Table of Contents
One needs a radio system operating any remote controlled vehicle. The essence of remote control is that one can send radio signals to a matching receiver via a hand-held transmitter, placed onboard the types of remote control cars or any other vehicle. The receiver thus can translate the signals into commands for action and these commands are therefore passed on to the hardwired components for the execution of orders either through mechanical or electronic processes.
Radio System Components
The primary purpose of any communication system is the transmission of intelligence signals from a destination source to another destination located some point away from the source. The system consists of elements like transmitter, receivers, channels, servos and electronic speed control.
The transmitter functions in taking the various positions of the control inputs or channels from the user and encoding them in some other formats. The encoded inputs then concatenate and encode together into packets or frames for getting transmitted or broadcasted via radio frequencies. Transmitters might perform processing on the control input for generating output channels, and in some cases, the channels get synthesized by a combination of inputs.
The transmitter processes the signals or messages into a suitable form for transmitting them over the channels of communication.
The receiver processes the received signals for recovering the proper message signals. The function of the receiver is to listen to the transmissions on any particular channel. On receiving a transmission, it decodes the frame, and each of the frequencies is decoded.
Receivers perform processing to the channels. In case of lack of signals, or receiving an invalid signal from transmitters, special processing may be performed by receivers.
Servos are actuators used for generating the position of channels from electronic outputs with the help of receivers. In fact, any device that generates the appropriate format can be able to control servos too.
Some of the servos might perform processing on the positioning signals for adapting it to any particular situation.
Types of RC Radios
There are seven types of RC radios:
- Radio system components
- Pulse position modulation
- Pulse code modulation
- Digital spread spectrum modulation
- Radio channels
- Helicopter radios
Electronic Speed Control (ESC)
ESC is another component that inputs servo signals and also generates physical output. In this case, it functions in the output voltage for controlling the electric motors in electric power models.
- The digital radio component consists of increased immunity to noise in the channels and the other outside interferences that are impossible to prevent in case of the communication channels.
- It offers flexible operation due to its advanced technology systems.
- Various types of messages and signals can be implemented in the similar format as that of the transmitter.
- The signals can encrypt for providing security for the sensitive database.
- The system is much complex
- Expensive method
Pulse Position Modulation (PPM)
PPM refers to the long-term encoding of the remote-controlled radios. Each of the controls comprises a pulse width that corresponds to the position. All the channels consist of pulses that are linked together in an orderly manner with a standard width of 0 pulses in between them. PPM shows up in servo control signals directly or indirectly. Among the several data encoding and decoding systems in the market, PPM is the oldest one. The system consists of a data frame that contains a synchronizing pulse which is again followed by some shorter pulses that is equal to the number of channels.
- One can inter-operate the transmitter, receiver and the servos for the signals are almost same.
- PPM system is cost-effective
- Different brands of receivers with individual transmitters can be used
- Fast transmission for operating quicker servos
- For its simple composition, errors can hardly get detected
- The receivers of PPM fail to spot the difference between valid and invalid servo pulses
- Servos start malfunctioning due to non-optimal antenna orientation
Pulse Code Modulation (PCM)
The PCM radios use similar frequency spectrum as the PPM ones. The values of individual control are somewhat digitized to bit resolutions (about 10 bits). Then the bits of all channels get concatenated together, and a sync header and checksum is then added. The receiver decodes after getting the frame and then the content goes for verification with the checksum.
- Successful servo movements even in case the model is far away.
- During slight glitches, servo position can be held.
- In case of complete failure of transmitter or disturbances, servos can be moved
- Faster transmission can be used in some cases.
- Servos do not get damaged by short or long pulses as in case of PPM
- Much expensive
- Sensitivity to the adjacent channels gets worse with PCM in comparison to PPM receivers
- One needs to be careful while flying near a transmitter from any adjoining channel
- Receivers of similar brand or transmitter need to be used due to various protocols.
- Transmission quality check is difficult due to small glitches
- Lack of early warnings might be troublesome
Digital Spread Spectrum Modulation
Digital spread spectrum modulation radios in the 2.4 GHz range of frequency and shares frequencies used by Wi-Fi, cordless phones, etc. DSM is the new member of the radio control block. Instead of fixed frequency, the transmitter and receivers are bound to each other remembering each other’s’ addresses. The transmitter turns on for finding channels and the receiver for the transmitters. One thus need not worry about channel confusion in this case.
- Free from random interferences for it has spread-spectrum radio signals
- There is zero possibility of another being on the channel
- A large number of channels
- High rated digital signal
- 4 GHz frequency range eliminates the chance of noise problems
- Shorter wavelength is a big issue
- Signal propagation issues
- Blanking issues by metallic objects
Servos are end units of radio controlled chains. The servos take the signals from the receivers and transform them into physical positions. The position is mainly used for moving and driving something on the model that may be a control surface, power control or some accessory. Servos are however essential for all RC car controller types.
Servos mainly comprise of motor, gearbox, feedback potentiometer and the electronic board placed inside a plastic cased box. The servo arm and servo cable with plugs are also stored outside.
- It is least expensive
- Used for precise angular controlling
- Can be used for continuous rotating movements
- Available in standard sizes
- Need to be modified for continuous rotations
- Demands for special driving circuits