Problems implementing a counter (Using Arduino Nano v3.1)

Projects Programming
1

Hi guys! I'm having trouble with some code and am hoping somebody could help me out.

What I'm trying to accomplish:
I have 1 digital input (pin 7), 1 digital output (pin 2), and the pin 13 LED also set as an output. What this program should do is turn ON the LED and pin 2 should be set to HIGH when there is no change in the input signal for 3 or more seconds.

For example: If the input is LOW for 3 seconds, both pin 2 and LED should turn ON. However, if the input signal is switching from HIGH to LOW or LOW to HIGH continuously, we want the LED to stay OFF and pin 2 set to LOW.

Current problem I'm running into:
I'm currently connecting my Arduino to a function generator (I'm using square wave pulses to simulate a digital signal). The LED and pin 2 turn off immediately when I power on the function generator which is awesome, but after a short delay, they will turn back on. I've made sure all my physical connections are correct and I believe it is my code that has some kind of problem...

Here's my code:

// these won't change:
int signalIn = 7; // the pin that the input signal is attached to (digital input)
int led = 13; // the pin that the LED is attached to (output)
int signalOut = 2; //the pin that we are setting the output signal to (digital output)

// Variables that will change:
int counter = 0;
int currentState = 0;
int previousState = 0;
int signal = 0;

void setup() {
// initialize pin 7 as an input:
pinMode(signalIn, INPUT);
// initialize the LED as an output:
pinMode(led, OUTPUT);
//initialize pin 2 as an output:
pinMode(signalOut, OUTPUT);
// opens serial port, sets data rate to 9600 bps
Serial.begin(9600);
}

void loop(){

signal = digitalRead(signalIn); // read input value
if (signal == HIGH)
{
currentState = 1;
}
else
{
currentState = 0;
}
if(currentState != previousState)
{
counter = 0;
digitalWrite(led, LOW);
digitalWrite(signalOut, LOW);
}
else
{
counter = counter + 1;
}
Serial.println(counter);

if (counter >= 3000)
{ digitalWrite(led, HIGH);
digitalWrite(signalOut, HIGH);
}
previousState = currentState;

}

I'd GREATLY appreciate it if someone could take it a look at it. If you need me to go into more detail please ask!

2

Hi rockdinosaur

You are heading kind of in the right direction. You are incrementing counter each time round loop(). You are resetting it to 0 if you see the state change. And you are testing when counter reaches 3000 (by which I guess you mean 3000ms without a state change).

The problem is that loop() executes much faster than once per millisecond.

Try replacing counter with

unsigned long startTime = millis();

Then, instead of resetting it to 0 when the state changes, set it to the current time as given by millis(), the number of milliseconds since the program began

if(currentState != previousState)
{
    startTime = millis();
    digitalWrite(led, LOW);
    digitalWrite(signalOut, LOW);
}

Delete this

else
{
counter = counter + 1;
}

And change this

if (millis() - startTime >= 3000)
{   digitalWrite(led, HIGH);
    digitalWrite(signalOut, HIGH);
}

You can also simplify this part of your code

signal = digitalRead(signalIn); // read input value
if (signal == HIGH)
{
currentState = 1;
}
else
{
currentState = 0;
}

Change it to this

currentState = digitalRead(signalIn);

Regards

Ray

3

Hey thanks for the reply! I changed my code but now the LED just stays on even when I'm sending in a pulse..