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Motors

Brushed DC Motor

Brushed DC motors are one of the most simple and easy to use motors because they don’t require technical skills these motors are widespread and can be seen anywhere around you. They are used in appliances, household appliances, toys and small vehicles (car, truck, mini aircraft). RC Aircrafts especially in helicopters and in small quad Because these motors are easy to connect and control by user or automatically, are the perfect and easiest choice for beginners and amateurs.

Brushed Motor Components

So understand the internal components of Brushed DC motors let’s take a motor like that used in small games which works on voltage (1-6 V).This motor has good RPM and torque. The following picture shows the basic shape of the motor:

you can see for yourself how simple this DC Motor is, as it has just few major components.

Components Discription:
  • Brushes – Supply the motor electric power from 2 Contacts inputs.
  • Contacts – Brings power from the power source.
  • Commutator – Delivers power when the rotor rotates.
  • Windings – Converts electricity to a magnetic field that rotates the axle.
  • Axle – Transfers the motion rotation of the motor to the applications.
  • Magnets – Static magnetic field for the windings to stable motion.
  • Bushing – Ring to less friction for the axle.
  • Can – Hard casing for the internal components of the motor.

Work theory

When the positive cathode has arrived at Contacts Electricity passes to Brushes Then Commutator Delivers power to Windings to generate magnetic field and who is attracted and repulsed with Magnets to rotate rotor. The rotation is repeated as long as electricity is present, To reverse the direction of the axis we change the electrodes and The greater the number of turns windings we can adjust the speed(RPM) better.


Brushed Motor Standards

Now we will study the choice of Brushed DC Motor As per motor standards that fit your aircraft or any vehicle. These standards should be reviewed in order to determine the speed and weight of any vehicle. As we said earlier, the choice of a battery depends on the type of your motor. Generally, there is more than one way to choose the motor, there are criteria set by the companies to estimate the expected load weight of the vehicle (from weight we can choose motor), and also we can see the motor information, manufacturers put us how much this motor can raise the total weight (motor weight, body, Battery, and additional equipment) and we must take a safety factor for the weight of the vehicle so that we can fly or move the vehicle in a fast and strong way, for example, if the vehicle motor can move the weight of 2 kg, we design the weight of the vehicle so that it is 1 kg so that the vehicle in the best condition and speed of flight. The standard:

  1. Voltage Range (V): Motors vary in the amount of operating voltage that can drive the motor rotor, directly affecting the speed and torque.
  2. Motor speed: Number of RPM as the number of revs increases, the speed of the motor increases but this affects the noise and overheating of the motor.
  3. Torque: Of course, the torque with the important parameters in the choice of motors, but this is due to the type of vehicle if the vehicle moving on the ground you need in high torque, but if the vehicle is a plane you need less torque to be able to move the propeller.

Selection 

Choosing the DC Brushed motors easy we can use this major formula to find RPM, torque and Power: 

P= (2 * pi * N * T)/60  ,  where  P: power – N: RPM –  T: Torque – pi=3.14

And we can use tachometer (device for measuring the RPM).

The following table shows some characteristics of commercial Brushed DC Motor:

Type

Rated Voltage (V)

Voltage Range (V)

Rated Load (mNm)

Starting Torque (mNm)

Rated Load Speed (rpm)

PYN13

3.0

0~4.0

0.1 (1gf.cm)

0.4

17,900

PNN3

1.5

0~3.0

0.03 (0.3gf.cm)

0.09

8,200

PNN7

1.5

0~3.0

0.1 (1gf.cm)

0.23

5,600

PNN13

3.0

1.0~4.0

0.15(1.5gf.cm)

0.5~0.6

8900~12000

PKN7

2.0

0~4.5

0.2 (2gf.cm)

0.4~0.6

3790~7050

PKN12

3.0

0~4.5

0.2 (2gf.cm)

0.63~0.9

7250~10540

M1N6

3~5

1.0~6.0

0.2~0.3 (2~3gf.cm)

0.67~2.07

5980~15600

M1N10

2~5

0.5~8.0

0.2~0.3 (2~3gf.cm)

0.78~1.90

3010~11220


Advantages and Disadvantages

Advantages:

  • This motor is easy to control as it is provided with only a positive and negative pole.
  • generate good torque at low-speed RPM.
  • low coast and suitable weight a lot of applications.
  • It does not require a controller so you can use it with the controller or not.
  • Easy to reverse rotation.
  • You can install gearbox to control speed and torque.

Disdvantages:

  • Brushes wear out over time so age is limited.
  • Have high electromagnetic noise and unwanted sound.
  • Exposed to temperature and decreased efficiency.
  • Hard to maintain.
  • limited RPM.

Also, read more about:

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