Photo Interrupter Sensor Questions

Using Arduino Sensors
#1

Hi

I am new to this forum but I have searched here to find answers, while I could answer many questions I have a few I couldn’t.

My project is using a HY860N Photo Interrupter, see picture for drawing, it is wired up as per SparkFun drawing I found.

The code I am using is

int photoPin = 1; //A1
int val;
void setup()
{
Serial.begin(9600);
}

void loop()
{
val= analogRead(photoPin);
Serial.println(val);
delay(1000);
}

Results in serial window…

37 //Open
37 //Open
38 //Open
37 //Open
37 //Open
1019 //Blocked
1018 //Blocked
1017 //Blocked
1016 //Blocked
1017 //Blocked
30 //Open
30 //Open
30 //Open
30 //Open
30 //Open

When I put a multimeter across 1 and 2 where marked on picture. I get about 0.2V when open and about 5V when blocked.

Q1. My question is why doesn’t this work when I use a digital pin?
Q2. Newbie question might be answered in the first question, the numbers in the results how do I calculate into voltage?

phot.jpg
phot.jpg2065×1473 536 KB

#2

What does the code look like for the failing digital version?

#3

To calculate voltage from raw ADC counts you need to know the value of the analog reference voltage and the ADC resolution. On a Uno, using the default reference, the reference voltage is the supply voltage (around 5V) and resolution is 10 bits. So the formula to calculate voltage (for Uno) is ADC counts * (Vref/1024).
The numbers shown should work with a digital input.

#4

Thank you for the answers, they are much appreciated.

Don't know what I was doing but the digitalRead is now working?

The code I am using is....

int photoPin = 7; //D7
int val;
void setup()
{
Serial.begin(9600);
pinMode(photoPin, INPUT); //works with or without this line?
}

void loop()
{
val= digitalRead(photoPin);
Serial.println(val);
delay(1000);
}

#5