refining the input from a HC SR04 sensor to a servo

Projects Programming
1

i am attempting to move a servo relative to the input from a HC SR04 sensor.

i have adapted some code from the new ping library and added a couple of lines myself (still a newbe)

the servo moves but erratically and not always in relation to the distance (i.e the sensor max range has been set to 100 cms, therefore i want the servo to go from 0 - 180 degrees as i move closer to the sensor) any ideas?

#include <Servo.h>
#include <NewPing.h>

#define TRIGGER_PIN  13  // Arduino pin tied to trigger pin on the Ultrasonic sensor
#define ECHO_PIN     12  // Arduino pin tied to echo pin on the Ultrasonic sensor
#define MAX_DISTANCE 100 // Sets the maximum ping range (in Centimeters)

Servo myservo;
NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); // NewPing setup of pins and maximum distance

void setup()
{
  Serial.begin(9600);
  myservo.attach(7);
}

void loop(){
  delay(50);
  int uS = sonar.ping();
  Serial.print("Ping: ");
  Serial.print(uS / US_ROUNDTRIP_CM); // Convert ping time to distance in cm and print result (0 = outside set distance range)
  Serial.println("cm");
  int servo = map (uS, 0, 100, 0, 255);
  myservo.write(uS);
}

thanks for looking (and not laughing to hard)

regards

Martin

2

the servo moves but erratically and not always in relation to the distance

Probably because your code has issues.

  int uS = sonar.ping();
  Serial.print("Ping: ");
  Serial.print(uS / US_ROUNDTRIP_CM); // Convert ping time to distance in cm and print result (0 = outside set distance range)
  Serial.println("cm");

Oh, look. Serial output that you didn't share.

int servo = map (uS, 0, 100, 0, 255);

Map the value from the ping sensor to 0 to 255, assuming it is in the range 0 to 100. What happens if it isn't in the range 0 to 100? The output won't be in the range 0 to 255.

  myservo.write(uS);

Not that it matters, since you are not using the output from the map function. Waste to time doing the mapping, isn't it?

3

@mgodsell1973, have you tried a "sweep" program to ensure the servo works the way you expect?