int relay=13;
void setup() {
// put your setup code here, to run once:
Serial.begin(9600);
pinMode(relay,OUTPUT);
digitalWrite(relay,HIGH);
}
void loop() {
// put your main code here, to run repeatedly:
int z=Serial.read();
if(z =='a')
{
digitalWrite(relay,LOW);
Serial.println("RELAY ON");
}
if(z =='b')

{
digitalWrite(relay,HIGH);
Serial.println("RELAY OFF");
}
}