There are different types of remote controlled toys. However, the most famous ones among them are RC cars, perhaps because they are the simplest of all other types. There are some differences in construction of different types of remote controlled toys, models and vehicles but there are some basic components that each remote controlled object must have. These basic elements of a remote controlled object include:
Transmitter: This is essentially the remote control device or simply the remote that you are going to hold in your hand and will use to control the toy. Functionally, it will convert the action you do like pressing a button, moving a joy-stick or turning a dial into appropriate electrical signal and transmit it over a wireless medium (transmission of radio waves) to the toy that you are controlling.
Receiver: This is the other end of the radio interface that will reside on the object you are controlling. The receiver will primarily comprise of an antenna and a circuit board that will be placed on the toy. The antenna will receive the radio waves or the radio signal sent by the transmitter. The electrical circuit board will convert those radio waves into electrical signal. The other section in the receiver will interpret the signals and decide what action to perform.
Actuator: Actuator is the mechanical section of the toy. A common example of an actuator is a motor. The purpose of the actuator is to convert the electrical signal into mechanical motion, so this is the part which will actually make your toy or its parts to move. In simple terms, the receiver will interpret the signals and use them to control the actuator that will eventually control the motion of your toy or any of its part.
Apart from these basic components, actual remote controlled toys will have many more detailed components and parts. These details will broadly vary according the type of toy you are referring to. As you can understand, a remote controlled car will have a completely different construction than a remote controlled airplane or for that matter, a remote controlled motorboat. In fact, even the type of actuators will vary drastically according to the type of toy or model.
Here are some brief descriptions to the type of systems used in different type of RC toys:
- An airplane may not have a motor to drive the propeller as it will be generally be run by a gas-powered engine. However, the actuator that may be in the form of a motor will be used to control the flaps, which incidentally will control the flight of the airplane.
- Similarly, in a sailboat the propelling force is the wind and the remote control is used to control the rudder that determines the direction of motion of the sailboat.
- Blimp requires helium or hot air for the rise or the lift. The small propellers are used to guide and control the motion through the use of remote control.
In some other type of toys that have other functions like holding and lifting, playing sounds, flashing lights etc., there can be other electronic circuit and control systems for those supplementary functions. This is the real beauty of the remote control functionality, as you can add a lot of controls to the device without making it complicated and difficult to handle.
Let’s look at each of these components in detail to learn about the working, construction and capabilities of each of the three basic components of a RC car system.
Transmitter – Remote Control
Transmitter or the remote control is generally the handheld unit of the RC toy system. This is the device that you will hold in your hand and use to control the functions of your RC toy. There can be various input mechanism depending upon the type of control, complexity and degrees of freedom of the RC toy and other factors. Some of the common types of controls include buttons, joysticks and scroll wheels. More advanced controls may also include touch pads or touch interfaces for more convenient and sophisticated control options.
This component is the major differentiating factor between a radio control and a remote control. Though both of these terms are used interchangeably these days, there is a minor difference. Remote control can be any type of control that is exercised from a distance (which may also include a wired medium), whereas, a radio control is specifically related to radio waves, so it is essentially wireless.
The remote control transmitter works by taking the input from user from the input medium. The input is then converted into appropriate electrical signal. To be able to handle multiple controls and use them unambiguously, each different type of input is converted into a unique electrical signal. These electrical signals are converted into radio waves by the antenna, which are incidentally transmitted to the receiver placed in the RC toy. The processing of electrical signals can include multiple steps such as modulation, encoding, encryption etc. depending upon the complexity of the system and level of secure communication required. For example, in a general RC toy, you may not require to do encryption of the signals. However, you need not go deep into these steps if you are not an electronics expert, as these systems will already be inbuilt in the RC toy systems that you use. In case, you are an electronics enthusiast, you can very play around with these circuits and customize them as per your requirements.
The radio control works by battery power that is generally a 9 volt battery. Specific frequency bands have been defined for use in RC toys, so that their functioning doesn’t interfere with any other type of communication. These frequencies are 27 MHz and 49 MHz. Some of the advanced models such as RC planes may even operate in 72 MHz and 75 MHz frequencies.
The complexity of the remote control depends on the number of control that a remote control can handle. The simplest version for an RC car can have only move forward and move backward controls. Most commonly used remote controls for RC cars include these 6 basic controls for cars:
- Forward
- Reverse
- Forward and Left
- Forward and Right
- Reverse and Left
- Reverse and Right
However, more advanced systems that may have other functions such as controlling speed, holding and lifting objects, playing sounds, flashing lights etc. and will require additional controls in the remote control. Further advanced remote controls may even be able to handle multiple toys.
The Toy – Receiver and Actuator
This is the main component of the RC toy system i.e. the actual toy. Though the actual composition and construction of the toy will vary according to the type (such as car, truck, airplane, helicopter, motorboat, sailboat), there are two basic essential components in the system. The first is the receiver which is the counterpart of transmitter and performs exactly the opposite function of what transmitter does. It will receive the radio signals through an antenna and will process and interpret them. The received radio signals will be converted into electrical signals. The processing will perform reverse steps as were done to generate electrical signals in the transmitter. For example, if the transmitter performed modulation, encoding and encryption, the receiver will perform decryption, decoding and demodulation in the appropriate order. Hence, we will obtain a signal that was generated on pressing the input medium. Now, this interpreted signal will be converted into an equivalent actuation signal which will run the actuator like the motor. As the electrical signals are generally at low voltage and current, whereas, the actuators work at higher voltages and currents, power electronics components are used to perform the conversion and drive the actuators. These circuits can control the speed and the degree of movement of the motors for precisely controlled motion of the RC cars.
Obviously, the structure of each different type of toy varies drastically; here we will specifically discuss the structures of RC cars and trucks. Both RC cars and trucks are basically forms of motor vehicles that have a chassis and four wheels (two front and two rear wheels) to drive the vehicle. An RC car or truck can perform basic motions including moving forward, backward, forward-left, forward-right, backward-left and backward-right. There can be various different configurations to make these motions possible. If only backward and forward motion is required, the RC car or truck only contains one motor that can drive either the front or the rear pair of wheels. If you also want to turn the RC car or truck, you will require on more motor which will give the turning motion. This second motor can be used in different configurations. Either you can use two motors to drive the two wheels (either front pair or rear pair) separately, so that the vehicle can turn based on relatively opposite motions of the two wheels i.e.
- if the left wheel moves forward and right wheel moves backward, the vehicle will turn right
- if the left wheel moves backward and right wheel moves forward, the vehicle will turn left
Or, you can drive one pair of wheels with one motor and use the second motor to turn the axle of the other pair of wheels.
Though both of these configurations will solve the purpose of turning the RC car or truck, the turning will not be exactly similar in both the cases with regard to turning radius. Generally, the turning radius of the former configuration will be lesser than the later. So, you will have to keep in mind your requirements and how you want to use your vehicle while designing the construction and choosing one of these configurations. If you have a larger or heavier vehicle, the power requirements will also change drastically in these two configurations. The former configuration of using two motors on different wheels of a pair will generally require less power than the other configuration where the second motor is used to turn the axle of a wheel pair. This is due to the simple fact that in the former case, both the motors are in the drive and therefore, the power of both the motors is spent in driving the vehicle and turning happens as an integrated process of the drive. However, in the second case, only one motor is acting as the drive while other is purely being used for turning purpose. Once the chassis and the drive is built, you can install the receiver of the remote control system on the vehicle.
Based on the complexity of the vehicle, the level of performance and the criticality of the tasks it needs to perform; there will be numerous other details that need to be incorporated into the design, both mechanical and electrical, of the RC car or vehicle. For example, the drive may not be a simple connection of the motor axle with the wheels and may include gear assemblies for providing more torque and controlling the speed. The gears may even be adjustable through remote control to provide more advanced control to the drive.
We will try to understand the working of an RC car in detail through an example how the signals are produced, interpreted and actuated through the components described above.
Suppose that you have a remote control car system having a remote control with four buttons (forward, backward, left and right) and a RC car with two separate motors driving two wheels of a pair independently.
The following table provides a summary of the relation between the input provided by pressing the buttons on the remote control and the action that is performed on the RC car:
| Button Combination | Motion of Car | Action of Wheels | |
| Left Wheel | Right Wheel | ||
| Forward | Forward | Forward | Forward |
| Backward | Backward | Backward | Backward |
| Left | Left | Stop | Forward |
| Right | Right | Forward | Stop |
| Forward + left | Left Forward | Backward | Forward |
| Forward + Right | Right Forward | Forward | Backward |
| Backward + left | Left Backward | Forward | Backward |
| Backward + Right | Right Backward | Backward | Forward |
In this configuration, you may not be able to control the speeds of the individual motors, so the turning will always be on a single radius.
When any particular button is pressed, the transmitter will generate a signal. The signal can be implemented in many possible forms. For the sake of this example, we will consider signals in the form of pulses which is also the most commonly used type of signaling. This is because using pulses is the mostly easily implemented form of signaling. A pulse is a combination of low and high level of voltage as depicted.
The frequency of the pulse is determined by the number of pulses generated in a second. Therefore, a pulse frequency of 27 MHz will mean that 27,000,000 pulses will be generated in one second. Accordingly, the duration of each pulse will be 1/27,000,000th of a second. The duration of a pulse (t) and the pulse frequency (f) are related mathematically as:
F = 1/t
One simple way of converting the press of a button to a signal is by specifying the number of pulses for each action. An exemplary combination can be:
Forward: 8 pulses
Backward: 16 pulses
Forward-left: 24 pulses
Forward-right: 32 pulses
Backward-left: 40 pulses
Backward-right: 48 pulses
This is just an example but the system you purchase may have any other combination or you may be able to define your own rules if you are constructing your own system. So, accordingly when a button is pressed on the remote control, the appropriate number of pulses will be generated by the transmitter. You can call this set of pulses a packet. Generally, each signal packet also comprises some start and end pulses that are different in frequency from signal pulses and are used to denote start and end of an action, so that the receiver can easily understand what action to perform. Otherwise, the signal will just be a continuous chain of similar pulses, which will make it impossible for the receiver to understand when to change the action.