Relay starts trigger about 6 times when connecting arduino to laptop

Question

I have a fairly simple code to turn a relay on-off every 2 seconds When i attach the USB of the arduino Uno to the laptop, it goes into a frenzy and the relay triggers on off for 6 times within 3-4 seconds and then it settles down. This however doesnt happen when connecting directly to the power output.

Is there something that needs to be wired to stop this happening ?

I am using an arduino Uno with a relay JQC-3FF-S-Z connected directly to the arduino pins.

const int ONOFF_TRIGGER_PIN = 2;

void setup() {
  // put your setup code here, to run once:
  pinMode(ONOFF_TRIGGER_PIN, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(ONOFF_TRIGGER_PIN, LOW);
  delay(2000);
  digitalWrite(ONOFF_TRIGGER_PIN, HIGH);
  delay(2000);
}

Answer 1

The markings on your relay suggest the coil is for 5VDC. But you have the coil supply wired to 3V3. Move the coil supply to 5V, and try again.