I got a problem with some LED's on my Arduino. The circuit has 4 LEDs (with 150 Ohm resistor) all of them are separately wired to 4 digital pins. 3 of the LEDs are working just fine but the 4th one is not working good. It is not shining bright enough. I measured the voltages of the output pins to gnd: on the 3 working leds I measured about 4.6V. On the not properly working led are just 2.5V. How is that possible? It is connected to a digital pin just like the other ones.
I am using an Arduino Nano. To the nano are not only the leds connected but also an SPI Display, an A/D-Converter, 9 LDR's (4 of them to the A/D-Converter, all of them are wired to a 5 kOhm resistor), and the 4 leds. I attached a picture of the circuit diagram. Is it possible that there is not enough current for the circuit or something like that? But I dont think so. I am using a 5V 2A power cord. 2A should be enough.
I checked in the Code if the pinMode is set to OUTPUT and it is. I switched out the Arduinos but the problem still occured.
The 3 working leds are connected to digital pin 2, 3 and 4. The not working one is connected to d12. Does this affect anything? I cant think of anything else that could be causing that.