Electromagnetic wand help

Hi,

I'm not sure where else to put this thread, as it doesn't REALLY fit into hardware, but it also doesn't fit anywhere else, and it applies most to the computer hardware end for usage.

I'm building an electromagnet "wand" for lack of a better term, something I can degauss hard drives with for easy secure disposal... anyway, I'm wondering if I can get some help. Diagram included at the bottom.

First, how I'm doing it:

I have a solid hardened steel bar that's about 3/4" diameter and pretty long... I'm cutting it to about a foot long or so, wrapping 16 gage stranded speaker wire (U'ed at the top end so I can have both connecting strands at the bottom) around most of it, and wrapping electrical tape along enough of the bottom for a good handle. The copper wire will connect to a cord, which will then connect to a rectifier (which converts AC to DC power, as DC is required for this), which will connect to an extension cord with a standard 110V 2 prong plug at the end, which I can then plug in to power the device.

I have the basics figured out, but have a few questions, namely:

Is there an easy (or easier) way to strip speaker wire? My current plan is to just take a razor blade and cut the insulation on one side, and peel it off. I imagine this is going to be somewhat difficult, as the strands are straight (not twisted much, if at all) in the wire. I've already tried wire strippers, and even if I can get a little bit off with them without breaking strands, once I'm up the wire somewhat, it gets very hard to work the insulation down the wire.

Secondly, can anyone recommend something to case the rectifier in? I'm NOT very experienced with home electrical projects... I know there's cases for pretty much everything, but a pointer with this would definitely help a LOT! The rectifier I'm going to get (unless someone thinks it won't work for this project) is:

http://www.amazon.com/Parts-Express...RDPI/ref=sr_1_1?ie=UTF8&qid=1330812689&sr=8-1

Thirdly, I'm thinking of incorporating a switch (either before, or after, the rectifier, or built in with the rectifier)... anyone have a suggestion for this? A simple toggle switch like the one below would be fine.

http://www.amazon.com/Parts-Express-Standard-Toggle-Switch/dp/B0002KR0S8/ref=pd_bxgy_e_img_b

And last but not least, is there a good way to ensure the copper wire won't move on the bar? I'm planning on wrapping it on itself at the top and bottom, but if there's some way to secure it better, I'd really like to know.

Thanks in advance for any and all suggestions.

Diagram:

 

You would probably be better off with a bulk tape eraser such as this one in the link.

http://www.ebay.com/itm/Radio-Shack...9711163?pt=BI_Blank_Media&hash=item3a71583c3b

Also, you wouldn't want to strip the wires in your diagram. No insulation=short circuit.

You would need to use wire such as this. About 16 gauge ought to do it or smaller gauge.

http://www.bulkwire.com/wire-cable/magnet-wire.html

 

Thanks for the suggestions. I'd prefer to make my own thingy vs. that bulk eraser... that doesn't seem nearly as powerful for one (magnetic tape is FAR easier to magnetically erase than hard drives), and I've always wanted to make my own electromagnet (just couldn't justify a reason for it until now).

I didn't even think about the short circuit part of the equation... not sure how I missed that. I thought the wire had to be in direct contact with the bar, though... hmm. I appreciate the link to the wire... looks to be what I'll be using, then! Too bad I've already separated the two speaker wires from each other (so I obviously can't return it), but it wasn't that costly in the first place.

Also, is 16 gage best, or should I use 18 or 20 gage?

Any tips for my other questions?:-D

 

The "bar" doesn't have to be made out of steel(residual magnetism), and it doesn't have to be a "bar". It could be a U shaped piece of aluminum or a steel(if you prefer) muffler bolt. If you use the muffler bolt then they have nuts on the ends of them to secure the wire.

The unit doesn't have to be a long thing, after all you're working with a 3.5 inch HD at max.

A plastic case about 5in X 5in by 1.5in thick should hold everything. You won't be having this thing operating for a long time period so plastic should be OK. Adjust your case size if you want to include the switch and the rectifier.

Since I'm not versed in electronics all that much I couldn't really tell you what gauge of wire to use. 18 and 20 gauge wire have more resistance than 16 gauge.

 

Well, the bar was free... so I'm using it. How could the bar be aluminum? I thought the bar had to have magnetic possibilities (aluminum doesn't). If that's the case, I can get my hands on aluminum bars as well.

I ended up ordering 20AWG wire from the site you referred me to. I'll have to search out cases now.

I wasn't able to purchase that rectifier due to shipping issues, but I ordered one off of eBay with similar specs (actually higher... 25A 1000V, though it shouldn't matter).

I agree the bar doesn't have to be that long, but my theory is that with a longer bar, the magnetic field will be stronger... I still haven't cut the bar to size, so I'll contemplate that. Anyway, back to the bar, I thought the core of an electromagnet had to be solid, and had to be magnetizable... I suppose I should research this a bit further.

EDIT: Yeah, the core has to be magnetizable... aluminum, etc. won't work.

 

Yes, you're correct about not using an aluminum core. From what I've read, it's best to use soft iron for the core instead of a hardened steel core. Hence the use of a U-shaped muffler bolt.

 

Yeah, I saw that too. I'll see how it goes with this for now... as I can't get any soft iron for free. Heck, even the hangers in our house are the plastic ones heh.

One concern I have... I've read that using higher power (outlet vs. battery) can create quite a lot of heat. So, I hope this thing doesn't get too hot. I definitely want one I can plug in, though... I don't want battery-based.

 

As I stated in my previous post, you will not be using this device for an extended period of time e.g. on for more than 1 minute. So you could use a momentary push button to activate it(only on when you're pushing the button).

I was talking about u-shaped muffler hanger bolt kits that you buy at an auto supply store.

 

This is true. I know what you were talking about as to the muffler mount... I just noticed on a site that it recommended cutting and bundling wire hangers to make a core.

I'll probably revisit this thread once the rectifier and wire get here, and I commence actually building this thing. I think I'll wait to figure out a switch until I get it working the way I'd like it to, as it's pretty easy to simply unplug it at this point. I AM curious what kind of heat it's going to generate.

 

Electronics is one of my major hobbies,I build and wind my own transformers from scratch using of course the USB transformer winding machine I've made:-D

1. Insulation of the wires which puppy wonder has already mentioned
2. The bar,it really needs to be an iron bar not steel or aluminium,iron or ferrite alloys have the best magnetic permeability "easily magnetised" and highest saturation "hold alot of magnetism" also mentioned
3.The bar must be insulated with paper masking tape 'used for decorating' not insulation tape,large magnets can get hot especially with AC as they act as a current choke which can melt through the insulation tape,i use masking tape in my transformers.
4. The size of the wire you would have use is about 10 times too thick to use with 110V,I wind high voltage secondary's on transformers with 0.12mm and 0.15mm 'enamelled' copper wire AWG 36 and 35 respectively,if you'd have plugged your diagram in it could easily have drawn in excess of 10 amps which would have immediately got hot,melted the tape and set your hand on fire then arced over to the steel bar and -
4.Don't use high voltage AC!This is really dangerous and completely unnecessary,if you had constructed what you have drawn without insulation you would have died if you had plugged it in,you would have been holding a live 110V death stick :-D A rectifier only turns the voltage to DC its doesn't lower the voltage to something you can hold.

Find a 12v power pack/charger for a toy or modem,the output on a decent size one is 1000-3000ma 12v but they can easily go up to 5-6 amps for a few seconds which should be enough to make a half decent magnet,if you can't find a powerful enough one you can use the 12v output from an old pc power supply "yellow and black wires from one of the molex connectors"

With this configuration I'd use the 20awg wire you've ordered which you have to use about 50-150 turns,the more turns the less powerful the magnet will be,the lower the turns the more current it will draw,too few turns and you'll pop your power pack,I'd experiment with a lot and work to less until you find the magnet is powerful enough to wipe hard drives.

I'd also make it small,as big as about half a cigar.

Can you link to the original design please? Is this some kind of industrial hard drive wiper for doing a 1000 hard drives a day or something?

For the switch I'd use a momentary switch also ,any that can hand about 5-10amps.

 

Thank you Rikky for your help. I didn't know how to answer all the questions. Good thing you've done all this before.

 

5 pound mini sledge, .44 auto mag, Glock, take your pick. Any of the three will render that drive useless after you get done.

 

Thanks for the advice!

Alright, so let me get this straight:

110V power = bad idea. They have the power converters that convert from 110V to 12V/5-6A for plugging car charger devices into a household outlet... would that work? Of course, that'd also negate my need for a rectifier... but I'd also have to figure out how many turns so I don't blow the fuse... hmm. Or I suppose, what if I DID use batteries... how long would they last? Say, D cell, 4 wired in parallel (right?).

I'm still going to try it with this steel bar, but I'll look into using an iron bar in the future... but seriously, will it make THAT big of a difference?

There is no original design to link to... haha. Hence, the MS Paint diagram.

 

That would work perfectly batteries wouldn't last very long at all and the magnet won't be very powerful,iron is better because it allows you to control the magnetic field,after you've magnetised steel it stays magnetic even when you turn off the power,Iron will make your magnet maybe twice as powerful but it all depends on the alloy of the steel bar.

To figure out how many turns you have to do some maths,in electronics there's just no way around it but its very easy,my initial estimate on the number of turns is too low also you will need quite a lot to createenough resistance at 12v.

Ohms law

http://www.hamuniverse.com/ohmslaw.html

So to work out how much current your wand will draw you need to divide the voltage by the resistance voltage = 12,to get the resistance put 1000 turns on your steel bar and cut the wire.

On enamelled wire you have to strip the enamel at the end to reveal the copper underneath as the coating won't conduct electricity so strip about an inch by scraping it with a craft knife or sandpaper,measure the resistance by touching each end of the wire with the multimeter probes.

Say you need to keep the current under 6 amps so you don't blow your your car charger

R = V / I (Resistance = Voltage divided by Current)

The voltage is 12V,the current is 6 amps so 12 divided by 6 = 2ohms,so put enough turns on the bar until you measure 6ohms with your multimeter or start taking turns off it,this way is better because you don't have to join more wire on.

You don't have to do it this way but its better to work it out on paper so you don't end up blowing your power pack,you may also want to give the power pack some breathing room so it doesn't blow so calculate your magnet to draw 5 amps if your power pack has a max of 6amps 12 divided by 5 = 2.4ohms.

If you get stuck you can always ask me I enjoy talking about it,I rarely get to talk about this stuff with anyone

 

Sorry this should read...

 

Hi,

Wire resistance is found on a chart in most any electrical Data book. Mine in in a very old ALLIED ELECTRONICS DATA BOOK. It's given as resistance per wire length. Magnetism is reduced by the square of the distance to the object you want to influence so through the case to the platters it will be reduced greatly. The case will also give some shielding. AC does a better job. The magnet is to be moved away from the object before the power is removed from the magnet. I would agree with brownizs and use the sledge hammer.

Good Luck, Jim

 

Agreed,Ac will do a better job of scrambling the information as it will induce an opposing magnetic field in the hard drive.

I came up with an low voltage AC solution as well if you wish to do it that way msc,simply take a a car power pack as we've discussed and inside you will find a rectifier bridge in the form of 4 diodes,basically you want to cut out these middle men so remove all the excess components and take the power straight from the two soldered contacts on the transformer.

This will give you 12V AC.

 

Thanks Rikky,

Another question... you mentioned wrapping the bar with an insulator (masking tape or whatever)... but if the wire is insulated (enamel coated) then why would I have to also wrap the bar? Or were you talking if I was using stripped wire (which I've already decided is a horrible idea lol)?

Also, since I already ordered the rectifier, what could I use to decrease the voltage or limit the amps? And what would be the ideal volts/amps for this project? I still want this sucker to be a foot long, with close to half (5" or so) for the handle. The car charger idea is a little too simple, now that I think about it. I'd really like to completely build this thing from scratch! :major

Also, say I do want to get an iron (soft iron seems best, right?) bar... I haven't checked eBay yet, but can someone recommend a good online source for buying them that would ship to me? I use an APO address (U.S. military stationed overseas). Unfortunately, a lot of eBay sellers and even online stores don't ship to APO/FPO. Priority shipping is a huge plus, as that takes a week to get here versus months for regular shipping. UPS, Fedex, etc. don't work, only USPS.

I have the tools to do this project... even a good soldering iron. I'd really like to make this thing work right. I'll likely have enough wire to do the steel bar now, and do an iron bar in the future... and if not, the wire doesn't cost much.

I haven't studied your math yet, Rikky, but I'll definitely be doing the equations to get the right number of turns, and I do have a multimeter to test it with.

Thanks again for all the help! It's great to get help, BUT at the same time it sure made me realize this project wasn't going to be NEARLY as simple as I thought it would haha.

 

Hi,

Ricky is right on about not using the line voltage. That's to protect the user mostly. An isolation transformer should be used. Also the enamel coating on Magnet Wire can easily be scrapped through which would short to the core and other parts of the wire that has been damaged. AC and moving away before turning off is a Jeweler's technique for de-magnetizing a watch.

Jim

 

AC now? I thought electromagnetic fields couldn't be produced with AC.

 

Exactly,if the bar in the centre become part of the circuit the electricity will short through the steel bar which will cause in most likely hood a fire,burnt hand and blown powerpack.

The way you limit the current is by using a lot of turns of wire or very thin wire,imagine the electricity as water flowing down a pipe,if you use a thin pipe less water flows,if you use a longer pipe again its harder for the water to flow down the pipe so less water flows.

There is a big difference between DC and AC where current is concerned,if you don't fancy the ohms equation you won't fancy the AC induction equations:-D Basically in an AC magnet because the magnetic field switches 50 times second the polarity of the magnet keeps switching,N/S S/N N/S this switching in effect opposes the current unlike in a DC magnet,in electronics this device is known as an inductor or choke because it chokes the current,inductance is measured in henry's and you will need college level maths to understand the equations.

It's much more fun anyway to use trial and error it doesn't have to be that complicated,just start with lots of turns first and work backwards,if it gets too hot add more turns,if it isn't powerful enough remove some wire.

There are only a couple of options as what power source you use,as I've said I would seriously advise against the use of 110V,the only other option is to use a power pack of some sort,if you decide to make your own transformer get ready for about a years of study to understand how they work,they are deceptively complex devices.

 

I'm giving you options Mc and explaining the pro's and cons of each design

All electrical currents produce a magnetic field,DC produces a polar stable magnetic field North always north,south is always south,AC electromagnets switch poles 50 times a second.

 

Hi,

AC is used in all degausing. Older CRT devices all have automatic degausing that activates for a short time every time you turn them on. CRT monitors sometime have auto and manual degausing. Tape erasers are all AC. Better tape recorders all used AC erasing (degausing).

Jim

 

Alright, so AC it is then.

As to the switching 50 times/second, is that the Hertz? If so, then wouldn't it be 60 times/second (isn't American power 60Hz, and European 50Hz?)?

And maybe I don't want to BUILD a transformer from scratch if it's that complicated... but at least use a transformer vs. using some sort of automatic conversion thingy made in China and encased in plastic already.

I'd still like to know what voltage/amperage I should be targeting for this device, and where I could get my hands on a soft iron bar.

 

If you say so I live in the UK:cool And yes its HZ.

Well if you do use the AC method as I suggested you'd have to disassemble the power pack and remove the transformer,I wouldn't consider using a pre built transformer as cheating or anything,I use them in my projects as often as possible its only when the spec I require isn't available.

As to the power rating that's all dependent on your power supply and cooling of your wand and how long you wish to use it for,a few seconds a couple of times a day to wipe drives and you can really ramp it up,if you would like to use it continuously to destroy large amounts of evidence :-D You'd have to run it at a lower power or add cooling to it.

Its all about heat dissapation,the biproduct of an inductive load in an AC circuit is heat and this is where a good iron core comes into play,the better the core the more restrictive it will be allowing you to pack a more powerful magnet into a smaller space or area,if you for example used just air with no core just a coil of wire the wires would instantly burn up even at low currents.

I would aim at about 12V 5amps,this will give you a device that consumes 60watts,a 60watt magnet will be quite powerful but the amount of heat will be become a problem if use for more than say 10 seconds.

If you would like to drastically improve the focused magnetic power of the device puppywonders idea of using a U shape is the best for this,all the most powerful magnets use this confugration because the magnetic field lines converge in the centre but that will add another layer of complexity again.

Don't forget to check Youtube for instructional videos and demo's of magnets for ideas and inspiration for your project.

http://www.youtube.com/results?sear...l97800l0l98273l49l29l0l9l9l10l88l1332l19l20l0

I am interested as well now I may even make one alongside you

 

Pardon for butting in, but I've been following this thread with some interest.

My question is, no matter how the degausser is made, how does one really know for certain that the data on the HD platters have been scrambled, shy of building a degausser strong enough to degauss a battleship or even a small steel boat? The uncertainty of this would lead me toward a Glock or drill-press method...then I'd know!

Good luck!

 

I've been busy lately, but am still doing this project.

I'm still trying to find somewhere I could purchase a soft iron bar. From some research, it appears mild steel is a decent alternative. I found this eBay item that I think I'll invest in eventually (after I get one built with the free bar I have)

Yes, the U-shape would be fun, but I'm sticking to a bar/wand for this project. I might do a U-shape one in the future.

Now, I have to figure out a transformer to convert 110V to 12V, and limit the amperage to 5A... I'm seriously an electrical novice, so if you want to steer me in a direction with this, that would be great!

EDIT: I suppose I could just purchase an AC adapter, but then wouldn't I have to disassemble it and remove the rectifier to keep it AC? Is there a simpler way?

 

Hmm... just found this, haven't checked if I can get it shipped here yet, though:

http://www.pegasuslighting.com/electronic-transformer-60w-12v-ac-plug-in.html

 

It's doesn't have to be 12v I only stated that because its the most common,get the most powerful one you can find,if you use one with less voltage you can use less turns of thicker wire.

Also you can't limit the current via the transformer,you limit the current by calculating how much wire to use,the transformer will put out as much current as possible until it blows up,that's why its important you use enough turns of the right size wire.

If you just build a simple device with a lot of turns and take your multimeter and set it to amps most do 10-20amps which is plenty and connect it in series with your power pack,you can test how much current its drawing.

I haven't time now but if you find how much resistance per length AWG20 you can work out roughly how much wire you need usuaing the equations I posted,it will be exact if you use DC,if you use AC to get an accurate number you will have to use an AC reactance equation.

http://www.allaboutcircuits.com/vol_2/chpt_3/2.html