DIY Brushless DC Motor (Newman Motor)

This project I present you is a affordable STEM project to teach our kids how to build a brushless DC electric motor with its electric controller and to learn basics about electromagnetism.

"A brushless DC electric motor (BLDC motor or BL motor), also known as an electronically commutated motor (ECM or EC motor) or synchronous DC motor, is a synchronous motor using a direct current (DC) electric power supply. It uses an electronic controller to switch DC currents to the motor windings producing magnetic fields which effectively rotate in space and which the permanent magnet rotor follows." (Wikipedia)

The motor design is inspired by the Newman motor.

Once the motor has been built, our kids can play changing resistances, diodes or capacitors to modify the speed or the torque of the motor.

The motor works connected to a USB port (5V and 300mA minimum) or connected to three 6V, 100mA solar panels in serial connection (you can see this solar version on Instagram)

It uses a list of materials very easy to find in whatever technology class.

I hope you like it.

• Small protoboard
• Small breadboard
• Enameled copper coil (33 milimeters diameter)
• Seven ring magnets (12 milimeters diameter)
• Two 100 ohm resistors
• Two 30 ohm resistors
• Two 5K ohm resistors
• Two 30K ohm resistors
• Two 22 microfarad capacitors
• Two 100 microfarad capacitors
• Two green leds
• Two 1N4007 diodes
• Two 2N5551 NPN transistors
• Wires
• Wooden rod (3 milimeters diameter)
• Pieces of wooden or plastic
• Three 6V 100 mA solar panels (optional)

To buid the rotor I have used the following:

• One wooden rod (3 milimeters diameter)
• Seven ring magnet (12 millimeters diameter)

You have to broken one magnet into little pieces of magnets and try to adjust the wooden rod between little pieces as you can see in the first image.

After that, place the other three magnets as you can see in the second image.

To build the stator I have used the following:

• Two wooden pieces (blue and green ones in the image)
• Two plastic pieces (black ones in the image)
• Enameled copper coil (33 milimeters diameter)
• Several black plastic to guide the copper coil turns
• A breadboard to connect the init and the end of each coil

Because it is very difficult to obtain the same pieces I have used, I have design for you in Tinkercad the skeleton of the motor ready to print. It could be a good exercise for our kids.

One you have printed the skeleton, you have to mount two coils with 300 turns each one. It is very important you to mark the init and the end of each coil.

After that, use a small breadboard to solder all the terminals to facilitate the connection with the control circuit.

The astable multivibrator is a type of cross-coupled transistor switching circuit that has NO stable output states as it changes from one state to the other all the time. The astable circuit consists of two switching transistors, a cross-coupled feedback network, and two time delay capacitors which allows oscillation between the two states with no external triggering to produce the change in state.

The basic transistor circuit for an astable multivibrator produces a square wave output from a pair of grounded emitter cross-coupled transistors as you can see in the gif where a basic circuit is simulated in Cocodrile Clip.

The kids can built the circuit in the protoboard to test the circuit works before to connect the coils.

The final result must be similar to the video embed

The circuit control is a basic astable multivibrator circuit as you can see in the Tinkercad image with a little changes with respect to the previous circuit:

• Replace the two 100 microfarad capacitors for two 22 microfarad capacitors
• Replace the two 30K ohm resistors for two 5K ohm resistors
• Remove the green leds
• Remove the upper 100 ohm resistor
• Replace the lower 100 ohm resistor for a one 50 ohm resistor (this value must be similar to the resistance of the coil)
• Insert a 1N4007 diode to connect the init of the coil and to avoid damage the circuit (j-30 point in the protoboard) (see the tinkercad image)
• Connect the end of the coil in the h-21 point in the protoboard (see the tinkercad image)
• Join the two coils in the protoboard: e-30 point (end upper coil) and d-30 point (init lower coil) (see the tinkercad image)

The simulation of this circuit in Crocodrile Clip is showed in the gif image.

A square wave output as in the basic astable multivibrator circuit above does not work in this motor because we need pulses of energy.

As you can see in the gif image, the circuit is generating pulses of energy instead a square wave form.

Other configuration of the motor your kids can test is shown in the Tinkercad circuit.

In this configuration the motor only uses the upper coil while the loqer coil is not connected.

This configuration works although the rotor does not turn propertly. It does not turn as smooth as the motor with both coils.