Project: 11

Introduction:

Wheel based small robots can be controlled with remote control but remote should be connected to robot with a wire. So it can move limited distance. To overcome this limitation we have to remove the wire between robot and remote, but robot should be controlled with same remote. How? Yeah, there is way to achieve this by sending controls through radio frequency (RF) remote control to robot, called as wireless control. Same way as anyone controls robot using wired remote, he can control it using wireless remote using RF technology. The new thing in this project is, total movement controlling of robot like start/stop, forward/reverse etc done through RF remote control.

Description:

In this project two dc motors controlled at a time using wireless transmitter (remote). A receiver circuit consists of RF receiver, decoder, micro controller and a motor driver circuit. This circuit gets control signals from remote wirelessly and controls two DC motors to control movements of robot. So let us see how it is done. Start with collecting all required components and equipments.

Required components and equipments:

Sr. no. Name of component Required quantity

1 RF Tx module(434Mhz) 1

2 RF Rx module(434Mhz) 1

3 HT12E 1

4 HT12D 1

5 LED 1

6 Resistor – 1KΩ (Quarter watt) 12

7 Resistor – 1MΩ (Quarter watt) 1

8 Resistor – 50KΩ (Quarter watt) 1

9 Pushbutton 4

10 DC motors – 2

11 Battery – 9V 1

12 Battery – 12V 1

13 L293D 1

14 Opto-coupler(MCT12E827Q) 4

15 Bread board 3

16 Arduino development board 1

17 connecting wires

Circuit diagram:

To build above circuit follow the step by step procedure

Procedure:

Transmitter section:

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

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

Step3: connect 17 pin to the 2nd pin of RF transmitter, and 14 pin connect to the ground.

Step4: 1-8 pins of HT12E are address pins, all are connected to ground. 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 data output pins 10,11,12,13 of decoder HT12D to the Arduino digital pins as inputs (6,7,8,9), and connect pins 5, 4, 3, 2 of Arduino to 1st pin of each opto-coupler. These pins will drive inputs of motor driver L293D to control 1st and 2nd motors.

Step2: connect 5th pin of each opto-coupler to Vcc and 2nd pin to the ground.

Step3: connect 4th pin of each opto-coupler to the motor driver input pins (2,7,10,15).

Step4: connect pins 3,4,12,13 of L293D to ground and enable pins (1,9) to Vcc (+5V). Pin 16 should be also connected to Vcc as its power supply for chip.

Step5: connect pins 3, 6 of L293D to motor1 and pins 11,14 to motor2. To drive motor with 12V supply, connect the +Ve terminal of 12V battery to the 8th pin of L293D.

Step6: connect 50KΩ resistor between decoder 15 and 16 pins of HT12D.

Step7: connect 14 pin of decoder to the 2nd pin of RF Rx module, and 17 pin connected to the LED indicator (it will glow when signal is received)

Step8: 1-8 pins of HT12D are address pins, they all are connected to ground. Connect pin 18 to Vcc and pin 9 to ground

Step9: 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 is the snap of the transmitter and receiver circuits build on bread board.

Now after building the circuit you are ready to run and test it. For that first understand how it works.

Working:

1. The HT12E encoder inputs are controlled by switches, this parallel data converted by encoder in to serial data and fed to transmitter input pin 2 from the encoder 17th pin.

2. Transmitted data is ASK modulated signal the data present in variations of the amplitude. The receiver within the range can receive the ASK signal and generates serial data same as at transmitter and fed to 14th pin of decoder(HT12D).

3. This serial data is converted in to parallel data by the decoder and the parallel data output is available at 10,11,12,13 pins of encoder.

4. This parallel data is given as input to arduino micro controller and it generates output on 6-7-8-9 pins. This pins are given as input to motor driver L293D through opto coupler

5. Motor driver L293D has two H-bridge circuits in side, each one controls a motor. L293D has two supply pins 16,8, 16th pin is for IC voltage supply and 8th pin is for motors power supply.

6. The decoder pins 10 – 11 controls the motor 1. When 10 and 11 pins are in the combination of logic 00 the motor is stop, if logic combination is 01 then motor rotates in clock wise direction and if logic combination is 10 then motor rotates in anti clock wise direction. Same for motor 2 that is connected to 12 and 13 pins.

7. According to this principle by using microcontroller programming we can decide robot movements like forward , backward, right, left.

8. The logic used by many engineers to write a program for wheel based vehicle is as below:

In above table motor11 motor 12 are Motor 1 connections and motor 21, motor 22 are Motor 2 connections. And ‘0’ equal to logic ‘0’, ‘1’ equal to logic ‘1’.

9. This is wirelessly controlled basic mechanical wheel based vehicle, we can add any other module to improve the applications just like camera, GPS, GSM, etc.

The working is completely based on the program embedded into Arduino. The complete program is as given here.

Troubleshooting:

When I am designing this project I faced a problem. The problem was transmitter signal is received properly but robot was not moving. It was just jerking. The problem was the battery. I used [email protected] amps battery, but 12V@4A or 12V@6A batteries are preferable for this project.

Some of the precautions that you should take while developing the projects are as follows.

Precautions:

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

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. At transmitter side resistor between 15 and 16 pins of HT12E should be between 750MΩ to 1MΩ and at receiver side resistor between 15 and 16 pins of HT12D should be between 30KΩ to 50KΩ.

4. Incase if you want to use any other battery please check the data sheets of HT12E/HT12D before.

5. When connecting L293D take care about power and ground pin connections.

6. Apply 12V at 8th pin of L293D.

Project Source Code

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//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 m11 = 6;
int m12 = 7;
int m21 = 8;
int m22 = 9;
 
void setup(){
  
  pinMode(tx1,INPUT);
  pinMode(tx2,INPUT);
  pinMode(tx3,INPUT);     // decoder output microcontroller reading as input.
  pinMode(tx4,INPUT);
  
  pinMode(m11,OUTPUT);
  pinMode(m12,OUTPUT);
  pinMode(m21,OUTPUT);           // led's as output.          
  pinMode(m22,OUTPUT);
  
  Serial.begin(9600);
}
 
void loop(){
  
  // reading data and storing in avariable for further use.
  int Tx1 = digitalRead(tx1);
  int Tx2 = digitalRead(tx2);
  int Tx3 = digitalRead(tx3);
  int Tx4 = digitalRead(tx4); 
  
   digitalWrite(m11,LOW);
    digitalWrite(m12,LOW);
    
    digitalWrite(m21,LOW);
    digitalWrite(m22,LOW);
    
  
  if (Tx1 == HIGH ){
    
    
    digitalWrite(m11,LOW);
    digitalWrite(m12,HIGH);
    
    digitalWrite(m21,LOW);
    digitalWrite(m22,HIGH);
    
    
   
  } else if (Tx2 == HIGH){
    
    
    digitalWrite(m11,HIGH);
    digitalWrite(m12,LOW);
    
    digitalWrite(m21,HIGH);
    digitalWrite(m22,LOW);
    
    
    
  } else if (Tx3 == HIGH){
    
    
    digitalWrite(m11,HIGH);
    digitalWrite(m12,LOW);
    
    digitalWrite(m21,LOW);
    digitalWrite(m22,HIGH);
    
    
    
    
  } else if (Tx4 == HIGH ){
    
    
    digitalWrite(m11,LOW);
    digitalWrite(m12,HIGH);
    
    digitalWrite(m21,HIGH);
    digitalWrite(m22,LOW);
    
    
  }
 
} 
//Program to 

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