Remote Circuit Diagrams

RF Remote Control Circuit for Home Appliances

In this project, I will show you how to design an RF Remote Control Circuit for Home Appliances. Using this circuit, you can control simple home appliances with the help of an RF Remote control.

Outline

  • Introduction 
  • RF Remote Control Circuit Principle
  • Circuit Diagram of RF Remote Control for Home Appliances without using Microcontroller
    • Circuit Components
    • Circuit Design
  • How to Operate this RF Remote Control Circuit?
  • RF Remote Control Circuit Advantages
  • RF Remote Control Circuit Applications
  • Limitations of the Circuit

Introduction 

In a previous post, we learned how to construct an IR Remote Control for Home Appliances. Have you ever attempted to create a wireless communication circuit without the use of a microcontroller? This post will show you how to use RF technology to manage your home appliances wirelessly.

The following is a list of home automation projects that use various technologies.

To construct a wireless remote, we used RF434 MHz modules. We can control the appliances within a 100-meter range using this remote. This project is divided into two components, one for the transmitter and the other for the receiver. We employ an HT12E encoder in the transmitter part and an HT12D decoder in the receiving area.

RF Remote Control Circuit Principle

When we press a key on the remote, the transmitter section emits an RF signal, which is received by the receiver section, which then switches the appropriate appliance.

This system has a four-channel encoder/decoder pair. The four switches provide input signals to the transmitter unit, while the four LEDs corresponding to each switch indicate output signals at the receiver.

Here, the encoder HT12E is used to convert parallel data to serial. This data is transmitted serially to receiver point through RF.

RF receiver receives the data serially and then gives to the HT12D decoder to convert it to the parallel. Four LEDs indicate the received data.

Circuit Diagram of RF Remote Control for Home Appliances without using Microcontroller

Circuit Components

  • HT12E encoder IC
  • HT12D decoder IC
  • RF 434 MHz transmitter and receiver
  • Resistors – 33KΩ, 750KΩ, 1KΩ, 
  • Relay Module
  • Lamp
  • Connecting Wires
  • Breadboards

Circuit Design

HT12E Encoder

This encoder IC is part of the 212 encoder series. This IC is mostly used to connect RF and infrared (IR) circuits. This IC converts a 12-bit parallel signal to a serial signal. There are four data bits and eight address bits in each of the 12 bits.

The transmitter enable pin is located on this IC. The address and data bits are delivered concurrently when the trigger signal is received on this pin. Upon receiving enable, the HT12E begins a four-word transmission cycle. The transmission cycle is repeated until the transmitter enable is reduced to a minimum.

RF Remote Control

HT12D Decoder

This decoder IC transforms serial to parallel input data. The VT (Legitimate Transmission) pin on this IC is high, indicating that the transmission is valid.

The HT12D can decode data in 12 bits (8 address bits and 4 data bits). Until new data is received, the output data remains unaltered.

It’s mostly employed in RF and infrared (IR) circuits. These decoders are mostly used for remote control applications such as burglar alarms, automobile door alarms, security systems, and other similar systems.

For communication, the encoder and decoder should have the same number of address and data bits.

RF Modules (434MHz)

This radio frequency module is used. 30 KHz to 300 GHz is the radio frequency range. The RF modules in this system use ASK (Amplitude Shift Keying) modulation.

RF transmission is superior to IR transmission because RF signals may travel larger distances than infrared signals. RF signals can travel even if there is an impediment, and IR primarily supports line-of-sight mode. In comparison to IR, RF communication is more reliable and powerful.

The frequency of the RF transmitter and receiver should be the same. These modules have a transmission speed of 1Kbps to 10Kbps.

How to Operate this RF Remote Control Circuit?

  1. Connect the circuit as shown in the diagram.
  2. Apply 9V supply to the transmitter and receiver sections.
  3. Press the button at transmitter section; you can observe that the Lamp connected to the relay at the receiver section will turn ON.
  4.  Now disconnect the power supply from transmitter and receiver sections.

NOTE: The data transmitted by default is HIGH, and when the button is pressed, the data is sent as LOW. Because the relay module employed here is an Active LOW relay, the lamp ordinarily remains off (as a HIGH signal is received) until the button is pressed, at which point it turns on (as LOW signal is received and relay is activated).

RF Remote Control Circuit Advantages

  1. Works for longer distances as compared to IR.
  2. RF signals can travel even there is an obstruction between transmitter and receiver.

RF Remote Control Circuit Applications

  • Used for remote control applications like burglar alarm, car door alarm, calling bell, security systems, etc.

Limitations of the Circuit

  • The mode of communication is complex.
  • It is better to use a microcontroller based system

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