Monday, October 31, 2011

How to give power to a toy plane with BLDC motors?

How Brushless DC motor fixed to toy airplane





Now we have tried few simple toy plane projects and you have some experience about how to make a toy plane. But still as I promised, we have not make our own toy plane yet. Actually we assembled some ready made toy planes correctly to get clear understanding about flying machine. This experience is really important when you make your own plane, reason is flying it not like any other motions if you made any single mistake your flying machine might not fly or might falling down. But this is not the case with other machines if you get any land vehicle or ship simple mistake will not do any harm to the machine or passenger. To fly any machine, you should make it very correctly and theoretical manner. That is why we go very slowly. But end result will very impressive once your own hand made plane flying.


Brushless DC motor rotor and stator
Today I am going to explain you about very important part of most of the electric toy planes. You might already know that we basically use two method to fly toy airplanes, either using small fuel engine or electro-mechanical method. Fuel engines are more powerful than electric motors, but electric motors are less complex method to use. So that we will first look at electric motors that can be used to make your toy plane. Every type of electric motors are not suitable to use to make your electric toy plane. Selecting a correct type, size and power of the motor is very important and you can not use as you want. Always you need balance the weight, size and power of your plane to fly it smoothly. There are mathematical methods that you can calculate all above features and select correct motor for your purpose. But I am not going to discuss in this article since most of us not very good in maths but we can use our common sense to select and design our plane. The primary problem is selecting a motor with less weight, less power consuming but high torque power. How we can archive all these things. As I mentioned earlier we can not use any type of motor to this purpose. Most of the time we use low voltage DC (Direct current) motors for toy planes. But normally DC motors do not give enough torque power with low voltages. Today we use special type of motors called Brushless DC Motors (BLDC) as high power low voltage motors. It is good to have simple understanding about what is means actually brushless dc motors. In a typical DC motors, there are permanent magnets and a spring armature rotating inside the permanent magnet core. This is totally electromagnetic method. When electricity run into electromagnetic armature, it creates magnetic field and due to that newly created magnetic field armature rotate little to adjust magnetic poles with permanent magnet core. With this 180 degree rotate another coil set of armature will contact with contact terminals and make another magnetic field. This new magnetic field again rotate the rotor or armature 180 degree. This cycle goes forever to rotate your motor rod. But this method has lot of drawback. This method is totally electro-mechanical method. The brushes eventually wear out, they making/breaking connections, you get sparking and electric noise. Also brushes limit the maximum speed of the motor, this motors are get heated very easily and finally brushes limit on how many poles the armature can have. So that typical DC motors are little bulky and heavy power consuming. To overcome most of these problems people introduced brushless motors. Then you don't have all the problem related to brushes, you get very smooth motion with very light power.

Brushless DC motor in computer fan
In brushless DC motors we use power electronic method to control the motion of the motor. We can use small cheap computers and power transistors to replace mechanical brushes and control our motor. In this motor we use same method as typical DC motor but in reverse order. That means we put the permanent magnets on the rotor and move the electromagnets to the stator. Then use a computer (here computer means very small per-programmed chips) to charge up the electromagnets as the shaft turns. Advantages over typical DC motor are as follows. Power electronic controls more precise than mechanical brushes. The computer can also factor the speed of the motor into the equation. This is why brushless motors are more efficient. No sparking and much less electrical noise. No brushes to wear out. These motors are very easy to cool and most them have built in cooling mechanism to long run. Only disadvantage with brushless motors are little expensive than typical DC motors.
Inside of BLDC
How DC motor works
Now you can understand that why brushless DC motors are important to us. Most of the toy plane are in the market use brushless DC motors as high speed, high power motors. These motors are always very small, very light weight and consume very less power. Even in brushless motors category we can find sub categories or different types of motors. Geared DC motors, stepper motors and special purpose motors. These motor types has its own advantages and disadvantages. Within this article series I will cover all these things, but I will more focus on practical implementation of real plane rather than theory parts. But as and when needs I will explain all these theories to have complete knowledge about flying.
Computer controller of BLDC









3 comments:

  1. I don't know anything about these gizmos you guys wanna play with. Powering a toy plane ahahaha etc
    come and say Hi, we could start a stylish friendship
    The Dolls Factory

    ReplyDelete
  2. nice blog checkout mine on

    http://www.onjokes.blogspot.com

    feel free to leave a comment

    ReplyDelete
  3. please tell about mathematic calculations for balance. I want to make a toy plane controlable by a mobile phone. Plz help

    ReplyDelete