SIK Circut 4 Question

Development Boards Arduino
1

I’m working my way through the Circuits in the SIK User Guide, I set up circuit 4 as instructed with two small modifications, one is that I installed one resistor for all of the LEDs and the other is that I Changed the LED Colors from what the SIK Uses To Red, Blue, Green, Yellow, Red, Blue, Green, Yellow. I uploaded the SIK code for circuit 4 and the LEDs Work as expected; except for the blue ones. they turn off when they should be On an turn on when they should be off, Reliably. :-? I tried putting the Blue LEDs in a different pin and they act the same way (off with HIGH and on with LOW) I tried uploading a Simple Code that Should turn the two blue LEDs on (Below) That Didn’t work Either. Ideas? Am I missing Something Obvious?

void setup() 
{
  pinMode(3,OUTPUT);
  pinMode(13,OUTPUT);
  pinMode(7,OUTPUT);
}

void loop() 
{
  digitalWrite(3, HIGH);  //Turns on LED #1 (pin 3)
  digitalWrite(7, HIGH);  //Turns on LED #5 (pin 7)
  digitalWrite(13, HIGH);  //Turns on LED #5 (pin 7)
  delay(2000);
  digitalWrite(13, LOW);  //Turns on LED #5 (pin 7)
  delay(2000);
}
2

one is that I installed one resistor for all of the LEDs

This could turn into trouble. For a beginner, each LED needs it's own resistor. They're only a few cents each.. I am actually surprised they work.. How do you have them connected and what's your power supply? Depending on how you have them connected, this could cause some LEDs not to work. Do some Googling about how to wire LEDs and what they really are.
3

I agree, and pay special attention to the flat edge on the side of the leds, and which pin in relation to that flat edge goes to the Arduino outputpin. And which one goes to the common resistor. One leg is usually longer than the other to make the distinction between the anode and cathode leg. (unless it is clipped off) Make clear photo’s that can show how it is connected, or make similar drawings as in the SIK guide:

https://learn.sparkfun.com/tutorials/si … tiple-leds

4

LEDS Need their own Resistor? :shock:

Oops. :oops:

I had a Jumper from GND on the Redboard to Point (e,30) on the breadboard, I then ran a resistor from (a,30) to the Ground Common. I put the Negative Side of the LED in the Negative Common and Connected the Positive Side (via Jumper Wire) to the pin on the Redboard.

Out of curiosity, Why do they each need their own Resistor?

5

Google “Why does an LED need resistors”

http://electronics.stackexchange.com/qu … ors-in-led