Weak Light From LED

<Usual disclaimer about being an Arduino-noobie/software guy - not a hardware tech>

I am working on getting the basic HelloWorld/Arduino version (Blinking LED) working with my new board (that I bought from Sparkfun).

I can download the program etc and get the LED to blink - but the problem is that the light from the LED is extremely faint.

I am using a 220 Ohm resistor - like I have read. I am using output pin 13. I am using the LED blink program from the Arduino examples. I tried two different LEDs with the same results.

I am powering my board with my USB cable.

By way of troubleshooting – I hooked the positive side of the LED up to the 5V pin on the board - and the LED came on very brightly - like I was expecting.

Would pin 13 just not be providing enough current? I need the 220 Ohm resistor – right?

The LED does come on/blink just like it should but it is just barely glowing.

Any pointers/debugging tips appreciated.


Pin 13 has a built-in resistor so you don't need your own to hook up an LED; so if you add your own resistor the light will be relatively faint. On the Arduino NG's an LED is built in as well. You should get a brighter light with another pin.