Decode and Send 433 MHz RF Signals with Arduino

This guide shows how to use an Arduino to decode 433 MHz signals from RF remotes, and send them with an Arduino and a 433 MHz transmitter to remotely control mains switches outlets.

Why Decoding RF Signals?

I’ve tried different methods of controlling the mains voltage, but some of the methods require:

• Experience dealing with AC voltage
• Opening holes in your wall/ceiling/switches
• Modifying the electrical panel
• Knowing the electrical rules for each country

It’s difficult to come up with a solution that is safe and works for everyone. One of the easiest and safest ways to remotely control appliances connected to mains voltage is using radio frequency (RF) controlled outlets. Why? Using remote controlled outlets have 5 benefits:

1. Fairly inexpensive
2. Easy to get
3. Works with ESP8266 and Arduino
4. Safe to use
5. Works in any country

Parts Required

For this tutorial, you need the following parts:

• Arduino UNO – read Best Arduino Starter Kits
• 433 MHz RF Remote controlled sockets
• 433 MHz transmitter/receiver
• Breadboard
• Jumper wires

Note: you need to buy remote controlled outlets that operate at a RF of 433MHz. They should say the operating RF either in the product page or in the label.

Example

Here’s how they look:

Setting the RF Channels

I’ve set my remote control to the I position.

The outlets must be both on the I position. I’ve selected channels 3 and 4 for the outlets (you can use any channel you want).

If you plug them to an outlet, you should be able to control the remote controlled outlets with your remote control.

Installing the RC Switch Library

The RC Switch library provides an easy way of using your ESP8266, ESP32, or Arduino to operate remote radio controlled devices. This will most likely work with all popular low-cost power outlet sockets.

1. Click here to download the RC Switch library. You should have a .zip folder in your Downloads folder
2. Unzip the .zip folder and you should get rc-switch-master folder
3. Rename your folder from rc-switch-master to rc_switch
4. Move the rc_switch folder to your Arduino IDE installation libraries folder
5. Then, re-open your Arduino IDE

Opening the Decoder Sketch

You need to decode the signals that your remote control sends, so that the Arduino or ESP8266 can reproduce those signals and ultimately control the outlets.

The library comes with several sketch examples. Within the Arduino IDE software, you need to go to File > Examples > RC_Switch > ReceiveDemo_Advanced. This next sketch opens:

/*
  Example for receiving
  
  https://github.com/sui77/rc-switch/
  
  If you want to visualize a telegram copy the raw data and 
  paste it into http://test.sui.li/oszi/
*/

#include <RCSwitch.h>

RCSwitch mySwitch = RCSwitch();

void setup() {
  Serial.begin(9600);
  mySwitch.enableReceive(0);  // Receiver on interrupt 0 => that is pin #2
}

void loop() {
  if (mySwitch.available()) {
    output(mySwitch.getReceivedValue(), mySwitch.getReceivedBitlength(), mySwitch.getReceivedDelay(), mySwitch.getReceivedRawdata(),mySwitch.getReceivedProtocol());
    mySwitch.resetAvailable();
  }
}

Having an Arduino board connected to your computer follow these instructions:

1. Go to the Tools tab
2. Select Arduino UNO board
3. Select the COM port
4. Press the Upload button.

Decoder – Schematics

After uploading the sketch, connect an 433MHz RF receiver to Digital Pin 2 of your Arduino UNO board:

Decode RF Signals (codes)

Open the Arduino IDE serial monitor and start pressing the buttons.

After pressing each button one time, you can see the binary code for each button (it’s highlighted in red):

Save your binary codes for each button press (you can also use the Decimal or Tri-State codes):

• Button 3 ON = (24Bit) Binary: 000101010101000101010101
• Button 3 OFF = (24Bit) Binary: 000101010101000101010100
• Button 4 ON = (24Bit) Binary: 000101010101010001010101
• Button 4 OFF = (24Bit) Binary: 000101010101010001010100

Save your Pulse Length: 416 Microseconds and Protocol: 1.

Send the RF Signals (codes)

You’ll need to customize the next sketch with your binary codes, pulse length and protocol:

/*
  Based on the SendDemo example from the RC Switch library
  https://github.com/sui77/rc-switch/
*/

#include <RCSwitch.h>
RCSwitch mySwitch = RCSwitch();

void setup() {
  Serial.begin(9600);
  
  // Transmitter is connected to Arduino Pin #10  
  mySwitch.enableTransmit(10);

  // Optional set pulse length.
  mySwitch.setPulseLength(REPLACE_WITH_YOUR_PULSE_LENGTH);
  
  // Optional set protocol (default is 1, will work for most outlets)
  mySwitch.setProtocol(REPLACE_WITH_YOUR_PROTOCOL);
  
  // Optional set number of transmission repetitions.
  // mySwitch.setRepeatTransmit(15);
}

void loop() {
  // Binary code - button 3
  mySwitch.send("000101010101000101010101");
  delay(1000);  
  mySwitch.send("000101010101000101010100");
  delay(1000);
  
  // Binary code - button 4
  mySwitch.send("000101010101010001010101");
  delay(1000);  
  mySwitch.send("000101010101010001010100");
  delay(1000);
}

In my case, the pulse length and protocol looks like this:

// Optional set pulse length.
mySwitch.setPulseLength(416);
 
// Optional set protocol (default is 1, will work for most outlets)
mySwitch.setProtocol(1);

Here’s a binary sender example (you have to replace with your own binary codes):

mySwitch.send("000101010101000101010101");

Sender Schematics

After uploading the sketch to your Arduino board, assemble this circuit:

Both of your outlets should be turning on and off continuously.

Wrapping Up

I hope you’ve found this guide useful. 

You can use the concepts learned in this tutorial with your ESP8266 or ESP32.

Thanks for reading.