DistanceBasedServo

Summary

The servo motor is driven and distance is measured by an ultrasonic sensor in this project. The servo swings to 180° if an object is detected within range; otherwise, it returns to 0°. A LED is turned on when an object is detected within range.

void main()
{
  int a;
  int counter;
  TRISB = 0b00000100;           //RB2 as Input PIN (ECHO)
  T1CON = 0x00;                 //Prescaler value set as 1:1

  while(1)
  {
    TMR1H = 0;                  //Sets the Initial Value of Timer
    TMR1L = 0;                  //Sets the Initial Value of Timer

    PORTB.F0 = 1;               //TRIGGER HIGH
    Delay_us(10);               //10uS Delay
    PORTB.F0 = 0;               //TRIGGER LOW

    while(!PORTB.F2);           //Wait for Echo

    T1CON.F0 = 1;               //Timer Starts
    while(PORTB.F2);            //Waiting for Echo goes LOW
    T1CON.F0 = 0;               //Timer Stops

    a = (TMR1L | (TMR1H<<8));   // Read Timer Value.                              

/*
    fosc = 20 MHz
    Internal Clock = fosc/4 = 5 MHz
    Time = (TMR1H:TMR1L)*(1/Internal Clock)*Prescaler
    Time = (TMR1H:TMR1L) * (1/5000000) * 1
    Time_us = Time/5
*/


    a = (a/58.82)/5;            //  Since the meter step interval is 0.2
                                //  microsecond, the counter value was converted to
                                //  microseconds by dividing it into 5.

    a = a + 1;                  //  Distance Calibration (Rounded up because
                                //  a is defined as an integer.)

    if(a>=2 && a<=50)           //  Check if the result is between 2cm and
                                //  10cm.
    {
       PORTB.F3=1;              // LED Turns On
       for(counter=0;counter<50;counter++)  //180 Degree
       {
           PORTB.F4 = 1;
           Delay_us(2200);
           PORTB.F4 = 0;
           Delay_us(17800);
       }

    }else{
        PORTB.F3=0;          //LED Turns Off

        for(counter=0;counter<50;counter++)    //0 Degree
        {
           PORTB.F4 = 1;
           Delay_us(800);
           PORTB.F4 = 0;
           Delay_us(19200);
        }
      }
    }
  }

Needs

Microcontroller (PIC family).

Ultrasonic sensor (HC-SR04, for example).

Servo motor.

LED to provide visual feedback.

Minimum electronics setup (wires, resistors, and a breadboard).

Usage

Connect the ECHO pin and TRIG pin of the microcontroller to the ultrasonic sensor.

Connect the servo motor to the output pin of the microcontroller.

Add an LED for detection indication.

Upload the code to the microcontroller.

Power on the circuit.

According to the measured distance, the servo will turn:

180° if 2–10 cm. 0° otherwise.

Example Output

Object detected within range → Servo turns to 180°, LED ON.

No object nearby → Servo rotates to 0°, LED OFF.