DIY Resistance wire - Page 1
Forum section: electronics / general

author: Labrat101
author_rank: Unknown
timestamp: January 14, 2022, 09:20:06 am
content: 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@ 50 amp .So not finding anything that was suitable . I went into.. How hard can it be to make itCopper wire ... NoSteel 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 chromeYes . looking Good . measured it 18mm is showing 1.1030.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 0.05for testing an quick repair of myelectronic load .These wire cleaning pads have a melting point of about 1500 C Resistance aprox 0.5per cmI 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 stuffHave Fun and don't burn your fingers .More Ideas welcome

author: jonpaul
author_rank: Super Contributor
timestamp: January 14, 2022, 11:58:10 am
content: 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

author: Kleinstein
author_rank: Super Contributor
timestamp: January 14, 2022, 12:22:42 pm
content: 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.

author: Zero999
author_rank: Super Contributor
timestamp: January 14, 2022, 01:12:00 pm
content: Does it copper plate easily? If so, perhaps that'll make soldering easier.50A through 50mΩ is 125W. How did you stop it vaporizing?

author: Labrat101
author_rank: Unknown
timestamp: January 14, 2022, 01:41:31 pm
content: Quote from: jonpaul on January 14, 2022, 11:58:10 amI 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 .

author: Labrat101
author_rank: Unknown
timestamp: January 14, 2022, 01:56:02 pm
content: Quote from: Zero999 on January 14, 2022, 01:12:00 pmI 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

author: Zero999
author_rank: Super Contributor
timestamp: January 14, 2022, 02:38:23 pm
content: Quote from: Labrat101 on January 14, 2022, 01:56:02 pmYou seem to be confusing the numbers.If it's 75mV per amp, then it has a resistance of 75mΩ, not 50mΩR = V/I = 1/0.075 = 0.075Ω = 75mΩIf it has a voltage drop of 0.75mV, at 50A, then the resistance is 0.75/50 = 0.015Ω = 15mΩBut 50A through 50mΩ is 125W.P = I2R = 502*0.05 = 50*50*0.05 = 2500*0.05 = 125WOr if that's not easy to understand.Calculate the volt drop:V = IR = 50*0.05 = 2.5VCalculate the power:P = VI = 2.5*50 = 125W

author: Labrat101
author_rank: Unknown
timestamp: January 14, 2022, 03:22:13 pm
content: Quote from: Zero999 on January 14, 2022, 02:38:23 pmYes sorry it was a typo ..I am using a 0.05But 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 & outThey pump out a lot of heatthe shunts are only going about 15 to 20 degrees above ambient . no forced cooling .

author: Benta
author_rank: Super Contributor
timestamp: January 14, 2022, 08:09:08 pm
content: 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.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 14, 2022, 08:22:23 pm
content: 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.

author: SilverSolder
author_rank: Super Contributor
timestamp: January 14, 2022, 08:34:42 pm
content: You need a different flux for soldering stainless steel, then it works just fine!Great idea...

author: Labrat101
author_rank: Unknown
timestamp: January 14, 2022, 09:33:19 pm
content: Quote from: Benta on January 14, 2022, 08:09:08 pmYour maths are correct . The unit i'm working on is a multi stage I forgot about the powersharing over 8 stages . Each shunt is only handling 1/8thof the total loading .I just had the one section under test . sorry for the confusion my bad .

author: Labrat101
author_rank: Unknown
timestamp: January 14, 2022, 09:47:52 pm
content: Quote from: RoGeorge on January 14, 2022, 08:22:23 pmCooking oil has a flash point about 280 -320 C . solder is melting around 330c depending on whattype . 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 whenpulled it locks and then solder to the copper .or crimping it also works fine .

author: RoGeorge
author_rank: Super Contributor
timestamp: January 14, 2022, 11:39:55 pm
content: Quote from: Labrat101 on January 14, 2022, 09:47:52 pmSo 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.

author: Refrigerator
author_rank: Super Contributor
timestamp: January 15, 2022, 12:10:41 am
content: 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.

author: Refrigerator
author_rank: Super Contributor
timestamp: January 15, 2022, 12:17:20 am
content: Quote from: Zero999 on January 14, 2022, 01:12:00 pmWhen 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.

author: coppercone2
author_rank: Super Contributor
timestamp: January 15, 2022, 05:17:08 pm
content: 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..

author: RoGeorge
author_rank: Super Contributor
timestamp: January 15, 2022, 06:22:06 pm
content: 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 likeLabrat101predicted. I've touched oil with a normal soldering tip of a solderingiron(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.

author: Labrat101
author_rank: Unknown
timestamp: January 15, 2022, 06:49:51 pm
content: Quote from: coppercone2 on January 15, 2022, 05:17:08 pmI 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 , 63/37Sunflower oil . I was not impressed it works , 40/60 Has low smoke point starts smoking @ 314c @ 360c need to open windowsVaseline worked well first attempt with 40/60 ok 63/37 better low temp 340cAmtech flux the fake stuff .. Horrible failedOrganic paste Mil Grade .... Failedmachine 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 .EDITALSo 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

author: coppercone2
author_rank: Super Contributor
timestamp: January 16, 2022, 01:02:21 am
content: hmm thats interesting that it outperformed the flux. That is a neat trick.

author: Labrat101
author_rank: Unknown
timestamp: January 16, 2022, 06:30:18 am
content: My tests were not done under any sort of quality control. Just try an go . So other people will get different results. Ie solder qualityIron 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 🧯❗☢