Magnets won’t break a computerized sewing machine

Posted by Eric Husman on Sep 14, 2012 at 11:38 am / Machines & Equipment / Trackback

I’m not sure where this concern about magnets is coming from, but perhaps a little perspective is in order.

Seriously, for a magnet to damage a computerized sewing machine, we’re talking about something that Wile E. Coyote would have to order from ACME. You wouldn’t have to put it on the machine; the machine — as well as your stove, washing machine, iron, refrigerator, and other appliances — would inexorably move toward it¹. It would affect fluorescent lights and old tube monitors. You would need to post warning signs for people with pacemakers. It, not the sewing machine, would be the most expensive piece of metal you own. If it is a permanent magnet, Chinese rare-earth miners would send New Years gifts to you for supporting their families. If it is a current-driven electromagnet, the board of your local power utility sends you Christmas cards.

The original computer memories were magnetic core memory. These were big 3-D networks of wire and little rings that had to be woven together. The Wikipedia article on this is very good. The lore when I was a freshmen engineering student was that IBM had done a study and found that the best place to make them was Hong Kong, where the women had the most adept fingers from a lifetime of sewing. A very strong magnet might indeed affect one of these, but the likelihood of any sewing machine having one is remote at best.

More recently, like the 1970s-1990s, people transferred files on floppy disks. These were basically made on the same principle as the old analog cassette tape, using a magnetic field and magnetic head. Magnets could definitely ruin one of these.

Most recently, though, files are transferred by Ethernet and memory stick and stored on hard drives. These should not be affected by the relatively weak fields you can generate with a magnet that is essentially an overgrown refrigerator magnet. I can’t speak to all of the possible computerized sewing machines out there, but very few if any of them will have hard disk drives, so that is not an issue. Even if they did, the drives themselves are encased in a metal container that shields the normal magnetic fields one is likely to encounter inside the computer. It is worth pointing out that the computer power supply itself has an enormous transformer that creates a fairly powerful (albeit mostly self-contained) magnetic field, and that every current-conducting wire generates a magnetic field – every one of them! Look inside your computer: there’s the power supply, a bunch of wires coming off of it whose purpose is to conduct current, the memory modules are sitting there unshielded on top of the mother board, and the hard drive is inside the case with all of this. Do you really suppose that if “magnets” were a concern for memory or hard drives, they would design the computer that way? Also, please see this article, in which PC World busts the myth that anything less than a magnet designed for the purpose could erase your hard drive.

That leads me to what is most likely inside the computer control for the sewing machine. This particular button hole machine does have a fancy interface to control the settings, which it remembers. That implies that there is a computer with a memory that persists after power-down. That computer is mostly likely a micro-controller running off of some kind of permanently hard-coded memory (or at least memory that requires special methods to change) that is not susceptible to magnetic fields, and the settings are stored on memory that is similarly resistant to magnetic fields.

As Grace suggests, the field should drop off rapidly with distance from the magnet. R^2 is the square of the distance, and the field falls off inversely proportional to this. At a point twice as far away, the field is 1/4; at a point 3 times as far away, 1/9. This is true if the magnet is in free space. However, if the magnet is stuck to a nice piece of steel, the field falls off even more rapidly in the direction of the steel. Given the nice thick steel plates that makes up these industrial machines, the magnetic field is not likely to permeate to the poor little computer that is, incidentally, underneath the table, all the way in the back. That’s like 3′ away through multiple steel plates. Generally speaking, you are not able to lift the magnet that would be capable of affecting the computer through that much shielding.

____________
¹ At 4:28 minutes begins the magnet segment where you can see everything from cars, buses, ocean liners, the Eiffel Tower and even satellites pulled into the magnet. Also, please note the author of this piece is Mr. Fashion-Incubator who is an electrical engineer ~kf

15 Responses to “Magnets won’t break a computerized sewing machine”

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David
September 14th, 2012
4:05 PM

As a science teacher I must say that this is nicely written. Well done.

Suzan
September 15th, 2012
11:12 AM

Uh… you might check with a sewing machine repair person on this one.
It’s the same reason you don’t want to leave magnets next to your hard drive. It can erase the hard drive.
The reason I was able to get my embroidery machine fixed when it needed a major part that wasn’t made anymore, was because the repair guy had so many machines with wiped hard drives. He said it was very common to have them come in that way because of magnets and he couldn’t do anything to repair them. Mine was a mechanical break so he was able to use parts off of all the machines he had lying around that he couldn’t fix.
The magnets on a stereo speaker are enough to do this. Go ahead, give it a try and get back to us. :)

TOS
September 15th, 2012
12:02 PM

Since I was using computers in the age of the floppy, I learned back then about the magnet threat, and didn’t stop to question whether it still made sense as technology progressed over the years. Thanks for clearing that up!

Kathleen
September 15th, 2012
1:13 PM

Suzan: follow the link from the post. It is a myth.

If this guy couldn’t fix [what you say he said was the problem], he would not be my first, second or third choice in a mechanic because it is nothing to swap out a drive. Presuming that at worst given magnets [can purportedly] erase data, they don’t destroy drives so there wouldn’t be anything wrong with the drives that reformatting and uploading data wouldn’t solve. Like I said, I would be leery of a mechanic that lacked critical troubleshooting and analysis skills.

Mr. F-I
September 15th, 2012
4:02 PM

Suzan

First, there is no hard drive in Kathleen’s button hole machine. I thought I made that clear in paragraph 6.

Second, you might want to read the PC World article linked above. If you still don’t want to take PC World’s word for it, try this. First hit: Cobolhacker stacks a whole bunch of rare earth magnets on a hard drive (with cool picture of same). Result? No change detected with chkdsk or of the MD5 hash that he made beforehand. He also suggests that nothing short of a degausser — a device designed for the purpose — would render the drive useless. Here is yet another site where someone stuck a 10 pound woofer speaker magnet on a drive and, though not as rigorous as the cobolhacker site (that’s hardly surprising), still no problem. I found one person who claimed to be able to erase a hard drive with magnets from K&J Magnetics. However, he also claimed to be able to erase flash drives the same way (without, apparently, pulling the iron out of his own blood), and K&J Magnetics doesn’t believe it and they refer people to the same PC World article as above, so … there is a pattern here.

A speaker magnet just isn’t in the same class as a degaussing magnet. Here’s a website where you can buy degaussers; they cost upwards of $3000, weigh 75 pounds, and require 220 VAC input. How do you suppose a speaker magnet compares with that?

celeste
September 15th, 2012
5:16 PM

I am glad to hear this, I was so worried after making a few purses with magentic closures that I was runing my machine. And I’ve been afraid to sew any since for fear of damaging it.
Turns out the problem I was having then – the sititching issues I had, were from bobbin winder being broken and not properly winding the bobbins. And, once that was fixed, the machine stitches were fine. But, the fear remained.
Happy to know, I can not worry about that any more!!!!
Thanks

Dara
September 15th, 2012
10:15 PM

Uggghhh, I hate sewing magnets on machines, but no they never seem to mess with the electronics. I would have really loved that excuse as a stitcher. People will actually pull the long chains out of the box of 1,000 and stick them directly to the machine for years of this particular task with no ill effect. I think this is a good obvious point to make.

Jen Rocket
September 15th, 2012
10:26 PM

I use pretty strong magnets on the head of my Juki DDL 5550-6 for pins and have never had any trouble. I am happy to see this blog about magnets on machines as people look at me funny when they see my pins on the front of my machine, thanks for giving a great explanation of the facts!

becky
September 16th, 2012
7:56 AM

I feel so much smarter after reading this! Thanks for educating us.

kay
September 17th, 2012
1:43 PM

On the other hand, a four year old shuffling across the carpet on a cold, dry day can pick up enough static charge to do some interesting things if they touch the right (wrong?) connector.

I use an old hard drive magnet on the bottom of a Corelle bowl to contain my pins… and it often seems to wind up on the bed of the machine while I’m fitting. No malfunctions not attributable to user error.

Mr. F-I
September 17th, 2012
7:09 PM

Kay, I would indeed be far more fearful of the effects of static discharge inside your computer. You do wear a grounding strap any time you’re poking around in there, don’t you?

Natasha E
September 18th, 2012
1:31 PM

I have one of those donut magnets used to switch the modes on a pacemaker or to turn it off post mortem. I haven’t had to use it for it’s original purpose since the newer style pacemakers don’t keep chugging on like the old ones but I use it by my machine for picking up pins and yet somehow my computerized machine hasn’t died either.

M-C
September 23rd, 2012
9:24 AM

Thanks for this post. I too started in the era of floppies (well, punch cards, but never mind) and didn’t question the magnets and sewing machines thing further as technology evolved. Took me a while to believe it, but I’m now convinced I can use my beloved magnetic pin bracelet around an electronic machine :-).
Wiping omelette off face..

How to organize needles
December 17th, 2013
5:21 PM

[…] As far as knowing which machine needle is in the machine, I stick the needle packet on the head with a magnet. And no, the magnet will not break the machine. […]

Ms. McCall
March 17th, 2014
8:51 PM

You may not believe me, but I have personally broken my hard drive with a magnet. I have a magnetic pin cushion, and it became stuck to the bottom of my macbook, right beneath the hard drive, as it was spinning. My husbands theory is that the magnet probably caused the spinning disk to wobble and become irreparably scratched by the needle and that’s what caused the damage. I don’t see anything in the linked articles where people did their experiments on a spinning drive, and I’m not claiming that the magnet degaussed my hard drive in the way that the NSA do it, only that it broke it beyond repair.

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