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Author Topic: Hot Coil Electromagnet  (Read 80210 times)
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I'm not sure what ION is using, but you should be able to see the spikes with a small coil, tucked between the turns of the nichrome coil, and with a larger pickoof coil placed at one end of the nichrome coil, all without amplification.  But you might have to have some amplification to see anything depending on how strong the signal is.     Do they even make small pickof coils, the size of a hall IC chip?   
   
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I will reiterate for the sake of those that may have missed earlier posts, but best to go back to page one for full details:

You don't need to put the pickup in between the turns. Most of the scope shots I posted had the mag probe at a right angle to the end of the coil or parallel to the end of the coil, and up to 1.5 inches away.

It greatly diminishes as you approach the center of the coil.

This also showed up readily with an old long relay coil with a soft iron slug through the center as a pickup device.

I also placed the heater into a large 6" hoop with about 50 turns of fine wire, with no magnetic core the pulse is easily visible.

I'm sure the Magnetek probe I am using is just a small slug of iron or ferrite with maybe 1000 turns of fine wire and perhaps a loading resistor. It is weakly attracted to a magnet. The probe shows orientation arrows along it's length. It reads 1.52k ohms.

Once the coil heats up the pulse disappears. It may be difficult to see it again until it is back down in temperature.

I get the pulse up until the point where the coil glows orange then it fades into the noise as the buzzing stops.

FYI the pulse reads about 350mV with this probe about a half inch from the end of the heater coil. This is equivalent to around 3.5 Gauss (with this probe, 100mV / Gauss), not very much. e.g. A large, linear wall wart produces about the same level at that distance.

Peterae said:

Quote
EDIT just an after thought, do you see the effect with the heater orientation to earth changed

How about a low volts relay coil with the core taken out, although this will only sit near the heater coil. not in between turns?

Orientation to earth does not matter.

The relay coil will work with or without core.

You seem to be getting plenty of low level noise from you hall sensor, but it looks random, nothing like the spikes I'm seeing. Strange.

We need to calibrate our probes before we can make meaningful measurements. Can you bring the hall effect sensors near a known low level magnetic field to get a rough idea if your pickup is linear and good at low levels?
« Last Edit: 2012-08-15, 02:47:38 by ION »


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Ion,

Peter needs to use a pickup coil like you, not a hall sensor.    A pickup coil responds to the RATE of CHANGE of the magnetic field, and the more rapid, the larger the signal induced.    On the other hand, the hall effect sensor just resonds to the MAGNITUDE of the magnetic field.   These spikes that you are observing are due to small magnetic changes that occur below the resolution of his sensor, or in the noise, so he won't be able to observe them properly.    Assuming he had a stronger signal, the hall effect would show a step response in the magnitude of the field, so where that step occurs, that's where a pickup coil would show the voltage spike.   One waveform is basicaly the derivative of the other, that's the difference.


Question:   have you tried a low current setting,  so that the nichrome coil produces those spikes all the time (maintain the temperature below the Curie temp)?   If the spikes are still present with such a low current level, than that's great.

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EM:

Yes I have the effect at lower current levels as I stated before, in the 2 to 3 amps range.

Also I doubt it would be very efficient as a means to perturb into resonance the secondary of a "Tesla coil" as the effect is weak compared to the expenditure of energy.

My main interest in this is to determine if the unique alloy produces an avalanche effect of domain flipping, and how can we determine an alloy to optimize the effect. Pure iron wire has no such effect. Maybe it has too much remanence due to it's purity and cannot change magnetization that quickly.

If Floyd Sweet was real and his VTA did indeed perform macroscopic domain flipping with a small excitation signal and only after conditioning the material, we may have an area ripe for more research. Just guessing.

 


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Re 32 SWG 1 meter length wire test.

Heater element is 19 Ohms and weakly attracted to a magnet.
Using the wire calculator you linked earlier it calculates using my wire diameter that a ft of Nichrome C is  5.800562 Ohm/Ft i measure 5.79119 Ohm/Ft it's the closest mach on that calculator.

I have switched to a relay coil now, with an iron core i am using my other bench scope which goes down to 5mV/Div

It looks like it is trying to show me a pulse as i have a little wiggle, also the waves are not in phase?

Shall i try another pickup coil without iron core or try thicker heater wire.

EDIT

I managed to get the relay coil closer and better aligned, the little pulses do not change from cold to hot.
[youtube]http://www.youtube.com/watch?v=-ZGnXkeTGHw&feature=youtu.be[/youtube]
« Last Edit: 2012-08-15, 09:13:54 by Peterae »
   
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...
My main interest in this is to determine if the unique alloy produces an avalanche effect of domain flipping,
...

I have an annoying problem. Even if there is an "avalanche effect of domain flipping", how could it be viewed by the probe? The alloy doesn't constitute the core of a coil, it is the wire itself, and so, it can be influenced only weakly by its own magnetic field which is not along the wire but in circles around the center of the conductor, inside and outside.
In my heater, the wire doesn't constitute a coil. It has the shape of a 50 branches star, each branch being formed by the wire going to and from the tip, in parallel. So the magnetic field should have a very low level inside the wire. Therefore I wonder how it can flip the domains. But if the domain flipping is the real explanation (and now we have only this one), considering the weak coupling of the magnetic field to the magnetic matter, considerable optimization of the process could be done.


   
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I have an annoying problem. Even if there is an "avalanche effect of domain flipping", how could it be viewed by the probe?
Quote
The alloy doesn't constitute the core of a coil,
it is the wire itself, and so, it can be influenced only weakly by its own magnetic field which is not along the wire but in circles around the center of the conductor, inside and outside.
In my heater, the wire doesn't constitute a coil. It has the shape of a 50 branches star, each branch being formed by the wire going to and from the tip, in parallel. So the magnetic field should have a very low level inside the wire. Therefore I wonder how it can flip the domains. But if the domain flipping is the real explanation (and now we have only this one), considering the weak coupling of the magnetic field to the magnetic matter, considerable optimization of the process could be done.

We can form the wire types into a toroidal  core or open  "I" section core, and wind over it with copper wire.

In the case of the toroidal core we can wind the wire on a small spool like a tape wound core. Then through the center of the spool with our copper wire. This may be a more meaningful way to test the materials magnetic properties.

For the open I section, we could cut the wire into 2-3 inch lengths and pack them into a small cardboard tube, then over wind the tube with copper.

Peterae: It is puzzling to me that you are not seeing the spikes I am seeing. Maybe thicker wire will help.

The relay coil should work with or without the core. It will be more sensitive with a core, but the magnetic core will add it's own signature though small.

I apologize if you feel you are going down a rabbit hole with this.


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I have tested power wirewound resistances like this one:


I have near two tens of them with different values. They don't work. I only observe almost flat steps each side of the zero crossing. No pulse.
According to http://www.resistorguide.com/wirewound-resistor/, the wire is NiCr. My resistances date the 70's, maybe not the same metal as today resistances. The wire is not attracted by neodymium magnets.

It is really important to clarify which alloy allows the effect. This surely explains the not conclusive result from Peterae, as well as the negative result with my toaster but positive with my heater.

   

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I am happy to keep trying different things and wire if need be  O0

certainly must be the alloy i think, i will run tests on the other sizes from this supplier first and then i am still waiting for some from a different supplier, we were working on the basis the correct alloy was Nickle 60% Chrome 40% with 20-25 Iron

I am just going back to the beginning of the thread to find out if ION has successfully wound one from new wire that works or wether it is a ready made heater only so far that works.

Maybe the wire needs to age and have a good coat of oxides.

EDIT you know when you compare ex's picture of the waveform and the one in my last video i can see little wisps above the pk of the waveform just like ex but smaller, yet mine do not go when hot but infact match his picture when his coil is hot, so maybe my coil heats too fast and they go before i get a chance to see them, if this is the case i need thicker wire and more mass to slow the heating process, i dont want to turn down the supply because my coil is only just picking anything up.
   
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Peterae:

Quick recap:

I tested 3 infra red heaters from different manufacturers, they all had the effect.
 All were an unidentified alloy loosely coiled in a quartz tube. All elements were mildly magnetic.

I wound a coil with 80% Nickel 20% Chromium and there was no effect.

Same with pure iron...no effect
Same with 45% Nickel 55% Copper...no effect

ex:

There is a special alloy of Nichrome used for resistance wire where the tempco is important, but I believe there is no iron content in it.  Manganin and Constantan are two that I know of. There are many names in the trade for slightly different alloys, but Nichrome heater wire has a large tempco by comparison to resistor wire where temperature stability is important.


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Here's 24 SWG much thicker

I've got to say this wire is quiet malleable, it winds quiet nicely on a pencil much much softer than spring steel for instance, i still get no sound when current flows, the pick up coil is picking up much better so the current is a lot larger and as it's thicker it takes longer to glow but still no sign yet, scope is now 20mV/Div as opposed to 5mV/Div in the previous video.

[youtube]http://www.youtube.com/watch?v=3YaICUEH2YU&feature=youtu.be[/youtube]

EDIT
I Just tried the thickest wire i have at 20SWG no sign of spike when cold, eventually popped my primary fuse 800mA to protect my 750mA variac, no point in me trying this gauge any longer just in case my variac pops.
« Last Edit: 2012-08-15, 19:15:40 by Peterae »
   

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I have found out, most of the heaters using the cheapest 60% Ni, 16% Cr, and the rest of Fe heating wire. I'm trying to get from this.

Nickel ferromagnetic at room temperatures, become non magnetic  at 355 celsius

Chromium antiferromagnetic, become paramegnetic at 34,85 celsius

Iron ferromagnetic, become paramagnetic at 770 celsius

Nice mixture of metals. I think as it has something to do with the temperature, would be good to know at which temperature the wire reach, when the pulses disappear.


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ION,

can you try to capture one of the voltage spikes at the zero crossing,  with the scope timebase set to the ns scale.   I'm thinking that these large voltage spikes are actually many many Barkhausen noise spikes that occur all about the same time, and at the time base setting you're looking at they all show up as one large spike.       

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Peterae:
Can you give the ebay ad links where you bought the wire? Something strange going on, I'd like to see if they may have made a a substitution.

EM:

Will do as time permits.


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I contacted the people i bought the wire from to ask for a data sheet, see attached.
I think i can say i can rule this alloy out.

So we have
Nominal Composition
Nickel 60%
Chromium 15%
Manganese 1.5%
Silicon 1.5%
Iron Balance 22%
Aluminium --

   

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This is a quote from ION
Quote
The heater stuff has a very noticeable (not weak) attraction to a magnet, It must be the 24% iron type.

Ha ha
My wire has a very weak attraction(well i tested the thin stuff, must try the thicker)  to a magnet  O0 now that is weird considering it has 22%

OK just checked wiretron.com

Nichrome C does indeed have a faint attraction to a magnet so it looks to me that your wire is not Nichrome C or Nichrome A as this has no magnetic attraction.

We need a resistance per foot reading on your wire and diameter measurement, this should identify it.  O0

As it will be coiled we could estimate the wire length by measuring the circumference of each turn to get wire length per turn and then measure the total resistance and how many turns it has.

   
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Removing the heater from the frame I obtained the following:

Dia of wire: 0.052"

Dia of wind: 0.339"

Turns per inch: 19

Overall length of all winding minus terminations: 20.15"

Length of wire: 33.98 ft. (calculated)

Measured resistance: 9.1 ohms.

This is a bit higher than 8.48 ohms for type C or 8.16 ohms for type A.

Visual inspection shows there has been some oxidation raising the resistance so it is impossible to tell the alloy.

Testing with the quartz sheet off shows a reasonably strong magnetic attraction.


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That's great news ION thanks for doing these tests, i just tested my thick wire with a neo magnet and i can hardly detect an attraction, very weak.

So either this wire is not C but i did check the resistance and it's pretty dam close, and the wiretron site also says type C is very weak magnetic attraction, i think this is all saying your wire is definitely not type C

and because the resistance is slightly lower than it should be i think there's only one on wiretrons site that fits and that is
Alloy 875
22.5% chromium
5.5% Alu
0.5% silicon
0.1% Carbon
71.4% Iron

The only fly in the ointment is i bet there's load's more alloys made by other companies as well  :'(

Quote
Alloy 875
Also called Kanthal A1, Kanthal, Alloy 875, Resistohm 145, Aluchrom 0, Alchrome 875, MWS-875, Stablohm 875

Here's some resistance data on major alloys
http://www.mwswire.com/resist3.htm

So using this wire data you have approx wire gauge 16 and you have about 0.2679 ohms/foot

looking at the data the nearest i can see is MWS-675

then looking up the properties MWS-675 only has slight magnetic attraction so it's not this one either.

that then leads us to MWS-800 or MWS-875
and checking the properties of these MWS-800 has no attraction and MWS-875 has a strong attraction

going down the resistance value order the next one we hit with strong magnetic attraction we get Alloy 42 , but the resistance of this is nearly 45% less than our measured value.

Conclusion it has to be Alloy 875  O0

Alloy 875 is cheap to make
http://tankii.en.alibaba.com/product/343122400-209485507/Alloy_875_Resistance_Wire.html

Quote
Detailed Product Description

Alloy 875, Also called Kanthal A1, Kanthal, Alloy 875, Resistohm 145, Aluchrom 0, Alchrome 875, MWS-875, Stablohm 875

High-temperature Heating Alloy TK1

 

TK1 large-sized cold-drawn wire products can be used for high-temperature resistance furnace. Practice has proved that: the product process is stable, integrated performance is good. Has good high temperature oxidation resistance and longer service life; excellent winding properties at room temperature processing, ease of processing molding; little rebound resilience and so on. Processing performance is better than 0Cr27Al7Mo2, high temperature performance is better than 0Cr21Al6Nb; operating temperature can reach 1400 °C. It performs better than Kanthal A-1 in some places.

 

Main specifications and uses:

Conventional Product specifications: 0.5 ~ 10 mm

 

Uses: mainly used in powder metallurgy furnace, diffusion furnace, radiant tube heater and all kinds of high-temperature furnace heating body.

 

MAIN CHEMICAL ELEMENTS AND PROPERTIES

Properties \ Grade
   

TK1

Cr
   

Al
   

Re
   

Fe

25.0
   

6.0
   

Suitable
   

Balance

Max Continuous Service Temperature(ºC)
   

Diameter 1.0-3.0
   

Diameter>3.0,

1225-1350°C
   

1400°C

Resisivity 20ºC (Ωmm2/m)
   

1.45

Density(g/cm3)
   

7.1

Approximate Melting Point( ºC)
   

1500

Elongation (%)
   

16-33

Repeatedly Bend Frequency(F/R) 20°C
   

7-12

Continuous Service Time
   

>60/1350

Micrographic Structure
   

Ferrite
« Last Edit: 2012-08-16, 22:22:37 by Peterae »
   
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You are right Peter, the stronger attraction to a magnet puts it out of either A or C category. I had not considered Kanthal or Alloy 875, but it makes perfect sense since it is a cheap alloy. Also the large amount of oxidation can now be explained. Sorry if I led you down the wrong path

Once again, the question that must be asked is why does pure iron not produce the effect while 74% does?

I will again run  the pure iron test at the highest current possible.

Testing the heater again removed from the frame at low current, 2-3 amps my waveform looks more like yours. At the highest current 11.5 amps right off the line, the large spikes appear at the zero crossings.

I counted the turns as best I could but it is difficult to see. Could be 19  or 20 turns per inch and this would affect the final resistance. I used 19 for my calculations, but 20 per inch would yield 5% more resistance.

Here are a couple of pictures:


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I make that 18  8)
I added some more to my previous post. O0

It also mentions it's use in radiant heating elements.

off to be now, i will try to locate a UK supplier tomorrow, good work ION  O0

EDIT just seen your quote on high current, i did calculate pk current on my tests and i am pretty sure i was way up near 6 amps or so as well.
   

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Luckily i can buy a complete 1200watt heating element, i could use a crock clip to adjust where i inject power for adjustment and they are cheap  O0
This wire is used in a furnace, What did SM say about furnaces  ;D

http://www.ebay.co.uk/itm/1200W-22-8-220V-Kanthal-A1-Heating-Element-Coil-Heater-Wire-/290755909737?pt=UK_Home_Garden_Washing_Machines_Dryers_Parts_Accessories_ET&hash=item43b2671869

PS i just ordered one, this is Kanthal A1

Here's the composition, the only worrying thing is that it says it's corrosion resistant.
Quote
The material is magnetic up to approximately 600°C (Curie point).

http://www.kanthal.com/products/material-datasheets/strip/kanthal-a-1/
« Last Edit: 2012-08-17, 10:06:10 by Peterae »
   
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I see that there is a big progress in the indentification of the alloy!  O0

On my side I have carried out a new test. I have wound 20 turns of a thin enamelled copper wire around the resistive wire. This is equivallent to have the resistive wire as a coil core. I connected the copper coil to the primary of a transformer to raise the voltage and monitored the signal at the secondary.
I have still the pulses.
Then I decided to check if the permeability of the resistive wire was changing with the pulses. I "magnetically polarized" the resistive wire with a near permanent magnet. Therefore if the permeability was modulated, the magnetic flux from the magnet also, and this should reinforced the pulses picked up by the copper coil.
Here is what I observed: the pulses disappear with the field from the magnet. Even a weak field has a strong effect. If the magnetic axis of the field is colinear with the resistive wire, the effect is the strongest, the pulses disappear completely. If the field is transverse, the pulses are only weakened.

I had doubts about the "quality" of the mains here, because the peaks of the sine are a bit flattened. If so, the pulses could result from "the derivative of the angle" when the signal departs from the sine shape. This new experiment discards any possible artefact in the previous measurements and confirms that the effect can only come from the magnetic properties of the resistive wire.

   
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An example of this would be ION able to detect the spike while others struggling. 

He has magic hand?  His mind manifested the effect? Scientific explanation materialized yet?   

Since at the outset we had not positively identified the material in the heater, other researchers may have failed by using the similar test setup with the wrong material under test.

By more careful analysis, Peterae has come a long way in identifying the material as Kanthal A1. This material is not used in all infra red heaters.

I do not have a metallurgy lab and was not able to positively identify the material under test at the outset.

We are getting closer. Kanthal has a very high iron content, more than likely the cause of the spikes due to magnetic saturation.

Progress is being made.

No magic hand or mind effect, just inferior science on my part. mea culpa!


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Inferior science? huh...
You are the one who noticed the effect for the first time.
"In the fields of observation chance favors only the prepared mind."
Louis Pasteur
 ;)

   
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Inferior science? huh...
You are the one who noticed the effect for the first time.
"In the fields of observation chance favors only the prepared mind."
Louis Pasteur
 ;)

Unfortunately I had the preconcieved notion that all infra red heaters were wound with a variation of Nichrome containing small amounts of iron, not enough to account for the "effect".

While I had heard of Kanthal A1, I had no good reason to believe it was being used in infra red heaters.

It was Peterae's discovery of the heater wire with high iron content that now dispels any chance that the effect is something special.

I formally apologize to anyone's time I may have wasted on this investigation.

On the flip side, I have learned a lot about many of the wire alloys and how they react under high currents, so it was not a waste of time for me.

I have also ordered a heater core made of Kanthal A1 to confirm my error.

This exercise also gave me the incentive to go through and inventory some of the many spools of wire I do have on my experimental shelf, Manganin, Karma, Alloy 11, Contantan, Chromel etc. Too bad I had no Kanthal A1 or this would have been put to bed many posts ago.

When I have some time, I would like to investigate some of these in a slightly different way, by winding the wires into a core, and overwinding with a fixed number of copper winds like a toroidal inductor in order to determine magnetic effects of the alloys.

I will continue to investigate the "effect", because like a child, I am in wonderment and who knows what can be learned or discovered.

For me it has been fruitful and educational.
« Last Edit: 2012-08-20, 17:17:36 by ION »


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