Ultrasonic sensor does not work if a relay is NC on arduino

Normally the ultrasonic sensor (HC-SR04 sensor) works as expected, but when I close the relay then it stop working.

The relay is for another job, nothing related to the ping sensor yet..

This is the code:

 * created by Rui Santos, http://randomnerdtutorials.com
 * Complete Guide for Ultrasonic Sensor HC-SR04
    Ultrasonic sensor Pins:
        VCC: +5VDC
        Trig : Trigger (INPUT) - Pin11
        Echo: Echo (OUTPUT) - Pin 12
        GND: GND

#define relay1 10

int trigPin = 11;    //Trig - green Jumper
int echoPin = 12;    //Echo - yellow Jumper
long duration, cm;
String cmd;

void setup() {
  //Serial Port begin
  Serial.begin (9600);

  Serial.println("Initializing Relay...");
  pinMode(relay1, OUTPUT);   

  Serial.println("Initializing Ultrasonic sensor...");
  //Define inputs and outputs
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);


void loop()

  if (Serial.available() > 0) {
    // read the incoming byte:
    cmd = Serial.readString();

    if (cmd == "relayOn"){
      //relay normally closed - ultrasonic sensor stop working here
      digitalWrite(relay1, LOW);       
    }else if (cmd == "relayOff"){
      //relay normally open
      digitalWrite(relay1, HIGH);

  // The sensor is triggered by a HIGH pulse of 10 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  digitalWrite(trigPin, LOW);
  digitalWrite(trigPin, HIGH);
  digitalWrite(trigPin, LOW);

  // Read the signal from the sensor: a HIGH pulse whose
  // duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  pinMode(echoPin, INPUT);
  duration = pulseIn(echoPin, HIGH);

  // convert the time into a distance
  cm = (duration/2) / 29.1;



Please post a wiring diagram (hand drawn, not Fritzing) and be sure to show all the power sources.

Also, post a link to the relay module product page or data sheet -- we need to know its current draw.