~ Power Socket Control with Arduino

This post contains some info on how do some basic home automation: it shows how cheap remote controlled power sockets can be managed using a computer. The aim is to power on or power off lights, a stereo or other devices remotely from a command shell.

The solution here uses an Arduino connected to a 433.33MHz transmitter. Via a Ruby script installed on the computer a command is send over serial to the Arduino. Subsequently the Arduino sends the command over the air to the power socket(s). If all goes well the power socket reacts by switching the connecting device on or off.

In the video below the process is shown. The command line interface controls the light via the Arduino. It should show the general idea.

The following Ruby script simply sends the binary control codes to the Arduino. For this type of power socket the code consist of a five bit group code and five bit device code. The Arduino is connected to /dev/tty.usbmodem411.

  















































  
require 'rubygems'
require 'serialport'

group = "11111";

lamp =      "01000" #B
kerstboom = "00100" #C
stereo =    "00010" #D

port = "/dev/tty.usbmodem411"  
baud_rate = 9600  
data_bits = 8  
stop_bits = 1  
parity = SerialPort::NONE


command = ARGV[1] == "on"

device_string = ARGV[0]
device = if device_string == "kerstboom"
    kerstboom
  elsif device_string == "lamp"
    lamp 
  elsif device_string == "stereo"
          stereo
  end

def send(sp,group,device,deviceOn)
  command = deviceOn ? "1" : "0"
  command.each_char{|c| sp.write(c)}
  group.each_char{|c| sp.write(c)}
  device.each_char{|c| sp.write(c)}
  sp.flush
  read_response sp
  read_response sp
end

def read_response(sp)
 response = sp.readline
 puts response.chomp
end

SerialPort.open(port, baud_rate, data_bits, stop_bits, parity) do |sp|
  read_response sp
  send(sp,group,device,command)
end

The code below is the complete Arduino sketch. It uses the RCSwich library, which makes the implementation very simple. Essentially it waits for a complete command and transmits it through the connected transmitter. The transmitter connected is a tx433n

  

































































  
#include <RCSwitch.h>

RCSwitch mySwitch = RCSwitch();

char command[12];//2x5 for device and group + command
int index = 0;
char currentChar = -1;

//the led pin in use
int ledPin = 12;

void setup() {
  //start the serial communication
  Serial.begin(9600);
  // 433MHZ Transmitter is connected to Arduino Pin #10  
  mySwitch.enableTransmit(10);
  //Led connected to led pin
  pinMode(ledPin, OUTPUT);
  Serial.println("Started the power command center! Mwoehahaha!");
}

void readCommand(){
  //read a command 
  while (Serial.available() > 0){
    if(index < 11){
      currentChar = Serial.read(); // Read a character
      command[index] = currentChar; // Store it
      index++; // Increment where to write next
      command[index] = '\0'; // append termination char
    }
  }
}

void loop() {
  //read a command
  readCommand();
  //if a command is complete
  if(index == 11){
    Serial.print("Recieved command: ");
    Serial.println(command);
    char operation = command[0];
    char* group = &command[1];
    //group is 5 bits, as is device
    char* device = &command[6];
    
    //execute the operation
    doSwitch(operation,group,device);
    //reset the index to read a new command
    index=0;
  }
}

void doSwitch(char operation, char* group, char* device){
  digitalWrite(ledPin, HIGH);
  if(operation == '1'){
    mySwitch.switchOn(group, device);
    Serial.print("Switched on device ");
  } else {
    mySwitch.switchOff(group, device);
    Serial.print("Switched off device ");
  }
  Serial.println(device);
  digitalWrite(ledPin, LOW);
}

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