// MCU BASIC: https://www.basic4mcu.com
// DateTime : 2020-09-08 오후 4:20:48
// by Ok-Hyun Park
//
#include <SoftwareSerial.h>
#define BT_RXD 7
#define BT_TXD 8
SoftwareSerial bluetooth(BT_TXD,BT_RXD);
//블루투스
#include <DHT.h>
#define DHTPIN  2
#define DHTTYPE DHT11
DHT dht(DHTPIN,DHTTYPE);
//DHT
#include <Wire.h>
#include "RTClib.h"
RTC_DS3231 rtc;
char          in_data;
unsigned long samplingTime,interval=1000,previousMillis=0;
//통신,RTC
#include <Servo.h>
Servo servo;
int servoPin=10;
int angle=0;
//Servo
#define SensorPin        A0   //pH meter Analog output to Arduino Analog Input 0
#define Offset           0.00 //deviation compensate
#define samplingInterval 1000
#define ArrayLenth       40   //times of collection
int           pHArray[ArrayLenth];
int           pHArrayIndex=0;
float         pHValue,voltage;
//PH
void setup(){
  Serial.begin(9600);
  bluetooth.begin(9600);
  dht.begin();
  if(!rtc.begin()){ Serial.println("RTC를 찾을 수 없습니다."); while(1); }
  if(rtc.lostPower()){
    Serial.println("RTC가 전원이 없습니다.시간을 설정합니다.");
    rtc.adjust(DateTime(F(__DATE__),F(__TIME__))); //rtc.adjust(DateTime(2017,1,27,12,56,0)); 이렇게 설정
  }
  servo.attach(servoPin);
}
//
void loop(){
  unsigned long currentMillis=millis();
  if(currentMillis-previousMillis>interval){ previousMillis=currentMillis;
    DateTime now=rtc.now(); //현재시간을 세팅
    Serial.print(now.year(),DEC); Serial.print('/'); Serial.print(now.month(),DEC);  Serial.print('/'); Serial.println(now.day(),DEC);    //년월일
    Serial.print(now.hour(),DEC); Serial.print(':'); Serial.print(now.minute(),DEC); Serial.print(':'); Serial.println(now.second(),DEC); //시분초
    float h=dht.readHumidity();
    float t=dht.readTemperature();
    Serial.print("습도: ");    Serial.print(h);    Serial.println("%");
    Serial.print("온도: ");    Serial.print(t);    Serial.println(" 'C"); Serial.println();
    bluetooth.print("습도: "); bluetooth.print(h); bluetooth.println("%");
    bluetooth.print("온도: "); bluetooth.print(t); bluetooth.println(" 'C");
    in_data=Serial.read();
    if     (now.hour()==16&&now.minute()==49&&now.second()==10){ servo.write(180); } //각도 180도로 움직임
    else if(now.hour()==16&&now.minute()==49&&now.second()==12){ servo.write(  0); } //각도 0도로 움직임
    else{ servo.write(0); }
  }
  if(millis()-samplingTime>samplingInterval){ samplingTime=millis();
    pHArray[pHArrayIndex++]=analogRead(SensorPin);
    if(pHArrayIndex==ArrayLenth)pHArrayIndex=0;
    voltage=avergearray(pHArray,ArrayLenth)*5.0/1024;
    pHValue=3.5*voltage+Offset;
    Serial.print("pH value: ");    Serial.println(pHValue,2);    Serial.println();
    bluetooth.print("pH value: "); bluetooth.println(pHValue,2); bluetooth.println();
  }
}
//
double avergearray(int*arr,int number){
  int i;
  int max,min;
  double avg;
  long amount=0;
  if(number<=0){ Serial.println("Error number for the array to avraging!/n"); return 0; }
  if(number<5){
    for(i=0; i<number; i++){ amount+=arr[i]; }
    avg=amount/number;
    return avg;
  }
  else{
    if(arr[0]<arr[1]){ min=arr[0]; max=arr[1]; }
    else             { min=arr[1]; max=arr[0]; }
    //
    for(i=2; i<number; i++){
      if(arr[i]<min){ amount+=min; min=arr[i]; } //arr<min
      else{
        if(arr[i]>max){ amount+=max; max=arr[i]; } //arr>max
        else          { amount+=arr[i];          } //min<=arr<=max
      }
    }
    avg=(double)amount/(number-2);
  }
  return avg;
}
int servoPin=10; 
서보모터 핀을 10번이나 11번으로 변경해서 다시 해보세요
millis()함수 및 소프트웨어 시리얼 등에서 타이머를 사용하기 때문에 일부 타이머의 기능에 제한이 생길 수 있습니다.
서보모터도 타이머를 사용합니다.