In this article we will be learning about the RF transmitter and receiver. We will also be considering some of its applications and features.
From the name, the RF module functions at radio frequency. Its frequency band usually spans between 30 kHz to 300 GHz. This digital data can be represented in the form of variations in the carrier’s wave amplitude in the RF system. Also, this modulation type is Amplitude Shift Keying, denoted as ASK.
The RF Receiver and RF transmitter are found in the RF module. Furthermore, the (Tx/Rx) transmitter/receiver pair’s frequency is 434 MHz. The RF transmitter usually accepts the serial data then delivers it wirelessly through radio frequency through its antenna attached to pin4. This transaction speed falls between zero and ten kilobits every second. The RF receiver which functions at similar frequency with the transmitter usually receives all the data that has been transmitted.
During the sending of logic zero when suppressing a carrier frequency fully, the transmitter usually does not draw any power, also consumes less power in the battery operation. Whenever logic once has been sent, the carrier is completely on to around 4.5mA having a power supply of 3 volts. The data is serially transmitted from a transmitter into a tuned receiver. Also, for the transfer of data, the rf transmitter and receiver will be connected to the two microcontrollers.
This transmitter helps in transmitting encoded serial inputs with the help of radio frequency. Then this Receiver module will receive the entire transmitted signal which is placed at a distance from the transmission source. Therefore, the RF signals will be transmitted at specific frequencies and baud rates.
Note that this RF receiver will only receive the data transmitted when it functions at a similar frequency with the transmitter. This transmitter module features RF tuned circuits as well as OP Amps for amplifying the carrier wave that has been received from the transmitter.
The RF transmitter can be described as a device creating radio signals that contains information whereby when an antenna is used, some distance is propagated. The earliest RF transmitters were known as spark gap transmitters usually found in-between two electrodes for creating RF signals. Just like lighting usually creates static on the radio, this spark gap creates a brief static moment on the receiver. The method was used with Morse code in sending information through via pulses.
The RF transmitters of today, though they are quite different, are usually based on some specific principles like the spark gap transmitters. Rather than spark gap, the modern transmitters make use of tubes or transistors. Also, the circuitry creates the oscillating RF signals at a specific range of frequency, which is carried to the antenna that is tuned so as to match its frequency.
RF Transmitters are utilized in different industries and applications. Usually, devices used with the integrated circuits usually integrate SMT technology, flat pack and THT or through hole technology. In the telecommunications industry, these RF transmitters are mainly designed to fit into a metal rack, which could be installed inside a cabinet.
Also, the RF transmitters are utilized in electronic article surveillance systems and radios which are found in different retail stores. Also, Inventory management systems make use of RF transmitters to serve as a substitute to barcodes.
Other considerations when you are choosing the RF transmitters are RF connectors, supply current, supply voltage, Special features, as well as packaging. Several RF transmitters are audible or visual alarms as well as LED indicators, which signal operating modes of signals like reception or power on.
Some others attach into coaxial cables and feature a port or connector to which you can attach the antenna. Typically, the RF transmitters, which are designed for outdoor uses, feature heavy-duty waterproof designs. Devices having a range of frequency switches and internal calibration are available as well.
The RF transmitters transport information in different ways. The spark gap transmitter carry information by just turning the signals off and on, which is called OOK (or the on off key). However, the modern transmitters achieve this in ways that are more complex.
- Amplitude modulation causes baseband signals to vary the height or amplitude of carrier waves so as to create the right information content.
- With frequency modulation, it causes instantaneous frequency of sine wave carries to leave the center frequency through an amount that is proportional to the modulating signal’s instantaneous value.
- Furthermore, the amplitude shift key helps in transmitting data through the varying of the transmitted signal’s amplitude.
- Frequency shift keys denoted as FSK can be described as digital modulation schemes that make use of at least two output frequencies.
- The Phase Shift Key can be described as digital modulation schemes hereby the transmitted signal phase is varied in line with baseband data signals.
During lots of projects out there, the RF modules are used in transmitting as well as receiving data due to its ability to have a huge volume of applications compared to IR. The RF transceiver module would always function in pairs. This means that it requires both a transmitter and receiver for sending and receiving data. The transmitter will send only the information and the receiver will only be able to receive it. Therefore data can only be sent from one specific end to the other.
Transistor modules are made of three main pins, which include ground, Din, and Vcc. This Vcc pin features a wide input voltage range between 3V and 12V. This transmitter usually consumes at least 9mA of current, and can reach a high 40mA when transmission is ongoing. This center pin can be described as the data pins for transmitting the signal. The signal is modulated utilizing the ASK, which is then sent on the air at a 433MHz frequency.
The RF receiver module features four major pins. These include Ground, Linear out, and Vcc. This Vcc pin has to be powered with a regulated 5 volts supply. This module’s operating current is below 5.5 mA. The Linear out and pins Dout is shorted altogether so as to receive the air’s 433 MHz Signal. The signal would then be demodulated so as to get the specified data and then sent out via the data pins.
In addition, the wireless 434 MHz RF module is majorly an Amplitude superheterodyne Keying ook based module (On-off Keying). The design of the RF module is done with respect to the RF receiver or RF transmitter with functions at a 433 MHz frequency. The RF module is usually used with pairs of encoders/decoders. This can be described as RF encoder and decoder interfacing boards having HT12E and HT12D IC chips.
The HT12E is useful for the encoding of data for the RF Transmitter as well as HT12D, which is used for decoding the data that the RF receiver has received. This module is made up of the SAW resonator that is tuned for the 433.xx MHz function. However, these functions are performed with the help of the switching transistor, as well as some passive components.
- It has a receiver frequency of 433 MHz transmitter
- Low consumption of power
- Operating voltage of the receiver is 5V
- Output power of the transmitter is 4~12 Dbm
- Supply voltage of the transmitter is 3V~6V
- Frequency range of the transmitter is 433.92 MHz
- Typical sensitivity of the receiver is 105 Dbm
- Current supply of the receiver is 3.5mA
Robotic Vehicles (Remote-operated)
This robot can be described as a moving vehicle, which is controlled remotely by a transmitting and receiving unit. For this case, the HT12E encoder that helps in the conversion of 4-bit data into serial output is used. Then the output’s RF module is fed into the HT12D serial decoder integrated circuit, whose output is fed into the first microcontroller pin to the fourth one.
The microcontroller’s transmitting end is then connected onto some pushbutton switches into the 3rd of the 20th pin of the microcontroller AT89C2051.
Robotics Without the Microcontroller Circuit Diagram
The pin14 of the encoder HT12E has low logic signals as the data signals function on the negative logic. This encoder helps in converting parallel signals into serial formats and then transfers them via the radio frequency transmitter at a rate of one to two kilobytes per second. These signals are then decoded into the parallel signals once the receiver receives it.
After inverting the signals, they will be applied onto the motor driver integrated circuit, in order to drive this motor. You can change the directions of the motor by varying those logics applied to the pins 15, 10, 7, 2.
In summary, an RF transmitter can be described as a device creating radio signals that contains information whereby when an antenna is used, some distance is propagated. RF Transmitters are utilized in different industries and applications. Usually, devices used with the integrated circuits usually integrate SMT technology, flat pack and THT or through hole technology.