Faraday Disk Dynamo (Homopolar Generator)

We made a Faraday disk dynamo (homopolar generator) for a group project at university. The disk, which is attached to a metal axis, will rotate and will convert the mechanical energy into electrical energy by using neodymium magnets which will be measured by a Voltage meter. The generator is named after Michael Faraday who invented it back in the 1800s.

You will need the following materials:

• 4 Wooden cubes (5 x 5 x 5cm)
• 1 Wooden board(20 x 20 x 2cm)
• 2 Wooden sticks (2 x 2 x 10cm)
• 2 Bearings (inner diameter = 0.08 cm, outer diameter = 2.1 cm)
• 1 Copper disk (radius = 0.1, thickness = 0.03 m)
• 2 Neodymium magnets (1x1x0.5 cm, 1.4 T)
• 2 Wooden slats (12 x 6 x 0.5 cm)
• 2 Aluminium strips (7 x 0.5 x 0.01 cm)
• 4 Aluminium plates (6 x 8 x 0.01 cm)
• 1 Non-conducting metal axis (diameter = 0.08 cm, length = 13 cm)
• 12 Bolts and nuts
• 1 Nuts (inner diameter = 0.8 cm)
• 1 Metal cillinder (inner diameter = 0.8 cm, length = 2 cm)
• 1 Metal screw
• 1 Circular metal plate with a hole in the middle (hole diameter = 0.8 cm)
• 2 Circular metal plates with a hole in the middle (outer diameter = 1 cm, hole diameter = 0.4 cm)
• 1 Small woorden cilinder (diameter = 0.5cm, length = 2cm)
• 4 Electrical wires
• 1 Voltmeter
• 16 Wood screws
• 4 Rubber rings (inner diameter = 0.07 cm)
• 1 Lustre terminal
• Ducttape

And the following tools

• drill machine
• pencil
• vise
• hammer

The best place to put the generator is on a wooden foundation. By building such a wooden foundation it will give a lot of stability for the generator when it is rotating with high rotating speeds. It also is easy to work with and is not expensive in contrast to other materials.

Take a square wooden board with dimensions (20x20x2 cm), 4 wooden cubes (5x5x5 cm) and 8 wood screws. Place the cubes under each corner of the board and screw 2 screws in each corner with a drill machine. The wooden foundation of the generator is now complete.

After finishing the wooden foundation it is time to build the foundation of the disk in order to attach the copper disk to the setup. Grab 2 wooden slats 12x6x0.5 cm, in these slats we will need to make a semicircle opening at the top for the bearings (see the picture attached for the finished slat). The diameter of this semicircle should be 2.1cm, which is the outer diameter of the bearings.

Now it is time to attach the wooden slats to the wooden foundation we build in step 1. Take 4 rectangular aluminum plates with dimensions of 6x8x0.01 cm. Now draw a line down the middle of the short side and use a vise and hammer to bend the aluminum plate by 90 degrees. Then drill 4 holes in the aluminum plates: 2 in the lower segment of the bended plate and 2 in the upper segment. Place the bended plates on either sides of the wooden slats and mark where the holes in the aluminum plates are on the wooden slats. Now drill holes with a drill machine at your markings in the slats in order to be able to attach the aluminum plates with nuts and bolts.

Now it is time to put the slats on the wooden foundation. The distance between the inner side of the two slats should be 8cm, otherwise the aluminium plates will not fit. To attach the slats to the foundation, place them in the right position and mark where the holes in the foundation should be drilled. Then use the drill machine and attach the slats, again, with nuts and bolts.

We made a semicircular opening in the wooden slats in order to put bearings there. Those bearings are needed to rotate the metal axis where the copper disk will be on. The bearings need to stay put and firm for it to provide stability to the generator, for this we will use aluminium strips

Use the vise to bend the strips so that you get the same semicircle as in the slats. Drill two holes in the flat part of the bended aluminum strips. The slat and the strip will together make a full circle, which has the diameter of the bearing. Take a bearing and put it in the slat, then put the aluminum strip on top of it. Leave no extra gap; they must be as tight as possible in order to provide stability. Now use 2 wood screws per slat and screw the aluminum strip to the slat with the bearing in it (see the picture attached).

Now take the metal axis (diameter = 0.08 cm, length = 13 cm) and the copper disk (radius = 0.1cm, thickness = 0.03cm). Bring these two parts to a technical proffesional and ask if he can attach the two parts in the following manner:

The disk needs to be in the middle of the axis. On one side of the axis, a screw thread needs to be made so that a nut can be attached. Make sure to put a small metal circular plate in between the not and the disk. On the other side of the disk, a metal cillinder with a hole of inner diameter 0.08 cm and length 2 cm needs to be put against the disk. In the side of this cillinder a hole needs to be made so that it can be tightly screwed to the axis with a regular screw. Now the disk is thightly assembled in the middle of the axis.

Now it is time to make the holders for the magnets.

You will need two wooden sticks (2x2x10 cm), two small circular metal plates with a hole in the middle (outer diameter = 1 cm, hole diameter = 0.4 cm). Screw the metal plates to the side of the stick so that the upper part of the plate is at the same height of the upper part of the stick (see the picture for clarification) and screw the sticks to the wooden foundation with a drill machine. The wooden sticks should each be 2 cm distanced from the copper disk and as far away from the centre of the disk as possible, but watch out: they cannot stick out further than the disk itself.

To avoid the magnets breaking the wooden sticks place a small woorden cilinder (diameter = 0.5cm, length = 2cm) between the and screw it in place from the outer side of the sticks with 2 screws on each side. Take the neodymium magnets (1x1x0.5 cm) and let them stick to the metal plates at the top of the wooden stick.

The Generator is now complete and it is time to make a closed circuit in order to measure the produced voltage.

Take two electrical wires and cut them cross sectional open in such a way that the copper wires stick out on both sides. Attach one end of the wires to the lustre terminal. Then attach the other side of one wire to one of the wooden slats in a way that it brushes the disk near the axis. Attach the other wire on one of the sticks so that it brushes near the far side of the disk. This can be done with ducttape. Lastly place the wires of your voltmetre to the other side of the lustre terminal.

Place a drill machine on side of the axis and turn it on so that the axis and the disk will rotate. You'll see that a voltage is produced!