LED doesn't work on UNO ver 3

I just bought for my 6 yo grandson at Radio Shack the Arduino UNO version 3 to use with the Make It: Robotics. I purchased a 5mm High-Output Infrared LED to use for the blinking light project. I followed the example on the video found on the Maker Shed's web page but no blinking LED attached to 13 and ground but the LED on the board blinked. So, I changed the delay times to ensure it was not an accident and it worked on the LED light on the board but not the LED I attached. I noticed that the LED in the photos on this site used for this first project shows a resistor attached to the long LED lead that plugged into slot 13. Should I have a resistor or am I missing code?


yes, you need a resistor to limit the current going through the led !
220 Ohm will do (190 too, as well as 240 or 330 Ohms) the more the resistor value, the less the amount of current, and the less the brightness (but it will still light enough withe the values above)

But..... an arduino Uno for a 6 years old boy ? :o :o
I doubt it will last long, especially if, as I suspect from your question, you can't help him

I just bought for my 6 yo grandson

Sure you did :wink:

I bought a scope for my wife.

Hi All,
The OP states it's an IR led, which you will not see flashing under normal condidtions, take a look at it with your digital camera to see it flashing.... But yes you still need that resistor.



oups, Cactusface, you're right, I didn't see that ! focused on the "6 yo ...." :grin:
anyway, yes, a resistor is needed :slight_smile:

Should I have a resistor or am I missing code?

You mean you have never used LEDs before?

Classic question! Walk before run and all that. :smiley:

Even if it did work, you would not see infrared .... when was the last time you saw light coming from a remote control?

I bought a scope for my wife.

Did you get tired of her borrowing yours ?