Introduction: Compass

Always getting lost? Build this compass out of a CD and a small magnet.

Step 1: Parts Layout

a compact disc (hopefully used / useless)
a small magnet
the outer case of a 50 pack of cd's. (can substitute anything that will hold water and a floating cd, a cd-case looks nice)
some hot glue
some water

Step 2: Glue Magnet to CD

Glue the magnet pretty much anywhere on the cd*, with a pole facing radially outwards. If the magnet's pole does not face radially outward the compass will be decieving.

To find the poles, place the magnet in the presence of other magnetic objects. The magnets will attach to each other along their poles if they have enough mechanical freedom to.

  • Depending on magnet size, glue-ing too far away from the cd's center will tip the cd (think center of mass). But, if the magnet is too close to the center the torque arm length about the center will not allow for the compass to spin / function properly.

Step 3: Find North

lay the cd+magnet into a bowl of water and watch is align itself with north. The attached video shows the compass aligning itself (it's a kind of boring video)

Comments

author
Gorilla22 made it! (author)2016-02-15

Sorry, where is the video?

author
kthomas29 made it! (author)2011-11-12

I would like to build a compass with a CD but my design is a little different. I would like your opinion if it would work. I would oppose two ring magnets on a dowel, the top ring magnet would be glued to the CD, so then the CD would levitate with the dowel down the center. Then I would take some metal wire touching the top magnet and extend it out to the end of the CD. I may have to counter the balance with maybe a copper wire on the other side. Do you think this would work?

author
nathanb made it! (author)2010-11-11

very good idea. ideal for urban survival.

author
nutsandbolts_64 made it! (author)2010-06-05

I suddenly got an idea! *rips t-shirt* Oh man... Now all I need is a sheet of PET...

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ve2vfd made it! (author)2006-09-19

So simple yet what a stroke of genius! I'll definetly be using this when doing compass instruction with my Scouts in a few weeks! A floating CD and a magnet is a lot more 21st century than the old "floating cork and magnetized sewing needle" trick. Thanks! Great idea!

author
ericscrum made it! (author)ericscrum2010-04-27

 Hey, the needle and cork has been around for years! (But this version looks like it could work a little better because the floating component has more surface area).

author
ysabet made it! (author)2008-07-24

NICE. Gonna try this one tonight! --puts on MacGyver disguise--

author
Ingerson made it! (author)2006-06-17

Really stupid question: how do you know which is the North face of the magnet?

author
PurpleJesus made it! (author)PurpleJesus2006-06-18

Not a stupid question.
1) build it, if it points away from the sun around noon (assuming your in the northen hemisphere) you have the southern pole of the compas magnet pointing toward the north pole.
2) if you want to get elaborate or just play with electro mag's check out this link... pay special attention the various "left hand rules" and how the wires are turned...
http://library.thinkquest.org/16600/intermediate/magnetism.shtml

author
savagenarce made it! (author)2006-06-16

At last! Something that old CDs can be used for! Tip: balance the weight of the magnet with a counterweight on the opposite edge of the disk to prevent tipping. A washer or two hot-glued to the disk will work nicely.

author
PeterTheUnGreat made it! (author)2006-06-16

Lovely simple Idea, the kids in my sunday school group are going to love making these! Pete

author
skot123 made it! (author)2006-06-16

We did this for a Cub Scout den project (pack 682 WA) this evening. We used a magnet from a Magnetix kit. We had a good discussion on compasses and magnetism. I had the magnet from a dismantled hard drive handy and we could see the repulsion/attraction from about 12”. The best part it got the scouts thinking; “What happens if you turn the magnet around?” and related questions and theories.

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mikesty made it! (author)2006-06-15

I'm so putting one of these on the dash of my first car :)

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wperry1 made it! (author)2006-06-15

This is really cool! If you added a few vertical lines around the spindle lid this could even be accurate enough to take a bearing. I think I'll make one of these up and keep it hand for the coming apocalypse :)

author
VelvetElvis made it! (author)2006-06-15

Simple and educational. Thanks.

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Bio: Will Bosworth, developing projects for HowToons @ SquidLabs.
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