Hi,
I'm really new to arduino. I connected 2 leds in a row to an output pin on my arduino uno r3. It's working fine. As I read a led has an internal resistance of 100 Ohm. 2 LEDs in a row should split there 5 V to 2.5V each. This way it should be no problem for the leds, shouldn't it?
Thanks for your help
Worry about your microcontroller. The absolute maximum current for the pins on the Uno is 40 mA but note the datasheet says:
Exposure
to absolute maximum rating conditions for extended periods may affect device reliability.
Really you shouldn't go much over 20 mA. Don't ruin your Uno just to skimp on a $0.02 resistor!
It's not about the controller. If I use a resistor in front of my two LEDs, they are darker.
They are darker because they are operating closer to rated spec. You can go ahead and use them without resistor for very bright light but be mindful this will significantly shorten LED's lifespan.
For breadboard use, this would be fine, it'd be easy to pull dead LED out and replace it. But for soldered in board, you don't want to stress PCB having to desolder old one out and solder in new one every so often.
lordg2009:
As I read a led has an internal resistance of 100 Ohm.
Where did you read that nonsence.
Leo..
Wawa:
Where did you read that nonsence.
On the internet. So it must be true.
PaulRB:
On the internet. So it must be true.
According to internet, Kim Jong-un is the hero and Donald Trump is the evil villain.
wilykat:
According to internet, Kim Jong-un is the hero and Donald Trump is the evil villain.
Much more reliable than the crap about internal resistance in LEDs.
lordg2009:
I'm really new to arduino.
So listen to the expert advice here and not crap from dubious sources. Where did you read this? My guess is on the Instructables site, that is normally crap.
Wawa:
Where did you read that nonsence.
Leo..
Some leds do have an internal resistor, I have never used these myself since they are quite expensive, but I guess the first step would be to figure out if this is the case
Chnek:
Some leds do have an internal resistor, I have never used these myself since they are quite expensive, but I guess the first step would be to figure out if this is the case
Wow they really exist!? That is weird. Here is what I found with a quick Google search.
http://www.mouser.com/ds/2/216/WP7113SGD5V-9485.pdf
lordg2009, could you post the datasheet or where you got these LEDs from? I would be nice to know that it was not merely a coincidence.