Introducing brushless DC motors

This week I’d like to introduce you to a new type of motor, called a brushless DC motor. Some people shorten brushless DC motor as BLDC motor. After building brushed DC motors for a few years, I yearned for a motor that would not be so hard to assemble the brushes and the commutator. This has been the number one problem when building a brushed DC motor. After searching the web, I found a website called Simple Electric Motors run by Mr. Serge Pozmantir. The website was devoted to Serge’s son, Stan, who won several Texas science awards with his motors and experiments. By now Stan has graduated and probably has a job somewhere.

Anyway, my sons were interested in learning how to build the BLDC motors so I bought a few. Below are two of the many kits you can purchase and build. Recently, Mr. Pozmantir has updated his website and it is much faster with better navigation than what he used to have.

BLDC Motor using optical control

BLDC Motor using optical control


The brushless motor above uses an opto interrupter circuit to make it work. Please note there are NO brushes to deal with. However, you must do some soldering and you have to be careful when you assemble these motors due to a sharp pins being used as part of the shaft. At the bottom of the picture you will see a small rubber grommet that covers the end of the sharp pin. The opto interrupter circuit is shown at the top of the picture. As the motor turns the circuit controls when to allow electricity to energize the electromagnet. This is a pretty fast motor, but not as fast as the one below.


BLDC Motor with Reed switch

BLDC Motor with Reed switch & transistor

This brushless motor uses a reed switch with a transistor to make it work. It is one of the simplest motors to assemble, is fast,  and it works very well at low voltages. The reed switch is shown on the left side of the picture between the motor shaft (with the “S” and “N” permanent magnets) and the upright support. If you look close you can see the reed switch is attached to the support. When the magnet on the shaft gets close to the reed switch, the two pieces of metal inside the glass tube become magnetized and are drawn to each other. At this point current flows through the transistor, the transistor opens, which then permits more current to flow to the electromagnet. As the magnet moves away, the reed switch moves back to its original position and no more current flows through the transistor and none through the electromagnet. Inertia keeps the motor running along with the reed switch and transistor circuit until the next magnet magnetizes the reed switch.

There is another kit that Mr. Pozmantir sells that uses a reed switch with a separate magnet that helps control the speed of the motor. If you want to learn more, hit the link above and check out the kits and experiments. They are put together well and you will enjoy building them.

Sometime in the future I will make videos of some of these BLDC motors and post them on the website, but in the meantime, enjoy these pictures.

Next week we will learn where these special BLDC motors are used.


Quote for the Day: “Make the little decisions with your head and the big ones with your heart. Do that, and you’ll be just fine.”   Kevin Roberts, CEO Saatchi & Saatchi, the largest advertising agency in the world








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