Before trying very complicated experiments, it’s wise to check the simple things, especially if they don’t take much time. The first thing to check is that your Arduino board works, and the very first example, Blink, is always a good place to start, because you are probably most familiar with it, and because the LED that is already on your Arduino means that you won’t depend on any external components.
Follow these steps before you connect your project to your Arduino. If you’ve already connected jumpers between your Arduino and your project, remove them for now, keeping careful track of where each jumper should go.
Open the basic Blink example in the Arduino IDE and upload it to the board. The onboard LED should blink in a regular pattern.
What if Blink doesn’t work?
Before you start blaming your Arduino, you should make sure that a few things are in order, as airline pilots do when they go through a checklist to make sure that the airplane will be flying properly before takeoff:
- Is your Arduino getting power, either from a computer though a USB cable or from an external power supply? If the green light marked PWR turns on, this means that your Arduino is getting power. If the LED seems very faint, something is wrong with the power.If you are using a computer, make sure the computer is on (yes, it sounds silly, but it has happened). Make sure the USB cable is plugged in all the way on both ends. Try a different USB cable. Inspect the computer’s USB port and the Arduino’s USB plug to see whether there is any damage. Try a different USB port on your computer, or a different computer entirely. If you have lots of USB cables on your workbench, make sure that the one plugged into your Arduino is the one that is plugged into the computer (yes, we’ve done this).If you are using external power, verify that the external power supply is plugged in. Make sure your outlet strip or extension cord is plugged in. If you are using an outlet strip with a switch, make sure it’s turned on.(If you are using a very old Arduino, verify that the power selection jumper is in the correct position. Modern Arduinos do this automatically and don’t have this jumper.)
- If the Arduino is brand new, the yellow LED marked L might start blinking even before you upload the Blink example. This is likely the test program that was loaded at the factory to test the board and is OK. But don’t take this to mean that you have uploaded successfully. Change the
delay()values to 100 to make the blinking faster and verify that you can upload successfully. - Verify that the sketch uploaded successfully.If upload failed, check first that your program has no errors by clicking Verify.
Try uploading again. On rare occasions, an upload will fail for no apparent reason, and will succeed the next time without changing anything.
Make sure you selected the proper board in the Tools menu. As you start to accumulate different Arduino boards, it’s a good habit to always make sure that the board selected is indeed the one you have connected.
Check that the port in the Tools menu is selected properly. If you unplugged your Arduino at some point, it might appear on a different port.
Sometimes you have to unplug the Arduino and plug it in again. If you have the Serial Port selection menu open, you have to close it (just move to another tab) and then go back to Tools→Serial Port and select the proper port.
Poor-quality USB cables can sometimes prevent the driver from finding the Arduino Uno. If your Arduino port doesn’t show up in the Port list, try using a known good USB cable.
Once you have the basic Blink example loaded and the LED blinking, you can be confident that your Arduino has basic functionality, and can proceed to the next step.
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