Working with Servos

Simple Servos

A servo is a motor whose rotation can be controlled precisely. Most servos only have a set rotation from around 0 - 270 degrees so they don't do a full rotation or keep turning in one direction. But the benefit of them is that you can get a precise position within their range. To control the position of the servo you pulse for a very precise time in microseconds, this tells the servo which position to move to for example 500 microseconds will set the servo to 0 degrees and 2500 will set the servo to 270 degrees. The servo then moves to the correct location.

Arduino code for controlling servo with an analog sensor (i.e. a slider)

The code below is a very simple example of how to control a servo with an analog input. Servo control to pin 10 and sensor to pin 2.

/**
servo mover
completed at 12:00 4/11/2008
Created by pete-rogers.co.uk
Servo mover moves a servo dependent upon a analog sensor signal from 0 - 1024

Connectors:
Servo to pin 10
Analog sensor to pin 2

**/
//constants
int servoPin = 10;

int sensorPin = 2;
int lower = 1700;
int higher = 2450;


//configerable
int inExtreme = 2500;
int outExtreme = 500;



int sensorNum;
int val;


void setup(){
   Serial.begin(9600);
}

void loop (){
 	delay(20);
 	Serial.println(val); 
  	checkSensor();
 	servoMove();
}//end loop


//checks the sensor and adjusts to servos range
int checkSensor(){
   val = analogRead(sensorPin);
   val = val * 2;
   val = val + 550;
   if(val < lower){
     	val = lower;
   }
   if (val > higher){
     	val = higher;
   }   
}

void servoMove(){
        digitalWrite(servoPin, HIGH);   	// Turn the motor on
        delayMicroseconds(val);        		// Length of the pulse sets the motor position
        digitalWrite(servoPin, LOW);    	// Turn the motor off
        
        
}//end servoMove