lighting up two leds at a time

Projects Programming
1

i have this code for a traffic light system and im trying to make 2 leds of one colour light up at the same time

this code gives me an error, im sure this isnt the way to do it but i dont know any other way as im not familiar with arduino code

int redone = 13;
int redtwo = 10;
int redthree = 7;
int redfour = 4;//defines pin number for each colour
int amberone = 12;
int ambertwo = 9;
int amberthree= 6;
int amberfour = 3;
int greenone = 11;
int greentwo = 8;
int greenthree = 5;
int greenfour = 2;

void setup(){ //this section of code only runs once
pinMode(redone, OUTPUT);
pinMode(redtwo, OUTPUT); //defines what each pin will be doing
pinMode(redthree, OUTPUT);
pinMode(redfour, OUTPUT);
pinMode(amberone, OUTPUT);
pinMode(ambertwo, OUTPUT);
pinMode(amberthree, OUTPUT);
pinMode(amberfour, OUTPUT);
pinMode(greenone, OUTPUT);
pinMode(greentwo, OUTPUT);
pinMode(greenthree, OUTPUT);
pinMode(greenfour, OUTPUT);
}

void loop() { //this section of code loops continuosly
digitalWrite(redone, redtwo, HIGH); //red on
delay(4000); //wait 4 seconds
digitalWrite(redone, redtwo LOW); //red off |at the same time - no delay()
digitalWrite(greenone, greentwo, HIGH);//green on
delay(5000); //wait 5 seconds
digitalWrite(greenone, greentwo,LOW); //green off
digitalWrite(amberone, ambertwo, HIGH);//amber on
delay(1000); //wait 1 second
digitalWrite(amberone, ambertwo, LOW); //amber off
} //loop is finished, now it restarts

2

You need to call the digitalWrite() method separately for each LED: sequential commands are about 62.5 nanoseconds apart, which makes them essentially simultaneous (port manipulation will get you a more simultaneous command, but it's not really worth it for LEDs).

Not this:

digitalWrite(led1, led2, HIGH);

this:

digitalWrite(led1, HIGH);
digitalWrite(led2, HIGH);
[code]

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3

With the Arduino library digitalWrite() you can only control one pin at a time. You can have a single pin control multiple lights. If the lights draw more power than a single Arduino pin can provide you can use a transistor to act as a current switch.

4

how do i know if i shortcircuited anything :confused:
the code works but none of the leds with resistors

5

Are the resistors connected the right way? That is, the anode/resistor to arduino pin, cathodes to ground?