Servo-control for generator start

   //   20180120 - no FREQ output D5

#include <LiquidCrystal595.h>
#include <Servo.h>

Servo myservo;  

int potpin = 0;  // analog pin A0 for pot
int val;         // variable to read the value from the analog pin
 
LiquidCrystal595 lcd (7, 8, 6);

const int ledPin = 13 ;
int ledState = LOW ;
long previousMillisA = 0 ;
long wait = 400 ;

float  FREQ = 0 ;
//  float  Freq = 0 ;

#define MainPeriod 400    // was 1000

long previousMillis = 0 ; 
volatile unsigned long duration = 0 ;
volatile unsigned int pulsecount = 0 ;
volatile unsigned long previousMicros = 0 ;


void setup()  {
  
  pinMode   (ledPin, OUTPUT) ;
  pinMode   (FREQ,   OUTPUT) ;
  myservo.attach  (10);                 // connects the servo to pin 10 
  
  lcd.begin  (20, 4);

  attachInterrupt  (0, myinthandler, RISING) ;  // input D3 
}

void loop() {
  
  val = analogRead (potpin);            // reads the value of the potentiometer (value between 0 and 1023)
  val = map  (val, 0, 1023, 0, 180);     // scale it to use it with the servo (value between 0 and 180)
  myservo.write (val);                  // sets the servo position according to the scaled value
  delay   (15);                           // waits for the servo to get there

   unsigned long currentMillisA = millis();
 
  if  (currentMillisA - previousMillisA > wait) {
    previousMillisA = currentMillisA;   

    if (ledState == LOW)
      ledState = HIGH;
    else
      ledState = LOW;
    digitalWrite (ledPin, ledState);
  } 
 
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= MainPeriod)
  {
    previousMillis = currentMillis;        
    unsigned long   Aduration = duration;
    unsigned long   Apulsecount = pulsecount;
    duration = 0; 
    pulsecount = 0;
    
    float Freq = 1e6 / float(Aduration);    

    Freq *= Apulsecount;                
    
   FREQ = Freq ;
   if  (isnan (FREQ))  FREQ = 0 ;   // to remove "nan" when near 0
   
   digitalWrite  (5,  FREQ) ;
    
    lcd.setCursor  (2, 0) ;
    lcd.print (Freq) ;             // for testing only - shows "nan"
    lcd.setCursor  (2, 1) ;
    lcd.print  (FREQ) ;             
      }
}
void myinthandler() 
{
  unsigned long currentMicros = micros();
  duration += currentMicros - previousMicros;
  previousMicros = currentMicros;
  pulsecount++;
}

[CODE]       
//   20180120 - no FREQ output D5
//   20180121 - remove led

#include <LiquidCrystal595.h>
#include <Servo.h>

Servo myservo;  

int potpin = 0;  // analog pin A0 for pot
int val;         

LiquidCrystal595 lcd (7, 8, 6);

long wait = 400 ;

float  FREQ = 0 ;

#define MainPeriod 400    // was 1000

long previousMillis = 0 ; 
volatile unsigned long duration = 0 ;
volatile unsigned int pulsecount = 0 ;
volatile unsigned long previousMicros = 0 ;


void setup()  {
  
  pinMode   (FREQ,   OUTPUT) ;
  myservo.attach  (10);                 // connects the servo to pin 10 
  
  lcd.begin  (20, 4);

  attachInterrupt  (0, myinthandler, RISING) ;  // input D3 
}

void loop() {
  
  val = analogRead (potpin);            // reads the value of the potentiometer (value between 0 and 1023)
  val = map  (val, 0, 1023, 0, 180);     // scale it to use it with the servo (value between 0 and 180)
  myservo.write (val);                  // sets the servo position according to the scaled value
  delay   (15);                           // waits for the servo to get there

  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= MainPeriod)
  {
    previousMillis = currentMillis;        
    unsigned long   Aduration = duration;
    unsigned long   Apulsecount = pulsecount;
    duration = 0; 
    pulsecount = 0;
    
    float Freq = 1e6 / float(Aduration);    

    Freq *= Apulsecount;                
    
   FREQ = Freq ;
   if  (isnan (FREQ))  FREQ = 0 ;   // to remove "nan" when near 0
   
   digitalWrite  (5,  FREQ) ;
    
    lcd.setCursor  (2, 0) ;
    lcd.print (Freq) ;             // for testing only - shows "nan"
    lcd.setCursor  (2, 1) ;
    lcd.print  (FREQ) ;             
      }
}
void myinthandler() 
{
  unsigned long currentMicros = micros();
  duration += currentMicros - previousMicros;
  previousMicros = currentMicros;
  pulsecount++;
}

/*
Thank you Leifjoha for this simple frequency counter that he left in the comments here:
https://circuitdigest.com/microcontroller-projects/arduino-frequency-counter-circuit
You made one measuring of time and then display the floating number of frequency. 
You will get a more correct measuring as an average of several measuring's. 
I have placed a for .. until loop with counter to 1000 and add up Ttime in variabel 
Tsum and then calculate frequency from Tsum/1000. 
You can also convert this frequency to an integer if you like frekvens=long(frequency+0.5);

I have a better way don't use pulseIn() function because this is an indirect way and 
have many complicated process's , but count the number of transitions from HIGH to LOW 
(or LOW to HIGH) in a second that is frequency.

**Frequency counter - count the number of trasitions from HIGH to LOW in a second.

Modified to operate an RC servo from 0 degrees to 180 degrees on pin 9, 
corresponding to a frequency input of 0 to 4000 Hz on pin 8. 
DNA-Robotics.com

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

long frekvens;//storing frequency - danish for frequency
long number; // counter for transitions
long time1; // starttime for 1 second in micros()
long time; // measering time in micros()

void setup()
{
pinMode(8,INPUT); //impuls ind p� digital ben nr 8
myservo.attach(9);  // attaches the servo on pin 9 to the servo object
Serial.begin(9600);//initialize the serial
}

void loop()
{
  number=0;
  time1=micros();
  do
  /* loop for one second*/
  {
    if (digitalRead(8)==HIGH)
    {
      do
      {
      /* empty loop waiting for transition*/
      }
    while (digitalRead(8)==HIGH);
    /* now from HIGH to LOW */
    number++;
    }
  time=micros();
  }
while (time<(time1+1000000));
  Serial.print(number);
  Serial.println(" Hz");
  number = map(number, 0, 4000, 0, 180);     // scale it to use it with the servo (value between 0 and 180) 
  myservo.write(number);                  // sets the servo position according to the scaled value 
  delay(15);                           // waits for the servo to get there 

//delay(1000);
}