#include <Stepper.h> 

const int analogPin = A0;
const int stepsPerRevolution = 200*4;  
Stepper myStepper(stepsPerRevolution, 8, 7);


void setup() {
  
  myStepper.setSpeed(60);
  Serial.begin(9600);
}

void loop() {
  int analogVal = analogRead(analogPin);

  if (analogVal > 430) { // 2.1V
  myStepper.step(stepsPerRevolution); 

} else if (analogVal <  390) { // 1.9V
  myStepper.step(-stepsPerRevolution); 
}
}