DIY DC Fixed Pole Model Generator for Students

In this project, I will be making a simple dc generator model. Most of the items I salvaged from different old devices. Even the meter is taken from a broken voltage stabilizer and modified to work as a galvanometer.

The yoke of the motor is cut to show how the internals work. I made this for students doing undergrad electrical machine courses. Thus, this is a really cheap and educative model.

List of tools needed

1 x DC motor salvaged from a broken printer

1 x AC volt meter salvaged from old stabilizer

1 x 100uF 16V capacitor

Tolsen rotary tool set

few 4mm thick wood board

Wires and soldering iron

Glue gun

A DC generator is a device that converts mechanical energy into electrical energy. The mechanical energy is often in the form of rotational like turning a turbine.

The basic principle is that when a conductor moves in a magnetic field it induces a voltage in the conductor. The faster we move the conductor the higher the emf would be produced. This is called Faraday's law. To constantly move a conductor we often turn it into a coil and embed it in a cylindrical shape metal called the armature.

The armature has a significant role in inducing a voltage in the coil. Several coils are wound around the armature known as the armature coils and these wires are connected to small metal segments called commutators. This mainly helps to convert the output voltage to DC. AC machines use slip rings instead of commutators to produce AC voltage.

To connect the motor to the output circuit we use some contacts known as brushes. which slide as we turn the generator. As we turn the motor we can extract the voltage from the brushes. The outer structure is called the yoke.

Learn more about the construction of a DC generator from this link

As you can see I have used a generic motor from a broken printer, which is not meant to be used as a generator. However, the basic principles are the same. You can find cheap generators online.

The generator I used contains permanent magnets to produce magnetic flux. However, most generators do not contain a permanent magnet instead they use electromagnets in shunt or series arrangements, which are powered by the voltage of the generator itself. For this project, I kept it simple and the motor I used has two permanent magnets inside.

As you can see from the .gif the motor rotates as I supply it with voltage(acting as a motor), and if I turn the shaft mechanically it will produce voltage at the output(acting as a generator).

Enough with the theory, I took the largest motor I found in the printer and cut the outer metal as shown. I was careful not to damage the internals.

After cutting, make sure the machine works. Supply a voltage at its terminal to check if it rotates.

Troubleshoot: If the motor does not rotate after supplying power, this may occur due to the following reasons

• The magnets are displaced and are hindering the movement of the armature. Use super glue carefully to attach them to their previous place.
• The bottom plastic cover may have been moved which hinders the movement of the shaft. Press on the bottom cover until the motor starts to rotate.

I made a design using SketchUp to get accurate measurements. I have added the file below, you can even 3D print it.

After exporting a 2D structure design using Layout, I contacted some carpenters to cut the individual parts, which I connected together using superglue and hot glue.

Model link: Link

Layout link: Link

Since I collected the meter from a 220V AC stabilizer it had to be adjusted. As you can see from the picture it contains a diode that converts the AC signal to DC along with a high resistance resistor to limit the current and voltage across the meter. I removed both of them.

The isolated meter without these passive components is very sensitive to low voltage and since the generator can only produce a voltage in the millivolt range, this is perfect for the project.

After you have gathered the modified meter, generator, the wooden parts; its time to assemble.

I used super glue and hot glue to attach everything. I made a flat groove on the motor shaft to support the handle properly.

Connect the meter directly to the output of generator, keep in mind the terminals determine which way the needle would move. So solder it accordingly.

And you are done creating a model. Simple and small generator to help you understand motors/generators better!

NB: The output voltage is not high enough to light the LED :), use gears to increase the speed.