Pair of Hearts Homopolar Motor

Make a pair of rotating copper heart motors...that unite to become one!

In this Instructable, I show how to make a special 2-piece homopolar motor with a bass speaker, some coins, a battery and two pieces of copper wire.
A neodymium magnet can be used instead of the bass speaker and coins.

This is a great display for Valentines Day...or any day of the year!

The homopolar motor is the simplest form of electric motor. It consists of a battery, a conductor, and a magnetic field.

Unlike other electric motors, the homopolar design doesn't require changing magnetic fields to work. It is a demonstration of the Lorentz Force.
For detailed info, see Wikipedia under "Homopolar Motor" and "Homopolar Generator".

The flat Heart shape is the most basic of homopolar motors. The Heart with legs is the next most simple shape. With a little ingenuity, the two shapes can be combined into one spinning body!




The above movie shows a bass speaker as the source of the magnetic field for the Heart homopolar motor. Pennies are used as a commutator.
Note: No neodymium magnet is needed in this case!   

Song is "Be Excellent To Each Other", courtesy EJ Gold, from the album "California Dreams" .





 The above movie shows a traditional neodymium magnet used as the magnetic field for the Heart motors. 

  Background music is a non-traditional band called Wolf Parade from Montreal, with "This Heart's On Fire".  (Used with band permission)
Note: Unfortunately, mere permission from the band was adequate for Warner Music, and the music of this video has been stripped from it by them.

Here is a YouTube video with the "This Heart's On Fire" song, so that you can try playing it at the same time as the above movie...http://www.youtube.com/watch?v=0Xq4o-kE-j8

Step 1: Materials and Tools

Materials:

-  3 foot (1 metre) of AWG 10 gage (preferred), or up to 18 gage, solid copper wire.  
-  Solder
-  AA battery (I recommend the Duracell AA NiMHrechargeable battery with 2650 MAh rating)
-  10 inch or better bass speaker (or use a good sized neodymium magnet)
-  7 Canadian magnetic pennies, or other coins as a commutator

- (optional) Neodymium magnet 1/2 inch x 1 inch minimum (such as # DX08 from K&J Magnetics )


Tools:

-  Pliers
-  Soldering iron
-  Vice
-  Wire stripper
-  D cell size battery or tube of same size (for forming wire)
-  nail or centre-punch

Comments

[slano]

Great instructable! I want to make a few of these that can last for a while. How can I assemble it to run for the longest possible time?

[mrfixitrick]

For longest run times use the best AA battery you can buy. I found the 2650 Mah NiMH rechargeables were best. Dimple the battery + post a little, and polish the hearts bearing points. Balance them perfectly. Use a powerful neodymium magnet.

[Bill WW]

Greetings from a neighbor just south of you.

Very nicely done Instructable. I have made homopolar motors using rare earth magnets, never thought about using the strong magnetic field of a speaker.

Copper is so nice to work with. I keep copper sheets and wire in my shop.

[mrfixitrick]

Hi Bill, and thanks for the comments!
I see that you list engineer on your profile...was the copper part of that work? How do you work with copper sheets?

[Bill WW]

Yes, engineer retired from work, but not play. I designed and built paper mills, some in BC and SK. The copper was given to me by a sheet metal worker friend, and I like to work with it, and brass, mainly because it is so much easier to work with than steel. Copper has excellent heat conductivity, and I have made a solar powered Stirling cycle engine using that property. See it here:
http://www.youtube.com/watch?v=WsKVp6RvV34
The top plate is copper painted black to absorb heat; copper cooling fins underneath do the cooling.

[mrfixitrick]

Really "cool" Stirling Engine you made. I didn't think they could run on straight sunlight without a lens!

Here is a concept...I was just listening to one of my favourite alternative inventors, MT Keshe, and he was describing his new nano-material solar panel that works on Earth radiation, and provides more power at night than regular panels do during the day!

So, it seems like tif you had the right nano-material, it would "catch" the radiations from the earth...and would allow your Stirling to run at night!

[Javier.Maria]

What can be used in place of the Canadian coins?

[mrfixitrick]

You can use steel washers, or flat neodymium magnets to replace the Canadian coins.

It's best to be both conducting and magnetic, however regular US coins can be used. Since they are not magnetic, they may have to be glued to each other to stay in place.

[sconcepcion]

can i use a wire from an extension cord?

[mrfixitrick]

An extension cord wire won't retain the heart form too well because it has multiple strands and is made to flex. If you twist the strands together tightly it will work better, but it may be frustrating.

A single strand (solid) copper wire is best, anywhere from 8 gage to 18 gage size. It's used in house wiring, and is available at a hardware store. Or find someone at a construction site, or an electrician, who will give you a cut-off waste end of a piece of solid core wire.

[duckythescientist]

Please be careful about dimpling the batteries. I was sprayed in the eye when I broke the surface of the metal of a Duracell AA while dimpling it for a homopolar motor. Luckily, I blinked in time (or whatever sprayed me wasn't caustic).

[mrfixitrick]

Thanks for the warning!

"Gently" dimple the battery positive terminal is definitely the key word.

[jcomtois]

Nice combination of arts&crafts and physics. One good way to straighten wire is to clamp one end in a vise, grab the other end with pliers and twist several full turns into it. For long pieces a drill works well instead of pliers. Twisting also hardens the wire.

[mrfixitrick]

Thanks for the helpful hints on wire bending!

[ahmedfarazch]

Please let me know what is the battery life?

[mrfixitrick]

The battery will last for up to an hour with the "flat heart", and as little as a couple of minutes with the double heart shape.

A fully charged battery must be used. I use a Duracell 2650 MaH Ni MH-type rechargeable battery. Sometimes it gets warm from the heavy amp draw.

[m.hutchinson]

Neat instructable, and great warnings for kids eating magnets. One thing though, AFAIK, the neodymium nickel oxide coating not because neodymium is poisonous, but is to resist corrosion, as the neodymium is very corrosive and will "rust" away quickly.

Question - does soldering the tip of the heart together provide electrical/magnetic benefits or is it more to keep the bare wires from catching on something?

[mrfixitrick]

Thanks for the comment on neodymium. It's interesting to note that the nickel plating is poisonous also, and many people including myself are allergic to it. (It's a common allergy for mechanics).

The tip of the heart is soldered to provide a good electrical connection to the commutator/magnet, and for better looks. It doesn't seem to affect the running to have "loose legs" on the heart.

[mrfixitrick]

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Please consider voting for this Instructable, and give it a good rating as well!

The "Vote Now" button is near the top of the instructable, and it can be rated in the middle of the right column.

[rimar2000]

Excellent Instructable, and very good idea!

[porcupinemamma]

Way cool!  10/10  You've got my vote.

[Stephen D. Alverez]

 Like the song and the instructable!

[womyntracy]

The shape that is created by the two hearts entwining is incredible!! 

[Kiteman]

Am I right in thinking that the "proper" heart's speed is self-limiting?

As soon as it reaches a certain speed, the bottom of the heart will lift away from the magnet, disconnecting the circuit, yes?

[mrfixitrick]

Exactly correct! The flat heart motor is self-governing, uses minimal power, and it can run for up to an hour that way.

The other two-legged heart shape will only go for a few minutes...and can overheat the battery because of high current draw.