In the previous post, I described to you the Radio or transmitter, and gave you a basic idea about the different “channels”. (See: Getting to know the “Radio” in Radio Control). In this post I would like to give you a basic idea about how the radio “communicates” with your airplane, and how the “electronics” are set up. There is a lot more in-depth information about each component that I will cover in later posts.
The main parts consist of:
- Electronic Speed Control (ESC)
- Servos (Number depends on the “channels”)
Let us now take a look at each component separately.
The most commonly used and popular batteries for electric aircraft are the LiPo Batteries or Lithium-Polymer batteries. They are lighter and provide much more capacity and voltage compared to the Nickel-cadmium (Ni-Cd) and Nickel-metal-hydride (NiMH) batteries. The LiPo batteries require special chargers and some amount of care to get a long life out of them.
Electronic Speed Control (ESC)
The ESC regulates the speed of the motor. The ESC is plugged into the receiver’s throttle channel and connected between the motor and battery pack. The Battery Eliminator Circuit (BEC) is a built-in feature that allows the ESC to power both the motor and the radio’s receiver with the same battery pack. When the voltage gets too low, the BEC circuit cuts the motor power and keeps the receiver operating properly so the pilot can land the plane.
The most popular type of motor being used for model airplanes today is the Brushless Outrunner Motor. They provide a greater power-to-weight ratio, but cost a little bit more than the traditional brushed motors. Outrunner motors produce a lower rpm, but produce more torque and can drive their propellers directly. This eliminates the weight and complexity of a gear box. The size of the motor is determined by the weight of your model airplane, which determines the size of the propeller. In essence, you need to choose a motor that will be able to generate the required rpm for the propeller. (Note: If this confusing, do not worry, it gets easier to understand when you start building your plane!)
The receiver is one component which you really cannot choose. It comes along with the radio, and works only with that particular radio on a certain pre-defined frequency. It is connected directly to the “servos”, and has a thin single wire antenna that extends outside the airplane. The receiver gets signals from the transmitter when you move a stick/control. These signals are then passed through to the servos, or ESC, which respond appropriately.
The number of servos varies according to the number of channels that the radio has and the model airplane requires. For example, a 3 channel airplane will have 2 servos, one servo connected to the rudder, and one connected to the elevator (P.S. The third channel is for the throttle or ESC). A servo consists of a set of gears that are directly linked to a “servo horn” or “arm”, located at the top of the servo body. The horn/arm connects directly to the control surface (rudder, elevator, etc) of the airplane via a rigid or flexible rod. When the receiver picks up a signal from the transmitter/radio, that signal is sent to the appropriate servo which causes the arm to either push or pull the rod, thus moving the corresponding control surface.
So…that was a primer into the world of RC electronics. This is the basic stuff that you need to know before you fly your first RC airplane. There is a lot of technical details regarding each of these components that you will eventually learn as you progress. Let’s be satisfied with these “appetizers” for the time being.
We are slowly getting towards the point where we start “building” our first model airplane. So, as always, stay tuned and “keep you eye to the skies”!!