int LED_1=3;
 int LED_2=5;
 int LED_3=6;
 int LED_4=9;
 int LED_5=10;

 //设置呼吸灯最大最小亮度
int minBrightness=0;
int maxBrightness=255;


int  a=random(1,20)
//设置呼吸灯的步长和延时时间
int fadeStep=255;
int delayTime=a/10;

void setup() {
  // put your setup code here, to run once:
  pinMode(3, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:

}
void fadeLED(int pin){
//逐渐增加亮度
  for(int brightness=minBrightness;brightness<=maxBrightness;brightness+=fadeStep){
    analogWrite(pin,brightness);
    delay(a);
  }
  //逐渐减小亮度
  for(int brightness=maxBrightness;brightness>=minBrightness;brightness-=fadeStep){
    analogWrite(pin,brightness);
    delay(a);
  }
}