. Those sites don't really fact check.

 
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Offline RoGeorge

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Re: DIY Resistance wire
« Reply #9 on: January 14, 2022, 08:22:23 pm »
He, he, nice idea!   :-+

If it doesn't solder well, try to solder under a drop of oil.  Oil will keep away the Oxygen so it won't oxidize the soldering zone.  Either motor oil or sunflower cooking oil could work, the idea is to keep the melted solder under oil while soldering.

This works to solder on Aluminum, so I suspect it might help soldering on this kitchen steel sponge, too.

Offline SilverSolder

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Re: DIY Resistance wire
« Reply #10 on: January 14, 2022, 08:34:42 pm »

You need a different flux for soldering stainless steel,  then it works just fine!

Great idea...
 

Offline Labrat101Topic starter

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Re: DIY Resistance wire
« Reply #11 on: January 14, 2022, 09:33:19 pm »
AFAIK, 0.05 ohm is the same as 50 milliohms.
I also get 125 W (P = I2R)

I don't understand your specifications/calculations here.
Perhaps this would more be something for allaboutelectronics or electronics-tutorials. Those sites don't really fact check.
Your maths are correct . The unit i'm working on is a multi stage I forgot about the power
sharing over 8 stages . Each shunt is only handling 1/8th of the total loading .
I just had the one section under test . sorry for the confusion my bad .
« Last Edit: January 14, 2022, 09:35:36 pm by Labrat101 »
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Offline Labrat101Topic starter

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Re: DIY Resistance wire
« Reply #12 on: January 14, 2022, 09:47:52 pm »
He, he, nice idea!   :-+

If it doesn't solder well, try to solder under a drop of oil.  Oil will keep away the Oxygen so it won't oxidize the soldering zone.  Either motor oil or sunflower cooking oil could work, the idea is to keep the melted solder under oil while soldering.

This works to solder on Aluminum, so I suspect it might help soldering on this kitchen steel sponge, too.
Cooking oil has a flash point about 280 -320 C . solder is melting around 330c depending on what
type . Plus it will Blue the Tip .  I will save the oil for cooking Eggs etc .
I did not solder it I used wedge lock push the wire into a thin copper tube with a brass wedge when
pulled it locks and then solder to the copper .
 or crimping it also works fine .
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Offline RoGeorge

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Re: DIY Resistance wire
« Reply #13 on: January 14, 2022, 11:39:55 pm »
He, he, nice idea!   :-+

If it doesn't solder well, try to solder under a drop of oil.  Oil will keep away the Oxygen so it won't oxidize the soldering zone.  Either motor oil or sunflower cooking oil could work, the idea is to keep the melted solder under oil while soldering.

This works to solder on Aluminum, so I suspect it might help soldering on this kitchen steel sponge, too.
Cooking oil has a flash point about 280 -320 C . solder is melting around 330c depending on what
type . Plus it will Blue the Tip .  I will save the oil for cooking Eggs etc .
I did not solder it I used wedge lock push the wire into a thin copper tube with a brass wedge when
pulled it locks and then solder to the copper .
 or crimping it also works fine .


So you think I was pulling your leg?  No.

I've soldered on Aluminium under a blob of oil.  Works just fine, something like this (not my video):


I was using sunflower oil, pour a little more oil than in that video, and I was using a soldering gun, where the tip is just a piece of solid copper wire that has to be replaced very often anyway, because soldering alloy slowly disolves the copper.  My soldering gun looks like this one (note how the tip is just a piece of solid copper wire):


Also, Sn/Pb 60/40 melts at about 180-190 Celsius, not at 330.  Your assumptions were incorrect.  When in doubt, it is better to ask "how's so" than to wrongly assume.   :-//
« Last Edit: January 14, 2022, 11:41:50 pm by RoGeorge »
 
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Offline Refrigerator

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Re: DIY Resistance wire
« Reply #14 on: January 15, 2022, 12:10:41 am »
I used a galvanized steel wire for a shunt once.
Steel is not great but that shunt was not going to get hot and was also easy to solder because of the zinc plating.
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Offline Refrigerator

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Re: DIY Resistance wire
« Reply #15 on: January 15, 2022, 12:17:20 am »
Does it copper plate easily? If so, perhaps that'll make soldering easier.

50A through 50mΩ is 125W. How did you stop it vaporizing?
When etching boards in copper chloride i noticed that if i dipped my stainless steel tweezers in the etchant they would self-plate with copper.
The copper layer was very well stuck and pretty durable, enough to solder on to.
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An expert of making MOSFETs explode.
 
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Offline coppercone2

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Re: DIY Resistance wire
« Reply #16 on: January 15, 2022, 05:17:08 pm »
Wow that oil trick is interesting.

I would imagine a very fine stainless brush could make it easier to solder to also, like 0000 stainless wool.

But also keep in mind getting copper foil that is the thickness of aluminum foil is not too expensive.

I try to stay away from aluminum.

Did you try a side by side comparison with oil and flux? I wonder if oil can be better then flux in this case. I also want to say some deep fryer oil I think has small amounts of citric acid in it and stuff, that might make it work even better.

vinegarette soldering? try some dressing lol, maybe the oils from herbs help too... (seriously). I love the copper chloride plating idea too..
« Last Edit: January 15, 2022, 05:21:50 pm by coppercone2 »
 

Offline RoGeorge

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Re: DIY Resistance wire
« Reply #17 on: January 15, 2022, 06:22:06 pm »
I've first read long time ago about soldering under oil on weird materials that otherwise doesn't solder, then seen the video with oil and Aluminium, and tried for myself out of curiosity.  It worked just fine, even with sunflower cooking oil.

Since then I've used the "solder under oil trick in order to avoid creating a layer of un-solderable oxide layer" trick, and it worked.  I've never tried to flood the soldering area with flux instead of oil.  All I can tell so far is:  trying to solder on Al without flooding the area with oil won't really work.

Later edit:
------------
If you try the oil trick with a soldering iron (not a soldering gun with expendable solid copper tips), and you cherish the life of your soldering tip, you better cover it in some Al foil before, so the oil doesn't actually touch the soldering tip of a classical soldering iron.

If you let the oil to directly touch a soldering tip that is not sacrificial, then be ready to lose that soldering tip, because most probably the oil will damage your tip, just like Labrat101 predicted.  I've touched oil with a normal soldering tip of a soldering iron (not soldering gun), and had a ver hard time cleaning the oil out of the soldering tip.  So don't do that.  Use a sacrificial tip instead, or wrap the soldering tip in kitchen Al foil wrap.
« Last Edit: January 15, 2022, 06:41:14 pm by RoGeorge »
 
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Offline Labrat101Topic starter

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Re: DIY Resistance wire
« Reply #18 on: January 15, 2022, 06:49:51 pm »
Wow that oil trick is interesting.

Did you try a side by side comparison with oil and flux? I wonder if oil can be better then flux in this case. I also want to say some deep fryer oil I think has small amounts of citric acid in it and stuff, that might make it work even better.

vinegarette soldering? try some dressing lol, maybe the oils from herbs help too... (seriously). I love the copper chloride plating idea too..
I did try that oil trick just out of curiosity .
I did several tests . sunflower oil, vaseline , Amtech flux the fake stuff , Organic paste Mil Grade, & machine oil ,
 Also tried 40/60 , 63/37   
 Sunflower oil . I was not impressed it works  , 40/60    Has low smoke point  starts smoking @ 314c  @ 360c need to open windows  >:(
 Vaseline  worked well first attempt  with 40/60  ok   63/37 better  low temp 340c 
Amtech flux the fake stuff  .. Horrible failed
Organic paste Mil Grade  .... Failed
 machine oil , failed smelly & smokey .
The sunflower oil is a tip killer .
Vaseline was about the best and did not stink .

The oxide from the foil made cleaning the soldering iron tip hard . 

 This not something I will do again .
EDIT
ALSo  vegetable oils contain acids  and aluminium foil is rolled and anodized* so there can be fumes that are not Human friendly .
*Anodized as not normal anodizing its surface is treated for food quality
« Last Edit: January 15, 2022, 07:09:27 pm by Labrat101 »
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Offline coppercone2

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Re: DIY Resistance wire
« Reply #19 on: January 16, 2022, 01:02:21 am »
hmm thats interesting that it outperformed the flux. That is a neat trick.
 

Offline Labrat101Topic starter

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Re: DIY Resistance wire
« Reply #20 on: January 16, 2022, 06:30:18 am »
My tests were not done under any sort of quality control.  Just try an go . So other people will get different results.  Ie  solder quality 
Iron Temps.  My iron is within +_ 3c . For copper .
Aluminum has different heat transfer rates .
..
In the past I have welded Aluminum with a flame and baking powder mix into a paste.
Works for thick Aluminum sheet.
& Aluminum welding rod . The correct flux is better.
..
Have fun 🧯❗☢

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