'Servo_Pointer' was not declared in this scope

Question

I can't seem to find the error I made; can anyone help me?

The error message: 'Servo_Pointer' was not declared in this scope

I get the error at the end of the code with the line: Servo_Pointer.write(servo_pos)

The code:

const int photo_left = A0;    // select the input pins for the photoresistor
const int photo_right = A1; 
const int ledPin_1 = 2; // These leds will be used for the testing of the pointing of the servo motor
const int ledPin_2 = 4;
const int ledPin_3 = 7;
const int ledPin_4 = 8;
const int ledPin_5 = 12;
const int photoValue = 0;  // variable to store the value coming from the photoresistor
const int numReadings = 10;
int readings[numReadings];      // the readings from the analog input
int readIndex = 0;              // the index of the current reading
int total = 0;                  // the running total
int average = 0;                // the average

void setup() {
  // declare the ledPin as an OUTPUT:
  pinMode(ledPin_1, OUTPUT);
  pinMode(ledPin_2, OUTPUT);
  pinMode(ledPin_3, OUTPUT);
  pinMode(ledPin_4, OUTPUT);
  pinMode(ledPin_5, OUTPUT);
  Serial.begin(9600);
  #include <Servo.h>
  Servo Servo_Pointer;
  Servo_Pointer.attach(9);
  int servo_pos = 0;
  // initialize serial communication with computer:
  Serial.begin(9600);
  // initialize all the readings to 0:
  for (int thisReading = 0; thisReading < numReadings; thisReading  ) {
    readings[thisReading] = 0;
  }
}

void loop() {
  Servo_Pointer.write(servo_pos); // tell servomotor to go to position in variable 'servo_pos'
  delay(15);          // waits 15ms for the servo to reach the position
  // turn the ledPin on
  delay(15);
}

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– Glorfindel, Commented Nov 10, 2020 at 21:25

Michel Keijzers · Accepted Answer · 2020-11-10 08:29:01Z

3

You should make Servo Servo_Pointer; global, i.e. place it outside the setupfunction, e.g. after the line int average = 0;.

In your code, it is a local variable within the setup function. When this function ends, the local variables within this function (such as Servo_Pointer ) do not exist anymore.

By making the variable global, you can use it anywhere. However, it's not a good coding practice to use global variables when not needed.

A benefit of making the variable global is that you can see the memory consumption of the instance of Servo_Pointer when compiling.

Also see the comment of timemage below: Don't put #include statements in the middle of your code, put them in the beginning of your code.

edited Nov 10, 2020 at 8:29

answered Nov 9, 2020 at 21:23

Michel Keijzers

13k7 gold badges43 silver badges59 bronze badges

1

Might be worth adding that it's at least unconventional to have an #include directive in the middle of your function.

timemage
– timemage

2020-11-10 02:22:58 +00:00
Commented Nov 10, 2020 at 2:22
@timemage Good catch, I did a search on Servo_Pointer missing that line.

Michel Keijzers
– Michel Keijzers

2020-11-10 08:27:27 +00:00
Commented Nov 10, 2020 at 8:27

Add a comment |

sa_leinad · Accepted Answer · 2020-11-14 12:41:18Z

You need to place the decleration outside of your setup() function. In other words, you need to move the following 3 lines and place then above your setup() function:

#include <Servo.h>
Servo Servo_Pointer;
int servo_pos = 0;

Your code should look like this:

#include <Servo.h>

const int photo_left = A0;    // select the input pins for the photoresistor
const int photo_right = A1; 
const int ledPin_1 = 2; // These leds will be used for the testing of the pointing of the servo motor
const int ledPin_2 = 4;
const int ledPin_3 = 7;
const int ledPin_4 = 8;
const int ledPin_5 = 12;
const int photoValue = 0;  // variable to store the value coming from the photoresistor
const int numReadings = 10;
int readings[numReadings];      // the readings from the analog input
int readIndex = 0;              // the index of the current reading
int total = 0;                  // the running total
int average = 0;                // the average
int servo_pos = 0;

Servo Servo_Pointer;

void setup() {
  // declare the ledPin as an OUTPUT:
  pinMode(ledPin_1, OUTPUT);
  pinMode(ledPin_2, OUTPUT);
  pinMode(ledPin_3, OUTPUT);
  pinMode(ledPin_4, OUTPUT);
  pinMode(ledPin_5, OUTPUT);
  Serial.begin(9600);
  Servo_Pointer.attach(9);
  // initialize serial communication with computer:
  Serial.begin(9600);
  // initialize all the readings to 0:
  for (int thisReading = 0; thisReading < numReadings; thisReading  ) {
    readings[thisReading] = 0;
  }
}

void loop() {
  Servo_Pointer.write(servo_pos); // tell servomotor to go to position in variable 'servo_pos'
  delay(15);          // waits 15ms for the servo to reach the position
  // turn the ledPin on
  delay(15);
}

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