I can't get red LEDs to light up on my ardoino uno r3, any ideas why?

Other Hardware LEDs and Multiplexing
1

[solved ]I have a ardoino uno r3 and am trying to run some LEDs on it, I can get blue and green ones to light up, but can only get the red ones (which are 160 ohms) to light up on pin 2 and 5v. And I have tried with different red LEDs as well.

Any ideas?
All help appreciated.
Thanks.

2

How about posting your code and your schematic?

Otherwise, it's all just guesswork.

3

Bones123:
can only get the red ones (which are 160 ohms)

You can't measure LEDs in Ohms like that. They are semiconductors and don't obey Ohm's law. LEDs are usually measured by their forward voltage (at a given forward current like 10mA), and their maximum forward current (usually 20mA for most 5mm LEDs) and of course their light output (peak wavelength, luminosity etc).

4

Here is my program hope this helps.

int ledPin1 = 2; 
int ledPin2 = 4; 
int ledPin3 = 5; 

int ledPin4 = 6;
int ledPin5 = 7;
int ledPin6 = 8;


void setup()                    // run once, when the sketch starts
{
  pinMode(ledPin2, OUTPUT);      // sets the digital pin as output
}

void loop()                     // run over and over again
{
  digitalWrite(ledPin1, HIGH);   // sets the LED on
  delay(500);                  // waits for a second
  digitalWrite(ledPin1, LOW);
  digitalWrite(ledPin6, LOW);
  digitalWrite(ledPin4, HIGH);
  digitalWrite(ledPin2, HIGH);
  delay(500);
  digitalWrite(ledPin2, LOW);
  digitalWrite(ledPin4, LOW);
  digitalWrite(ledPin3, HIGH);
  digitalWrite(ledPin5, HIGH);
  delay(500);
  digitalWrite(ledPin3, LOW);
  digitalWrite(ledPin5, LOW);
  digitalWrite(ledPin6, HIGH);
  
}
5

pinMode(ledPin2, OUTPUT);

Must set ALL ledPins to output, not just one.
Leo..

6

(hand waving in air) pick me... pick me!

Bones123:
I can get blue and green ones to light up, ... to light up on pin 2 and 5v.

reason:

void setup()                    // run once, when the sketch starts
{
  pinMode(ledPin2, OUTPUT);      // sets the digital pin as output
}
  
}

Shouldn't the other pins be declared as outputs?
cuss- Wawa beat me to it - lol.

7

Thank you all so much. I tried setting all the relevant pins to output, and because of that all the LEDs light up equally as bright.
So thank you all again.
Kip

8

For anyone interested here's my revised program.

int ledPin1 = 2; // LED ball 1 red
int ledPin2 = 4; // LED ball 2 red
int ledPin3 = 5; // LED ball 3 red

int ledPin4 = 6;
int ledPin5 = 7;
int ledPin6 = 8;

void setup()                    // run once, when the sketch starts
{
  pinMode(ledPin1, OUTPUT);      // sets the digital pin as output. 
  pinMode(ledPin2, OUTPUT);
  pinMode(ledPin3, OUTPUT);
  pinMode(ledPin4, OUTPUT);
  pinMode(ledPin5, OUTPUT);
  pinMode(ledPin6, OUTPUT);
}

void loop()                     // run over and over again
{
  digitalWrite(ledPin1, HIGH);   // sets the LED on
  delay(500);                  // waits for a second
  digitalWrite(ledPin1, LOW);
  digitalWrite(ledPin6, LOW);
  digitalWrite(ledPin4, HIGH);
  digitalWrite(ledPin2, HIGH);
  delay(500);
  digitalWrite(ledPin2, LOW);
  digitalWrite(ledPin4, LOW);
  digitalWrite(ledPin3, HIGH);
  digitalWrite(ledPin5, HIGH);
  delay(500);
  digitalWrite(ledPin3, LOW);
  digitalWrite(ledPin5, LOW);
  digitalWrite(ledPin6, HIGH);
  
}