Difficulty level: 1 (simple, no special tools required)
Kits covered: Kits #15-17
We are proud to be the first to design a simple educational brushless motor kit utilizing a reed switch as a sensor and make it public in 1999. Simple conventional motors where the coil rotates in a magnetic field have much longer history going back more than a hundred years.
There are many variations of this motor type. Most of them use permanent magnets to create a static magnetic field (some industrial and more complicated motors use electromagnets for this purpose). Rotors may have different designs; the simplest one is just a coil of wire.
For this motor to work the electrical current has to go through rotating coil at certain moments. This is achieved by modifying the ends of coil as follows:
The wire ends lay on metal stands, connected to the battery. It creates a commutator, where the stands serve as brushes.
When un-insulated (bare copper) parts of the coil wire contact the metal stands the current from the battery flows through the coil making it an electromagnet with North and South poles. This electromagnet interacts with the permanent magnet (North and South poles attract each other while the same poles repel). Motor starts to spin until the contact is broken when an insulated part of the coil end comes into contact with the stand. However the coil continues to spin due to inertia and then the process continues. Technically speaking this motor is a single pole pulse motor.
This is a simplified explanation of the principles of operation for this motor. The direction of the force that creates the rotating motion can be found by using Fleming’s left-hand rule.
We have three different types of conventional motor kits that allow performing some experiments with these motors:
- Kit #15 allows building one of four configurations with one or two magnets placed at the bottom, top, or on the sides and experiment with 4 different voltages: 1.5, 3, 4.5 and 6 Volts using included jumper wire. You may also experiment with different size wire coils.
- Kit #16 provides parts to compare regular ceramic (grade 5) and very strong neodymium (grade N50) magnets and experiment with the distance between the magnet and the coils of different size.
- Kit #17 is a very inexpensive simplified version of these motors designed for groups of students (shown at the top of this page).
Recently we designed RPM measurement tools that allow real speed measurement for these motors. They available as a full kit or just an attachment and work not only on kits #15-17 but also on most other motors where the coil rotates in a magnetic field.
Kits #15-17 are simple and inexpensive. However all motors of this type (including all we found on the internet!) have the same problems.
Building them requires a lot of accuracy in balancing the coil and stripping off the insulation. They are also not very stable and require frequent cleaning. Practically nothing could be attached to these motors.
It is actually easier to assemble any of the reed switch motor kits shown at our site. They are much more stable, reliable, may run non-stop for a long time, and are powerful enough to do some real work. Students usually understand quicker the principles of the reed switch motor operation and these motors have a proven record of working every time without any struggle.
New! Watch All Experiments For Simple Electric Motors With Rotating Coil video on our YouTube channel.