Now we are ready for the moment of truth, it's time to plug your Arduino in and power it up. The easiest way to do this is to plug one end of the USB cable into the Arduino and the other end into a computer. The computer will then power the Arduino.
For an Arduino UNO, you'll need a USB cable with a square B-type end:
Make sure that the USB cable is plugged in directly to a computer port. Sometimes monitors or keyboards have a USB port you can plug into. Most of the time this is fine, but I strongly suggest you plug it directly into the computer as that will eliminate any possible problems. Same goes for USB hubs - skip those for now and go direct
Later on, once you've verified you can power the Arduino and upload sketches no problem, then you can try plugging it into other ports.
OK anyways, so plug int he USB cable and check that your Arduino looks like this:
In particular, make sure the green ON LED is lit! The yellow or red L LED might also be lit or blinking, and the RX and TX LEDs might be blinking or lit right after plugging in - this is normal.
If no lights or blinking occurs, double check:
- Is the USB cable plugged into the computer and into the Arduino?
- Try another USB cable
- Check there's nothing metallic touching the Arduino that could be shorting out the device
- Is the computer on?
- Try another USB port, USB cable, and computer?
If you still can't get it working, your Arduino may be faulty.
Next up, you can do a quick bootloader test - this will let you know that the Arduino chip has been programmed with a bootloader which is required!
While powered, click the Reset button - you will see the L LED blink 3 times very rapidly. Don't worry about counting the blinks, just make sure it flashes quickly when reset.
Another way to power up the Arduino is to plug in a battery or wall adapter into the DC jack.
Verify that you have a 9V DC 100mA or greater power adapter, with a 2.1mm barrel plug and positive tip.
If the box doesn't have any information about the adapter, you can look for these clues.
Make sure the symbol near the bottom of the label is present. It means that the outside of the plug is negative and the inside is positive. A center-negative plug will not work with the Arduino.
To verify the DC plug is the right shape, just try plugging it in. If it doesn't fit or is wobbly, it's the wrong kind. You can learn how to test wall adapters using a multimeter here.
Plug in the adapter and verify you get the green ON light!
If not, double check:
- Is the DC adapter plugged in?
- Is the DC adapter the right kind? Check voltage, polarity, plug size, etc.
- Try another adapter.
If you still can't get it working, your Arduino or wall adapter may be faulty.