The Radio Frequency RF remote control circuit has wide range of applications and we have been using this in our daily life. And its important for Electronics engineers and hobbyist to understand the operation of RF based wireless remote control to achieve long distant communication. This article brings you brief explanation of RF transmitter and receiver circuits through which you can achieve the long distant communication and also can be used as a RF based wireless remote control.
RADIO FREQUENCY (RF) TRANSMITTER:
The transmitter part of the our wireless remote control comprises of two components a Encoder HT12E and a ASK RF transmitter module which is used for data transmission. The IC HT12E was a Encoder IC which is capable of converting 12 bit parallel data inputs into serial outputs. These 12 bits are classified into 8 address bits(A0-A7) and 4 data bits (D0-D3). The address bits are used to provide secured wireless transmission between the transmitter and the receiver. The address bits used in the transmitter should be similar to the bits used in the receiver part for enabling communication between the Tx and Rx modules. To understand the working of this circuit better i strongly recommend you to go through this article Working of HT12E encoder.
In the above circuit as you can see that the pins D0 to D3 are assigned for the feeding the data into the encoder. The pins can be connected to switches enabling the logic 1 or logic 0 to the Encoder IC. The address pins was grounded and if you want your communication to be secured , vary the address bit values in the encoder and remember to use the same address value in the decoder.
The input data bits are encoded by the IC and it was obtained through DOUT pin of the IC and it can be directly fed into the transmitter module. These transmitter uses ASK signalling scheme for wireless transmission of bits. The Tx module is of various types and you can choose the one which suits your requirements such as distance of transmission and power consumption.
RADIO FREQUENCY RADIO RECEIVER:
The Receiver is comprised of HT12D a matching decoder IC and a ASK RF receiver module for receiving the incoming signal from the transmitter. The HT12D was a matching decoder IC to the HT12E which was consists of similar 8 bit Address bits (A0-A7) and 4 data output pins (D0-D3) to obtain the input data sent through the HT12E IC. For detailed description of this decoder IC check out this article Working of HT12D decoder.
The address bits A0-A7 was connected to ground since the all the address bits in the encoder also connected to the ground. The HT12D IC has a special pin known as VT which gives out high signal when the connection between the transmitter and receiver was established. The Decoder IC checks the address values of the incoming signal and then sends out the high signal to the VT pin, a LED was connected to it for indication of signal connection establishment.
RF TRANSMITTER AND RECEIVER MODULES:
Here is the pin diagram of RF transmitter and receiver modules used in the circuit diagram.
The Antenna size also holds a significant position in a RF based wireless communication link. The suggested Antenna length is 17cm for modules of operating frequency around 433 Mhz. Now your circuit is ready and you can now use it either as Remote control or send simple data through wireless medium.