Resistors  with steel ? leads . - Page 1
Forum section: electronics / general

author: Kevin.D
author_rank: Frequent Contributor
timestamp: April 16, 2013, 09:09:57 am
content: So I Was getting low on those inbetween values for breadboarding so ordereda cheap E24 series resistor pack from honk kong :-http://www.ebay.com/itm/E24-Metal-Film-Resistor-1-4W-1-170-values-assortment-kit-1700-pcs-/121067604797 .they supposed to be 1% so i just tested a few and found them all in spec except for the low decade which was out dpending on how I measured them.It turns out after measuring the leads they are made of a metal or something that is magnetic with a high resistance of 9mOhms/per cm .All my own resistors I checked for comparison are copper and have ~ 1 mohm/cm lead resistance .OK so this might be acceptable ? on high decade values where that is a small portion of the total resistance but on the low decade where 40mOhms is like 4% of a 1 Ohm resister how can they sell them as a 1% resistor ?.It turns out all the other components (diodes,capacitors) I ordered from them also have leads made of this high resistance metal. (After checking I found some a few other cheap components I bought from other places also had these leads).Sorry my calculation of current was wrong when I was measuring the resistance of the leads ,it should have been ~ 2.5 mOhm/cm for these ,and the copper ones I had where about ~ .25 mOhms /cm.

author: David_AVD
author_rank: Super Contributor
timestamp: April 16, 2013, 09:51:46 am
content: Buying components via eBay can be very hit and miss. I generally don't trust many of the sellers to offer acceptable quality components.

author: nctnico
author_rank: Super Contributor
timestamp: April 16, 2013, 10:51:43 am
content: Lots of components have 'steel' leeds. It has been like that for at least 20 years.

author: Psi
author_rank: Super Contributor
timestamp: April 16, 2013, 11:03:13 am
content: I got some cheap CAT5 once that was actually copper plated steel.Soldering to it was quite tricky as the copper plating was very thin.You only really got one shot to solder it to something before it gave problems. (Solder stopped sticking after a few seconds of heat)(Not that you normally solder CAT5, i was just using it for other things)

author: Kevin.D
author_rank: Frequent Contributor
timestamp: April 16, 2013, 11:47:20 am
content: Quote from: nctnico on April 16, 2013, 10:51:43 amReally I didn't know that then,. Yes I have had some components with non copper leads before like a few diodes etc (but even those only have a small difference between them and copper leads ,like 2x higher) but 90% of my stuff has copper leads , but this is the first batch of resisitors I personally have ever had with non copper leads .I mean these are very ferromagnetic ,so how does this effect things like self inductance etc. ? And also like I say for tolerance when using low value resistors <10 ohm you better make sure you dont have to much lead on them when in the breadboard .

author: ddavidebor
author_rank: Super Contributor
timestamp: April 16, 2013, 04:07:51 pm
content: Yeah more than a lot, pretty all resistors has steel pin.Precision <10ohm resistor are expensive and boring, you need to considerate pin resistivity, soldering, and also traces resistivity

author: G7PSK
author_rank: Super Contributor
timestamp: April 16, 2013, 06:17:39 pm
content: Lots of things you think are copper these days are copper plated or even just copper wash, most copper coins are just that here in the uk copper washed iron or steel you pick them up with a magnet, copper plated steel has been used by the telephone industry for many years so it is quite likely that cat 5 cable comes from the same factories, I have some 1950's 60's transistors that have iron leads, I did wonder if they were made that way in order to help prevent heat conduction to the germanium inside, I well remember the warnings about using heat sinks when soldering, I still have one, a sort of aluminium tweezers.

author: metalphreak
author_rank: Frequent Contributor
timestamp: April 17, 2013, 03:42:04 am
content: Cheaper coaxial cable is sometimes used in situations where it's all high frequency signals. They use copper clad steel cores instead of full copper as all of the conductor current flows through the outer edge due to the skin effect.For cheap resistors, using high conductivity leads is... silly. It's a resistor - the whole point is to impede conductivity. Also, where are you measuring from? This will affect your results too. Typically you stick that resistor into a board and then cut off 90% of the lead anyway. If there is 10mOhm of resistance in that short bit of lead that is typically used, then you can make the actual resistive element 990mOhms. It has no real bearing on the ability to make a precision resistor with those lead wires.How accurate is your multimeter? Good contact between the probes and the leads? Did you zero out the probe resistance? When you get down to such low values, the precision of measurement in terms of calculating a % becomes so much more critical. You really need to be doing 4 terminal measurements for accuracy.

author: peter.mitchell
author_rank: Super Contributor
timestamp: April 17, 2013, 03:04:11 pm
content: Quote from: Psi on April 16, 2013, 11:03:13 amUghk soldering cat5....Because of the availability of CAT5 (and 6 now) I have done some nasty things with it, not limited to but including, inductors, rope, current shunts/precision resistors, heating elements, did i mention rope?, mod wires (for power devices), breadboarding and prototyping, baluns on the end and used it for long distance video, rope, long distance power (3 phase, 60v, no zero crossing in the output)

author: ftransform
author_rank: Frequent Contributor
timestamp: April 18, 2013, 02:38:03 am
content: Quote from: peter.mitchell on April 17, 2013, 03:04:11 pmDid you ever escape from a burning building with it? Might be good to keep a 1000' roll around.

author: peter.mitchell
author_rank: Super Contributor
timestamp: April 18, 2013, 07:51:13 am
content: Nope, not quite, however, I did make a hammock out of it though.

author: kfitch42
author_rank: Frequent Contributor
timestamp: April 19, 2013, 06:52:55 pm
content: Quote from: ftransform on April 18, 2013, 02:38:03 amI always thought it was funny when the 1000 foot box is labelled in Spanish... those must be some tiny pies to fit 1000 of them in a box