Nano pins go low when written as high

[bot51]

I am not sure what the problem is, but when I run the following code, the LED connected to pin 5 does not blink. However, when I turn the LED around. It kind of works, but when the pin is low, the led turns on?! I have tried different variations of the code, different Nanos, different LEDs, but I always get the same result.

The entire circuit is just an LED with its cathode connected through a 220 ohm resistor to ground, and it anode connected to pin D5. You heard that right, the positive side of the LED is connected to ground, and it works!!!

I am not sure why this is happening, but I have been puzzling over it for the past three hours.

#define new_led 5

void setup() {
  pinMode(new_led,OUTPUT);
  Serial.begin(9600);
}

void loop() {
  digitalWrite(new_led,HIGH);
  Serial.println("on");
  delay(3000);
  digitalWrite(new_led,LOW);
  Serial.println("off");
  delay(3000);
}

[LarryD]

Your LED wiring should be either that of D5 or D6.

[bot51]

What do you mean?

[LarryD]

If your LED is wired similar to D5 then you need a LOW on the Arduino output to turn on the LED.

If your LED is wired similar to D6 then you need a HIGH on the Arduino output to turn on the LED.

You decide on what your requirements are

[bot51]

I am still not able to get it to work...

[LarryD]

Please show us a good image of your wiring.

[Paul_B]

More to the point, a good image of your LED.

If it works with the "anode" to negative, then you have clearly mis0identified the anode.

[LarryD]

I worked in a electronics factory 40+ years ago.

Every now and then we would get a run of diodes marked backwards.

Remember one PCB had one of these diodes installed backwards, it was passed in QC, after all it worked.

[bot51]

Which pins have internal pull down resistors?

[bot51]

The entire circuit is just an LED with its cathode connected through a 220 ohm resistor to ground, and it anode connected to pin D5.