Radio Frequency Relay Control

ABSTRACT: The RF relay control, as the name suggests, operates at Radio Frequency. The corresponding frequency range varies between 30 kHz & 300 GHz. In this RF system, the digital data is represented as variations in the amplitude of carrier wave. This kind of modulation is known as Amplitude Shift Keying (ASK). Transmission through RF is better than IR (infrared) because of many reasons. Firstly, signals through RF can travel through larger distances making it suitable for long range applications. Also, while IR mostly operates in line-of-sight mode, RF signals can travel even when there is an obstruction between transmitter & receiver. Next, RF transmission is more strong and reliable than IR transmission. RF communication uses a specific frequency unlike IR signals which are affected by other IR emitting sources. This RF module comprises of an RF Transmitter and an RF Receiver. The transmitter/receiver (Tx/Rx) pair operates at a frequency of 434 MHz. An RF transmitter receives serial data and transmits it wirelessly through RF through its antenna connected at pin4. The transmission occurs at the rate of 1Kbps - 10Kbps.The transmitted data is received by an RF receiver operating at the same frequency as that of the transmitter. The RF module is often used along with a pair of encoder/decoder. The encoder is used for encoding parallel data for transmission feed while reception is decoded by a decoder. HT12E-HT12D, HT640-HT648, etc. are some commonly used encoder/decoder pair ICs.

BLOCK DIAGRAM

TRANSMITTED SIDE: RECIEVER SIDE:
CIRCUIT DIAGRAM:

COMPONENTS USED:

• Encoder IC-HT12E

• Decoder IC-HT12D

• RF data transmitter module

• RF data receiver module

• Buffer IC-74541

• Relay driver IC-ULN2803

ENCODER: HT12E is an encoder integrated circuit of 212 series of encoders. They are paired

References: : http://www.circuitstoday.com/remote-control-circuit-through-rf-without-microcontroller#ixzz1YVVT7Q34 : http://jaspreetscodezone.blogspot.com/2008/01/interfacing-relays-using-parallel-port.html#ixzz1YQCdbpTh http://www.circuitstoday.com/remote-control-circuit-through-rf-without-microcontroller#ixzz1YVVhj6ju