light intensity sensor

Forum 2005-2010 (read only) General Exhibition
1

I wanted a light intensity sensor for my stevenson's screen.

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1268871131

I used a PerkinElmer Photoconductive Cell type VT9ØN3.

http://www.datasheetcatalog.org/datasheet/perkinelmer/VT500.pd

The arduino program:

/* Simple program to demonstrate the light sensor
The circuit and the constants are described in
the pdf file.
*/

unsigned int rec_data = 0; //the integer received
const double RK = .00139; //circuit and device constant
const double gamma = 0.85; // the device power constant
const double V = 8.0; //the circuit supply voltage
const int analogpin = 0; // Analog input pin

void setup() // run once, when the sketch starts
{
Serial.begin(9600); // initialize serial communication with computer
}

void loop() // run over and over again
{
rec_data = analogRead(analogpin); // read the analog in value;
Serial.print("adc value = " );
Serial.print(rec_data); // print the adc value to the serial monitor:
Serial.print("\t light intensity = ");
double vo = (rec_data * 5.0) / 1024.0; //the voltage at the adc
vo = pow(RK * (V/vo -1) , -1.0/gamma); //the light intensity
Serial.print(vo,DEC); // print the light intensity
Serial.println(" lux");
delay(5000);
}//end of loop

Using my indoor weather program we log 24 hours:

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1265087241

The variations are due to clouds moving through the sensor's field of vision.

The circuit and calibration details are available from:
Download LIGHT.pdf