我的代码进入if-else语句，但不会在该语句中运行命令

Question

我这部分代码有问题

if ( drop_count > 9 )
{
    time_end = ( millis() ) / 1000;
    //read time final
    //cal final - first
    timereal = time_end - time_start;
    Serial.print( "time = " );
    Serial.println( timereal );
    drop_velo = 720 / timereal;
    Serial.print( "drop velo = " );
    Serial.println( drop_velo );
    Serial.print( "dm = " );
    Serial.println( dm );

    //if(drop_velo<dml||drop_velo>dmh)
    if ( drop_velo != dm )
    {
        Serial.print( "enter if" );
        //digitalWrite(1,HIGH);delay(1000);}
        tone( 1, 800, 1000 );
    }

    drop_count = 0;
}

如果它进入if ( drop_velo != dm )块，它应该打印"enter if"并且蜂鸣器会发出一些声音。可以正常打印"enter if"，但蜂鸣器不起作用。我不知道我在做什么错。我只测试了蜂鸣器，而且效果很好。

这还是我的完整代码：

#include <Wire.h>
#include <LiquidCrystal_PCF8574.h>
#include <Keypad.h>
#include <StepperMotor.h>

LiquidCrystal_PCF8574 lcd( 0x27 );
StepperMotor motor( 10, 11, 12, 13 );
int motorSpeed = 1;
int motorSteps = 30;

#define led 13

const byte ROWS = 4; //four rows
const byte COLS = 4; //three columns
char keys[ROWS][COLS] =
{
    {'1', '2', '3', 'A'},
    {'4', '5', '6', 'B'},
    {'7', '8', '9', 'C'},
    {'*', '0', '#', 'D'}
};
String num;
int ml;
int df;
int m;
int dm;
int dmh;
int dml;
int count = 0;
int analogPin = A0;
int val = 0;
int drop_count = 0;
int drop_velo;
int countWater = 0;
unsigned long time_start = 0, time_end = 0;
int timereal;

byte rowPins[ROWS] = {9, 8, 7, 6}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {5, 4, 3, 2}; //connect to the column pinouts of the keypad

Keypad keypad = Keypad( makeKeymap( keys ), rowPins, colPins, ROWS, COLS );

void( * resetFunc )( void ) = 0;

void setup()
{
    Serial.begin( 9600 );
    pinMode( led, OUTPUT );
    digitalWrite( led, LOW ); // turn off LED
    motor.setStepDuration( motorSpeed );
    pinMode( 1, OUTPUT );
    lcd.setBacklight( 225 );
    lcd.begin( 16, 2 );

    while ( count = '0' )
    {
        lcd.setCursor( 0, 0 );
        lcd.print( "(ml*dropfac)/min" );
        //lcd.setCursor(0, 1);
        //lcd.print("ml,drop fact,min");
        char key = keypad.getKey();

        if ( key == 'A' )
        {
            ml = num.toInt();
            Serial.print( "ml:" );
            Serial.println( ml );
            num = '0';
            lcd.clear();
            lcd.setCursor( 0, 1 );
            lcd.print( "ml:" );
            lcd.print( ml );
            lcd.blink();
        }
        else if ( key == 'B' )
        {
            df = num.toInt();
            Serial.print( "drop factor:" );
            Serial.println( df );
            num = '0';
            lcd.setCursor( 0, 1 );
            lcd.print( "drop factor:" );
            lcd.print( df );
            lcd.blink();
        }
        else if ( key == 'C' )
        {
            m = num.toInt();
            Serial.print( "min:" );
            Serial.println( m );
            num = '0';
            lcd.clear();
            lcd.setCursor( 0, 1 );
            lcd.print( "min:" );
            lcd.print( m );
            lcd.blink();
        }
        else if ( key == 'D' )
        {
            delay( 1000 );
            resetFunc();
        }
        else if ( key == '*' )
        {
            break;
        }
        else
        {
            num = num + String( key );
        }
    }

    dm = ( ml * df ) / m;
    Serial.print( "drop/min" );
    Serial.println( dm );
    lcd.clear();
    lcd.print( "drop/min" );
    lcd.print( dm );
    dmh = 105 / 100 * dm;
    dml = 95 / 100 * dm;
    delay( 5000 );
}

void loop()
{
    pinMode( 1, OUTPUT );
    digitalWrite( led, HIGH ); // shows forward rotation
    motor.step( -motorSteps );
    //Read water
    val = analogRead( analogPin );

    if ( val > 100 )
    {
        drop_count = drop_count + 1;
    }

    Serial.println( drop_count );

    //waterDrop++;
    if ( drop_count == 1 )
    {
        //read time first
        time_start = ( millis() ) / 1000;
    }

    if ( drop_count > 9 )
    {
        time_end = ( millis() ) / 1000;
        //read time final
        //cal final - first
        timereal = time_end - time_start;
        Serial.print( "time = " );
        Serial.println( timereal );
        drop_velo = 720 / timereal;
        Serial.print( "drop velo = " );
        Serial.println( drop_velo );
        Serial.print( "dm = " );
        Serial.println( dm );

        //if(drop_velo<dml||drop_velo>dmh)
        if ( drop_velo != dm )
        {
            Serial.print( "enter if" );
            //digitalWrite(1,HIGH);delay(1000);}
            tone( 1, 800, 1000 );
        }

        drop_count = 0;
    }

    char key = keypad.getKey();

    if ( key )
    {
        if ( key == 'D' )
        {
            delay( 1000 );
            resetFunc();
        }
    }

    lcd.clear();
    lcd.print( "drop velo = " );
    lcd.print( drop_velo );


    delay( 100 );

    /*motor.step(1000);
    delay(2000);
    motor.step(-1000);
    delay(2000);*/
}