const int pin = 4;
const int ch = 0;
const int freq = 50;
const int res = 12;

//adjust the value
int val_close = 175;
int val_open  = 220;

void setup() {
  Serial.begin(921600);
  ledcAttachChannel(pin, freq, res, ch);
  ledcWrite(pin, val_close);
  Serial.print("start setup");

}

void loop() {
   ledcWrite(pin, val_open);
   delay(1000);
   ledcWrite(pin, val_close);
  delay(500);
}