Using pull up resistor to turn LED on dim?

Forum 2005-2010 (read only) Hardware Interfacing
1

My arduino is currently on the repair bench so I cannot test it myself.
Is it possible to set the pull up resistor on a non PWM pin to get three brightness (OFF, LOW, HIGH) of the LED?

2

Well the internal pull-up with input pin mode will enable a small amount of current for maybe high efficiency leds, however when moving to output mode and off there is still the requirement for a current limiting series resistors. So it's worth experimenting with, but probably dependent on what specific led you try.

Lefty

3

2.2K resistor is suitable for regular red LED?

4

2.2K resistor is suitable for regular red LED?

Well 175 ohms will give you 20ma of current, which is the normal max recommended continous current for standard red leds. However even 1,000 ohms will give some small amount of light. 2,2k, I'm not sure, you would have to try it out and see.

Lefty