Project: 8

Introduction

The basic RF (Radio Frequency) communication system has RF Tx and RF Rx modules, and RF encoder-decoder chips HT12E-HT12D. Using this model we can control four loads with four switches. If we want to connect more loads then we can use others IC’s like HT640-HT648, but when we want to connect lot of loads and wants to perform different sequence of operations on these loads then these circuits are not suitable. In that case we need micro controller at receiver side. By using microcontroller we can handle lot of loads and perform different sequence of operations e.g. LED, servo motor, DC motor, alarm, speaker, series of LED’s etc.

The new approach in this project is, it uses microcontroller along with HT12D to control more loads and to improve performance.

Description:

In this project, transmitter is same as basic model but receiver has an additional component – a micro controller. It is connected with decoder chip. The data pins of the decoder connected to microcontroller. Different loads (devices like motor, buzzer, alarm, LED etc) are connected to microcontroller. Here in this project I have connected four LED’s as load.

As the data pins of decoder that are connected to micro controller, if any one pin is high then we can assign specific operation in microcontroller program. Based on this logic in this project I have programmed four LED sequence blink operations.

The advantages of using microcontroller are

1. we can increase number of loads

2. we can program different operation on loads

3. we can program different tasks for different loads

Find it interesting? Let us see how it is done. But before starting first, gather require components and other equipments

Required components and other equipments

1. RF Tx module (434Mhz). — 1

2. RF Rx module (434 MHz) – 1

3. HT12E – 1

4. HT12D – 1

5. LED — 5

6. Resistor – 1KΩ (Quarter watt) — 8

7. Resistor – 1MΩ (Quarter watt) — 1

8. Resistor – 50 K Ω (Quarter watt) – 1

9. Battery – 9V — 2

10. Bread board. — 3

11. Pushbuttons — 4

12. 8×1 DIP switches – 2

13. Arduino development board — 1

14. Resistor network 8×1@1K – 2

15. Connecting wires

Circuit diagram:

Now follow the step by step procedure to build the circuit given in above circuit diagram

Procedure:

Transmitter section:

Step1: connect the four push buttons to the data input pins (10,11,12,13) of HT12E, with pull down resistors (1KΩ).

Step2: connect 1MΩ resistor between 15 and 16 pins of HT12E.

Step3: connect 17 pin (Dout) to the 2nd pin of RF Tx module, and connect 14 pin (TE – Transmission Enable) to the ground.

Step4: 1-8 pins of HT12E are address pins, all are connected to ground through 8×1 DIP switch with pull down resistor network (8×1@1KΩ). Pin 18 is connected to Vcc and pin 9 is connected to ground.

Step5: Connect RF Tx module’s pin 1 to the ground, pin 3 to the Vcc and pin 4 to the antenna.

Receiver section:

Step1: connect the four LED’s to the digital output pins (6,7,8,9) of Arduino development board, with current limiting resistors(1KΩ).

Step2: connect HT12D output pins (10,11,12,13) to the Arduino development board digital pins as inputs.

Step3: connect 50KΩ resistor between 15 and 16 pins of HT12D.

Step4: connect 14 pin to the 2nd pin of RF transmitter module, and connect 17 pin to the LED indicator (it will glow when signal is received)

Step4: 1-8 pins of HT12D are address pins, all are connected to ground through 8×1 DIP switch with pull down resistor network (8×1@1KΩ). Connect pin 18 to Vcc and pin 9 to ground.

Step5: Connect RF Rx module’s 1, 6, 7 pins to the ground, pins 4 & 5 to the Vcc and pin 8 to the antenna.

Here are the snaps of the circuit build on bread board

Pictures:

Now let us see how it works.

Working:

1. HT12D output pins are connected to microcontroller digital pins (10,11,12,13) as input pins, and four led’s are connected to the Arduino digital pins as output.

2. When switch1 is pressed at transmitter side, the data sequence sent to the receiver. At receiver side pin 13 of decoder makes 10th pin of Arduino active high. As per program the led’s start blinking from left to right with a delay of 500 milliseconds in between.

3. When switch2 is pressed from transmitter, the data sequence sent to the receiver. At receiver side, pin 12 of decoder makes 11th pin of Arduino active high. As per program the led’s will blink from right to left with delay of 500 milliseconds in between

4. When switch3 is pressed from transmitter, the data sequence sent to the receiver and at the receiver side pin 11 of decoder makes 12th pin of Arduino active high. As per program the led’s will turn ON in sequence and later turns OFF in sequence from left to right with delay of 100 milliseconds in between.

5. When switch4 is pressed at transmitter side, the data sequence sent to the receiver and pin 10 of decoder makes 13th pin of Arduino active high. As per program the led’s will turn ON in sequence from right to left and later it turns OFF in sequence from left to right with delay of 100 milliseconds in between.

6. Without microcontroller we can control (ON/OFF) only one led at a time with one switch, but with microcontroller we can control many leds with one switch and also generate different LED chasing effects with different switches.

Following precautions has to be taken while running and testing the project

Precautions:

1. Address lines should be same at both transmitter and receiver.

2. At transmitter 14th pin of HT12E should be connect to ground or connect a switch between ground and the 14th pin to reset the encoder.

3. In the transmitter circuit the resistor connected between 15 and 16 pins of HT12E should be between 750MΩ to 1MΩ. And at receiver side the resistor connected between 15 and 16 pins of HT12D should be between 30KΩ to 50KΩ.

4. Incase if you want to use any other battery, checkout the data sheet of HT12E/HT12D first.

Project Source Code

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//Program to
 

//decoder 10,11,12,13 output pins connected to arduino 10,11,12,13 digital pins as input.
int tx1 = 10;
int tx2 = 11;
int tx3 = 12;
int tx4 = 13;
//decoder 10,11,12,13 output pins connected to arduino 6,7,8,9 digital pins as input.
int led1 = 6;
int led2 = 7;
int led3 = 8;
int led4 = 9;
 
void setup()
{
  pinMode(tx1,INPUT);
  pinMode(tx2,INPUT);
  pinMode(tx3,INPUT);              // decoder output microcontroller reading as input.
  pinMode(tx4,INPUT);
  pinMode(led1,OUTPUT);
  pinMode(led2,OUTPUT);
  pinMode(led3,OUTPUT);           // led's as output.         
  pinMode(led4,OUTPUT); 
  Serial.begin(9600);
}
 
void loop()
{
  // turn off all the LEDs first
    digitalWrite(led1,LOW);
    digitalWrite(led2,LOW);
    digitalWrite(led3,LOW);
    digitalWrite(led4,LOW);
  // reading data and storing in a variable for further use.
  int Tx1 = digitalRead(tx1);
  int Tx2 = digitalRead(tx2);
  int Tx3 = digitalRead(tx3);
  int Tx4 = digitalRead(tx4);  
  if (Tx1 == HIGH)
{
    digitalWrite(led1,HIGH);
    delay(500);
    digitalWrite(led1,LOW);
    delay(500);
    digitalWrite(led2,HIGH);          // left to right sequence
    delay(500);
    digitalWrite(led2,LOW);
    delay(500);
    digitalWrite(led3,HIGH);
    delay(500);
    digitalWrite(led3,LOW);
    delay(500);
    digitalWrite(led4,HIGH  );
    delay(500);
    digitalWrite(led4,LOW);
    delay(500);
  }
 else if (Tx2 == HIGH)
{
   digitalWrite(led4,HIGH);
    delay(500);
    digitalWrite(led4,LOW);
    delay(500);
    digitalWrite(led3,HIGH);
    delay(500);
    digitalWrite(led3,LOW);                   //right to left sequence
    delay(500);
    digitalWrite(led2,HIGH);
    delay(500);
    digitalWrite(led2,LOW);
    delay(500);
    digitalWrite(led1,HIGH  );
    delay(500);
    digitalWrite(led1,LOW);
    delay(500);   
  }
else if (Tx3 == HIGH)
{
    digitalWrite(led1,HIGH);
    delay(100);
    digitalWrite(led2,HIGH);
    delay(100);
    digitalWrite(led3,HIGH);
    delay(100);
    digitalWrite(led4,HIGH);       
    delay(100);
    digitalWrite(led1,LOW);                  //led’s will on in sequence and later off in sequence  //                                        
    delay(100);                                          //from left to right with 100 milliseconds each//
    digitalWrite(led2,LOW);
    delay(100);
    digitalWrite(led3,LOW);
    delay(100);
    digitalWrite(led4,LOW);
    delay(100);   
  }
else if (Tx4 == HIGH)
{
   digitalWrite(led4,HIGH);
    delay(100);
    digitalWrite(led3,HIGH);
    delay(100);
    digitalWrite(led2,HIGH);
    delay(100);
    digitalWrite(led1,HIGH);
    delay(100);
    digitalWrite(led1,LOW);             //led’s will on in sequence  from right to left and later off
    delay(100);                                    //in sequence from left to right with 100 milliseconds each.
    digitalWrite(led2,LOW);
    delay(100);
    digitalWrite(led3,LOW);
    delay(100);
    digitalWrite(led4,LOW);
    delay(100);
    }
}
###