Batteryless Homopolar Motor

Hello Friends!!!

English is not my native language, anyway, I think this instructables might help a few people around the world.

There is nothing new about the homopolar motor itself. Instructables has many of them published... My idea here is to avoid draining out a new battery, since, basically, a Homopolar motor is almost a pure short circuit. So I supply the current using an old cellphone chager.

- The video on the first page has subtittles.

You will need:

-Old cellphone charger (most of them are able to supply 5VDC at 0,5 A.

- 2 round neodimium magnets 15 mm diameter 6 mm thicknes. (dimensions are not critical but they need to be strong!)

- about 10 inches of magnetic wire (0,5 mm diameter will do).

- A hexagonal head, 8 mm diameter steel bolt, 65 mm length, dimensions are not critical, just for you to have an idea about the length.

- About 10 inches of a rigid wire, 0,7 mm diameter wire, insulated, (it is important to be rigid, a good magnetic wire will do too).

- A piece of steel sheet , about 3 x 3 inches, only to keep the bolt standing. Dimensions are not critica again.

- An old AA size old battery, you will use the positive pole as a bearing, just to keep the loop spinning in its due position.

- tin solder

- insulating tape,

- pliers

- sandpaper

- tin welder

1-Start off by removing the positive pole of the battery with the help of pliers and a fine screw driver.

2- Solder the positive pole to the magnetic wire. Do not forget to remove the enamel with a sandpaper or burn it with matches. If you don't have a welder you can try to glue (superglue) the magnetic wire to the positive pole, but you must be sure that there is electric contact between the pole and the wire.

- Now, on the top of the hexagonal head glue a small piece of insulating tape to prevent the positive pole to make electric contact with the steel bolt.

- With the help of insulating tape fix the magnetic wire and positive pole along the length of the bolt (see picture)

- Now with the help of two neodimium magnets, mount the bolt on the steel sheet piece , and be sure to keep the magnetic wire as close as possible to the side of magnets (see the picture)

- With the help of insulating, keep the magnetic wire on its place fixing it on the steel plate. This is necessary because whe magnet wire on the side of the neodimium must not be an obstacle to the spinning loop.

- Everyone who tried to make an homopolar before knows that there many shapes for the spinning loop, in my case this shown on the picture was the one that worked best. Since the cellphone charger has limitations on how much current it can provide you must consider that the loop must not impose too much friction against the side wall of the magnets.

- The exact dimensions of the trinagular loop are no critical, since they depend ont the length of bolt you are using.

- be sure, on the upper contact of the loop, to remove the insulation in order to allow the electric current pass through it. Of course, remove the insulation on both ends, in a way that barely touch the sides of magnets.

- Place the loop on the upper pivot of the bolt and make sure it rotates freely against the side walls of magnets.

- Now it's time to connect the cellphone charger. In my case I had one aleready prepared for it, but, you can cut the phone connector and expose the two wires, the positive and negative 5VDC. The polarity is not very important here but you will connect one wire to the steel plate, which makes electric contact wilh the neodimium magnet and the other wire to the magnetic wire which is connected to the upper pivot.

- Sometimes you must help the loop to start spinning, sometimes it will start by itself.

- Note: Practical assemblies rarely work the first time. There's nothing wrong with that, sometimes there are variables that were not considered before. By the way, you really learn when you are able to track and serch what is not working.

- Persist, that will teach you a lot!!!

- Many people make homopolar motors like this, but I see that sometimes they don't fully understand how it works, and then, they cannot understand how three phase induction motors work as well... they do not understand the principle behind it. And that is why I consider this motor beautiful in its simplicity but huge in its wisdom.

- It has to do with a phenomenon that appears when a wire conducting electric current (or charges in movement) experiences when it is in immersed in a magnetic field: It appears a perpendicular force pushing it. So, in a motor this wire is placed in a position that this force trnslates into a torque which makes the loop to rotate. It has to to with the Lorentz force.

- There is a practical rule known in electromagnetism as "right hand rule" (I know in some places the use other positions for the hand..) which simplifies visualization of this phenomenon. Fingers aligned with magnetic field line forces (B vector, from North to South pole) , thumb aligned with dicrection of current (on the wire) and the force that appears coming out from the palm of hand. This force makes the loop to spin.