Outrunner Brushless Motor

This instructable was created in fulfillment of the project requirement of the Makecourse at the University of South Florida (www.makecourse.com).

This project consists of a simple outrunner brushless DC motor, controlled by an infrared (IR) remote. Being familiarized with how electromagnets and brushless DC motors work, will make the understanding of this project easier, and it will be useful in case any troubleshooting is needed.

Step 1: Tools, Materials and Components

- (1) Arduino UNO

- (1) Dual H Bridge DC Stepper Motor Drive Controller L298N for Arduino

- Enameled copper wire, 0.0055'' diameter (two pieces of at least 35 m each are required)

- (1) Breadboard

- (1) Infrared Sensor

- (1) Remote control (IR remote) (with batteries)

- Breadboard jumper wires (10 Male to Male, 4 Male to Female)

- (4) 9V holder

- (3) 9V battery clips

- (1) bearing (Inner diameter: 5 mm; Outer diameter: 14.7 mm)

- (1) 5 mm diameter shaft (5 cm, minimum length)

- (6) Neodymium magnets (15x15x4 mm)

- Soldering iron kit

- Plastic box (20x12x6 cm)

- (4) 4-40 Nuts

- (4) 4-40 Screws

- 3D printer

- (4) 9V batteries

- (1) 4x4 cm copper lamina (it is not necessary to have a 4x4 lamina, since this will be cut and use as a soldering surface, but a 4x4 lamina will suffice)

- Sandpaper

- Epoxy

Step 2: MAKING THE MOTOR

3D PARTS

The motor consists of three 3D printed parts, the base, the stator, and the rotor. The base has an opening in the center to hold the bearing and four arms in the bottom to solder the ends of the of the electromagnets.

The stator has 12 arms in which the copper wire will be coiled, and its hallow center will allow for it to fit in the middle of the base.

The rotor is outer most part, it has 12 small fitting spaces, 6 of which will be use to place the permanent magnets. It also has a small hole on the center, in which the shaft will be placed.

When the 3D parts are printed, it is advisable to sand them, to ensure they will fit. At this point the bearing can be placed in the center of the base. It is not necessary for the bearing to reach the bottom of the base, but you may want to fit all its width (the bearing's) inside the center of the base. And you can also cut small rectangles (1.5x1 cm) from the copper lamina and paste them I the bottom surface of the arms of the base (one rectangle in each arm).

The 3D part files are included in this page.

COILING

The coiling will be done in the stator. For this you will need to wrap the enameled copper wire around the arms of the stator 3D printed. To do this hold one end of the copper wire and leave a margin of about 10 cm, from this point you can start coiling one of the arms of the stator. Try to make the coil as organized as you can, it is recommended to start at the inner most part of the arm, and coil 100 loops while moving towards the outer most part, then coiling again 100 loops while moving inwards (all in the same arm), it is important to count the number of loops while coiling, and to finish coiling the arm in the inner most part. It is essential for the functionality of the project that you remember in which way this was coiled. Then (still using that same string of wire, DO NOT CUT IT) once the 200 loops for that arm have been coiled, you will skip the adjacent arm and start coiling the next one (you will be coiling every other arm). However, this time you will need to change the direction of your coiling (which means that if the previous arm was coiled clockwise, the present arm will be coiled counterclockwise, and vice versa). After you coiled 6 arms wit 200 loops each, you will need to leave again 10 cm of margin and cut the wire string.

Repeat the process with a second string of copper wire, coiling the remaining 6 arms.

After this you should have four end of wires (two pairs, one pair for each string of wire). Now is time to fit the stator in the base, and to pass those four ends of wire through the openings at the bottom of the base. The 10 cm margin may be excessive, so it is probably better to cut the wires’ ends closer to the bottom, and leaving only about 1 cm protruding from the bottom. Gently, with sand paper, remove the coating from the ENDS (those protruding segments) of the copper wire until you can see the copper. Place each one of those ends over the copper lamina rectangles at the arms of the base, and solder them to 4 different jumper cables. Each one of those cables now represents one end of a string of wire.

PASTING THE PERMANENT MAGNETS

You will find that the rotor has 12 small
fitting spaces but only 6 of them will be used.

With gloves and the Epoxy you can paste one of the neodymium magnets in one of this fittings, but make sure to know which pole of the magnet is facing inwards. After that, you will skip the adjacent fitting space and paste another magnet into the next space (you will be pasting magnets every other space), but this magnet has to have the opposite pole facing inwards (which means that if the last magnet you pasted had a north pole facing inwards, the present magnet has to have a south pole facing inwards). Repeat the process until you pasted 6 magnets. For this part it is advisable to paste no more than 2 magnets at a time, with at least a 30 minutes of wait until resuming the activity. This is to prevent the magnets from sticking to each other before the epoxy dries.

Once this is done you can put the shaft through the rotor until 3 cm are protruding in the inside of the rotor (the hole in the rotor is tight enough to keep the shaft in place).

Finally fit the shaft in the bearing of the base, with the rotor covering the stator.

Step 3: BOX AND PERIPHERALS SET UP

The motor works with a remote control, which sends a signal to

an IR sensor. The sensor communicates with the Arduino UNO, and this one communicates to a Dual H Bridge that runs the motor.

There is a schematic of the IR sensor connections and a picture showing the Dual H Bridge connections. Notice that the brown wire coming out of the Dual H Bridge turns into the white wire that connects to the Arduino. There are also useful videos (from other authors) under “Useful Resources”.

The four wires coming from the motor, as said before, represent the four ends of the pair of wires that make the coils. You will need to connect the wires pertaining to the same wire string in the same side of the L298N Dual H Bridge (either to OUT1 and OUT2, or to OUT3 and OUT4). Depending on how you wired the motor you may need to rearrange the cables in the outputs, but always keeping each line in opposite sides of the L298N.

The box is mainly to store the circuitry.

In order to have a better reception for the IR sensor, it is placed outside the box and connected to the breadboard by a small hole in the cover of the box which is aligned to the correct pins in the breadboard.

In addition to this, the cover will also need another small opening to pass the cables of the motor through.

Some other openings can be done such as the ones to screw the battery holders, the ones to pass the battery clips through, as well as the ones to allow for the Arduino communication with the computer once it is inside. However, these are not completely necessary since the batteries can be placed inside the box, and the Arduino can be programmed before putting it into the box.

Step 4: PROGRAM

This is the Arduino sketch to run the motor, notice that it requires a library (from another author):

The library can be found in the Makecourse web page (http://makecourse.weebly.com/week9segment1.html), although it was not design in the Makecourse.

The sketch is called Tutorial_IR_Remote5_library, and it is commented for better understanding.

Step 5: Useful Resources

Useful tutorial video for the Dual H Bridge:

Brushless DC Motors: