More than less than confusion

Projects Programming
1

When I include an "if" statement with a "more than" or "less than" comparison, the output is opposite of what I intended. For example:

if (number > 20){
digitalWrite(ledRed, HIGH);
}
else{
digitalWrite(ledRed, LOW);
}
}

In this example I want the led to come on when the number is > 20, but it comes on in reverse. If I flip the sign it does what I want, but I would rather the code be correct than have a work around for the result I want. Any suggestions?

2

How have you wired your LED?

3

I'm using the lilypad protosnap. There led is on pin #9. The red comes on all the way up to 20 and at 20 goes off. If I change the ">" to "<" it gives the the desired output.

Here's the full code:

int ledRed = 9;

void setup()
{
Serial.begin(9600); // send and receive at 9600 baud
pinMode(ledRed, OUTPUT);
}

int number = 0;

void loop()
{
Serial.print("The number is ");
Serial.println(number); // print the number

delay(1000); // delay half second between numbers
number++; // to the next number

if (number > 20){
digitalWrite(ledRed, HIGH);
}
else{
digitalWrite(ledRed, LOW);
}
}

Thanks for the help.

4

I think it would make more sense to increment number before you print its value out. Also, the LED will be on forever once it increments past 20.

5

You need to build a simple script that does nothing more than set the LED pin HIGH. Does the LED come on, then, or go off? It sounds like you have the LED wired wrong.

6

I think the LED is probably wired in a desirable way but that it goes on when the input is low and off when high.

7

Just ran the simple code to turn it on and off, and LOW is on while HIGH is off. I guess it is reversed on the protosnap board. Thanks for the help.