Problem with the LED blink example sketch

Projects Programming
1

Hello,
the Blink example sketch should turn on an LED on for one second, then off for one second, repeatedly.
But I can see something different. An LED turns on for one second, then off for one second. It is repeated fifteen times and then an LED blinks three times quickly. It is still repeating.

I have Arduino Uno and I am a beginner.
Thanks for your help.

2

This sounds like it is resetting for some reason. Try changing the delay to slow it down, do you still get the rapid blinks?
It could be your serial port is being polled by the operating system, this would cause a periodic reset. Try running it with the serial monitor open, that will stop the port from being opened / closed.

3
  1. I changed the delay, but it still blinks quickly. The rapid blinking is repeated after about 33 seconds.
  2. When is the serial monitor open, sketch works well.
  3. When I opened the serial monitor during the rapid blinking, I can see this text:
Binary sketch size: 1 084 bytes (of a 32 256 byte maximum)
processing.app.SerialException: Serial port 'COM4' already in use. Try quiting any programs that may be using it.
	at processing.app.Serial.<init>(Serial.java:171)
	at processing.app.Serial.<init>(Serial.java:92)
	at processing.app.SerialMonitor.openSerialPort(SerialMonitor.java:207)
	at processing.app.Editor.handleSerial(Editor.java:2481)
	at processing.app.EditorToolbar.mousePressed(EditorToolbar.java:353)
	at java.awt.Component.processMouseEvent(Component.java:6260)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
	at java.awt.Component.processEvent(Component.java:6028)
	at java.awt.Container.processEvent(Container.java:2041)
	at java.awt.Component.dispatchEventImpl(Component.java:4630)
	at java.awt.Container.dispatchEventImpl(Container.java:2099)
	at java.awt.Component.dispatchEvent(Component.java:4460)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4574)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4235)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
	at java.awt.Container.dispatchEventImpl(Container.java:2085)
	at java.awt.Window.dispatchEventImpl(Window.java:2475)
	at java.awt.Component.dispatchEvent(Component.java:4460)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
4

So, some process on your PC is interfering with the serial port that the Arduino is connected to, causing the Arduino to reset, over and over. You need to figure out what that is, and stop it.

Do you have any bluetooth stuff on the PC? Some bluetooth scanning software is not well behaved (that's polite for "is completely shitty") with respect to how it interferes with other uses of the serial ports.

5

When I opened the serial monitor during the rapid blinking,

Open it before the rapid blinking.

6

It was the Sony PC Companion 2.1.
Thank you both.