How Do RC Transmitters and Receivers Work?

Under radio control, we mean a system that allows controlling different models (planes, gliders, cars, boats, etc …) wirelessly.

The remote control is used to drive the car. It contains an electronic circuit, the transmitter, which transforms the actions of the driver on the joysticks or the steering wheel of the remote control into radio signals sent to the radio receiver of the car.

The whole system is composed of:

• a transmitter,
• a receiver,
• several control elements that are installed in the model.

The transmitter

The transmitter transforms the commands given to the control sticks into signals and transmits them to the model.

Each lever is mechanically connected to a potentiometer. When moving the lever, the axis of the potentiometer is turned.

A potentiometer is an electrical circuit that transforms the position of the rod into an electrical signal: an electrical resistance. The potentiometer thus gives the electrical measurement of the part of the lever to the electronic circuit of the remote control.

The radio

When the antenna of the remote control is traversed by a current, it emits electromagnetic waves.

These waves propagate in space and are collected by the receiving antenna (like waves on the sea, but invisible).

The electromagnetic waves generated in the receiving antenna an alternating current of the same frequency as that which travels the transmitting antenna.

The receiver

The receiver located in the model transforms the radio signals sent by the remote control into an electrical impulse, which they are retransmitted to the various control elements.

The control elements

The control elements (servos, drives) thus transmit the pilot commands to the model.

These orders can:

• Result in control surface movements (e.,g. on an airplane, elevator movement up or down, or a car the steering angle of the front wheels). In this case, the control element is a Servo.
• Result in a change of rotational speed of an electric motor, so the speed of the model. In this case, the control element is a dimmer.

The operation is different according to the type of car:

• For a thermal car, there is a receiver battery, a receiver, a servo steering, a servo to adjust the flow of fuel to the engine.
• For an electric car, there is a propulsion battery, a receiver, a steering servo, and a dimmer that controls the amount of electricity sent to the electric motor.

In detail: the operation of the drive

• The drive is an essential element: it connects the motor to the battery and controls the motor according to the signal received by the radio receiver.
• It allows controlling the speed of the electric motor.
• The use of an electronic drive eliminates the servo and the mechanical movement (on old RC cars).
• It allows for linear acceleration and well-controlled braking. Some drives also have a reverse function.

In detail: the operation of the servo motor

The servo or servo motor is a motor coupled to a gearbox (a small set of gears) and a spreader (a rod that pivots), able to maintain a position with a range of -45 ° to + 45 °.

On remote-controlled cars:

• There is always at least one servomotor for the steering. So when you turn the steering wheel on the remote control, the servomotor will follow the movement, and the front wheels will rotate with the same angle.
• There may be others, for gases, brakes …