kofiaddaquay (22) [Avatar] Offline
#1
Was really excited to see my LED light show up. It DID... and then it went out right away.

I thought maybe the USB cables power was too strong, so i switched it to an AC power supply for Arduino... It stayed on for about 10 seconds, then it died (LED was dead after that).

Why is that? Are my LEDs bad or something? i am using 3.3 volts
Lyza Gardner (12) [Avatar] Offline
#2
Hi!

There are several things that could be going on... let's see if we can figure it out.

You say you are "using 3.3V". Do you mean the 3.3V pin on the Arduino Uno?
Don't worry about USB-supplied power being "too strong" for the Uno (assuming the other end is plugged into your computer's USB port or a small USB charger). There is an on-board voltage regulator on the Uno that will take care of regulating the voltage down to its needed 5V.

"Stayed on for 10 seconds and then died" makes me worry that even a short amount of time plugged in without a resistor may have blown your LED. That's more sensitive than I've seen before! Did you try again with a new LED?

Given that it lit up at all, that means the LED was plugged in the correct way (anode in 3.3V, cathode in GND). My hunch is that the LED failed after 10 seconds; 3.3V through an LED without a resistor (as explained in the chapter) is not ideal, but I should expect it to last longer than 10 seconds!

Let me know how you get on! Good luck!