Electrical Demagnetizer

[Bernd]

First a warning.
WARNING: If you do not understand electricity do not attempt this. If you are afraid of being electrocuted you probably will be, DO NOT ATTEMPT THIS THEN Have an electrician wire this for you.

For a while now I’ve wanted to make a demagnetizer. I got tired of picking up one allen wrench and having one or two others attached to it. I saw a thread on HMEM a while back about a demagnetizing tooling. I though why buy one when you can make one out off some parts around the shop. What I’m using is a transformer or I should say part of a transformer out of a micro wave oven. The first picture shows all the parts need for a test set up.

On the bottom left is what a transformer from a micro wave oven looks like when all together. Notice it has two windings on it. The top winding is of lighter gage wire than the bottom. You need to disassemble the transformer and use the smaller gage wiring. Also you will need a bulb wired in series with the winding. This is in case of a short. The bulb will light brightly if there is a short. This is all temporary wiring and is not going to be used in the final version of this tool.


Here’s a drill that somehow has gotten magnetized.


I’ve plugged in the demagnetizer, you can see the faint glow of the spot light. As you get near the magnet you can feel the drill start to vibrate from the 60Hz frequency. Before you get it all the way through the chips have fallen off.


And there you have it. One demagnetized drill.


Now that I know this setup works it will be permanently mounted in a box with complete wiring and power switch plus a circuit breaker or fuse. All self contained.

Remember electricity can harm you. If you are in doubt stay away from it.

Bernd

[websterz]

The day after I drop $40.00 on a demag'er you go and show me how to make one..

[John Stevenson]

I have heard of people taking the rotor out of a single phase AC motor and passing the parts thru the hole in the middle.

John S.

[framey]

cheaper option is to tap it on the side of something else thats how i always do it lol

[Bernd]

The day after I drop $40.00 on a demag'er you go and show me how to make one..

Sorry about that websterz, I could reinburse you the $40. How's a buck a month sound? (hidding under table)

John has also got a good idea, except his would be round.

I've tried banging against something else. All it did was remove the chips. The tool was still magnetized.

Bernd

[andyf]

For small items like Allen keys and drills, I just pass them though the loop of a Weller soldering gun. Get them some distance away before releasing the trigger. Same with screwdrivers, though they have to be dipped in and out because the handle won't go through the loop.

And the loop is hot, of course, so watch your fingers.

Andy

[websterz]

I regularly make small batches (50 or so) parts out of 4140. After hardening and surface grinding them there is always some residual magnetism in them. I bought a 4x6 surface demag'er from Enco planning to spread the parts out on a thin piece of card stock and treating a whole batch at a time. Plus it will be big enough to do drills, hand tools, etc. Just under $40 with free shipping. Cheaper than scrapping my microwave I guess...

[Krown Kustoms]

Nice utilization of scavenged parts.
I love seeing something so simple turned in to a tool.

So......are you using the bulb as a fuse/circuit breaker? I see it as a good indicator of a 'dead' short but are you going to utilize it in the perminant fixture?
A small neon bulb and a fuse would also act as a indicator to tell you if it was on or not.

I am already looking for a small transformer to build this 'need to have' tool.

Thanks for the idea. -B-

[75Plus]

I have an old bulk tape eraser from the 4 and 8 track days that does a good job of erasing the magnetism from tools and small parts. It also doubled as a degausser for the earlier color tv's that did not have automatic degaussing.

Joe

[Weston Bye]

Where I work one of the maintenance technicians came to me with a steel detail that kept picking up magnetism causing the steel parts that it was supposed to guide to stick and not flow smoothly.  I made a quick demagnetizer from an automotive air conditioner clutch coil and a 12 volt, 3 amp transformer.  This was convenient because we make the coils.  The coil is a freestanding bonded coil, no bobbin or other supporting structure.  The nice thing about the coil-transformer arrangement is the low operating voltage.  The coil does get warm, but can be left on indefinitely without damage - after all, it was designed to survive the +140°C environment of the engine compartment.  Also, the coil has a large bore, allowing large or wide parts to be demagnetized.

If one were to be salvaged from an A/C clutch, the steel shell would have to be removed; carefully machined away on the lathe, mill or with a Dremel.

[John Stevenson]

Trying to get simpler, what about using a torroid transformer on it's own ?

John S.

[Bluechip]

J S

Don't think it would work .. all the magnetic flux is in the toroid .. or should be ..

Dave BC

[Bernd]

I regularly make small batches (50 or so) parts out of 4140. After hardening and surface grinding them there is always some residual magnetism in them. I bought a 4x6 surface demag'er from Enco planning to spread the parts out on a thin piece of card stock and treating a whole batch at a time. Plus it will be big enough to do drills, hand tools, etc. Just under $40 with free shipping. Cheaper than scrapping my microwave I guess...

Being close to a transfer station (junk drop off) I've picked up the dead micro-waves. I've got at least a dozen or so transformers.

The reason I started collecting these was/is I found an article on the net about making your own spot welder using two rewound transformers. I've got the article stored some were on my disk drives.

I'm sure you could find them laying out on the curbside on pickup day.

Bernd

[Bernd]

Nice utilization of scavenged parts.
I love seeing something so simple turned in to a tool.

So......are you using the bulb as a fuse/circuit breaker? I see it as a good indicator of a 'dead' short but are you going to utilize it in the perminant fixture?
A small neon bulb and a fuse would also act as a indicator to tell you if it was on or not.

I am already looking for a small transformer to build this 'need to have' tool.

Thanks for the idea. -B-

I learned this trick back in my early days of model railroading. The club I belonged to used an automotive bulb of a certain size in there power to the track. Shorts occured many times through in the wiring because people would throw the wrong swtich. So instead of buring out power supplies the light would light up and show a short indication. This method never let the magic smoke out.

So concider the bulb as a sort of indicator. If the coil develops an internal short the bulb will light up giving an indication of such. A fuse should always be incorporated into a system like this along with a power on indicator light.

Another thing that's useful is the very, and I mean very, strong magnet that is incorporate with the micro wave emitter. About as strong as the magnets in a disk drive. They are useful also. Another little how to I want to post eventually.

Now all I need to do is make it permanent. And of course with my project list being as long as some criminals arrest list..... well you know the rest. 

Bernd

[Darren]

Nice idea Bernd, my only concern is the voltage on the second winding on a microwave transformer. Usually around 11Kv from the ones I've tested.

I don't suppose the voltage of the transformer makes too much difference for de-magnetising so perhaps a 12V one would be safer?

Just a thought ...

JS, Dave is right, you can't get inside the windings on a toroid like you can with an EI transformer coil ...  

[John Stevenson]

OK, it's just that the torroid already has a big hole in the middle so I thought............ and thought...... OK forget it 

John s.

[Bluechip]

Hi Troops

Mine was made from a defunct pistol drill. The armatures usually go Pfttt. leaving the stator OK.

They often have two screws holding 'em together, just cut one out to make the air gap as per attached C-O C.

(Yes, I know it's not very convincing Mr. Stevenson, to professional Electric Motor Consultants, look upon it as a 'Generic Artists Impression' ..   )

Put a bit of U-shaped plastic to make a trough, draw the driver/whatever through a few times.



Used to work, I used it with a Variac, but just stick a 60/100W filament lamp in series with the contraption to limit the current.

Bernd.. good scheme using lamps to limit current, specially made ones were used on the 80-0-80 VDC telegraph signalling supplies, called Baretters.

Darren.. didn't think Microwave Trannies went that high, about 2kV?, unless they wind up off load? No matter, you're dead anyway .. rare or bien cuit, it's curtains.

Dave BC

[John Stevenson]

(Yes, I know it's not very convincing Mr. Stevenson, to professional Electric Motor Consultants, look upon it as a 'Generic Artists Impression' ..   )


Dave BC

I much prefer 'Bodger extraordiniar ' instead of Electric Motor Consultant 

Darren, I thought the microwave idea was to gut the tranny and just use the mains input coil and dump the nasty singed bollocks bits ?

John S.

[Darren]

Dave, you are right ... I missed the point.... decimal that is  

John, I suppose if the laminations are removed then there can be no secondary voltage? So Bernd, sorry, you are prob quite ok with what you have done. If I remember rightly (it's been quite a while since I looked at a micro tranny)  are the two coils are side by side and not one on top of the other as in normal windings. Therefore you could separate the HV coil.

Is that what you did Bernd?

Edit, went back and had another look, yes I can see you have only used the primary coil. 110v or 220V ? Forget what I said earlier about the HV coil. Except that anyone playing around with one of these should realise that before they pull it apart the secondary coil can kill you in an instant if you power it up and get a Zap   

Last time I was playing with these I was powering some old radio valves, now I have a nice 4.3KV transformer with a 3.2Kv tap that weighs 57Kg (decimal correct this time   )

[Bernd]

Nice thought Darren. Will have to run it through my auto-transformer (variable voltage transformer) to see. As long as it's AC voltage.

Added after reading your message: If you take a look at the original picture you'll see that the transformer on the left is what comes out of the micro-wave oven. The top coil is the primary or mains. It has the larger dia. wire. The secondary has the smaller wirer. As you'll notice in the second picture that all I have is the secondary coil. The one with the finer gage wire. I tried the primary/mains with the lamp in series and the bulb lite up brightly and almost no magnetism in the coil.

Yes, you do need to seperate them. The reason I seperated them was I had to prove to a neighbor who does scrapping he can get about 4 pounds of clean copper out of them. You need to grind out the weld that holds them together.

Bernd

[John Stevenson]

Darren,
i was just going on the pic's in the first post.
Example tranny on the left and then the rest of the pics with an open coil, no laminations, that's why i suggested a torroid.

John s.

[Darren]

John,

I still don't think it would work as you cant remove the laminations to get inside the coil. The center hole in a toroid isn't the same thing as far as I know?

[Bluechip]

(Yes, I know it's not very convincing Mr. Stevenson, to professional Electric Motor Consultants, look upon it as a 'Generic Artists Impression' ..   )


Dave BC

I much prefer 'Bodger extraordiniar ' instead of Electric Motor Consultant 

Darren, I thought the microwave idea was to gut the tranny and just use the mains input coil and dump the nasty singed bollocks bits ?

John S.

Surely Master Bodger Extrordinaire ?      M.B.E.  ....

Bend of knee, tug of forelock etc ?

Dave BC

[Darren]

Ah, I seeeeeeee Bernd, yes the secondary coil would have more turns and a higher field.

And a higher resistance for the mains circuit, jolly good thinking Batman 

[Bernd]

This may answer some questions about toroidal transformers - http://en.wikipedia.org/wiki/Transformer

Bernd