Phototransistor and Arduino

Development Boards Arduino
17

Ok- I have a small set up here:

https://www.dropbox.com/sc/ufppnh3eoz2dz9q/NXXnSCY2m9

I am running two of my phototransistors (PT344-6C): one into A) and another into digitalPin 2 (I am using analogRead to get the data out). Resistors are 1 M Ohm. I tried lower values (10K down to 220 Ohms, but only read 0’s). I tried no resistor when I only had 1 phototransistors reading from A0 (1021-1023… no surprise here).

Here is a typical output for the pins away from the light:

DigitalPin2: 163, Pin A0: 52

DigitalPin2: 161, Pin A0: 47

DigitalPin2: 159, Pin A0: 46

And here is what it looks like when I put the diodes up close to my desk lamp:

DigitalPin2: 855, Pin A0: 1020

DigitalPin2: 853, Pin A0: 1023

DigitalPin2: 852, Pin A0: 1021

For sake of completeness, here is my code:

int sensePin = A0;
int sensePinTwo = 2;
void setup(){
analogReference(DEFAULT);
pinMode(2,INPUT);
Serial.begin(9600);
}

void loop(){
  Serial.print("DigitalPin2: ");
  Serial.print(analogRead(sensePinTwo));
  Serial.print(", Pin A0: ");
  Serial.println(analogRead(sensePin));
  delay(100);
}

With two pins, if I pull the first resistor, I no longer see values of 1022-1023 but they’re more in the ballpark of 963. I suspect that - after looking at the spec. sheet- the 5V supplied by the arduino will not be sufficient.

Thoughts, ideas or criticisms?

Drew