the output pins are not effected by serial reading

hello every one :
I’m using arduino Uno to receive and read the sensor data by using serial read and then to control the DC motor speed.
the arduino can receive and read sensor data correctly. but the motor speed is not effected by that data.
can any one guide me to solve this problem.
here is my simple code

const int pwm_motor1 =9;
const int pwm_motor2 =11;
const int dir1 =8;
const int dir2 =12;
void setup()
{
 // Set pin as output for 'M1'
    pinMode(pwm_motor1, OUTPUT);
    // Set pin as output for 'M2'
    pinMode(pwm_motor2, OUTPUT);
    pinMode(dir1, OUTPUT);
    pinMode(dir2, OUTPUT);
      Serial.begin(9600); // Initialize serial port to send and receive at 9600 baud
     
}

void loop()
{
 while (Serial.available()) 
  {
   char angle = Serial.read();
      
      Serial.print(angle);
      
  if(angle >= 0 && angle <= 30)
   
   {
    // write output for 'M1'
    analogWrite(pwm_motor1, LOW);
    digitalWrite(dir1,LOW);
    // write output for 'M2'
    analogWrite(pwm_motor2, LOW);
    digitalWrite(dir2,LOW);
   }
else if(angle > 30 && angle <= 90)
{
  analogWrite(pwm_motor1, HIGH);
    digitalWrite(dir1,LOW);
    // write output for 'M2'
    analogWrite(pwm_motor2, HIGH);
    digitalWrite(dir2,LOW);
   }
}
}

char angle = Serial.read(); // You’re reading in one char at a time
.
.
if(angle >= 0 && angle <= 30) // but yet you are looking for an actual value.
.
else if(angle > 30 && angle <= 90)

You should write a function or something that gets one or two chars and converts them into the values you want.

Please note that angle is a char so if you type 30 angle will be first 3 and thereafter it will be zero.

you must read in multiple characters, convert that into an integer and then you can do the motor math.

void loop()
{
 while (Serial.available()) 
  {
   char angle = Serial.read();
      
      Serial.println(angle);  // <<<<<<<<<<<<<<<<<<<<<< CHANGE THIS LINE TO SEE
      
  if(angle >= 0 && angle <= 30)
   
   {
    // write output for 'M1'
    analogWrite(pwm_motor1, LOW);
    digitalWrite(dir1,LOW);
    // write output for 'M2'
    analogWrite(pwm_motor2, LOW);
    digitalWrite(dir2,LOW);
   }
else if(angle > 30 && angle <= 90)
{
  analogWrite(pwm_motor1, HIGH);
    digitalWrite(dir1,LOW);
    // write output for 'M2'
    analogWrite(pwm_motor2, HIGH);
    digitalWrite(dir2,LOW);
   }
}
}

PS,
using CTRL-T in your IDE before posting, saving or uploading makes your code more readable!

Servo test code that shows how to capture a character string representing a number into a number for use in the code.

// zoomkat 7-30-10 serial servo test
// type servo position 0 to 180 in serial monitor
// for writeMicroseconds, use a value like 1500
// use serial monitor to test

String readString;
#include <Servo.h> 
Servo myservo;  // create servo object to control a servo 

void setup() {
  Serial.begin(9600);
  myservo.attach(9);
}

void loop() {

  while (Serial.available()) {

    if (Serial.available() >0) {
      char c = Serial.read();  //gets one byte from serial buffer
      readString += c; //makes the string readString
      delay(3);
    } 
  }

  if (readString.length() >0) {
    Serial.println(readString);
    int n = readString.toInt();
    Serial.println(n);
    myservo.writeMicroseconds(n);
    //myservo.write(n);
    readString="";
  } 
}

thank u so much for replay actually i have tried some coding to change char into integer but it's not working can i have that coding to see the differences?

mohammed-ali: can i have that coding to see the differences?

Sure, it is common code.

mohammed-ali:
i tried this code but i got error ( invalid conversion from ‘char’ to ‘const char*’)
can you tell me what is my mistake ?

void loop()

{
while (Serial.available())
  {
   char a = Serial.read();
  int angle = atoi(a);
    Serial.print(angle);

A single char is not a string,

so, what should i do? if the data printed in serial monitor in this form -0.24 -0.25 -0.3 -0.3 -0.25 -0.24 -0.23 -0.23 -0.32 -0.37 -0.4 -0.65 -0.93 -1.21 -2.94 -4.8 -5.24

Gather a number into a chr array. When you see a CR that is carriage return, replace that with a null meaning a zero then use atof to convert it into a float variable.