LiuJiajia

About radio control car frequencies and encoders

Every radio control car needs the proper parts to function well. The encoder is an imperative piece. The encoder has the function to take the information that you provide the position of the control levers or buttons to control and produce a coded signal. This signal is a signal feature, which is digital and of low frequency or within the range of the AF, the frequency of the pulses of the radio control car channels is as much 2 KHz. So the stage is also called low-frequency, and then at the stage of the transmitter we talk about the order of several tens of MHz.

The interpretation of the radio control car data can be done in different ways, once in the first radio controls were coded as only a single channel controlled, or at most two. Today it is necessary to control multiple servos and this should be occupying a single frequency of transmission to carry the information of 3, 4, 6 or more channels at the "same time", so it is necessary to encode the position of each of these servos.

The encoding method must be such that the servo should mimic the position of the joystick as closely as possible and with minimum delay. The position is an analog variable; this means that from one point to another there are infinitely many points in between. Then the radio control car encoder must use a method that in addition to carrying 6-channel information, it must be analog and sent to "real time "to the servos (imagine a time delay between when we moved the lever until it" reacts "the servo) would be catastrophic.

Encoding methods used are "Pulse Position Modulation" (PPM) which means pulse position modulation, which is the most widely used by most radio equipment, and is used in all circuits published here, to now.

We also have PCM, "Pulse Code Modulation" or pulse code modulation. Is a type of encoding more complex and usually requires the use of microcontrollers, both the computer transmitter and receiver. It is certainly much better than PPM for several reasons.

Finally the present "Pulse Width Modulation" (PWM) meaning in the Width Modulation Pulse and this is the signal that gives the standard radio control car PWM servo. The servo does not understand anything but this and here is where this whole mess points of the treatment given to the signal.

A signal generator or encoder base should try to achieve the following objectives:

-         Encode the position of a potentiometer in short periods of time.

-         In a transmission of 30ms (max) control several independent channels.

-         To make it as efficient on the information it carries.

-         Send a sync signal to be interpreted in the decoder.

Modular RF stage in both AM and FM signals without producing spurious or take up much bandwidth. It must be easy to introduce pre-programmed radio control car signals. The reality is that the channel used to send many channels is one and the data travels in a bit stream. That is cool information channels sequentially. This means that real time is not as intended, but many times per second.

Article Tags: Radio Control

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